Juvenile Crab Stage Research Articles

Molecular identification and putative role of insulin growth factor binding protein-related protein (IGFBP-rp) in the swimming crab Portunus trituberculatus

The insulin-like growth factor/insulin-like polypeptide (IGF/ILP) signaling is vital for growth, physiological metabolism, development, and reproduction. Insulin-like growth factor-binding protein (IGFBP) is involved in the insulin signaling pathway in both vertebrates and invertebrates and is critical for various physiology functions. Herein, we cloned and characterized the full-length cDNA of IGFBP-rp in the swimming crab, Portunus trituberculatus (PtIGFBP-rp). The deduced amino acid sequence of PtIGFBP-rp was found to contain three key domains (insulin-like binding (IB) domain, the kazale-type serine protease inhibitor (KAZAL) domain, and the immunoglobulin-like C2 (IGc2) domain). Results showed that PtIGFBP-rp shared the same expression pattern as P. trituberculatus insulin androgenic gland hormone (PtIAG) transcripts during the embryonic larval, juvenile crab stage and the androgenic gland (AG) developmental cycle. Moreover, PtIGFBP-rp transcripts were also present in high abundance in hepatopancreas, muscle, and androgenic glands. The regulatory relationship between PtIGFBP-rp and PtIAG was investigated by RNA interference and co-localization assays, which showed a co-localization relationship and feedback regulation between them. Bilateral eye stalk ablation (ESA) increased the expression of PtIGFBP-rp in the AG at 7 d after surgery. These results demonstrate the involvement of PtIGFBP-rp in the signaling regulatory network of IAG in P. trituberculatus.

Effect of methyl farnesoate and farnesoic acid during 5th zoea and megalopa metamorphosis in the mud crab Scylla paramamosain Estampador, 1950 (Decapoda, Brachyura, Portunidae)

Abstract The mud crab Scylla paramamosain is one of the economically important aquaculture species in China. The larval development of the mud crab is characterized by two significant morphological changes, from the 5th zoea (Z5) to the megalopa (M) stage and from the M to the first juvenile crab (C1) stage. In this study, we found that methyl farnesoate (MF) could prohibit the Z5 to M metamorphosis in a concentration-dependent manner, and that a concentration of 10 μM MF could completely prohibit the Z5 metamorphosis. Farnesoic acid (FA) could also prohibit the Z5 metamorphosis, but its effects seemed to be concentration-independent. In addition, MF could delay rather than prohibit the M to C1 metamorphosis, while FA had no effect on the M to C1 metamorphosis at all. To summarize, it is hypothesized that either absence of MF and FA, or at least very low levels of these substances, might be necessary for a successful Z5 to M metamorphosis.

Cloning and expression analysis of <italic>CYP</italic>302<italic>a</italic>1 from <italic>Scylla paramamosain</italic>

