Megalopa Stage Research Articles

The causes of asymmetry in the chelae of the mud crab Scylla paramamosain Estampador, 1950 (Decapoda: Brachyura: Portunidae)

Abstract The asymmetry trait in brachyuran crabs is mostly expressed by the different sizes or particular details of the two chelae. The causes for this asymmetry have been rarely investigated in the economically important crab Scylla paramamosainEstampador, 1950. We found that the asymmetric chelae first appeared in the megalopa stage. The examination of four “right-handed” and two “left-handed” mothers and their 521 megalopa offspring indicated that this trait might not be influenced by dominant alleles, since 86.0% –99.0% of megalopae exhibited the right-handed phenotype in the four offspring of the right-handed mother, whereas about 93.1% and 100% megalopae exhibited the right-handed phenotype in the two left-handed-mothers’ offspring. The percentage of left-handed individuals at different stages also supports this hypothesis. We provide evidence that the amputation of the handed chela will result in a “handedness reversal,” and that the food type might influence the speed of the reversal. Crabs that were fed with fish blocks had a faster handedness reversal than those who were fed with commercial pellets feed, perhaps because of the increase in effort in individuals feeding on fish blocks.

Variations in vertical distribution of developing snow crab Chionoecetes opilio and red snow crab Chionoecetes japonicus (Crustacea, Decapoda, Majoidea) larvae in experimental temperature gradients

ABSTRACT In the Sea of Japan, field studies have found snow crab and red snow crab larvae occur between the surface and depths of up to 550 m and 1100 m, respectively. In this region, snow crab larvae hatch at depths of 240–260 m and red snow crab larvae hatch at 1000–1500 m. To understand their vertical distribution during the larval period, we investigated the upward swimming speed of newly hatched larvae (first-stage zoea) and the behaviour of all larval stages (first and second zoeal and megalopal stages) in a temperature gradient under laboratory conditions. Our results showed that the larvae have the potential to reach the surface within a few days of hatching. As the larvae developed, they preferred greater depth and lower temperatures; although they temporarily rose to higher levels immediately after each moult. The zoeae and megalopae of both species did not occur beyond the 16 and 6°C temperature layers, respectively. The preferred position of the larvae in the gradient temperature did not differ between the two species. The present study suggests that Chionoecetes larvae transported to unsuitable temperatures may not die, but could escape from low temperatures by upward swimming and from high temperatures by sinking.

Environmental Transmission of Symbionts in the Mangrove Crabs Aratus pisonii and Minuca rapax: Acquisition of the Bacterial Community through Larval Development to Juvenile Stage.

Aratus pisonii and Minuca rapax are two brachyuran crabs living with bacterial ectosymbionts located on gill lamellae. One previous study has shown that several rod-shaped bacterial morphotypes are present and the community is dominated by Alphaproteobacteria and Bacteroidota. This study aims to identify the mode of transmission of the symbionts to the new host generations and to identify the bacterial community colonizing the gills of juveniles. We tested for the presence of bacteria using PCR with universal primers targeting the 16S rRNA encoding gene from gonads, eggs, and different larval stages either obtained in laboratory conditions or from the field. The presence of bacteria on juvenile gills was also characterized by scanning electron microscopy, and subsequently identified by metabarcoding analysis. Gonads, eggs, and larvae were negative to PCR tests, suggesting that bacteria are not present at these stages in significant densities. On the other hand, juveniles of both species display three rod-shaped bacterial morphotypes on gill lamellae, and sequencing revealed that the community is dominated by Bacteroidota and Alphaproteobacteria on A. pisonii juveniles, and by Alphaprotobacteria, Bacteroidota, and Acidimicrobia on M. rapax juveniles. Despite the fact that juveniles of both species co-occur in the same biotope, no shared bacterial phylotype was identified. However, some of the most abundant bacteria present in adults are also present in juveniles of the same species, suggesting that juvenile-associated communities resemble those of adults. Because some of these bacteria were also found in crab burrow water, we hypothesize that the bacterial community is established gradually during the life of the crab starting from the megalopa stage and involves epibiosis-competent bacteria that occur in the environment.

