Marine Embryos and Larvae

Many marine organisms have a well-known adult sessile stage. Unfortunately, our lack of knowledge regarding their larval transient stage hinders our understanding of their basic ecology and connectivity. Larvae can have swimming behavior that influences their transport within the marine environment. Understanding the larval stage provides insight into population connectivity that can help strategically identify areas for restoration. Current techniques for understanding the larval stage include modeling that combines particle attributes (e.g., larval behavior) with physical processes of water movement to contribute to our understanding of connectivity trends. This study builds on those methods by using a previously developed retention clock matrix (RCM) to illustrate time dependent connectivity of two species of shellfish between areas and over a range of larval durations. The RCM was previously used on physical parameters but we expand the concept by applying it to biology. A new metric, difference RCM (DRCM), is introduced to quantify changes in connectivity under different scenarios. Broad spatial trends were similar for all behavior types with a general south to north progression of particles. The DRCMs illustrate differences between neutral particles and those with behavior in northern regions where stratification was higher, indicating that larval behavior influenced transport. Based on these findings, particle behavior led to small differences (north to south movement) in transport patterns in areas with higher salinity gradients (the northern part of the system) compared to neutral particles. Overall, the dominant direction for particle movement was from south to north, which at times was enhanced by winds from the south. Clam and oyster restoration in the southern portion of Barnegat Bay could serve as a larval supply for populations in the north. These model results show that coupled hydrodynamic and particle tracking models have implications for fisheries management and restoration activities.

Two new species of trilobites of the Trochurinae subfamily from the Middle Devonian (Eifelian) of the Tafilalt region (Morocco) are described. In addition, a new genus (Basseiarges gen. nov.) is proposed in order to include one of them (Basseiarges mellishae sp. nov.). The main characteristics that make it different from the other members of the subfamily Trochurinae are its peculiar cephalon and pygidium, and the saw-shape of the ridge that connects the genal spines, which is similar to that present on the pygidium border. The second species described here is Akantharges mbareki sp. nov. from Tinejad. Both them are compared with the previously described species of the genus Akantharges. In addition, the first description of the hypostome of a member of the genus Akantharges is included.

During the Devonian Nekton Revolution, ammonoids show a progressive coiling of their shell just like many other pelagic mollusk groups. These now extinct, externally shelled cephalopods derived from bactritoid cephalopods with a straight shell in the Early Devonian. During the Devonian, evolutionary trends toward tighter coiling and a size reduction occurred in ammonoid embryonic shells. In at least three lineages, descendants with a closed umbilicus evolved convergently from forms with an opening in the first whorl (umbilical window). Other lineages having representatives with open umbilici became extinct around important Devonian events whereas only those with more tightly coiled embryonic shells survived. This change was accompanied by an evolutionary trend in shape of the initial chamber, but no clear trend in its size. The fact that several ammonoid lineages independently reduced and closed the umbilical window more or less synchronously indicates that common driving factors were involved. A trend in size decrease of the embryos as well as the concurrent increase in adult size in some lineages likely reflects a fundamental change in reproductive strategies toward a higher fecundity early in the evolutionary history of ammonoids. This might have played an important role in their subsequent success as well as in their demise.

To characterise central neurons in the pedal ganglia of both male and female green lipped mussel, Perna canaliculus immunohistochemical techniques were used. Mollusc antibodies were used against neuropeptides and neurotansmitters known to control reproduction and spawning. Anti-ELH and anti-APGWamide showed very strong immunoreactivity in small type of neurons. Anti-5-HT and anti-DA immunoreactivity was mostly in large type of neurons. The labelled neurons are consistent with descriptions of neurosecretory cells implicated in the control of reproduction and spawning on the basis of earlier histological staining techniques used in this species. The use of selective immunological markers for peptides and amines appears to be a, promising tool for further characterisation of neurosecretory cells, and to isolate an'tl characterise neuropeptides and other biologically active materials involved in the control of reproduction in Perna canaliculus.

Due to an error in their calculation, the standard errors reported in table 1 of the article [1] were too small. Please see the revised table 1 for correct s.e. Correction of this error does not change the conclusions of our work. Additionally, we would like to clarify that the strong treatment effects found in this experiment are likely the result of a combination of factors including, but not limited to, the ecology of the focal species, the flume apparatus, the chemical comparisons being tested as well as the concentration of the chemical cues tested. The chemical cue concentration is likely higher than the organisms would experience in nature and therefore likely a form of supernormal stimuli. Simply put, supernormal stimuli are bigger and more intense than normal, and elicit a larger than normal response from the animal [2]. Here, the naturally occurring olfactory

Background Cephalopods represent a rich system for investigating the genetic basis underlying organismal novelties. This diverse group of specialized predators has evolved many adaptations including proteinaceous venom. Of particular interest is the blue-ringed octopus genus (Hapalochlaena), which are the only octopods known to store large quantities of the potent neurotoxin, tetrodotoxin, within their tissues and venom gland. Findings To reveal genomic correlates of organismal novelties, we conducted a comparative study of 3 octopod genomes, including the Southern blue-ringed octopus (Hapalochlaena maculosa). We present the genome of this species and reveal highly dynamic evolutionary patterns at both non-coding and coding organizational levels. Gene family expansions previously reported in Octopus bimaculoides (e.g., zinc finger and cadherins, both associated with neural functions), as well as formation of novel gene families, dominate the genomic landscape in all octopods. Examin...