In arthropods, periodic molting plays an important role in the growth, reproduction and morphogenesis. Periodic ecdysis is affected by a variety of environmental and own factors, the most important of which is controlled by the concentration of steroid hormones, and ecdysone (Ecd) whose mainly active form is 20-hydroxyecdysone(20E) is the most important steroid hormone. Moreover, ecdysteroids play important roles in regulating the growth, development and reproduction, CYP302al is the key enzyme in biosynthesis of the ecdysteriods. We obtained a full-length of <italic>CYP</italic>302<italic>a</italic>1 cDNA sequence from the mud crab <italic>Scylla paramamosain</italic> firstly, which was named as <italic>Sp</italic>-<italic>CYP</italic>302<italic>a</italic>1 in present study. The length of <italic>Sp</italic>-<italic>CYP</italic>302<italic>a</italic>1 was 3 032 bp, with a predicted 1 617 bp open reading frame (ORF) encoding 538 amino acids with a predicted molecular weight of 61.14 kDa, a 5′UTR of 205 bp and a 3′UTR of 1 210 bp. And the putative protein sequence of <italic>Sp</italic>-<italic>CYP</italic>302<italic>a</italic>1 contained 5 conserved domains including helix-C, helix-K, helix-I, PERF and heme-binding. Moreover, we found that there were no signal peptide sequences and transmembrane domains in the the putative protein sequence by Signal 5.0 Server and TMHMM. The phylogenetic tree showed that <italic>CYP</italic>302<italic>a</italic>1 of <italic>S</italic>. <italic>paramamosain</italic> was clustered with that of <italic>Portunus trituberculatus</italic> and <italic>Penaeus vannamei</italic>, and then together with other species. The amino acid sequence deduced by the <italic>Sp</italic>-<italic>CYP</italic>302<italic>a</italic>1 sequence was clustered with <italic>CY</italic>302<italic>A</italic>1 of <italic>Portunus trituberculatus</italic> and <italic>Penaeus vannamei</italic> into a small branch, and then clustered with <italic>CY</italic>302<italic>A</italic>1 of other species, and then clustered with the amino acids of <italic>CYP</italic>306<italic>A</italic>1, <italic>CYP</italic>307<italic>A</italic>1, <italic>CYP</italic>315<italic>A</italic>1, <italic>CYP</italic>314<italic>A</italic>1 and <italic>CYP</italic>18<italic>A</italic>1 encoded by other members of the <italic>P</italic>450 genes. We analyzed the expression pattern by real-time PCR (qRT-PCR). The results showed that transcript of <italic>CYP</italic>302<italic>a</italic>1 was mainly detected in the Y-organ (YO) and far exceeded other tissues both in males and females. And during the larval development, the expression of <italic>Sp</italic>-<italic>CYP</italic>302<italic>a</italic>1 kept fluctuating from zoea I to the second juvenile crab stage with the highest expression in Z3 stage. Furthermore, during molting process, the levels of <italic>CYP</italic>302<italic>a</italic>1 in Yo were extremely low during postmolt (stages A and B), and then began to increase and reached the peak at pre-molt stage (stage D), then declined. In this study, the <italic>CYP</italic>302<italic>al</italic> gene of <italic>Scylla paramamosain</italic> was cloned and identified through sequence analysis, combined with tissue distribution, larval spatiotemporal expression, and molting cycle changes. We hypothesized that <italic>CYP</italic>302<italic>al</italic> might play an vital role in the molting of <italic>S</italic>. <italic>paramamosain</italic>.

Identification and Sexually Dimorphic Expression of a FoxL2-like Gene in Mud Crab (Scylla paramamosain): Potential Roles in Male Differentiation and Development

Monosex breeding technology has received enormous attention for the Scylla paramamosain, an economic crustacean species with distinctive sexual dimorphism. However, the molecular mechanism of gonadal development and sexual differentiation still remain inconclusive. In this study, we reported the cloning, characterization of a FoxL2-like gene with male-biased expression in the mud crab (SpFoxL2). The SpFoxL2 encoded a putative forkhead-box protein with 352 amino acids. Phylogenetic tree revealed the SpFoxL2 was clustered with the invertebrates FoxL2 homologues, most closed to E. sinensis. By quantitative real-time PCR, it was shown that the SpFoxL2 was expressed in intestine, ovary and testis, with the highest expression level in testis. During gonadal development, the expression level of SpFoxL2 in ovary was lower than that in testis at all stages. The expression level of SpFoxL2 constantly declined from stage I to stage V in ovary. While, there is a rising tendency from stage I to stage IV in testis. Notably, this male-biased expression pattern could be detected as early as the juvenile crab stage I (CI stage) before morphological sexual differentiation in the mud crab. By fluorescence in-situ hybridization, SpFoxL2 mRNA was found located in both somatic and germ cells in gonads. In testis, it was most strongly localized in the meiosis germ cells (spermatocytes). While in ovary, the signal became weaker in the meiosis germ cells (oocytes). The results imply that the SpFoxl2 may play an important role in male differentiation and development, laying a foundation for future research on sexual differentiation of the species.

Food Restrictions Affect the Larval Metamorphosis and Early Juvenile Performance in a Neotropical Mangrove Fiddler Crab (Leptuca cumulanta).

