Megalopa Stage Research Articles

The systematic position of Ergasticus (Decapoda, Brachyura) and allied genera, a molecular and morphological approach

The complete larval series (zoea I, zoea II and megalopa) of the crab Ergasticus clouei is described and illustrated based on plankton samples from Mediterranean waters. The zoea II and megalopal stages, previously unknown, are described here for the first time. Nucleotide sequence analysis of two gene regions (16S rDNA and Cox1 genes) confirmed the assignment of these larvae to Ergasticus clouei. The molecular analyses and the morphology of the larval stages revealed large differences between Ergasticus and Inachus, the type genus of the family Inachidae. In fact, E. clouei larvae presented a series of morphological characters, such as antennal shape and mouthparts setation pattern that placed them closer to the family Oregoniidae. The phylogenetic analyses also showed significant support for the monophyly of the Oregoniidae + Ergasticus group. The data argue for removal of Ergasticus and the related genera (Bothromaia, Pleisticanthoides, Parapleisticantha and Pleistacantha) from the Inachidae and their placement within the Oregoniidae as a separate subfamily, Pleistacanthinae Števčić, 2005. Our results demonstrate that larval stages provide reliable morphological traits, independent from those of adults, to help resolving relationships among Majoidea genera.

Morphology of the larval stages of a Mediterranean population of the allochthonous Say’s mud crab, <i>Dyspanopeus sayi</i> (Decapoda: Brachyura: Panopeidae)

In this study the complete larval development (including four zoeal stages and a megalopa stage) of Dyspanopeus sayi is described and illustrated in detail based on larvae reared in the laboratory. Ovigerous females were collected in Alfacs Bay, Ebro Delta (NW Mediterranean) where the species was recently introduced. These larval stages were compared with others collected in the plankton from the same area, the larval stages described previously for this species and the larval stages of the two other Panopeidae that inhabit the Iberian Peninsula: Panopeus africanus and Rhithropanopeus harrisii. Differences were found in both zoeal and megalopal larval characters between D. sayi and the other two species, which could raise doubt about their placement in the same family.

Molecular characterization, tissue expression of acyl-CoA ∆9-desaturase-like gene, and effects of dietary lipid levels on its expression in the hepatopancreas of the Chinese mitten crab (Eriocheir sinensis)

Acyl-CoA Δ9-desaturase has important functions in fatty acid metabolism and cell membrane fluidity regulation. In this study, we isolated and characterized the acyl-CoA Δ9-desaturase-like cDNA encoded in Eriocheir sinensis (Chinese mitten crab) from the hepatopancreas by performing rapid-amplification of cDNA ends. To the best of our knowledge, this study is the first to perform this procedure in crustaceans. The full-length cDNA is 2419bp long and encodes a polypeptide with 347 amino acids that are highly homologous to related genes found in insects. Gene expression analysis (real-time quantitative PCR) revealed that acyl-CoA Δ9-desaturase-like transcripts were widely distributed in various tissues, in which a high expression level was observed in the hepatopancreas. A significantly increasing trend was also observed in the hepatopancreas at the megalopa stage to the maturity stage of the Chinese mitten crab. Acyl-CoA Δ9-desaturase gene expression is regulated by a number of developmental, dietary, hormonal, and environmental factors; thus, we determined the effects of acyl-CoA Δ9-desaturase-like mRNA expression in the hepatopancreas after the crabs were fed with different diets for 168days. The different diets were as follows: control diet without oil lipids (with 3% basic lipid of the fundamental diets); fish oil diet (FO; with added 3% of the fundamental diets); soybean oil diet (SO; with added 3% of the fundamental diets); and FO/SO diet (1:1; with added 3% of the fundamental diets). Results showed that the FO diet elicited a strong increasing effect on the amount of acyl-CoA Δ9-desaturase-like genes compared with control and SO diets.