The present study was aimed to evaluate the effects of Artemia enrichment with baker's yeast Saccharomyces cerevisiae (Y) and Chaetoceros gracilis (C) on growth performance, stress resistance as well as fatty acid profile of Litopenaeus vannamei post larvae (PL) for 15 days. Newly hatched Artemia franciscana nauplii (N) served as a control group. Survival did not change among different experimental groups. PL in C and N groups had the highest (767.0± 117.0µg) and the lowest (367.0± 44.0 µg) dry weight, respectively, and PL in Y group showed intermediate value (567.0± 117.0µg). PL in Y and N groups had the highest (52.3 ± 2.9%) and the lowest (31.3 ± 2.8%) survival rate, when exposed to the fresh water stress test, respectively. The concentrations of eicosapentaenoic acid and docosahexaenoic acid were higher in Artemia enriched with C. gracilis than other groups. Moreover, the n-3 to n-6 PUFA ratio was significantly higher in PL fed C group than other treatments. In conclusion, feeding enriched Artemia with C. gracilis or S. cerevisiae can improve growth performance and stress resistance in L. vannamei PL.

Dans le cas où une version électronique native de la thèse existe, l'Université ne peut garantir que la présente version numérisée soit identique à la version électronique native, ni qu'elle soit la version officielle définitive de la thèse.

The best insight into the development of Devonian phacopids has been obtained from Trimerocephalus lelievrei Crô nier & Feist, 1997, a Famennian phacopine from Morocco, where changes in size and shape have been quantified. In this study, a morphometric approach has been used: (1) to retrodeform and then establish patterns of morphological variation in a well preserved but tectonically deformed assemblage belonging to another phacopine species Weyerites ensae (Richter & Richter, 1926), a Famennian phacopine from Thuringia, and (2) to establish patterns of developmental and evolutionary changes within two closely related species: Weyerites ensae and Trimerocephalus lelievrei. The method of retrodeformation using a set of discrete points presumed to be homologous on all studied individuals, has demonstrated that the next analyses are possible on the retrodeformed material as compared to the undeformed material. Morphometric analysis based on outline analysis has permitted demonstration of progressive shape change in agreement with ontogenetic ordination and a comparison of changes in size and shape in Weyerites ensae. The main changes in shape appear to occur in the meraspid period, whereas increase in size takes place mainly in the holaspid period. This pattern, already reported for Trimerocephalus lelievrei, can be generalized for phacopine trilobites from the Late Devonian. Moreover, the comparison of the two ontogenetic trajectories has shown that most of the differences are related to 'structural' changes, probably linked to a relative pre-post-displacement. The results suggest that ecological adaptation may be studied by examining the changes in development that occur within species through time and space. & Ontogeny, phacopine trilobites, quantification, Upper Devonian.

The best insight into the development of Devonian phacopids has been obtained from Trimerocephalus lelievrei Crô nier & Feist, 1997, a Famennian phacopine from Morocco, where changes in size and shape have been quantified. In this study, a morphometric approach has been used: (1) to retrodeform and then establish patterns of morphological variation in a well preserved but tectonically deformed assemblage belonging to another phacopine species Weyerites ensae (Richter & Richter, 1926), a Famennian phacopine from Thuringia, and (2) to establish patterns of developmental and evolutionary changes within two closely related species: Weyerites ensae and Trimerocephalus lelievrei. The method of retrodeformation using a set of discrete points presumed to be homologous on all studied individuals, has demonstrated that the next analyses are possible on the retrodeformed material as compared to the undeformed material. Morphometric analysis based on outline analysis has permitted demonstration of progressive shape change in agreement with ontogenetic ordination and a comparison of changes in size and shape in Weyerites ensae. The main changes in shape appear to occur in the meraspid period, whereas increase in size takes place mainly in the holaspid period. This pattern, already reported for Trimerocephalus lelievrei, can be generalized for phacopine trilobites from the Late Devonian. Moreover, the comparison of the two ontogenetic trajectories has shown that most of the differences are related to 'structural' changes, probably linked to a relative pre-post-displacement. The results suggest that ecological adaptation may be studied by examining the changes in development that occur within species through time and space. & Ontogeny, phacopine trilobites, quantification, Upper Devonian.

A comprehensive study, incorporating histology, light microscopy, scanning electron microscopy, immunochemistry and confocal microscopy, was performed to investigate embryogenesis and larval development of the New Zealand Greenshell™ mussel, Perna canaliculus. Detailed observations with this multi-technique approach revealed a gastrula stage at 18 hours post-fertilization, with the appearance of a blastopore, apical sense organ and enclosing vegetal pole. Early D-stage larvae showed limited alimentary organogenesis and clear initiation of a developing nervous system. Shell morphology of D-larvae was characterized by a flat, hinged, pitted-punctate prodissoconch I shell, followed closely by commarginal growth lines within the prodissoconch II shell. Early umbo larvae had a protruding functioning velum, and well-developed posterior adductor and velar retractor muscles. Significant progression in neuronal development occurred just before the umbo stage with noticeable paired cerebral, pedal and visceral ganglia. Shell morphology was characterized by further prodissoconch II secretion with a more rounded umbonate appearance. During the transition through the pediveliger stage, rapid development of the gill rudiment, eye spot and functioning foot was observed with ongoing neuronal development. The first appearance of the dissoconch shell layer took place during this transition, at which point the nervous system was highly distinct with innervations extending throughout muscle regions and between ganglia. This study provides the first comprehensive documentation of the developmental stages of P. canaliculus larvae from fertilization to settlement. The study highlights the advantages of using a combination of techniques to understand larval development and provides crucial information to identify larval performance during larval rearing.