Early Succession of Community Structures and Biotic Interactions of Gut Microbes in Eriocheir sinensis Megalopa after Desalination.

As an enduring Chinese freshwater aquaculture product, the Eriocheir sinensis has a high economic value and is characterized by a catadromous life style that undergoes seawater-freshwater migration. However, little is known about their gut microbial status as they move from saltwater to freshwater acclimatization. Here, we sampled and cultivated Eriocheir sinensis megalopa from three aquaculture desalination ponds and investigated their gut microbiota diversity, community structures and biotic interactions from megalopa stage to the first juvenile stage after desalination for 9 days. Our results revealed that during the transition from megalopa to the first juvenile in Eriocheir sinensis, a significant change in gut microbial composition was observed (for instance, changes in relative abundance of dominant phyla), which was, however, not influenced by different sampling sites. The species diversity (such as the richness) of the gut microbiota showed a hump-shaped pattern along the succession. However, the compositional differences of the gut microbes showed constantly increasing patterns during the succession after freshwater adaption for all three sampling sites. Further co-occurrence analysis also showed that the complexity of the ecological networks in gut microbes was significantly enhanced during the development, such as increasing numbers of network links, connectivity and modularity, and was confirmed by decreasing average path length and proportions of negative links. Taken together, the differences in community structures and biological interactions of gut microorganisms were more pronounced in Eriocheir sinensis megalopa during desalination than in diversity and species compositions. This implies that the gut microbes of Eriocheir sinensis megalopa would become more robust and adaptive during the developmental process.

Beneath the surface: co-habitation of recruits of the land crab Johngarthia lagostoma and its relevance for conservation on oceanic islands

Abstract Gecarcinid crabs have their life cycles in antagonistic scenarios, with their larvae developing in the sea and the juvenile/adult phases occurring on land. Adults migrate from land to sea to release their larvae, which return to land upon reaching the megalopa stage. Recruitment and early instar traits in gecarcinids crabs remain unknown, leading to some species lacking age-specific information. Despite massive recruitment observed in some insular gecarcinid species (e.g. Gecarcoidea natalis), recruits are generally expected to be few and exhibit cryptic behaviour, potentially occupying the burrows of conspecifics. We evaluated whether recruits of Johngarthia lagostoma on Trindade Island, Brazil, co-inhabit larger conspecific burrows, analysing this occurrence and examining their growth patterns, density, and body size across different lunar phases. Johngarthia lagostoma recruits inhabit conspecific burrows, either abandoned or occupied by adult crabs, but always with leaves stored in the inner chamber. Recruits in co-inhabiting behaviour reach a maximum carapace width of 7.3 mm, and after that, they are likely detected by the adults and possibly cannibalized or leave burrows naturally. During the full moon, the higher density and smaller size of recruits were recorded, indicating a recruitment lunar phase. It is crucial to ascertain the prevalence of co-inhabitation behaviours in other land crab species to expand the knowledge about recruitment patterns in these key community species.

Transcriptomic Responses of a Lightly Calcified Echinoderm to Experimental Seawater Acidification and Warming during Early Development.

Ocean acidification (OA) and ocean warming (OW) are potential obstacles to the survival and growth of marine organisms, particularly those that rely on calcification. This study investigated the single and joint effects of OA and OW on sea cucumber Apostichopus japonicus larvae raised under combinations of two temperatures (19 °C or 22 °C) and two pCO2 levels (400 or 1000 μatm) that reflect the current and end-of-21st-century projected ocean scenarios. The investigation focused on assessing larval development and identifying differences in gene expression patterns at four crucial embryo-larval stages (blastula, gastrula, auricularia, and doliolaria) of sea cucumbers, using RNA-seq. Results showed the detrimental effect of OA on the early development and body growth of A. japonicus larvae and a reduction in the expression of genes associated with biomineralization, skeletogenesis, and ion homeostasis. This effect was particularly pronounced during the doliolaria stage, indicating the presence of bottlenecks in larval development at this transition phase between the larval and megalopa stages in response to OA. OW accelerated the larval development across four stages of A. japonicus, especially at the blastula and doliolaria stages, but resulted in a widespread upregulation of genes related to heat shock proteins, antioxidant defense, and immune response. Significantly, the negative effects of elevated pCO2 on the developmental process of larvae appeared to be mitigated when accompanied by increased temperatures at the expense of reduced immune resilience and increased system fragility. These findings suggest that alterations in gene expression within the larvae of A. japonicus provide a mechanism to adapt to stressors arising from a rapidly changing oceanic environment.