Ontogeny of sinking velocity, body density, and phototactic behaviour in larvae of the coconut crab Birgus latro: Implications for larval dispersal and recruitment in the sea

As a basis for understanding the larval dispersal and recruitment processes of the coconut crab, Birgus latro, in the sea, we examined the ontogenetic changes in the passive sinking velocity, body density, and phototactic behaviour to different light intensities and wavelengths of the zoeal and megalopal stages of laboratory-reared larvae. Six levels of light intensity, from 310μmolm−2s−1 to 0.0031μmolm−2s−1 in 10% decrements, and 14 light wavelengths in the range of 400–660nm in 20nm increments were tested. The controls were tested in the dark. The coconut crab larvae showed negative buoyancy. The mean sinking velocity was 7.5mms−1 in the first zoeal stage, which increased significantly to ~10mms−1 after the third zoeal stage. The mean body density was 1.085–1.089gcm−3 in the first to third zoeal stages; it then decreased significantly to 1.072–1.075gcm−3 in the fourth zoeal and megalopal stages. This ontogenetic pattern in body density differs from those of other decapod crustacean species and may be related to the emigration behaviour of the megalopae from the sea to the land. The coconut crab larvae were generally photopositive, with the strength of their positive phototactic behaviour decreasing at lower light intensities and with age. Higher incidences of positive phototactic behaviour were recorded at spectra of 400–660nm, 400–620nm and 400–600nm for the first, second, and third zoeal stages, respectively. The spectral sensitivity of the fourth zoeal stage showed peaks at around 400–420nm and 500–580nm, suggesting that the larval distribution in the sea changes at the fourth zoeal stage. The overall phototactic behaviour of the megalopae was weak, and the behavioural responses varied at light wavelengths above 520nm. Thus, their phototactic behaviour may have little effect on their migration to the coast.

Seed Production of Commercially Important Portunid Crab, Charybdis Feriata (Linnaeus)

To develop aquaculture activities mass seed production technology is essential. Hence in the present study an attempt was made to produce seeds in controlled condition. The complete larval development took a span of 22-26 days. According to Duncan’s multiple range test the larval duration is more or less same for I and III zoeal stages. Similarly II, IV, V and VI zoeal stages are also similar. However, I and III and II, IV, V and VI zoeal stages are significantly varied between each other. A maximum of 95% of survival was observed during the first zoeal stage and thereafter the survival was gradually decreased. The survival percentage shows that mortality was high in all zoeal and megalopa stages. The survival rate of zoeal and megalopal stages are significantly varied each other

Effects of water availability and migration timing from sea to land on survival and moulting in megalopae and juveniles of the coconut crab, Birgus latro: implications for mass production of juveniles

Populations of the coconut crab, Birgus latro (Linnaeus, 1767), have been depleted by overharvesting and environmental degradation. The aim of this study was to develop artificial propagation technologies for the restocking and conservation of this species. Coconut crabs migrate from the sea to land as megalopae, carrying gastropod shells. We examined the effects of sea-water availability and the timing of their involuntary migration from sea to land on the survival and moulting of megalopae and juveniles by culturing them individually in containers with dry “land” but with or without aquatic “sea areas.” The schedule of their involuntary migration to the land in the test containers was set at ages of 5 and 10 days after metamorphosis to the megalopal stage, and at ages between 12 and 16 days, when the megalopae walked steadily while wearing a shell. The treatments did not affect the moulting of the animals. The animals survived in the containers with seawater areas. In contrast, all those in the containers without sea areas died, and severe mortality occurred after the animals moulted to the crab stage, suggesting that water availability may protect the animals from desiccation in air during and after ecdysis. Old megalopae (10 days old) appeared to be more active than young megalopae (5 days old) in walking and manipulating shells at first landing, although the three different schedules of migration to land did not affect the survival of the animals. Our results highlight the importance of water availability in culturing coconut crab juveniles.

The effect of poly-β-hydroxybutyrate on the performance of Chinese mitten crab (Eriocheir sinensisMilne-Edwards) zoea larvae

Two experiments were conducted regarding the effect of poly--hydroxybutyrate (PHB) on the survival and development of Chinese mitten crab (Eriocheir sinensis Milne-Edwards) larvae. Different PHB delivery approaches (particulate, enriched in filter feeding prey, or a combination of both) and feeding levels were applied to crab larvae from the zoea 2 (Z2) up to the megalopa stage. Bio-encapsulation into rotifers and Artemia at a PHB dose of 100mgL(-1) seemed an efficient approach to deliver PHB to the larvae and resulted in a significantly enhanced survival, development rate and osmotic tolerance. The results indicate that PHB should only be applied as a feed additive rather than as a food source, and that the availability of an adequate amount of nutrients seems to be of major importance for the PHB to induce these beneficial effects.