Previous studies have suggested an involvement of catecholamines in the control of several larval behaviors, such as feeding, locomotion, and induction of settling and metamorphosis. In the present study we employed aldehyde-induced, blue-green fluorescence to indicate catecholamines in cells within representatives of two bivalve families, the Pectinidae (Placopecten magellanicus) and the Mytilidae (Mytilns ediilis). Larvae were examined at different stages of development before and also shortly after settlement. The general distribution of fluorescent cells was similar in the two species. By midveliger stage, several fluorescent cells and fibers were located along the outer rim of each velar lobe, and a pair of flask-shaped cells was located lateral to the mouth. A single fiber from near the mouth projected to a region beneath the apical tuft. In the pediveliger, the cells by the mouth were joined by an additional two to four fluorescent cells. The developing foot also contained numerous such cells, some of which had processes that penetrated the epithelium on the "sole" and bore ciliated terminals. Fluorescent somata were also located around the edge of the mantle. Centrally projecting fibers appeared to terminate in the pedal and abdominal ganglia, which also contained a few fluorescent somata. After settlement, the velar lobes and resident fluorescent somata disappeared, but fluorescent cells in the foot persisted as this latter organ grew. Fluorescent cells within the developing gill were connected with the abdominal ganglia by means of fibers. Control preparations labeled with antibodies raised against serotonin indicated that the aldehyde-induced fluorescence was not due to the presence of indoleamines. The present study not only confirms previous chromato

The sea star Anasterias minuta broods the embryos in the oral region; embryos then block the mouth and prevent the parent from taking up nutrients during the brooding period. Here, we analysed content of carbohydrates in different organs as well as in eggs, embryos and juveniles of A. minuta. We found that these biochemical components are used mainly by the pyloric caeca and the body wall as reserve substances to endure the periods of reduced consumption rates of non-brooding females and males and the long-term starvation of brooding females. The ability to translocate carbohydrates from females to embryos and juveniles observed in other species of sea stars was not confirmed.

Since Barrande (1852) first illustrated a trilobite larva, aspects of trilobite ontogeny and early development have received a great deal of attention (see Beecher, 1895; Størmer, 1942; Whittington, 1957; Hu, 1971; Chatterton, 1980). Much of this literature, however, is purely descriptive and very little has been done to incorporate these works into a biological synthesis. During the past several decades a great deal has been learned about the role of larval ecology in monitoring biogeographic distributions, cohort survivorship and taxonomic longevity among modern marine invertebrates. This growing body of knowledge has provided the basis for many new insights regarding patterns of extinction and survivorship and macroevolution evident within the fossil record (see Jablonski, 1986; Jablonski and Lutz, 1983).

Many living marine animals exhibit striking colour patterns on their external skeletons or on exposed flesh. Such colour patterns surely existed in fossil animals, but usually have faded, partially or more often completely, or have been modified by diagenesis. Some reported patterns may indeed have resulted from diagenesis alone and thus are not original. Here we assess colour patterns in trilobites in Devonian specimens from North America and in new material from Germany. Specimens of Eldredgeops crassituberculata (Stumm, 1953) from the Middle Devonian Silica Shale, Sylvania, Ohio show spots on the pleurae, a brown band on the axial ribs and shadowy brown patches on the glabella. We advance reasons why these are most likely original. Distinctive patterns in the pygidia of Scutellum geesense Rud. & E. Richter 1956, Calycoscutellum sp., Scabriscutellum scabrum (Goldfuss, 1842) and Thysanopeltella acanthopeltis Barrande 1852 from the Devonian of Germany are illustrated here. Several specimens from different localities show a medium brown band fading to whitish towards the margin of the pygidium. These patterns are most unlikely to be random or, as argued here, diagenetic. They represent, in our opinion, original colour bands. We speculate that these colour patterns may have functioned as camouflage in a shallow-water visual world determined by ever-changing patterns of light.

Bivalve metamorphosis is a developmental transition from a free-living larva to a benthic juvenile (spat), regulated by a complex interaction of neurotransmitters and neurohormones such as L-DOPA and epinephrine (catecholamine). We recently suggested an N-Methyl-D-aspartate (NMDA) receptor pathway as an additional and previously unknown regulator of bivalve metamorphosis. To explore this theory further, we successfully induced metamorphosis in the Pacific oyster, Crassostrea gigas, by exposing competent larvae to L-DOPA, epinephrine, MK-801 and ifenprodil. Subsequently, we cloned three NMDA receptor subunits CgNR1, CgNR2A and CgNR2B, with sequence analysis suggesting successful assembly of functional NMDA receptor complexes and binding to natural occurring agonists and the channel blocker MK-801. NMDA receptor subunits are expressed in competent larvae, during metamorphosis and in spat, but this expression is neither self-regulated nor regulated by catecholamines. In-situ hybridisation of CgNR1 in competent larvae identified NMDA receptor presence in the apical organ/cerebral ganglia area with a potential sensory function, and in the nervous network of the foot indicating an additional putative muscle regulatory function. Furthermore, phylogenetic analyses identified molluscan-specific gene expansions of key enzymes involved in catecholamine biosynthesis. However, exposure to MK-801 did not alter the expression of selected key enzymes, suggesting that NMDA receptors do not regulate the biosynthesis of catecholamines via gene expression.