Sporadic fluctuations in food availability may affect larval biology and post-metamorphic development in many marine invertebrates. In an experimental study in the laboratory, we investigated whether different regimes (1, 3, and 5 days) of initial starvation or feeding affect the survival and duration of the last planktotrophic larval stage (i.e., megalopa) of the neotropical mangrove fiddler crab Leptuca cumulanta. Newly metamorphosed crabs originating from megalopae starved for 1 and 3 days were cultured through the first 5 juvenile stages to further evaluate whether prior nutritional experience affects the post-larval performance of this species. All megalopae that were starved continuously died, while 80% of the larvae that were fed constantly metamorphosed successfully into the juvenile stage. Megalopae initially starved for 3 and 5 days exhibited lower survival (55% and 30% of larval metamorphosis, respectively) than larvae starved for only 1 day (85%) or fed constantly. The starvation periods (1, 3, and 5 days) also significantly prolonged the mean megalopal stage duration (12.8, 13.9, and 14.3 days, respectively) compared to the continuous feeding regime (10.6 days). Survival of the megalopae subjected to different periods of initial feeding (1, 3, and 5 days) was significantly lower (15.0%, 57.5%, and 62.5%, respectively) than survival of the larvae fed constantly. The mean megalopal stage duration, by contrast, did not vary among megalopae initially fed for 3 and 5 days or fed continuously (10.4 days). The larval starvation did not affect survival and carapace shape of juveniles, but it did alter their intermolt period, growth, and body size. These carryover effects were stronger in the first juvenile crab stage than in other juvenile stages. Our results indicate that the timing and duration of the starvation or feeding regime experienced by the megalopae may affect their successful survival and developmental period until metamorphosis to juvenile life. In addition, the preceding larval starvation associated with a prolonged larval period may also affect early juvenile performance in specific crab stages of L. cumulanta.

Impacts of nutritional stress on the survival and developmental time to metamorphosis in megalopa larvae of the exploited mangrove crab, Ucides cordatus (Ucididae)

ABSTRACTTemporal variation in food availability may affect the early life-history stages of many decapod crustaceans in the pelagic environment. Here, we investigated whether temporary food restrictions affect the survival and developmental period in the last larval stage (i.e. megalopa) of the mangrove crab Ucides cordatus. We further examined whether the prior nutritional history experienced during the megalopal life affects the body size (carapace width) of the first juvenile crab stage of this species. Megalopae were subjected to five different periods (1, 3, 5, 7, and 9 days) of initial starvation followed by constant feeding (‘Point of No Return’ experiment), or initial feeding with subsequent food deprivation (‘Point of Reserve Saturation’ experiment). They were also starved or fed (Artemia sp. nauplii) constantly in two control groups. Our results showed that U. cordatus megalopae may tolerate only one day without food, but need to feed for at least three, five or seven days at the beginning of their development to avoid a significantly lower survival and/or a delay in larval metamorphosis when compared to larvae fed constantly. However, megalopae initially fed from one to seven days may produce juveniles of smaller body size than those larvae fed for nine days or constantly.

Myosin Va from Eriocheir sinensis: cDNA cloning, expression and involvement in growth and development.

Myosin Va, a member of the myosin superfamily, has been widely identified associated with processes of cellular motility, which include neurotransmitter release and synaptic plasticity during neurodevelopment. However, the function of myosin Va in the growth and development of crustaceans has not yet been reported. In this study, a full-length cDNA of myosin Va (named as EsMyoVa) was cloned from the Chinese mitten crab, Eriocheir sinensis, and the expression patterns were detected in different tissues and larval developmental stages. The full-length cDNA of EsMyoVa was 6037 bp in length. Real time quantitative reverse transcription PCR (qRT-PCR) analysis showed that EsMyoVa transcript has a wide tissue distribution pattern and is expressed in zoeae, megalopa, juvenile crab stages and adults. In order to further study the function of this gene, we used RNAi technology in the muscle, hepatopancreas, gill, and gonad. After double-stranded RNA (dsRNA) injection, the expression level of EsMyoVa was significantly decreased in all tissues in both sexes and the gene knockdown effects of dsRNA persisted for at least 6 days. Subsequently, the role of EsMyoVa was revealed by silencing the transcript through one month injections of Myosin Va dsRNA. Crabs with reduced levels of EsMyoVa transcripts displayed a dramatic slowing in growth rate and considerably higher mortality compared to control groups, which indicated that this gene had important role of regulating growth and development.