DISTRIBUTION OF SHRIMP AND CRAB LARVAE IN SEAGRASS BED AT CUA DAI ESTUARY, QUANG NAM PROVINCE (2009-2010)

A study on the abundance pattern of shrimp and crab larvae in seagrass beds at Cua Dai estuary was conducted during the field trips of Project KC 09-26/06-10 in April and September 2009. A total of 6 stations in the tidal flat of seagrass beds were selected. Shrimp and crab larvae samples were collected using trawl nets. The result showed that the species composition of demersal larvae is not diverse with 13 species recorded and average abundance is 202 individual/100m2. Penaeidae and Palaemonidae are common families with 5 species/family. Planktonic larvae included 9 taxon with 156 individual/100m3. Penaeidae and Palaemonidae are dominant larvae with 34% and the larvae of Caridae, Crab larvae (megalop stage) with 11% a total of planktonic larvae.

The zoeal development of Platymaia wyvillethomsoni Miers, 1886 (Crustacea: Decapoda: Majoidea: Inachidae) described from laboratory reared material

The spider crab Platymaia wyvillethomsoni was reared in the laboratory, from hatching to the megalopal stage at 20°C. The larval development comprises two zoeal stages and a megalopa. The zoeal stages are described for the first time and compared with those of the four known species of the family Inachidae from the northern Pacific. The zoeal characters (carapace spines, antenna, mouthpart appendages, pleon and telson fork) of P. wyvillethomsoni are significantly different from those of two Achaeus species from northern Pacific and other inachid genera (Inachus and Macropodia) from the Atlantic. Therefore, this species should not be placed in the family Inachidae based on zoeal morphology. A provisional key for the identification of known zoeae of the family from the northern Pacific is provided.

Larval stages of Areopaguristes japonicus (Miyake, 1961) (Decapoda: Anomura: Diogenidae) described from laboratory reared material

Areopaguristes japonicus (Miyake, 1961) is recorded from South Korean waters for the first time with the collection of an ovigerous female. The zoeal and megalopal stages of this species are described from laboratory reared material and compared to larvae of eight other described Diogenidae species from the northwestern Pacific. The larvae of A. japonicas are distinguished from those of other diogenids by mediodorsal spines on zoeal pleomeres 3 and 4 and having a spine on the mediodorsal margin of the megalopal pleomere 2. A provisional key for identifying diogenid zoeas from the northwestern Pacific is provided.

Live Foods for Juveniles’ Production of Blue Swimming Crab, Portunus pelagicus (Linnaeus, 1766)

The study were aim to demonstrate the affects of live food type’s i.e., mixed diatom, Artemia nauplii and rotifer on survival rate and molt time of larvae stage till 1st day juvenile crabs (C1) of P. pelagicus. Three types of feeding regimes given to the crab larvae through out the study trials are with and without mixed diatom, with and without Artemia nauplii and with and without rotifer. The study shows that zoea fed with rotifer alone was not enough to sustain survival in the next zoea stages and to promote metamorphosis up to megalopa stage. Survival of zoea fed with Artemia nauplii alone shows that this type of food is not suitable for the very early zoea stages. The study also shows that the adding of mixed diatom to larvae rearing system where rotifer and Artemia nauplii is main food items did not produced high survival rate as compared to larvae rearing fed on rotifer and Artemia nauplii alone. The results of the study demonstrated that the food types not only effect survival rate but also the growth of crab larvae. The study generally ended that the combination diet of rotifer and Artemia nauplii alone is enough to produced C1

Different pathways in the larval development of the crab Ucides cordatus (Decapoda, Ocypodidae) and their relation with high mortality rates by the end of massive larvicultures