AllsTRACT-The genus Otarion Zenker, 1833, first appears in the Wenlock simultaneously with Cyphaspis Burmeister, 1843, as the oldest known species of each occur together in the southern Mackenzie Mountains of the Canadian Northwest Territories. The genera are unambiguous sister groups, a relationship supported most compellingly by a uniquely derived and distinctive pattern of juvenile cephalie spines, shared also with the Carboniferous genus Namuropyge Richter and Richter, 1939. This sister group relationship permits the development of a robust and stratigraphically correlated hypothesis of relationship among the adequately known species of Otarion. Otarion, Cyphaspis, and Namuropyge constitute the tribe Otarionini. The Mississippian genus Dixiphopyge Brezinski, 1988, may also belong to Otarionini. Namuropyge is a paedomorph, likely derived from a Degree Six or Seven meraspid of an older species of uncertain position in the Otarion-Cyphaspis clade. Three Wenlock species of Otarion occur in stratigraphie succession in a single section in the Mackenzie Mountains. Analysis of morphological change with time, and of sequential ontogenies, suggests that the Silurian history of the genus was dominated by incidents of peramorphosis. New species are Otarion huddyi, O. beukeboomi, and O. coppinsensis. Otarion brauni Perry and Chatterton, 1979, is revised.

Competent larvae of different marine bivalve species were treated with GABA and epinephrine at different concentrations and times of exposure to test the ability of the drugs to induce settlement and metamorphosis. GABA induced both settlement and metamorphosis in the mussel Mytilus galloprovincialis, the clams Venerupis pullastra and Ruditapes philippinarum and the oyster Ostrea edulis. Maximum induction of settlement (N39%) was achieved after exposure of V. pullastra larvae to 10 À4 M GABA; this concentration of GABA also induced the highest percentages of metamorphosis in the four species studied. Epinephrine was identified as an active inducer of settlement and metamorphosis in bivalve molluscs. Exposure to 10 À5 M epinephrine induced significant levels of settlement in Mytilus, Venerupis and Ostrea. In contrast, epinephrine failed to induce settlement behaviour in Ruditapes. Maximum induction of metamorphosis was produced by 10 À5 M epinephrine in mussels, clams and oysters; Ruditapes showed the highest percentage of metamorphosis (N78%). This is the first report in which the involvement of GABA in the settlement and metamorphosis of bivalve molluscan larvae is demonstrated. It was also recognised that epinephrine plays a role not only in inducing metamorphosis but also in initiating settlement.

The flat oyster Ostrea edulis (L.) is a species native to Europe and a highly valued product for consumption. Rearing the oyster larvae, through the settlement and metamorphosis processes, is extremely critical for researchers and the hatchery industry. Settlement and metamorphosis in marine invertebrates typically occur in response to environmental, chemical and/or physical cues. The effect of several environmental factors, bacteria biofilms and analogues of natural inducers on settlement and metamorphosis of different bivalve larvae has been reported. However, there are no studies about the effect of chemical inducers on the settlement and production of flat oyster larvae under laboratory and hatchery conditions. In the present study, competent larvae of the flat oyster O. edulis were induced to settle by exposure to the neurotransmitter GABA, L-DOPA, the catecholamines epinephrine and norepinephrine, and IBMX, under laboratory conditions. After 24 h, maximum percentages of settlement were induced by 10 −4 M IBMX, 10 −4 M L-DOPA, 10 −5 M GABA and 10 −6 M epinephrine. Exposure to IBMX and norepinephrine also induced significant levels of settlement in Ostrea after 48 h. In contrast, 10 −4 , and 10 −5 M epinephrine and 10 −6 M L-DOPA failed to induce significantly higher settlement rates than the control larvae. GABA was found to be the most effective inducer. Maximum settlement rate was achieved by 10 −4 M GABA (>64%), four times higher compared to the control larvae. Exposure to 10 −5 M and 10 −6 M GABA also induced a significantly higher larval settlement. Mortality of O. edulis larvae was not affected by the chemical inducers. In hatchery conditions, GABA was an active and fast inducer of settlement and metamorphosis. 10 −6 M GABA promoted synchronisation of larvae and positively affected the spat growth.

The oral-brooding sea star Anasterias antarctica is distributed on the coasts of South Patagonia and north of Antarctic Peninsula. This species is a potential predator of shellfish Mytilus chilensis, an important commercial resource for Beagle Channel region. The aims of this work were to study the variation in the gonad index (GI), to establish the brooding season, to determine the reproductive effort of both sexes, and to assess the concentration of liposoluble antioxidants and production of reactive oxygen species (ROS) in male and female gonads and embryos of A. antarctica during the year. Four samplings were performed: three during the brooding season and one during the non-brooding season. Individuals sampled during the brooding season were assigned to one of the three groups: brooding females, non-brooding females, and males. Individuals sampled during the nonbrooding season were assigned to one of the three groups: sexually mature females, sexually non-mature females and males. Histological observations allowed determining that only females incubate the embryos on the oral surface for seven months. Males showed a strategy characteristic of broadcast spawners, whereas females spawned only a small number of eggs, as it is characteristic of brooders and as observed in other species of asteroids. Males show a significant increase in GI before spawning (from 1% to 15%) and then a marked decrease. During gametogenesis, testes showed a low level of β-carotene and high production of ROS. Between May and October; brooding and non-brooding females showed similar values of ROS production and concentration of antioxidants. Mature females had a significantly higher GI and lipid soluble antioxidant concentration than non-mature females. ROS production was higher in non-mature females. In A. antarctica embryos, ROS production increased and liposoluble antioxidant defenses decreased along development. The reproductive effort of males was about 25% lower than that of females, probably because of brooding costs. Gonadal maturation occurred in summer in both sexes, in concordance with an increase in the concentration of liposoluble antioxidants and the minimum values of ROS production. This suggests a strategy of oxidative damage prevention and gamete protection through allocation of antioxidants to mature gonads. The β-carotene and α-tocopherol accumulation in ovaries would protect not only maturing oocytes but also embryos, given that these antioxidants would be transferred to eggs. Along the reproductive cycle, A. antarctica gonads are protected from oxidative processes, mainly by β-carotene. Further, during gonad maturation, protection increases with the increase in α-tocopherol concentration and the decrease in ROS, whose highest and lowest values coincide with maximum gonadal maturation.