Individual growth pattern of juvenile stages of the Chinese mitten crab (Eriocheir sinensis) reared under laboratory conditions

The specific growth pattern of Chinese mitten crab, Eriocheir sinensis, during the juvenile stages was investigated under an individual rearing system for 160 days, including parent crab selection, hatchery management, larval stages, and juvenile cultivation. There were 36 males and 40 females developed from megalopa to the juvenile crab stage 10 (M–C10), with a total survival of 38%. The survival rate in early stages (M–C3) remained less than 80%, which was lower than that in latter stages (> 90%). The intermoult duration sharply increased in an exponential manner (y = 3.1059e0.2149x R2 = 0.9383) from 4 ± 0.54 days to 38 ± 6.26 days. The increments in wet weight, carapace width, and carapace length per moult were recorded throughout the experiment, which followed certain patterns with progressing moulting time. In addition, moulting increment in wet weight varied greatly from C1 to C6, with a minimum increment of 108.09%. Meanwhile, the specific growth rate markedly increased in the early stages and subsequently decreased, mainly because of significant increases in the intermoult duration starting from C6 stage. Males and females could be differentiated at C4 based on sexual dimorphism in the abdomen, and the most distinct changes in female and male juvenile crabs occurred in the shape of the abdomen and amount of cheliped fluff, respectively.

Effects of temporary starvation and feeding on the survival and developmental time to metamorphosis in megalopa larvae of two Neotropical mangrove crab species, genus Sesarma (Sesarmidae)

Temporal variation in pelagic food supply may affect the larval development and recruitment success of many decapod crustaceans in marine coastal ecosystems. In the present study, we experimentally investigated the degree of nutritional vulnerability in megalopa larvae of two sesarmid crab species (Sesarma curacaoense and S. rectum) subjected to different conditions of nutritional stress. In the laboratory, Sesarma megalopae were initially starved for up to 9days followed by a constant feeding period in one experiment (i.e., point of no return), or they were fed at the beginning of their development for up to 9days followed by a continuous period of food deprivation in a second experiment (i.e., point of reserve saturation). Megalopae were also constantly reared in the absence and presence of food (Artemia sp. nauplii) in two control groups. The larval response to the different experimental conditions was evaluated through the percentage of survival (=% metamorphosed larvae), developmental time to metamorphosis, and Nutritional Vulnerability Index (= PRS50/PNR50). All megalopae died when reared under constant starvation whereas 100% of the larvae metamorphosed into the first juvenile crab stage after 13.1±4.4days (S. curacaoense) or 12.4±1.2days (S. rectum) when continuously fed. In the first experiment, the starvation periods did not affect the mean developmental time of the megalopae through metamorphosis (13.6±4.3days) of S. curacaoense and only those larvae initially starved for 7days presented the lowest percentage of metamorphosis to juvenile crab (73%). In S. rectum, by contrast, megalopae starved from 5 to 9days exhibited lower percentages of metamorphosis (≤86%) compared to larvae starved for 1 or 3days or those constantly fed. Furthermore, megalopae starved for 7 and 9days delayed by 1.6 and 3.5days their metamorphosis, respectively, compared to larvae constantly fed. In the second experiment, the Sesarma megalopae initially fed for only 1day presented lower percentages of metamorphosis (≤73%) than megalopae fed for 3 or more days or continually (≥93%). The mean developmental time to metamorphosis was shorter with 1day (8.1±0.7days in S. curacaoense) or 3days (11.3±1.6days in S. rectum) of temporary feeding. The estimated values of the PNR50 and PRS50 indices were respectively 7.34 and 0.93days for S. curacaoense and 9.01 and 1.78days for S. rectum. These values provided a Nutritional Vulnerability Index of 0.13 for S. curacaoense and 0.2 for S. rectum, indicating a reduced dependence on exogenous food by the megalopae of these two sesarmid crab species. This starvation tolerance associated with a short megalopal development should increase the likelihood of successful survival into the benthic life phase and avoid latent effects of the larval nutritional stress and/or delayed metamorphosis on early juvenile performance of both Sesarma species.

Metamorphosis of the edible mangrove crab Ucides cordatus (Ucididae) in response to benthic microbial biofilms