One of the most limiting factors affecting the larval rearing of Ucides cordatus in the laboratory is a period of high mortality, which usually occurs late in the course of the larviculture during the metamorphosis from the zoeal to the megalopal phase. The objective of the present research was to analyze the post-embryonic development of U. cordatus on an individual basis and, in particular, to search for patterns linking disturbances in the molting process to the high larval death rates observed in massive larvicultures. A total of 50 larvae were individually reared from hatching to metamorphosis into the megalopal phase under controlled conditions, fed a combination of microalgae and rotifers. The survivorship rate was 70% until zoea V. The 35 surviving zoea V larvae followed two different pathways. Eleven underwent metamorphosis directly to megalopa, eighteen molted to zoea VI and six died as zoea V. In the last molting event, only two zoea VI larvae reached the megalopal stage, while the remaining sixteen died. In further observation under microscope, 13 of the dead zoea VI showed characteristics of the pre-molt stage and pereiopods disproportionably large in relation to the carapace. The observed pattern resembles the Molt Death Syndrome (MDS) described for other decapod species, in which larvae die in the late pre-molt phase of the molting cycle. We suggest that U. cordatus larvae develop disturbances in the molting process similar to the MDS described for other species and that these disturbances are related to a more complex pathway involving the emergence of larval stage zoea VI.

Characterization of two isoforms of antiliopolysacchride factors (Sp-ALFs) from the mud crab Scylla paramamosain

In the previous study of the mud crab (Scylla paramamosain) hemocyte proteins, which interacted with a bacterium, Vibrio parahaemolyticus, a protein known as antilipopolysaccharide factor (Sp-ALF) was isolated in addition to a serine proteinase homolog (Sp-SPH) protein. In the present study, we further reported the characterization of two isoforms of the mud crab ALF – Sp-ALFs genes (designated as Sp-ALF1 and Sp-ALF2, respectively) based on our previous result. The Sp-ALF1 and Sp-ALF2 cDNA contained 1070 bp and 731 bp, respectively, with 123 deduced amino acid residues. Alignment of deduced amino acid sequences showed that Sp-ALFs possessed high identity with other known ALFs from crustaceans and exhibited an overall similarity of 57.7% to those of ALFs compared. Phylogenetic tree analysis revealed a clear group of each species and also suggested that ALFs from Scylla genus and those from Portunus genus were closely related. Tissue distribution analysis in adult crab implied that both Sp-ALF1 and Sp-ALF2 were mainly expressed in hemocytes. The mRNA transcripts were also found in embryo (I, II, III and V), zoea-I and juvenile crab, but were rarely observed in the megalopa stage. To further identify the biological activity of Sp-ALFs, recombinant proteins (rSp-ALFs: designated as rSp-ALF1 and rSp-ALF2, respectively) were obtained by expression in Pichia pastris, and the synthetic peptide fragments (sSp-ALFs: designated as sSp-ALF1 and sSp-ALF2, respectively) including the putative LPS binding loop were also prepared for antimicrobial test. The results indicated that both rSp-ALFs and sSp-ALFs were highly effective against most of the Gram-positive bacteria and Gram-negative bacteria tested. In contrast to cecropin P1, a membrane integrity assay revealed that Sp-ALFs did not affect the Escherichia coli by disruption of membrane integrity. Additionally, the recombinant Sp-ALFs proteins exhibited strong antiviral activity against an important aquaculture pathogen, white spot syndrome virus, in crustaceans. Taken together, these data suggested that Sp-ALFs might play a key role in immune defense against microbial infection in the mud crab S. paramamosain.

The complete larval development of Panopeus lacustris Desbonne 1867 (Brachyura: Panopeidae), from the Amazon region, reared in the laboratory

AbstractLarvae of the mud crab Panopeus lacustris were reared in laboratory from ovigerous females collected in the estuarine area of the Caeté River in the Amazonian region. The complete development of this species consisted of four zoeal and one megalopal stages, which were described and illustrated in detail. The results are compared with those of other previous studies on larval development of the species belonging to the genus Panopeus and then briefly discussed.

