Post-metamorphic Phase Research Articles

Carryover effects of chronic exposure to ammonium during the larval stage on post-metamorphic frogs.

Water contamination poses an important challenge to aquatic fauna, including well-documented effects on amphibian larvae. However, little is known about how contamination during the larval stages may affect post-metamorphic phases, or whether resistance may have evolved in some populations. In this work, we tested the hypothesis that chronic exposure to ammonium (a common contaminant in agroecosystems with confirmed effects on anuran tadpoles) during the larval stage of Pelophylax perezi frogs would affect growth and locomotor performance of metamorph, juvenile, subadult and adult stages. We also predicted that the effects of ammonium would be milder in offspring originated from parental agroecosystem frogs than those originating from forests. We compared tadpoles from both habitats either reared in untreated water or chronically exposed to ammonium. We found that exposure to ammonium during the larval stage inflicted effects on morphology (different measures of body size) and swimming speed after metamorphosis until adulthood. However, these effects were not always consistent through post-metamorphic stages and the effects differed as a function of treatment and habitat. In adults, body size and condition were greater in non-ammonium and ammonium exposed individuals, respectively. These differences were not detectable in metamorphs, for which only ammonium-exposed individuals from agroecosystem showed reduced body size in intermediate post-metamorphic stages. In turn, treatment reduced jumping distance only in agroecosystem adults, subadults and juveniles, which was opposite to the trend observed just after metamorphosis. These changes of patterns throughout the ontogeny of P. perezi could be due to processes such as compensatory growth, delayed energy costs derived from it, or early sexual differences that could be present even before they can be accounted for. In summary, this study suggests that exposure to ammonium during larval stages can result in diverse biological and long-term outcomes in later life stages.

Transcriptome dynamics during metamorphosis of imaginal discs into wings and thoracic dorsum in Apis mellifera castes

BackgroundMuch of the complex anatomy of a holometabolous insect is built from disc-shaped epithelial structures found inside the larva, i.e., the imaginal discs, which undergo a rapid differentiation during metamorphosis. Imaginal discs-derived structures, like wings, are built through the action of genes under precise regulation.ResultsWe analyzed 30 honeybee transcriptomes in the search for the gene expression needed for wings and thoracic dorsum construction from the larval wing discs primordia. Analyses were carried out before, during, and after the metamorphic molt and using worker and queen castes. Our RNA-seq libraries revealed 13,202 genes, representing 86.2% of the honeybee annotated genes. Gene Ontology analysis revealed functional terms that were caste-specific or shared by workers and queens. Genes expressed in wing discs and descendant structures showed differential expression profiles dynamics in premetamorphic, metamorphic and postmetamorphic developmental phases, and also between castes. At the metamorphic molt, when ecdysteroids peak, the wing buds of workers showed maximal gene upregulation comparatively to queens, thus underscoring differences in gene expression between castes at the height of the larval-pupal transition. Analysis of small RNA libraries of wing buds allowed us to build miRNA-mRNA interaction networks to predict the regulation of genes expressed during wing discs development.ConclusionTogether, these data reveal gene expression dynamics leading to wings and thoracic dorsum formation from the wing discs, besides highlighting caste-specific differences during wing discs metamorphosis.

Amino acid digestibility of protein and energy ingredients of plant origin in bullfrog (Lithobates catesbeianus)

Due to increasing demand of ingredients of animal origin, studies on the availability of nutrients in ingredients of plant origin are worthy in carnivorous species including bullfrog. This study aimed to determine apparent digestibility coefficients (ADCs) of amino acids (AAs) in three ingredients as plant protein sources (soybean protein concentrate (SPC), corn gluten meal 60 % (CGM), soybean meal (SM)) and two ingredients as plant energy sources (corn grain (CG) and wheat bran (WB)) which commonly use in bullfrog diets. A reference diet and five test diets containing 69.5 % of the reference diet, 30 % of each test ingredient and 0.5 % of chromium (III) oxide as an inert marker were prepared. Among plant protein ingredients, CGM showed better digestibility of essential amino acids (EAAs) (> 80 %) at the three post-metamorphic (initial, growing and finishing) phases of bullfrog development, except tryptophan which presented a low digestibility at growing and finishing phases. Among plant energy ingredients, CG presented better digestibility of AAs at both initial and growing phases than WB which showed better digestibility only at finishing phase. It was observed that methionine and lysine are the most limiting EAAs in tested ingredients, indicating that additional amounts of these AAs should be supplemented when these ingredients are used in bullfrog diets.