Benthic microbial communities can play an important role in the induction of larval metamorphosis in marine invertebrates. The role of biofilms in recognizing the parental habitat is unknown for the ecologically and economically important mangrove crab Ucides cordatus, a species suffering from environmental pressures such as habitat degradation and disease. In the laboratory, we experimentally tested the influence of biofilms grown in offshore and estuarine waters on the moulting rates and developmental time to metamorphosis (TTM) of the last larval stage (megalopa) of U. cordatus. Here, we specifically studied whether: (i) megalopae of this larval-exporting species respond differently to marine (MB) and estuarine biofilms (EB), (ii) biofilms previously immersed (24h) in adult crab-conditioned seawater (ACSW; i.e. conspecific chemical cues) exhibit a greater effectiveness (i.e. by inducing higher moulting rates and shorter TTM) on larval metamorphosis than non-immersed ones and (iii) biofilms pre-immersed (24h) in ACSW decrease their effectiveness when incubated (24h) in pure filtered seawater (FSW) before offering them to megalopae. U. cordatus megalopae metamorphosed to the first juvenile crab stage (JI) in response to both MB and EB, however the moulting rates were significantly higher and development TTM shorter in the presence of EB compared to MB. The metamorphosis-inducing effects were significantly enhanced when both types of biofilms were pre-immersed in ACSW, suggesting that conspecific cues can be absorbed and stored by microbial matrix. The higher inductiveness of EB compared to MB persisted after previous contact with ACSW. Furthermore, EB exhibited a significantly greater biomass production (measured as dry weight) than MB, and when immersed in ACSW, both groups of biofilms significantly increased in biomass (maintaining the hierarchy EB>MB), suggesting that water-soluble chemical substances emitted by the adult crabs may have been absorbed and metabolized by the biofilms. The metamorphic inductiveness and biomass production decreased when both groups of biofilms that were previously kept (24h) in ACSW were thereafter immersed (24h) in FSW. All megalopae successfully moulted to JI after accelerated TTM when reared in ACSW, regardless of presence or absence of biofilms, corroborating that conspecific stimuli are the most effective metamorphosis-stimulating cues tested so far in U. cordatus. The fact that EB improved the moulting rates and shortened the development TTM indicates that megalopae can recognize and respond to microbial assemblages typical for specific environments. This should be ecologically important during larval recruitment by facilitating settlement in appropriate habitats for the post-metamorphic development of early benthic recruits. In addition, the influence of EB could encourage colonization of new estuarine areas and aid natural recovery of U. cordatus in mangrove habitats where crab populations have suffered significant reduction due to deforestation, fishing pressure or diseases.

Two transcripts of HMG-CoA reductase related with developmental regulation from Scylla paramamosain: Evidences from cDNA cloning and expression analysis.

3-Hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductases (HMGRs), which catalyze the conversion of HMG-CoA to mevalonate, may have an important role in the synthesis of methyl farnesoate (MF). In this study, we obtained two HMGR cDNA sequences termed Sp-HMGR1 (membrane-bound form) and Sp-HMGR2 (soluble form), which encode 967 and 654 amino acids, respectively. The two cDNAs possess entirely identical sequences except that Sp-HMGR1 is 1,382 bp, which encodes a sterol-sensed domain (SSD; a membrane-bound domain) and was first found in crustacean HMGR, larger than Sp-HMGR2. Thus, it was deduced that these cDNAs might be derived from a single genomic DNA sequence. Sp-HMGRs have the typical features of the HMGR class of proteins. However, residue 844 in Sp-HMGR1, which is usually occupied by a Ser residue in other species, has an unusual Ala substitution. This Ser is thought to be involved in enzyme activity regulation by reversible phosphorylation. A putative "PEST" sequence that, until now, has only been found in crustacean species was also identified in the C-terminus of both transcripts, and a sterol-sensing domain, which was first found in crustacean species, was identified in Sp-HMGR1; these findings suggest that Sp-HMGR might function in some special regulatory mechanism. Furthermore, the quantitative real-time polymerase chain reaction results showed that the two transcripts have different expression patterns; Sp-HMGR2 was mainly expressed in the mandibular organ (MO) of adult crabs, whereas Sp-HMGR1 was mainly expressed in other tissues and fertilized eggs up until the fourth juvenile crab stage. The fluctuating gene expression seemed to suggest a relationship between Sp-HMGRs and the development of the crab, especially during the larval stage. Besides, the fluctuation of Sp-HMGR1 in ovary, brain, and thoracic ganglia during the ovary development seemed to have some correlation with the nutrition accumulation of ovaries, whether the SSD domain evolved in this process deserve further investigation. Moreover, it remains unclear whether the significant variation in ovary, brain, and thoracic ganglia during ovary development suggests that other tissues in addition to the MO could synthesize MF.