Isolation of the C-type lectin like-domain cDNAs from the mud crab Scylla paramamosain Estampador, 1949, and its expression profiles in various tissues, during larval development, and under Vibrio challenge

Scylla paramamosain Estampador, 1949 is one of the most precious marine crabs farmed in China. The crab is prone to infection by microbes at various stages during its growth, leading to high mortality. C-type lectin has a characteristic carbohydrate recognition domain and plays an important role in the immunity system. A cDNA library from the mud crab S. paramamosain was constructed using the SMART technique. Two complete cDNA sequences showing high identities with the C-type lectin gene were isolated from the library. The two full-length C-type lectin cDNAs of S. paramamosain (SpLec1 and SpLec2) consist of 746 and 834 bp, respectively. Quantitative realtime PCR analyses revealed that the C-type lectins were expressed mainly in haemocytes, muscle and hepatopancreas, with the highest expression level found in hepatopancreas. The C-type lectin mRNA expression in continuous developmental stages during zoeal phases were also examined by quantitative real-time PCR. After infection with Vibrio parahaemolyticus (Sakazaki, 1963) at a concentration of 2.3 × 10 6 cfu/ml, the temporal expression of SpLec1 and SpLec2 mRNA in the megalopa stage was first increased, reached a maximum, and then dropped to the original level again. The research of C-type lectins in Scylla paramamosain could shed new light on studies on immunity and moulting in the mud crab.

Development and functional morphology of the larval foregut of two brachyuran species from Northern Brazil

Feeding is an important factor for the successful rearing of larvae of the crab species. Further information on the morphological features of the foregut may to reveal larval feeding behaviour and or/whether there is a lecithotrophy in some or even in all stages of the larval cycle. In the present study, the structural development of the foregut and their digestive functions were examined in larvae of two brachyurans, Uca vocator and Panopeus occidentalis, reared in the laboratory. During larval development, the foreguts of the larvae in the first and last zoeal stages and in the megalopa stage were microscopically examined, described and illustrated. The zoeal foreguts of both species were well developed, showing specialization with a functional cardiopyloric valve and a filter press. The megalopa stage had a complex and specialized gastric mill similar to that found in adult crabs with the appearance of rigidly calcified structures. These results support the hypothesis that the feeding behaviour of each larval stage is directly related to the morphological structure of the foregut. Such facts strongly indicate that all larval stages of both U. vocator and P. occidentalis need an external food source before completing the larval development in a planktonic environment.

First results of embryonic development, spawning and larval rearing of the Mediterranean spider crabMaja squinado(Herbst ) under laboratory conditions, a candidate species for a restocking program

The Mediterranean spider crab, Maja squinado, is depleted due to overfishing. The crab has virtually disappeared from areas where it was abundant, such as the Balearic Islands and the Catalan coast. Maja squinado, is economically and ecologically very valuable, and it is essential to obtain information on its biology and rearing conditions to attempt to repopulate the damaged stocks of the species in the Mediterranean basin. Herein, we describe the first successful rearing of M. squinado under laboratory conditions. Our results show that M. squinado is an excellent candidate for restocking using cultured juveniles. Two consecutive broods with a 1–4 day interbrood period were observed in the laboratory in wild-caught females, the maximum observed duration of embryonic development of the egg mass being 32 days at 18.4 ± 0.9°C, and went through four different stages. The complete larval and first juvenile development was studied in laboratory cultures fed enriched Artemia metanauplius. At 19.6 ± 0.6°C, development from hatching to first crab moult took 17 days, and it comprised two zoeae stages and one megalopa stage. The survival rate at the different stages was monitored, and 7.13 ± 2.3% was achieved at the first crab instar.

Morphology of the complete larval development of the symbiotic crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae)

Larval development of the symbiotic crab Sestrostoma balssi (Shen, 1932) (Varunidae: Gaeticinae) inhabiting Russian waters of the Sea of Japan is described and illustrated for the first time from material reared in the laboratory. The development includes five zoeal and a single megalopal stages. The first megalopa was attained at 20–22°C 35 days after hatching. The present paper is the first description of the complete larval development in the genus Sestrostoma. The larvae of S. balssi share all principal characters of the family Varunidae but are distinguished from the typical varunid larvae by the absence of a well-developed antennal exopod in the zoea and the presence of an 8-segmented antennal flagellum in the megalopa.