Early life stages of the invasive Atlantic blue crab Callinectes sapidus in the Western Mediterranean Sea

The early life cycle of the Atlantic blue crab Callinectes sapidus includes seven zoeal stages that develop in coastal waters, and a later megalopal stage that colonizes estuaries. Although these stages have been largely studied in native ecosystems, very little is known about larval patterns in smaller-scale, invaded, estuarine environments such as those available in the Mediterranean Sea. The general aim of this study is to assess the distribution and abundance of early life stages of C. sapidus in the communication channels of the Albufera lagoon with the Mediterranean Sea, and in adjacent coastal waters. Different sampling methods were employed to target each life stage. (1) For zoeae, planktonic tows were conducted using a 300 μm manta net along 200 m transects parallel to the coastline at distances of 300, 1000 and 3000 m from the shore. (2) A small and manageable passive collector model was used to capture megalopae and juveniles in estuarine areas. This system was first tested from 2020 to 2021 in a single channel, with a weekly sampling frequency, and two more channels were added in 2022. Additionally, intensive daily sampling was conducted in one of the channels from September to November 2022 during the settlement peak. Results showed that zoeae of C. sapidus were more abundant in August 2021, at 1000 m from the coast, and appear to have a disjoint temporal distribution with zoeae of other crab species. Megalopae and juveniles were more abundant from September to November at all sampling sites and times. In 2022, collectors featured a dominance of megalopae at two of the sites (ca. 73%), while the site with the lowest salinity showed a dominance of juveniles (84%). For megalopae, comparative results from the intensive and the regular sampling campaigns showed that time of residence within collectors is just a single day. For juveniles, higher numbers were detected with increased deployment time, suggesting a need for enhanced habitat complexity.

Effects of four diets on the metabolism of megalopa metamorphosis of the mud crab, Scylla paramamosain

Dietary intake is an essential source of energy and nutrients, and plays an irreplaceable role in the breeding of S. paramamosain seedlings. In this study, live Artemia nauplii (LA), compound feeds (CF), frozen copepods (FC) and frozen adult Artemia (FA) were utilized as feed during the megalopa stage. To determine the impact that diet has on the metabolism of crablets that underwent metamorphosis from the megalopa stage, analyses of both metabolomics and fatty acid content were conducted. In the LC-MS-based metabolomics analysis, a total of 104, 205 and 83 significantly different metabolites (SDMs) were identified after being fed with FC, FA, and CF, respectively, as compared to the LA group. Furthermore, significant differences in KEGG compounds among the three comparisons exhibited similarity and were mainly associated with categories such as “Lipids”, “Hormones and transmitters”, and “Peptides”. The fatty acid content analysis indicated that the ΣMUFA was significantly higher in the LA and CF groups compared to the other two groups. In contrast, the highest level of ΣPUFA was found in the LA group. In addition, the CF group showed significantly higher expression levels of the fatty acid synthesis genes, FAS and ACC. Conversely, the expression level of the fatty acid decomposition-related gene CPT1 was the highest in the LA group. In comparison with the FA group, the expression level of FABP3 was significantly decreased in the LA and CF groups. In summary, there were significant differences observed in the metabolic profiles of crablets that metamorphosed from the megalopa under different diets. Our experimental results suggested that LA is more advantageous in the cultivation of the S. paramamosain megalopa compared to the other three diets. While it remains a diet that cannot be entirely substituted at present, LA has the potential to improve the culture performance of the S. paramamosain megalopa. The current study could provide valuable data into the development of artificial diets necessary for the future of the mud crab seedling breeding industry.