Larval growth and biochemical composition of the protected Mediterranean spider crab Maja squinado (Brachyura, Majidae)

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 20:13-21 (2014) - DOI: https://doi.org/10.3354/ab00540 Larval growth and biochemical composition of the protected Mediterranean spider crab Maja squinado (Brachyura, Majidae) G. Rotllant1,*, G. Guerao2, N. Gras2, A. Estévez2 1Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas, Passeig Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain 2IRTA, Unitat Operativa de Cultius Experimentals, Ctra. Poble Nou, Km 5.5, 43540 Sant Carles de la Ràpita, Tarragona, Spain *Corresponding author: guio@icm.csic.es ABSTRACT: The spider crab Maja squinado is restricted to the Mediterranean Sea, and as captures of this species became very rare in the last decades, it is a protected species. To improve spider crab production in experimental or commercial hatcheries and allow the future success of re-stocking programmes, knowledge of larval growth and biochemical characteristics is mandatory. In the present study, larvae from 4 different batches were studied. Larvae were examined to determine the larval instar and moulting stages. In each moulting stage for all larval instars, carapace length, dry weight, ash and proximal composition (protein, carbohydrates and lipids) were measured. Metamorphosis began at 14 d posthatching (dph), with metamorphosis to the first juvenile crabs completed in about 90% of the specimens at 17 dph. Survival dropped from 59.25 ± 19.53% to 33.49 ± 19.53% between the zoea II and megalopa stages, and only 7.74 ± 1.94% of newly hatched larvae (NHL) reached the first juvenile crab stage. NHL weighed 120.40 ± 18.95 µg, increasing their dry weight and ash content 6-fold after metamorphosis. Dry weight also increased through the moulting cycle in each larval instar, while ash content was higher in early premoult stages. Proximal composition increased between 8- and 6-fold from NHL to megalopa in the premoult stage and then decreased 2-fold during metamorphosis. Lipid and protein content varied among moulting stages from the postmoult to the premoult stages, with more significant alterations seen during the megalopa instar stage. KEY WORDS: Decapoda · Majoidea · Larval instars · Moult stages · Size · Biomass · Protein · Lipids Full text in pdf format PreviousNextCite this article as: Rotllant G, Guerao G, Gras N, Estévez A (2014) Larval growth and biochemical composition of the protected Mediterranean spider crab Maja squinado (Brachyura, Majidae). Aquat Biol 20:13-21. https://doi.org/10.3354/ab00540 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 20, No. 1. Online publication date: January 13, 2014 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2014 Inter-Research.

Carry-over effects of delayed larval metamorphosis on early juvenile performance in the mangrove crab Ucides cordatus (Ucididae)

Competent larvae of most benthic marine invertebrates including brachyuran decapod crustaceans can delay their settlement and metamorphosis in the absence of suitable environmental cues. This however may carry significant costs for the post-larval performance and fitness of early benthic juveniles. In this paper, we examined in the laboratory whether delayed larval metamorphosis affects early juvenile performance of the mangrove crab Ucides cordatus, measured as survival and growth through the first five juvenile crab stages (JI–JV). We further investigated whether ‘carry-over’ effects of an extended larval period vary intraspecifically among juveniles from three different hatches (F1–F3). Ucides megalopae were cultivated in two treatments. In the first one, the control, megalopae were cultivated continuously in exposure to conspecific crab odours (adult-conditioned seawater=ACSW) until moulting to the first juvenile crab stage. In the second, the delay-treatment, settlement-competent megalopae were kept for 20days in pure filtered seawater without metamorphosis-triggering odours. From day 21 onwards, megalopae were transferred to ACSW to induce larval moult. The results showed that delayed metamorphosis affects early juvenile survival and growth of U. cordatus. In the delay-treatment, survival rates of juveniles (JI–JV) from F1–F3 were 11–31% lower and intermoult development periods 1.5–4.2days longer than in the control. Delayed juveniles (F1–F3) exhibited 9.2–14.1% smaller body sizes (carapace width) and 1.4–3.9% lower growth rates mostly in the first two moulting events compared to specimens derived from non-delayed megalopae. Most of the detrimental effects were observed in almost all five crab stages studied, indicating that the costs of delayed metamorphosis may persist throughout early juvenile development. Juvenile morphology, however, was not affected. Our study also showed that carry-over effects of delayed larval moult vary intraspecifically among offspring produced by different females. This plasticity in phenotypic effects could relate to differences in the nutritional state, health or age of the females, to stressful environments during embryogenesis or to genetic differences. The observed carry-over effects of delayed settlement on early juvenile performance may affect the overall recruitment success and population dynamics of U. cordatus. In the field, such a situation would appear when new mangrove areas void of conspecific crabs are colonized or when degraded sites are re-populated by larvae originating from elsewhere populations.