A Provisional Model of Demography in Desmognathus ocoee (Amphibia, Plethodontidae)

A provisional model of survival and demography in two populations of the salamander Desmognathus ocoee in the Cowee and Nantahala mountains of North Carolina was derived from existing data on growth, metamorphic timing, age at first reproduction, and fecundity. The model assumed stationary populations with stable age distributions (R0 = 1.0, r = 0), wherein observed ages at first reproduction in females were equal to optimal ages. Survivorship was partitioned into pre- and post-metamorphic phases, i.e., egg/larval survival and juvenile/adult survival. Premetamorphic survival estimates were fitted to the model to meet the requirement that R0 = 1.0. Equivalence of optimal and observed age at first reproduction in females, as proposed, could reflect synergistic tradeoffs between (1) growth and reproduction, and (2) mortality and reproduction. The two populations show extreme similarity in life history and demography, in contrast to differences between the Cowee and Nantahala desmognathine assemblages.

Effect of triclosan on anuran development and growth in a larval amphibian growth and development assay.

A larval amphibian growth and development assay was performed to evaluate the potential effects of environmentally-relevant concentrations of triclosan (TCS) on amphibian development and growth. Xenopus laevis were exposed to TCS 0.0 (control), 6.3, 12.5 and 25.0 μg l-1 (estimated maximum tolerable concentration) until 10 weeks post-metamorphosis. At median metamorphosis time (Nieuwkoop and Faber stage 62), five larvae per replicate were collected for snout-vent length, hind limb length and body weight measurements, and histopathological examination of thyroid glands. Endpoints evaluated at test termination were based on draft guidance (USEPA, ) and included: survival; snout-vent length; body weight; gender; nuptial pad development (males); and liver, kidney, gonad and gonadal ducts histopathology. Exposure to TCS did not decrease survival, induce general signs of toxicity, affect median metamorphosis time or alter sex ratios. Exposure to TCS 12.5 and 25 μg l-1 increased growth during the metamorphic stages relative to the control, but did not influence growth during the post-metamorphic phase. Overall, several statistically significant findings were found in larvae exposed to TCS, such as a decrease in the prevalence of stage 3 Müllerian ducts in the anterior trunk sections of TCS 25.0 μg l-1 dose group females as compared to controls; most were not considered toxicologically relevant. Copyright © 2017 John Wiley & Sons, Ltd.

Biological characteristics of smolts of European river lamprey Lampetra fluviatilis from the Chernaya River basin (Gulf of Finland, Baltic Sea)

Smolts of European river lamprey Lampetra fluviatilis from the Chernaya River basin are described. Expansion of variation limits is suggested on the basis of comparative analysis of taxonomically significant characters of this population and the species area. Structure of gonads and intestine of specimens preparing themselves for the feeing phase of their life cycle is described and some changes during the feeding phase are reconstructed. The scheme of analysis and description of smolts is suggested, the last may be applied to other lamprey species. The term “smolt” is rightfully used for juvenile anadromous lampreys making downstream migration. Biology of parasitic nonanadromous species of lampreys during the feeding phase (juvenile postmetamorphic phase) differs from biology of smolts.

Ontogenetic changes in nucleic acid, protein contents, and growthof larval and juvenile Japanese flounder

In order to estimate relationships among growth potential and biochemical indicators of Japanese flounder, RNA and DNA as well as protein indices were measured from 5 days after hatching (DAH) to 45 DAH. Results showed that the RNA/DNA ratio and protein/DNA ratio had obvious relations with instantaneous growth rate (GM) and length-based instantaneous growth rate (GL) during the premetamorphic period. Significant negative correlations among protein/DNA ratio and GM and GL were then observed during metamorphosis. During the postmetamorphic phase, the RNA/DNA ratio was positively correlated with GM and GL. Data indicated that body growth of Japanese flounder is mostly hyperplastic before 20 DAH, hypertrophic until 27 DAH, and hyperplastic until the end. In order to investigate the effect of diel periodicity on RNA/DNA ratio in larvae of the fed and starved groups, an experiment was conducted for 2 days. Results showed that the average RNA/DNA ratio in the daytime was higher than that in the dark and the ratio in fed larvae was higher compared with that in starved ones. In order to examine starvation effect on RNA/DNA ratio, experiments were conducted from 20 DAH to 27 DAH. Juveniles were divided into five groups: a fed group and groups starved 1, 2, 3, and 4 days followed by refeeding. Results showed that the RNA/DNA ratio increased in the fed group and declined continuously in the starved group. After refeeding, the recovery of the RNA/DNA ratio was observed for 1-day, 2-day, and 3-day starved treatments but was not found for the 4-day starved treatment.