Comparative transcriptome analysis reveals the growth and development in larval stages of the swimming crab Portunus trituberculatus

Portunus trituberculatus, an economically important marine crab that was widely distributed along the coast of China, has been in short supply of high-quality crab seedlings in recent years. The larval development of P. trituberculatus is regulated by numerous biological processes at different biological levels, particularly regarding gene expression during the larval development process. Understanding the changes in these critical genes can help further regulate these biological processes to increase crab seedlings’ survival and improve crab quality. In this study, the molecular mechanisms of morphological and physiological changes in larval stages of P. trituberculatus were investigated using DNA microarrays. A total of 109,533 unigenes were obtained, of which 16 genes were differentially expressed during the whole development stages with evident timeliness. The enrichment analysis and comparison of differentially expressed genes (DEGs) showed three types of physiological activities, chitin development, energy metabolism, and neuroendocrine development. The physiological activities were evident in the early development of P. trituberculatus, especially at the Z4-M stage, which is crucial for the growth and development of crab larvae. These DEGs, cuticle proteins, retinol dehydrogenase (RDHs), Juvenile Hormone Epoxide Hydrolase (JHEH), and other vital genes were differentially expressed at the Z4-M stage. Moreover, the insulin-like androgenic gland (IAG), which was reported to be associated with sex differentiation, was highly expressed in the megalopa stage, indicating that the gender differentiation divide may occur at the beginning of this stage. Overall, this research provides a theoretical basis for the development of the swimming crab larvae, which could contribute to the artificial growing seedlings technology of P. trituberculatus.

Study of filtration, digestion and absorption of Chlorella pyrenoidosa by juvenile Chinese mitten crab (Eriocheir sinensis)

While previous studies have reported that the zoea and megalopa stages of Eriocheir sinensis can filter phytoplankton in water bodies, it remains unclear whether juvenile crab (E. sinensis) possess the same ability. The objective of this study was to investigate whether juvenile crabs (average body weight 9.51 ± 1.57 g) can filter and absorb phytoplankton. Firstly, stomach and intestinal contents of juvenile crabs were analyzed, and their filter-feeding ability was tested under different pellet feed ratios using a blood cell counter. It was found that juvenile crabs cultured in Chlorella pyrenoidosa suspension contained large quantities of the algae in their stomach and intestinal contents compared to the control group, which were cultured with no C. pyrenoidosa. Additionally, the filtration rate of juvenile crabs to C. pyrenoidosa decreased with the increase of pellet feed proportion. Finally, the ability of juvenile crab to digest and absorb C. pyrenoidosa was studied through 15N stable isotope labeling technology. The δ15N values in muscle and intestinal tissue of group filtered with 15N labeled C. pyrenoidosa were significantly higher than group filtered with unlabeled C. pyrenoidosa and control group. The results indicated that juvenile crab could filter, digest and absorb C. pyrenoidosa, expanding our understanding of the feeding ecology of this species. This has significant implications for the ecological culture of E. sinensis and the potential for sustainable aquaculture practices.

On their way to the north: larval performance of Hemigrapsus sanguineus invasive on the European coast—a comparison with the native European population of Carcinus maenas

The Asian shore crab Hemigrapsus sanguineus has become invasive in North Europe and it co-occurs and competes with the native European shore crab Carcinus maenas. Both species develop through a feeding and dispersive larval phase characterised by several zoeal and a settling megalopa stage. Larvae of marine crabs are vulnerable to food limitation and warming has the potential to exacerbate the negative effects of food limitation on survival and growth. We quantified the combined effects of temperature and food limitation on larval performance (survival and growth) of H. sanguineus and we compared our results with those reported on performance of C. maenas larvae, under the same experimental design and methodology. Larvae from four females of H. sanguineus collected on Helgoland (North Sea) were experimentally reared from hatching to megalopa, at four temperatures (range 15–24 °C) and two food conditions (permanent vs. daily limited access to food). Larval survival of H. sanguineus was low at 15 °C and increased with temperature, in contrast to the high survival reported for C. maenas larvae in the range 15–24 °C. Food limitation reduced survival and body mass of H. sanguineus larvae at all temperatures, but without evidence of the exacerbating effect caused by high temperatures and reported for C. maenas. By contrast, high temperature (24 °C) mitigated the negative effect of food limitation on body mass on H. sanguineus larvae. Advantages of H. sanguineus over C. maenas appear especially under the increased temperatures expected from climate change.