Redescription of megalopa and juvenile development of Pachygrapsus gracilis (Decapoda: Grapsidae) from the Amazon region, reared in the laboratory

This present study re-describes the megalopa stage and provides detailed morphological descriptions and main growth changes observed in stages I through VII of the juvenile instars of the dark shore crab Pachygrapsus gracilis (Saussure, 1858), from the Amazon region. The specimens in this study were reared in the laboratory and the megalopae were collected at Ajuruteua beach in northeastern Pará, Brazil. Previous studies had described the megalopa of P. gracilis from Mexican waters, as well as those of Pachygrapsus transversus (Gibbes, 1850) and Pachygrapsus marmoratus (Fabricius, 1787). A comparison between the Mexican and Amazonian populations of P. gracilis revealed significant morphological differences. The main difference is the presence of 3 elongated setae on the 5th pereiopods of individuals of the Amazonian population. The setal number and their arrangement in the appendages also differed. In P. gracilis, the male and female genital openings are observed from the juvenile instar III, whereas differentiation in male pleopods is observed only in juvenile instar V. In females, the pleopods undergo rapid differentiation during juvenile instar VI. These morphological comparisons and other observations on development are briefly compared and discussed with reports for other species.

Thermal tolerance of larval stages of the Chilean kelp crab Taliepus dentatus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 429:157-167 (2011) - DOI: https://doi.org/10.3354/meps09059 Thermal tolerance of larval stages of the Chilean kelp crab Taliepus dentatus Daniela Storch1,2,*, Miriam Fernández1, Sergio A. Navarrete1, Hans-Otto Pörtner2 1Estación Costera de Investigaciones Marinas and Center for Advanced Studies in Ecology and Biodiversity, Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile 2Alfred-Wegener-Institut für Polar- und Meeresforschung, Integrative Ecophysiology, Postfach 120161, 27515 Bremerhaven, Germany *Email: daniela.storch@awi.de ABSTRACT: Physiological responses of larval stages can differ from those of the adults, affecting key ecological processes. Therefore, developing a mechanistic understanding of larval responses to environmental conditions is essential vis-à-vis climate change. We studied the thermal tolerance windows, defined by lower and upper pejus (Tp) and critical temperatures (Tc), of zoea I, II, and megalopa stages of the Chilean kelp crab Taliepus dentatus. Tp limits determine the temperature range where aerobic scope is maximal and functioning of the organism is unrestrained, and were estimated from direct observations of larval activity. Tc limits define the transition from aerobic to anaerobic metabolism, and were estimated from the relationship between standard metabolic rate and temperature. Zoea I showed the broadest, zoea II an intermediate, and megalopae the narrowest tolerance window (Tp). Optimum performance in megalopae was limited to Tp between 11 and 15°C, while their Tc ranged between 7 and 19°C. Although Tc may be seldom encountered by larvae, the narrower Tp temperatures can frequently expose larvae to unfavorable conditions that can drastically constrain their performance. Temperatures beyond the Tp range of megalopae have been observed in most spring and summer months in central Chile, and can have important consequences for larval swimming per­formance and impair their ability to avoid predators or settle successfully. Besides the well-documented effects of temperature on development time, variability in field temperatures beyond Tp can affect performance of particular larval stages, which could drive large-scale varia­bility in recruitment and population dynamics of T. dentatus and possibly other ­invertebrate species. KEY WORDS: Metabolic rate · Critical temperature · Heart beat rate · Larvae · Megalopa · Sea surface temperature · Recruitment · Zoea Full text in pdf format PreviousNextCite this article as: Storch D, Fernández M, Navarrete SA, Pörtner HO (2011) Thermal tolerance of larval stages of the Chilean kelp crab Taliepus dentatus . Mar Ecol Prog Ser 429:157-167. https://doi.org/10.3354/meps09059 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 429. Online publication date: May 16, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.