Habitat use, relative growth and size at maturity of the purple stone crab <em>Platyxanthus crenulatus</em> (Decapoda: Brachyura), calculated under different models

Summary: We describe the most noteworthy changes occurring during the post-metamorphic phase in both sexes of the purple stone crab Platyxanthus crenulatus. Spatial structure of the populations by size and early changes in colour pattern and relative growth of chelae suggest an ontogenic migration from intertidal to deeper waters. Before reaching maturity and laying eggs, females undergo a tight sequence of morpho-physiologic changes over a narrow size range (44-64 mm carapace width [CW]). In contrast, males undergo two main phases related to sexual maturity. Early in their lives, they develop sperm and accelerate the relative growth of the chelae (35-45 mm CW). Morphologic maturity of males comes later, when relative growth rate reaches the maximum and decelerate (65-70 mm CW). Adult males are larger and develop conspicuously largest chelae than females. Morphometric analyses were performed by two different techniques: the traditional procedure, which describes relative growth relationships as power functions; and an alternative, smoothing spline–based model that is nondependent on previous assumptions. The results of the alternative analysis were coherent with other reproductive indicators and ancillary observations, allowing a more comprehensive understanding of the relative growth. We provide supporting material containing the respective script written in R program to be used freely in future studies.

A Dynamic Energy Budget (DEB) model for the keystone predator Pisaster ochraceus.

We present a Dynamic Energy Budget (DEB) model for the quintessential keystone predator, the rocky-intertidal sea star Pisaster ochraceus. Based on first principles, DEB theory is used to illuminate underlying physiological processes (maintenance, growth, development, and reproduction), thus providing a framework to predict individual-level responses to environmental change. We parameterized the model for P. ochraceus using both data from the literature and experiments conducted specifically for the DEB framework. We devoted special attention to the model’s capacity to (1) describe growth trajectories at different life-stages, including pelagic larval and post-metamorphic phases, (2) simulate shrinkage when prey availability is insufficient to meet maintenance requirements, and (3) deal with the combined effects of changing body temperature and food supply. We further validated the model using an independent growth data set. Using standard statistics to compare model outputs with real data (e.g. Mean Absolute Percent Error, MAPE) we demonstrated that the model is capable of tracking P. ochraceus’ growth in length at different life-stages (larvae: MAPE = 12.27%; post-metamorphic, MAPE = 9.22%), as well as quantifying reproductive output index. However, the model’s skill dropped when trying to predict changes in body mass (MAPE = 24.59%), potentially because of the challenge of precisely anticipating spawning events. Interestingly, the model revealed that P. ochraceus reserves contribute little to total biomass, suggesting that animals draw energy from structure when food is limited. The latter appears to drive indeterminate growth dynamics in P. ochraceus. Individual-based mechanistic models, which can illuminate underlying physiological responses, offer a viable framework for forecasting population dynamics in the keystone predator Pisaster ochraceus. The DEB model herein represents a critical step in that direction, especially in a period of increased anthropogenic pressure on natural systems and an observed recent decline in populations of this keystone species.

Daily behavioral activities of bullfrog Lithobates catesbeianus (Shaw 1802)

Studies on the daily behavioral activities of bullfrogs in laboratories may indicate avenues for appropriate technical management for this specie culture. Twenty-four post-metamorphic phase Lithobates catesbeianus (Shaw 1802) bullfrogs had their daily activities described. The animals were housed in six experimental stalls and feed was offered once a day at random times over 10 days of filming. Behavioral activity in each stall was recorded for the first 15 minutes of every hour in a 24-hour period. As results, we observed that ingestion and movement on dry ground were more common at dawn and rare in dark; inactivity on dry ground occurred more in the late night and at dawn. Consequently, there was preference for sheltering less at dawn and in the end of dark phases. The inactivity behavior in the water was more frequent during the early dark phase, showing an inverse relationship with respect to preferred times for feed ingestion. As a result of observed behaviors, we recommended that feed offerings for bullfrogs in captivity are during the light phase of day and that it is available until the following morning.