Dietary effects on larval survival and development of three sesarmid crabs

Semi-terrestrial brachyuran sesarmid crabs are the most diverse and important faunal components of mangrove forest and temperate coastal communities worldwide. To establish a stable larval rearing method for understanding their larval developmental processes including molecular mechanisms of molting and metamorphosis, we examined the effects of diet on the survival and growth of three sesarmid crabs, Chiromantes haematocheir, Orisarma intermedium, and O. dehaani under larval development. Zoea of each species, immediately after hatching, were reared under different feeding conditions as follows: non-feeding; fed only nutrition-enriched rotifers; fed only Artemia (brine shrimp) nauplii; and fed a combination of both nutrition-enriched rotifers and brine shrimp. Larvae of each species survived almost to megalopa when they were fed both rotifer and brine shrimp, but all C. haematocheir larvae had died by zoeal stage 2 when they were only fed brine shrimp. Chiromantes haematocheir larvae could survive into the megalopa stage when fed only nutrition-enriched rotifer, whereas both O. dehaani and O. intermedium showed 50% or less survival and metamorphosis rates into megalopa. The duration of larval development and survival rates of the three crabs were shorter and higher, respectively, in the mixed feeding group (both rotifer and brine shrimp) than when only fed rotifer or brine shrimp. This study provides baseline knowledge of the interspecific variability in larval survival and duration under different diets for sympatric sesarmid crab species.

Larval development of the blue crab Callinectes sapidus: effect of enriched rotifers as live food

Understanding nutrition and its effect on growth is essential for developing diets in commercially important species. This study aimed to evaluate the larval development of Callinectes sapidus fed with rotifers (Brachionus plicatilis) enriched with Chlorella pyrenoidosa (Ch) as a main protein source and a lipid emulsion (Spr) rich in highly unsaturated fatty acids. The enriched compositions had seven ratios Ch/Spr (w/w): 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60. The enriched rotifers with each ratio were called diets. Lipids increased progressively between 100/0 and 40/60 (7.48 to 11.30 g 100 g-1), as well as energy (21.88 to 23.16 kJ g-1), but the protein level did not show a clear trend (63.93 and 67.50 g 100 g-1). The production response of blue crab larvae showed significant differences within diets (P < 0.05). The highest survival (29 to 34%) was obtained in the 50/50 and 40/60 treatments. In the 40/60, 50/50, and 60/40 diets, the larval cycle was shorter (P < 0.05), and the megalopa stage was reached between 49 and 52 days of culture. Metamorphosis to megalopa occurred between the fifth and eighth molts; its corresponding weight varied from 0.72 to 1.33 mg, the length varied from 2,632 to 2,926 µm, and Le Cren´s condition factor varied from 0.83 to 1.16. The most important factor in the production response was the diet lipid content, which was significantly correlated with the survival, weight, length, and condition factor of C. sapidus larvae. Findings of the present study can be applied in future efforts towards mass culture of blue crab larvae in the Caribbean and can also potentially be used to study other crustacean species with similar characteristics.

The effectivity of probiotic containing Bacillus spp. applicated in the rearing of mud crab Scylla tranquebarica larvae to produce crablet