Three new species of Cyphaspides are proposed: C. ammari, C. nicoleae, and C. pankowskiorum. These species are based on specimens obtained from Middle Devonian (Eifelian) strata of the Bou Tchrafine Group, near Erfoud, in the Province of Errachidia, southeastern Morocco. The present contribution enhances our knowledge of Cyphaspides by providing details of three new species that are based on well-preserved, complete, and articulated types. The genus Cyphaspides is discussed, and an emended diagnosis is provided. The paleobiogeography, ontogeny, and relationships of the genus are discussed.

Understanding the degree of connectivity between coastal and island landscapes and nearby coral reefs is vital to the integrated management of terrestrial and marine environments in the tropics. Coral reef fish are capable of navigating appropriate settlement habitats following their pelagic larval phase, but the mechanisms by which they do this are unclear. The importance of olfactory cues in settlement site selection has been demonstrated, and there is increasing evidence that chemical cues from terrestrial sources may be important for some species. Here, we test the olfactory preferences of eight island-associated coral reef fish recruits and one generalist species to discern the capacity for terrestrial cue recognition that may aid in settlement site selection. A series of pairwise choice experiments were used to evaluate the potential role that terrestrial, water-borne olfactory cues play in island-reef recognition. Olfactory stimuli tested included near-shore water, terrestria...

Tetrodotoxin (TTX), is a potent neurotoxin targeting sodium channels that has been identified in multiple marine and terrestrial organisms. It was recently detected in the Opisthobranch Pleurobranchaea maculata and a Platyhelminthes Stylochoplana sp. from New Zealand. Knowledge on the distribution of TTX within these organisms is important to assist in elucidating the origin and ecological role of this toxin. Intracellular micro-distribution of TTX was investigated using a monoclonal antibody-based immunoenzymatic technique. Tetrodotoxin was strongly localized in neutral mucin cells and the basement membrane of the mantle, the oocytes and follicles of the gonad tissue, and in the digestive tissue of P. maculata. The ova and pharynx were the only two structures to contain TTX in Stylochoplana sp. Using liquid chromatography-mass spectrometry, TTX was identified in the larvae and eggs, but not the gelatinous egg cases of P. maculata. Tetrodotoxin was present in egg masses of Stylochoplana sp. These data suggest that TTX has a defensive function in adult P. maculata, who then invest this in their progeny for protection. Localization in the digestive tissue of P. maculata potentially indicates a dietary source of TTX. Stylochoplana sp. may use TTX in prey capture and for the protection of offspring.

The nauplius is the earliest free-living stage in the development of most crustaceans, except in the majority of the Malacostraca. Several character states of the nauplius larva are used as constitutive for the Crustacea as a whole. The nauplius shows the following structural characters: a median (nauplius) eye, at least three pairs of head appendages (first and second antennae, where the second antenna bears an arthrite; mandibles), a posteriorly directed fold (the labrum) extending over the mouth, and a cephalic (¼ nauplius) shield. Extant taxa such as the

Most sea urchins are gonochoric broadcast spawners, with indirect development through free-living planktotrophic larvae. However, some species produce large eggs that are retained and brooded by the female, leading to morphological changes between sexes

Red shrimp, Farfantepenaeus brasiliensis, larvae's response to different concentrations of live foods (diatoms Chaetoceros gracilis: 20-100 × 10 3 cells/mL; flagellate Tetraselmis chuii: 2-10 × 10 3 cells/mL and Artemia nauplii [NA]: 1-5 NA/mL) was investigated in three experiments. Experimental assessments were based on four variables: survival rate, weight gain, development index (DI), and resistance to salinity stress. A combination of C. gracilis 80 × 10 3 cells/mL, T. chuii 2 × 10 3 cells/mL, and Artemia 4 NA/mL provided the best experimental response. Specifically, F. brasiliensis larvae fed with the above-mentioned optimal concentrations of microalgae and Artemia grew faster and reached the postlarval stage in less time (168 h) than larvae in other feeding regimes evaluated. The effect of C. gracilis concentration on larval growth, survival, and the DI demonstrated that microalgae-based foods could be a highly productive alternative to more traditional aquaculture feeding regimes.

Aquaculture of New Zealand’s endemic green-lipped mussel (Perna canaliculus) is an industry valued at NZ$ 336 M per annum and is ~ 80% reliant on the natural supply of wild mussel spat harvested at a single location—Te Oneroa-a-Tōhē—Ninety Mile Beach (NMB)—in northern New Zealand. Despite the economic and ecological importance of this spat supply, little is known about the population connectivity of green-lipped mussels in this region or the location of the source population(s). In this study, we used a biophysical model to simulate the two-stage dispersal process of P. canaliculus. A combination of backward and forward tracking experiments was used to identify primary settlement areas and putative source populations. The model was then used to estimate the local connectivity, revealing two geographic regions of connectivity in northern New Zealand, with limited larval exchange between them. Although secondary dispersal can double the dispersal distance, our simulations show that sp...