Temperature effects on larval survival, larval period, and health of hatchery-reared red king crab, Paralithodes camtschaticus

We tested the effects of two rearing temperatures (8 and 11°C) on survival, larval period, and health of red king crab (Paralithodes camtschaticus) larvae in eight hatchery-scale 1200L tanks as part of a stock enhancement feasibility study. Larvae were stocked at a density of 50larvaeL−1. Survival did not vary from the newly hatched first stage zoea to the glaucothoe and first juvenile crab stage (C1) between the two temperatures. Survival averaged 50% from stocking to the glaucothoe stage and 20% from stocking to C1. Overall, 480,000 Z1s were stocked and 96,200 C1s were produced. Larval periods were significantly shorter at the higher temperature, averaging 21days from stocking to glaucothoe and 35days from stocking to C1 at 11°C compared to 30days to glaucothoe and 50days to C1 at 8°C. Specific attributes of larval health measured in this study included the size and relative number of lipid droplets in the anterior region of the larval gut as a measure of stored energy reserves and percentage of the surface of the larval exoskeleton fouled with filamentous bacteria. Quantitative assessment of accumulated lipids as measured by maximum lipid droplet diameters and relative numbers of lipid droplets in the anterior region of the gut was not significantly different between larvae reared at the two temperatures, suggesting that larvae were able to accumulate similar quantities of lipid energy reserves at both temperatures. Filamentous bacterial fouling was greater during the late Z4 stage in the larvae reared at 8°C compared to those reared at 11°C, which was likely due to the longer intermolt duration at the lower temperature allowing more time for bacterial accumulation on the exoskeleton. We found that red king crab larvae can be cultured in a substantially shorter time period without compromising survival or health by increasing rearing temperature from 8 to 11°C.

The early life history of Chiromantes ortmanni (Crosnier, 1965) (Decapoda: Brachyura: Sesarmidae): morphology of larval and juvenile stages

The early life history of the sesarmid crab Chiromantes ortmanni (Crosnier, 1965) was studied at constant laboratoryconditions, and the complete larval and early juvenile development are described. Chiromantes ortmanni showsintraspecific variability in the pattern of larval development, which typically includes 5 or, less frequently, 6 zoeal stagespreceding the megalopa. The regular pathway (with 5 zoeal stages) required ca 18–20 days. During this time span, zoealsize (carapace length) increased by a factor of 2.2 from 0.33 to 0.73 mm, while biomass (measured as zoeal dry mass andcontents of carbon, nitrogen and hydrogen) showed an 8-fold increment. The megalopa moulted after 10–12 days to thefirst juvenile crab stage, the total larval development from hatching to metamorphosis taking approximately one month(or ca. 4 days longer in larvae passing through an additional zoeal stage). First egg-laying was observed 8.5 months later,at a female carapace width of 14.4 mm. After an embryonic development time of 26–27 days, a total of 3,470 larvaehatched during two subsequent nights. Hence, the minimum generation time (from hatching to first offspring release)comprised slightly more than 10 months. Unlike the regular zoeal stages, the supernumerary stage VI showed atypicalcharacters for Sesarmidae larvae, especially in the setation pattern of the first maxilliped and the segmentation of theendopod of the second maxilliped. Some characteristics presented an intermediate morphology between that of the zoeaV and the megalopa. The first juvenile stage (crab I) is described in detail, while only the most relevant morphologicalchanges and sexual differentiation are highlighted for subsequent crab stages (II–IX). Males and females can bedistinguished from instar V onward, based on sexual dimorphism in the pleopods and the presence of gonopores in thefemales. The morphological characters of all larval stages and of the first juvenile crab are compared with those of other Chiromantes spp.