Changes in RNA, DNA, protein contents and growth of turbot Scophthalmus maximus larvae and juveniles

The growth potential of turbot Scophthalmus maximus larvae and juveniles was studied using nucleic acid-based indices and protein variables. The experiment was carried out from 4 to 60 days post hatching (dph). A significant increase in instantaneous growth rate during metamorphosis and retarded growth rate during post-metamorphic phase were observed. Ontogenetic patterns of DNA, RNA and protein all showed developmental stage-specific traits. The RNA:DNA ratio decreased up to 12 dph, then increased rapidly till 19 dph and fluctuated until 35 dph followed by a decline to the end. The RNA:DNA ratio was positively correlated with growth rate of juveniles during the post-metamorphic phase, whereas this ratio was not a sensitive indicator of growth during the pre-metamorphic phase and metamorphosis. The protein:DNA ratio showed a similar tendency to the RNA:DNA ratio. Changes of DNA content and protein:DNA ratio revealed that growth of S. maximus performed mainly by hyperplasia from 4 to 12 dph and hypertrophy until 21 dph during the pre-metamorphic larval phase. Growth was dominantly hypertrophical from the early- to mid-metamorphosing phase and hyperplastic thereafter. The results show that the DNA content and protein:DNA ratio can evaluate growth rates of larval and juvenile S. maximus on a cellular level.

Tectonic evolution along the Col del Lis-Trana Deformation Zone(internal Western Alps)

This paper describes the tectonic evolution of the Col del Lis-Trana Deformation Zone (LTZ), a N-S striking structure located in the internal sector of the northern Cottian Alps, in the hanging-wall of the first-order discontinuity (the Canavese Line) and representing the eastern border of the Alpine wedge. The detailed geological mapping and structural analysis of the two tectonometamorphic Units cropping out in the area has allowed the activity of the LTZ to be defined, related to two late- to post-metamorphic deformation phases (D4 and D5). This activity strongly modified the pre-existing syn-metamorphic structural setting, resulting from three main deformation phases (D1, D2 and D3). The LTZ is defined by i ) the clockwise rotation at the macroscale both of syn-metamorphic structural elements and of lithological contacts from E-W to N-S strike directions, and by ii ) the structural association of faults, cleavages and folds, mainly related to the reactivation of the pre-existing syn-metamorphic anisotropies. The D4 phase is characterized by the development of N-S major faults and by NNW-SSE and NNE-SSW minor faults, linked in a through-going shear zone with dextral shearing and minor reversal component, whereas the D5 phase is associated with the activity of E-W faults and with the reactivation of the D4-related structures mainly characterized by normal and sinistral-normal movements. The kinematic analysis of the D4-related structures yields a sub-horizontal NE-SW shortening direction, comparable with the regional shortening that affected the Western Alps during the Late Oligocene-Early Miocene and which caused the dextral movements along the Canavese Line. The extensional regime related to the D5 event is interpreted as the effect of the uplift with the subsequent isostatic re-adjustment of the alpine wedge. Since the LTZ is a very persistent structure (more than 20 km in length) it may be reasonably considered as a deep-rooted shear zone, which could reach 7–10 km of depth. Based on these assumptions the LTZ may be interpreted as a sub-parallel structure of the postulated southern prolongation of the Canavese Line, both representing steep fault strands of a regional dextral transpressive flower structure that bounds the alpine wedge on the internal side.

Enzymatic activity of lipase in post-metamorphic phase bullfrogs

The knowledge of the digestive system of bullfrogs is an important step for the determination of their nutritional requirements throughout growth phases. With the objective of evaluating the enzymatic activity of lipase in the intestinal content of bullfrogs (Rana catesbeiana Shaw, 1802), 100 animals with median weight of 3.6 g were distributed in stalls under controlled temperature and photoperiod. The frogs, selected at the post-metamorphic phase, received commercial extruded diet ad libitum throughout the 87-day experiment. The collections of the intestinal content were performed by the desensitization of the frogs in ice and water at 0ºC and subsequent isolation of the small intestine. Determination of lipase activity was performed with a commercial enzymatic kit (Lipase-Bioclin, MG, Brazil), first measured in samples taken at day three (3.46 UI). During the initial phase the bullfrog possesses low lipase hydrolysis capacity was found, having a specific activity of 217 UI mg-1. In the subsequent period both lipase activity and specific lipase activity continuously increased. Lipase activity as a function of bullfrog weight fell after day twenty and reached 0.33 UI g-1, for frogs of medium weight (179 g). Feed for bullfrogs at the post-metamorphic phase weighing more than 10 g can have larger amounts of ingredients containg lipids, due to the increased digestive capacity of these frogs.