The new ellipsocephaloid trilobite speciesKingaspidoides spinirecurvatushas a spectacular morphology because of a unique set of two long and anteriorly recurved spines on the occipital ring and the axial ring of thoracic segment 8. Together with the long genal spines this whimsical dorsally directed spine arrangement is thought to act as a non-standard protective device against predators. This is illustrated by the body posture during different stages of enrolment, contrasting with the more sophisticated spinosities seen in later trilobites, which are discussed in brief.Kingaspidoides spinirecurvatusfrom the lower–middle Cambrian boundary interval of the eastern Anti-Atlas in Morocco has been known for about two decades, with specimens handled as precious objects on the fossil market. Similar, but far less spectacular, spine arrangements on the thoracic axial rings are known from other ellipsocephaloid trilobites from the Anti-Atlas of Morocco and the Franconian Forest region of Ger...

All chordates share several characteristic features including a dorsal hollow neural tube, a notochord, a pharynx and an endostyle. Unlike other chordate taxa, ascidians have a biphasic life-history with two distinct body plans. During metamorphosis, the larval nerve cord and notochord degenerate and the pharyngeal gill slits and endostyle form. While ascidians, like other marine invertebrates, metamorphose in response to specific environmental cues, it remains unclear how these cues trigger metamorphosis. We have identified a novel gene (Hemps) which encodes a protein with a putative secretion signal sequence and four epidermal growth factor (EGF)-like repeats which is a key regulator of metamorphosis in the ascidian Herdmania curvata. Expression of Hemps increases markedly when the swimming tadpole larva becomes competent to undergo metamorphosis and then during the first 24 hours of metamorphosis. The Hemps protein is localised to the larval papillae and anterior epidermis of the...

Synopsis Metamorphosis is both an ecological and a developmental genetic transition that an organism undergoes as a normal part of ontogeny. Many organisms have the ability to delay metamorphosis when conditions are unsuitable. This strategy carries obvious benefits, but may also result in severe consequences for older larvae that run low on energy. In the marine environment, some lecithotrophic larvae that have prolonged periods in the plankton may begin forming postlarval and juvenile structures that normally do not appear until after settlement and the initiation of metamorphosis. This precocious activation of the postlarval developmental program may reflect an adaptation to increase the survival of older, energy-depleted larvae by allowing them to metamorphose more quickly. In the present study, we investigate morphological and genetic consequences of delay of metamorphosis in larvae of Herdmania momus (a solitary stolidobranch ascidian). We observe significant morphological and genetic changes during prolonged larval life, with older larvae displaying significant changes in RNA levels, precocious migration of mesenchyme cells, and changes in larval shape including shortening of the tail. While these observations suggest that the older H. momus larvae are functionally different from younger larvae and possibly becoming more predisposed to undergo metamorphosis, we did not find any significant differences in gene expression levels between postlarvae arising from larvae that metamorphosed as soon as they were competent and postlarvae developing from larvae that postponed metamorphosis. This recalibration, or convergence, of transcript levels in the early postlarva suggests that changes that occur during prolonged larval life of H. momus are not necessarily associated with early activation of adult organ differentiation. Instead, it suggests that an autonomous developmental program is activated in H. momus upon the induction of metamorphosis regardless of the history of the larva.

The present study examined the appearance, ossification and growth of the bones that form the oral cavity in early larval stages of laboratory reared red sea bream (Pagrus major) for 380 h after hatching. The fundamental elements of the oral cavity appeared 11 h after initial mouth opening (HAMO). Development in the red sea bream, based on the osteological development of the feeding apparatus, was divided into three phases following the first feeding (24 HAMO; mean total body length 3.3 mm). The first phase was the early sucking phase (24 to 80-100 HAMO; approximately 3.9 mm), during which the head and bones increased in size. The intensified sucking phase (to 200-220 HAMO; approximately 4.9 mm) was defined by the appearance of new structural elements and a continued enlargement of the head and bones. Finally, during the transition phase (beyond 300 HAMO; approximately 5.6 mm), larvae used grasping as well as sucking to feed, new elements appeared, ossification began, size increased and teeth were acquired. As the larvae advanced through these three phases, the ability to feed by sucking was enhanced by the appearance and growth of new bones. The developmental phases appear to be linked to the transition from endogenous to exogenous nutrition resources under laboratory rearing conditions and to diversification in the size and components of wild food organisms.

Highlight ResearchThe qualitative bioactive assay on terpenoid compound of six macroalgae species were tested.The effect of six macroalgae extracts as inducer mediating settlement to juvenile Perna viridis were observed.Three macroalgae species were potentially promote the retention of juvenile P. viridisThe low retention of juvenile of green mussels (Perna viridis) in the aquaculture holding system has become a constraint for its production. The depress number of juvenile mussel on the collector rope might be caused due to both limited spawning season and their secondary settlement behaviour. Therefore, providing suitable substrate which able to improve green mussel seed retention is required. One of the solutions is by applying inducer mediating settlement as substrate enrichment in order to optimize the retention of juvenile P. viridis. The potential substrates thought to have these inductive activities is seaweed. Seaweed bioactive compound which may improve juvenile mussel rete...