Early juvenile development of Mediterranean Liocarcinus depurator (Crustacea: Decapoda: Brachyura: Portunidae)

The early juvenile crab stages (C1 to C5) of the portunid crab Liocarcinus depurator (Linnaeus, 1758) were obtained in the laboratory from megalopae captured from the plankton in the northwest Mediterranean. Morphological development through these stages is described and compared with previous juvenile descriptions and adult morphology. The definitive adult morphology of carapace teeth is only apparent from stage C4. The incision on the lower orbital margin of the carapace and the mesial lobe (“portunid lobe”) of the endopod of the first maxilliped starts to be evident from C3. Stage C5 is already very similar to that of the typical adult crab. Male and female crabs can be distinguished from stage C2 onwards, based on sexual dimorphism in pleopods. The morphology and size of Mediterranean juvenile crabs was compared with the previous description of individuals reared in the laboratory from ovigerous females from British North Atlantic waters.

Morphological description of the megalopa and the first juvenile crab stage of Chiromantes eulimene (Decapoda, Brachyura, Sesarmidae), with a revision on zoeal morphology

The complete larval development of a sesarmid crab from East Africa, Chiromantes eulimene (De Man 1895) was obtained through laboratory culture. It consists of five zoeal stages and a megalopa, followed by metamorphosis to the first juvenile crab. The morphology of all zoeal stages is revised and compared with previous descriptions. The megalopa and the first juvenile crab stage are, for the first time, fully described in detail and compared with those of other known species of the genus Chiromantes and further sesarmid crabs. The megalopal morphology of C. eulimene presents the typical combination of features that characterize sesarmid megalopae. The first crab stage is also similar to that of other sesarmid species, for which morphological descriptions are available.

Early juvenile development of Armases rubripes (Rathbun 1897) (Crustacea, Brachyura, Sesarmidae) and comments on the morphology of the megalopa and first crab

This article provides a description of the early juvenile stages of Armases rubripes and indicates some differences and additional details found in the megalopa and first juvenile crab stage compared with previous descriptions. The main characters that permit identification of the subsequent juvenile stages were assessed, as well as the moult interval and increment during successive moults and the beginning of development of the secondary sexual features. Megalopae of A. rubripes were collected from the Ubatuba region, São Paulo, Brazil using plankton and neuston nets. Morphological changes in body parts have been recorded for each stage and sex, as well as the duration of the intermoult period was noted. Possible effects of laboratory holding time on growth were checked by means of analysis of covariance. The importance of standardization of the terminology of setae is emphasized.

Development and growth of the early juveniles of the spider crab Maja squinado (Brachyura: Majoidea) in an individual culture system

The spider crab Maja squinado is an endangered Mediterranean species; therefore, culturing it successfully is essential for developing restocking programs. The survival, growth and development of post-larval stages (juvenile crabs, C1–C8) were studied using larvae obtained from adult individuals collected in the Catalan Sea. The juvenile crab stages were cultured individually from a megalopal stage using a semi-open recirculation system to obtain the precise growth data of each juvenile crab stage until C8. Development up to C8 at 20 °C lasted 154 ± 10 days. Survival from C1 to C8 was 5.8%. Moult increment values in cephothoracic length were similar in all the crab stages (21–35%). Intermoult duration (9 ± 1 in C1–C2 to 51 ± 8 days in C7–C8) increased sharply from juvenile stage 5. Males and females can be distinguished from C4 based on sexual dimorphism in the pleopods and the presence of gonopores. The allometric growth of the pleon is sex-dependent from C4, with females showing positive allometry and males isometric growth. The juvenile growth rate was lower compared with that of the previously studied Atlantic species Maja brachydactyla.

Influence of natural settlement cues on the metamorphosis of fiddler crab megalopae, Uca vocator (Decapoda: Ocypodidae)

Megalopae of many decapod crab species accelerate their development time to metamorphosis (TTM) when exposed to natural physical and/or chemical cues characteristic of the parental habitat. In the present study, the influence of natural settlement cues on the moulting rates and development TTM in megalopae of the fiddler crab Uca vocator was investigated. The effects of mud from different habitats (including well-preserved and degraded-polluted mangrove habitats) and conspecific adult 'odours' (seawater conditioned with crabs) on the induction of metamorphosis were compared with filtered pure seawater (control). 95 to 100% of the megalopae successfully metamorphosed to first juvenile crab stage in all treatments, including the control. However, the development TTM differed significantly among treatments. Settlement cues significantly shortened development, while moulting was delayed in their absence. The fact that megalopae responded to metamorphosis-stimulating cues originating from both adult and non-adult benthic habitats demonstrates that settlement in this species may occur in a wider range of habitats within the mangrove ecosystem, including impacted areas.