Atividade da amilase em rã-touro durante a fase pós-metamórfica

O objetivo deste trabalho foi avaliar a atividade da amilase no quimo da rã-touro, Rana catesbeiana Shaw 1802 (3,6 a 200 g). Oitenta e sete animais foram distribuídos em baias-testes com temperatura e fotoperíodo controlados. As rãs selecionadas na fase pós-metamórfica receberam ração comercial extrusada ad libitum. Durante 87 dias de experimento, foram efetuadas 29 coletas em intervalos de 1 a 8 dias. As coletas do conteúdo intestinal foram feitas mediante a insensibilização das rãs em gelo e água e isolamento posterior do intestino delgado das mesmas. Para os testes da atividade da amilase, foram utilizados kits enzimáticos comerciais. A atividade da amilase foi observada a partir do terceiro dia e apresentou aumento até alcançar estabilidade, quando os animais pesavam 4,35 g. Do sétimo dia até o final do experimento, ocorreu a manutenção da estabilidade da atividade (137,44 UI) e atividade específica da amilase (14.688 UI mg-1).

Crecimiento y supervivencia de larvas de Echinometra lucunter (Echinoidea: Echinometridae) alimentadas con las microalgas Chaetoceros gracilis e Isochrysis galbana

Larval growth and survival of Echinometra lucunter (Echinoidea: Echinometridae) fed with microalgae Chaetoceros gracilis and Isochrysis galbana. Thirty sexually mature sea urchins (Echinometra lucunter; diameter 45.8 ± 17.5 mm) were collected at Macanao, Margarita Island, Venezuela (11°48’29” N / 64°13’10” W). They were injected potassium chloride (50 M) directly into the celomic cavity. After two minutes 90% spawned (17 females and 10 males), the others never spawned. Fertilization was 87.0 ± 12.6% (1:100 oocytes/sperm) at 29 ± 2oC. The fertile eggs were placed in three treatment gropsu with nine containers (18 liters; 2 eggs/ml) each, all with bottom aeration. Treatments were: Chaetoceros gracilis; Isochrysis galbana, and a mixture of both microalgae (respectively: 20 000 and 60 000 cell/ml for each microalgae, 1:1 for the mixture). Salinity, pH, temperature and larval survival were determinated daily. The study ended when the post-metamorphic phase was completed. The embryonic development time was 16.3 ± 0.2 h until the prism stage at pH 8.4 ± 0.1; 38 ± 1 psu and 28 ± 1.4°C. The two-arms larval stage was reached at 24 h: 33 min, with a total length of 190 ± 16.3 μm fed on C. gracilis, 152 ± 19.0 μm with I. galbana and 182.4 ± 14.1 μm with the mixture. The larvae next to metamorphosis reabsorbed the arms and had the characteristic shape of juvenile urchins at 12 days with 670.2 ± 22.2 μm fed on C. gracilis, 665 ± 12.1 μm fed on I. galbana and 670 ± 14.1 μm fed on the mixture. The accumulated survival to the juvenile stage was 14.7 ± 3.8% when fed on C. gracilis, higher than the other treatments (5.4 ± 1.2; 14.0 ± 2.6). E. lucunter is an excellent prospect to be commercially cultured because of its short embryonic (16 hours) and larval development time (12 days) and good survival rate when fed on monoculture (C. gracilis and I. galbana) or mixed diet (we recommend C. gracilis). Rev. Biol. Trop. 53(Suppl. 3): 337-344. Epub 2006 Jan 30.

Atividade da tripsina em rã-touro na fase pós-metamórfica

Com o objetivo de avaliar a atividade enzimática da tripsina no conteúdo intestinal da rã-touro (Rana catesbeiana Shaw, 1802), 320 animais com peso médio de 3,6 g foram distribuídos em baias-teste com temperatura e fotoperíodo controlados. As rãs selecionadas na fase pós-metamórfica receberam ração comercial extrusada ad libitum. Durante 87 dias de experimento, foram efetuadas 29 coletas em intervalos de 1 a 8 dias. As coletas do conteúdo intestinal foram feitas mediante a insensibilização das rãs em gelo e água e posterior isolamento do intestino delgado. Após cada coleta, todo o material foi congelado em nitrogênio líquido e armazenado em freezer, para posterior liofilização. A determinação da atividade da tripsina foi realizada utilizando-se Benzoil-D, L-Arginina p-nitroanilida (D, L-BApNA) como substrato. A atividade da tripsina foi registrada no primeiro dia de experimento; a fase inicial foi marcada pelo aumento da atividade da tripsina até a estabilidade, quando os animais ainda estavam na fase de imago. O período subseqüente (até o final do experimento) foi caracterizado pela manutenção da estabilidade da atividade e pela atividade específica da tripsina. Pode-se concluir que a rã-touro apresenta capacidade para digestão de alimentos de origem protéica, recomendando-se, na fase inicial, uso de ração rica em proteína.