Competent larvae of the black scallop Chlamys varia (L.) were treated with the neurotransmitter gamma-aminon-butyric acid (GABA), the catecholamine epinephrine, and 3-isobutyl-1-methylxanthine (IBMX), at different concentrations and times of exposure, to test the effects of exposure to the compounds on larval settlement. After 24 h, maximum percentage of settlement (>30%) was induced by 10-5 M epinephrine. After 48 h, maximum settlement rate was also achieved by 10-5 M epinephrine (>54%). Exposure to 10-6 M epinephrine and to 10-6 M GABA also induced significantly higher larval settlement than in control larvae. By contrast, IBMX failed to induce significantly higher settlement rates than in the control larvae. Epinephrine and GABA were identified as active inducers of settlement in C. varia, and were not toxic to black scallop larvae. This is the first report in which the involvement of epinephrine and GABA in the settlement of C. varia larvae is described.

Trinucleoids have been considered as a superfamily of the Order Asaphida, based on: a pre-occipital glabellar tubercle, a cephalic median suture in most ancestral forms, and the presence of broadly similar globular protaspid larvae in the life cycle. Recent discoveries cast doubts on the monophyly of the two last characters. This study provides a phylogenetic analysis whose main purpose is to test the affiliation of trinucleoids. The topology of the strict consensus tree obtained indicates that trinucleoids share a more recent common ancestor with members of the Order Ptychopariida than they do with any asaphid. The stratigraphically higher and most derived trinucleoids are well defined and easy to recognize. Their basal representatives can also be identified with confidence, in spite of substantial variation in the diagnostic characters of the group. These early trinucleoids are similar enough to the typical basal 'ptychopariid' bauplan to suggest ancestry within that diffuse and poorly defined trilobite order. Indeed, Ptychopariida is presently regarded as being paraphyletic. We consider that raising trinucleids to ordinal status, by proposing the Order Trinucleida, will make it easier to decipher higher level relationships among trilobites. This action, sustained by improved morphological and ontogenetic information of Cambro-Ordovician trilobites, reveals convergences of the three characters that have been used to support the inclusion of trinucleids within Asaphida. Based on this new information, we propose six distinct morphotypes of commutavi protaspis and, as a probable sensorial organ, that the cephalic axial tubercle migration might be caused by an increase in the height of the glabella and thus may not bear an important systematic signal. Moreover, the tree topology provided herein offers a preliminary overview of evolution within the order. Alsataspididae and Raphiophoridae are paraphyletic, suggesting that more investigation is needed to define them clearly. Dionidae appears to be more closely related to Raphiophoridae than to Trinucleidae, suggesting that the character state of 'a perforated fringe' evolved more than once.

Middle and Upper Ordovician Triarthrinae from the Precordillera of San Juan, Argentina, include the Whiterock/Llanvirn Porterfieldia turneri (Baldis and Pöthe, 1995) and P. acava new species, and the early Caradoc Triarthrus jachalensis (Harrington and Leanza, 1957). Each of these species is described based on silicified material, including ontogenies, from the Las Aguaditas Formation. Porterfieldia maanssonae new species from the lower member of the Gualcamayo Formation (late Arenig) at Río Gualcamayo, San Juan Province, and Río Guandacol, La Rioja Province, is closely allied to P. turneri. Two protaspid stages are present in Porterfieldia, whereas mineralized protaspid stages are apparently lacking in Triarthrus jachalensis. Triarthrus jachalensis was capable of sphaeroidal enrollment by meraspid degree 2. Precordilleran species bear closest comparison to others from Spitsbergen (Porterfieldia acava n. sp. and P. parapunctata) and Sweden/Norway (Triarthrus jachalensis and T. linnarssoni).

The Greenshell™ mussel, Perna canaliculus, is the most lucrative aquaculture species in New Zealand; however, losses of commercial juvenile mussels (spat) are common and can drastically reduce the yield of adults. Modification of seeding density is a potential method to manage loss of spat (~ 1-20-mm shell length), by reducing biofouling and intraspecific competition. Understanding the stress responses of spat in production systems during the early stages of aquaculture is a high priority for mussel farmers who aim to manage and optimise mussel production. Here, the effects of seeding density (low: 257, mid: 515, and high: 1030 mussels 10 cm −1 of culture rope), space (depth, site), and time (December 2019 and February 2020) on oxidative stress responses (total antioxidant capacity [TAC] and lipid peroxidation [LP] biomarkers) in spat and their viability (freshwater immersion test) were assessed in the Marlborough Sounds, New Zealand. The effect of seeding density on TAC was variable among depths, sites, and times, whereas seeding density had no impact on LP. In late summer (February 2020), oxidative stress appeared to be higher compared to early summer (December 2019). This indicates that mussels were exposed to more stressful conditions later in summer, although this did not reduce their short-term viability. This research found that seeding density had no major impact on oxidative stress biomarkers and suggests that stress responses and viability of Greenshell™ mussel spat during the summer months are not affected by the seeding density levels measured in this study.

Farmed adult Greenshell™ mussels were exposed to a range of conditions immediately after harvest to evaluate the effects on emersion survival and the implications for live transport. Two experiments were performed, coinciding with the mussel harvest season during summer and winter 2017. In the summer experiment, a wide range of conditions were tested to identify alternatives to be evaluated in more detail during the winter experiment. The postharvest experimental conditions selected included transient re-immersion at different temperatures, cold and heat-shock, tidal simulation, and packing with ice. These treatments aimed to either reduce postharvest stress and/or give the mussels a potentially beneficial physiological and behavioural advantage to help them cope with emersion. The mussels' responses in terms of gaping and survival differed between summer and winter, and among and within treatments. Sub-ambient temperature seawater exposure after harvest tended to improve the survival time of the mussels in both seasons, the effect being dependent on both temperature and duration of the exposure. Some of the differences observed could be explained by the conditions (in the wild and in the laboratory) to which the mussels were exposed before emersion and the different capability that each mussel has to cope with stress. However, the exact mechanisms driving these changes are not fully understood and require further investigation. This study, nevertheless, indicates that emersion survival (i.e. live mussel shelf-life) could be extended by re-immersion after harvest combined with a sub-lethal cold-shock followed by immersed recovery before transportation. If the commercial shelf-life of live product can be significantly extended, the implications for food quality and safety will also need to be evaluated. A similar approach could be applied in other shellfish such as other species of mussels as well as oysters or clams to improve shelf-life, considering their physiological capabilities and behaviour and how those are affected by environmental conditions in different seasons or regions.

Low numbers and unreliable wild catch of the native £at oyster, Ostrea angasi, spat has resulted in the NSW £at oyster industry being reliant on hatchery-produced spat. The need to produce culchless spat in the hatchery stimulated investigation of several catecholamines to induce metamorphosis in O. angasi larvae. Larvae were treated with one of four neuroactive catecholamines (epinephrine, epinephrine bitartrate, L-Dopa and GABA) at one of four concentrations (10 À 3 , 10 À 4 , 10 À 5 or 10 À 6 M) for one of three treatment durations (0.5,1^2 h) to determine morphogenic action for culchless spat production. Epinephrine bitartrate at 10 À 3 and 10 À 4 M and epinephrine at 10 À 3 , 10 À 4 and 10 À 5 M, for a treatment duration of 1^2 h, produced signi¢cantly greater numbers of spat and culchless spat, compared with any other treatment combination. The other catecholamines tested did not induce a sig-ni¢cant increase in the total number of spat or culchless spat, over untreated controls. Separate trials found that long-term treatment (24 h) with epinephrine bitartrate and epinephrine at morphogenic concentrations inhibited metamorphosis. Consecutive daily use of epinephrine bitartrate increased the numbers of spat and culchless spat produced, but did not a¡ect larval or short-term post-larval survival. Treatment with 10 À 3 M epinephrine bitartrate or 10 À 4 M epinephrine for 1h is recommended for routine commercial production of culchless £at oyster spat.

Many living marine animals exhibit striking colour patterns on their external skeletons or on exposed flesh. Such colour patterns surely existed in fossil animals, but usually have faded, partially or more often completely, or have been modified by diagenesis. Some reported patterns may indeed have resulted from diagenesis alone and thus are not original. Here we assess colour patterns in trilobites in Devonian specimens from North America and in new material from Germany. Specimens of Eldredgeops crassituberculata (Stumm, 1953) from the Middle Devonian Silica Shale, Sylvania, Ohio show spots on the pleurae, a brown band on the axial ribs and shadowy brown patches on the glabella. We advance reasons why these are most likely original. Distinctive patterns in the pygidia of Scutellum geesense Rud. & E. Richter 1956, Calycoscutellum sp., Scabriscutellum scabrum (Goldfuss, 1842) and Thysanopeltella acanthopeltis Barrande 1852 from the Devonian of Germany are illustrated here. Several specimens from different localities show a medium brown band fading to whitish towards the margin of the pygidium. These patterns are most unlikely to be random or, as argued here, diagenetic. They represent, in our opinion, original colour bands. We speculate that these colour patterns may have functioned as camouflage in a shallow-water visual world determined by ever-changing patterns of light.

The high proportion of brooding (50 to 70% depending on phyla) compared with broadcaster species among invertebrates living along the coast of the Southern Ocean has been traditionally interpreted as an adaptation to local environmental conditions. Currently, however, species with a planktotrophic developmental mode are ecologically dominant along coastal areas, in terms of abundance of individuals. The fact that Kerguelen Island is inhabited by such species and that the French base Port-aux-Français, with its equipped marine laboratory, made it possible to address questions as to why are there so many brooders in the coastal waters of the Southern Ocean and if the apparent ecological success of broadcasters related to their developmental mode. We argue that the present shallow Antarctic benthic invertebrate fauna is the result of two processes acting at different temporal scales. First, the high proportion of brooding species compared with coastal communities elsewhere corresponds ...

Many marine invertebrate larvae undergo complex morphological and physiological changes during the planktonic—benthic transition (a.k.a. metamorphosis). In this study, transcriptome analysis of different developmental stages was used to uncover the molecular mechanisms underpinning larval settlement and metamorphosis of the mussel, Mytilus coruscus. Analysis of highly upregulated differentially expressed genes (DEGs) at the pediveliger stage revealed enrichment of immune-related genes. The results may indicate that larvae co-opt molecules of the immune system to sense and respond to external chemical cues and neuroendocrine signaling pathways forecast and trigger the response. The upregulation of adhesive protein genes linked to byssal thread secretion indicates the anchoring capacity required for larval settlement arises prior to metamorphosis. The results of gene expression support a role for the immune and neuroendocrine systems in mussel metamorphosis and provide the basis for f...

The presence of bollandiine trilobites is reported for the first time in the early Carboniferous of Moravia, the Czech Republic. Bollandia persephone (Hahn & Hahn, 1970) and B. cf. megaira (Hahn & Hahn, 1970) were recovered from pelitic shales of late Tournaisian age within the Březina Formation exposed in Mokrá quarry, near Brno. Along with other taxa, these two species constitute a trilobite assemblage with few affinities to other Carboniferous associations known from the Czech Republic, but resemble an assemblage from the late Tournaisian of the Harz Mountains. Morphological characters of Bollandia species are interpreted as being indicative of an epibenthic mode of life, with possible adaptations for digging and for predatory/scavenging feeding habits.