Changes in RNA, DNA and protein contents of laboratory-reared Japanese flounder Paralichthys olivaceus during metamorphosis and settlement

: By means of biochemical analyses on an individual basis, developmental changes in nutritional status during metamorphosis and settlement were examined in laboratory-reared Japanese flounder Paralichthys olivaceus. Although whole-body DNA content increased gradually throughout metamorphosis and settlement, the RNA content generally remained constant during the late metamorphosing stage and postmetamorphic phase. Subsequently, the RNA : DNA ratio decreased drastically from the late metamorphosing stage to the postmetamorphic phase following a continuous elevation in the ratio during early and mid-metamorphosing stages. The changes in protein content coincided well with RNA content. The protein : DNA ratio also peaked at the postmetamorphic phase and decreased for several days thereafter, suggesting the occurrence of hypertrophy until the postmetamorphic phase, followed by hyperplasia. It is speculated that the nutritional status of Japanese flounder becomes lower when associated with entry to the final phase of metamorphosis and/or settlement at which feeding habits drastically change. Poor nutritional status of the newly settled juveniles may increase their vulnerability to predators in the nursery ground.

Developmental expression and distribution of amphibian glutathione transferases

This work is aimed at detecting the expression and location of embryonic Bufo bufo GST (bbGSTP1-1) and adult B. bufo GST (bbGSTP2-2) during toad development, in order to assign a putative role to these enzymes also on the basis of their compartmentalization and to verify whether during the premetamorphic liver ontogeny the bbGSTP2-2 form appears. This study was also performed in the adult liver (the primary site of Pi class GST expression) and in the mature ovary, to discern if the embryonic form derives from maternal form. The results show that the embryos and the ovary express only bbGSTP1-1. Moreover, bbGSTP1-1 distribution is the same both in the early embryos and in the ovary: this strongly suggests that bbGSTP1-1 is of maternal origin. As development goes on, a wide distribution of bbGSTP1-1 all over the differentiating organs is observed. The embryonic liver expresses exclusively the bbGSTP1-1 form, while the adult liver is highly positive only towards the bbGSTP2-2 form. This implies that the switch towards the adult bbGSTP2-2 form occurs in metamorphic or postmetamorphic phases and that the detoxication metabolic requirements of the embryo may be completely fulfilled by the bbGSTP1-1 isoenzyme.

Postlarval development in shallow and deep-sea ophiuroids (Echinodermata: Ophiuroidea) of the NE Atlantic Ocean

The postlarval phase is an essential period in the life history of marine invertebrates; vulnerable to high mortality, it ultimately influences the distribution and abundance of adult populations. In the deep NE Atlantic, a large number of postlarval ophiuroids have been found during certain times of the year, but their identification is difficult. The present work describes the ontogenesis of 12 post-metamorphic shallow-water or deep-sea ophiuroids from samples collected during the Biofar and Rockall Trough Programmes in the NE Atlantic Ocean. Analysis of the postlarval development reveals that species can be identified from a very early post-metamorphic phase using particular morphological characters. The ontogeny of homologous structures reveals similarities within related groups. However, at the same time, these structures give rise to different adult structures in different taxa. Data on the postlarval development ofOphiura affinissuggest that this species is more closely related to the genusOphioctenand a change in generic status is proposed.

Postlarval development in shallow and deep-sea ophiuroids (Echinodermata: Ophiuroidea) of the NE Atlantic Ocean

The postlarval phase is an essential period in the life history of marine invertebrates; vulnerable to high mortality, it ultimately influences the distribution and abundance of adult populations. In the deep NE Atlantic, a large number of postlarval ophiuroids have been found during certain times of the year, but their identification is difficult. The present work describes the ontogenesis of 12 post-metamorphic shallow-water or deep-sea ophiuroids from samples collected during the Biofar and Rockall Trough Programmes in the NE Atlantic Ocean. Analysis of the postlarval development reveals that species can be identified from a very early post-metamorphic phase using particular morphological characters. The ontogeny of homologous structures reveals similarities within related groups. However, at the same time, these structures give rise to different adult structures in different taxa. Data on the postlarval development ofOphiura affinissuggest that this species is more closely related to the genusOphioctenand a change in generic status is proposed.