Probiotic bacteria in larvae rearing is expected to suppress pathogenic bacteria and improve water quality. The research aimed to determine the effectivity of probiotic bacteria containing Bacillus subtilis and B. licheniformis on larval rearing of purple mud crab Scylla tranquebarica to produce crablet. The larvae were stocked in nine units of conical fiber tank, fed Rotifers, Brachionus plicatilis, and nauplii Artemia sp. The probiotics tested, namely, A). RICA-4, containing the bacterium Bacillus subtilis, B). RICA-5 containing B. licheniformis, C). A combination of probiotics RICA-4 and RICA-5. The administration of each probiotic with a density of 108 CFU g−1 (5 mg L−1) was given to the water media for larvae rearing. The lowest nitrite and Total Organic Matter in the zoea stage were found in treatment B. At the megalopa stage, treatment B’s lowest TOM concentration occurred and was significantly different (p<0.05) from treatment C. On the other hand, the highest population of Vibrio spp (5.5x103 CFU mL−1) was obtained in treatment A. In contrast, treatment C had the highest bacteria population (4.8x104 CFU mL-1). On day 19, the megalopa in treatment B was more abundant than in treatments A and C causing crablet production in treatment B (280.5±47.50 ind. tank −1) was significantly higher (p<0.05) than crablet production in treatment C (196.5±29.50 ind. tank −1) and A (161.0±21.00 ind. tank −1). Therefore, improving water quality in treatment B may have an important factor in enhancing crablet production.

Comparative transcriptome, digital gene expression and proteome profiling analyses provide insights into the brachyurization from the megalopa to the first juvenile in Eriocheir sinensis

Eriocheir sinensis larva normally experiences 11 stages. The reduced abdomen folded beneath the thorax is the most prominent characteristic of morphological alteration from megalopa to juvenile crab. Up to date, the molecular mechanisms of brachyurization remain a mystery. Here, transcriptome library, digital gene expression (DGE) libraries and proteome libraries at two developmental stages [the megalopa stage of E. sinensis (stage M) and the first stage of juvenile crab (stage J1)] of the Chinese mitten crab larva were constructed for RNA sequencing and iTRAQ approaches followed by bioinformatics analysis, respectively. In total, 1106 genes and 871 proteins were differentially expressed between the stage M and stage J1. Moreover, several important pathways were identified, including biosynthesis of secondary metabolites, metabolic pathways, focal adhesion, and some disease pathways. Besides, muscle contraction, oxidative phosphorylation, calcium signaling, PI3K-Akt, DNA replication pathway, and integrin signaling pathway also had important functions in brachyurization process. Furthermore, the components, actin, actin-related protein, collagens, filamin-A/B, laminin, integrins, paxillin, and fibronectin had up-regulated expression levels in M stage compared to J1 stage.

Occurrence of mangrove pebble crab, Philyra malefactrix (Kemp, 1915) in Kali estuary, Karwar and its laboratory reared zoea and megalopa stages

Marine biology,marine ecology,Phytoplankton, marine algae, zooplankton, nekton, benthos, corals and coral reefs, ecology, zoogeography and systematics, primary production and experimental work on ecosystem including energy flow at different trophic levels, population dynamics and theoretical models, recycling of matter, influence of environmental factors on metabolic activity, marine microbiology, mariculture and experimental work on propagation of cultivable species, biology of fishes, marine reptiles, sea birds and mammals, physical, chemical, geological and meteorological features of the environments related to marine biology, marine environmental damage caused by pollution and engineering works, underwater observations, conservation of living resources, modifications in methodology and techniques and development of new apparatus related to marine sciences

Potensi Minyak Buah Merah (Pandanus conoideus) Sebagai Suplemen Pakan Induk Kepiting Bakau untuk Meningkatkan Performa Telur dan Larva

The effort to provide the seeds of mud crabs should be increased. The problem faced is the survival rate of larvae to reach megalopa stages are still low. Research has shown that nutrients contain antioxidants in the brood feed can keep the quality of reproduction. The red fruit Pandanus conoideus endemic plant of Papua Province in Indonesia, contain antioxidant nutrients are assumed be served to prevent oxidation of the egg so that it can improve the quality of the ovaries and subsequent larval survival. Experiment with feed delivered to mud crab Scylla serrata weighing 400-500g / ind. The experiments conducted using a completely randomized design with three composisitin of feed and three individual as replication. The feed A (control): flesh fish of Decapterus sp. 100g; Feed B: fish of Decapterus sp. 23g, squid 40g, and 37g RFO; Feed C: fish of Decapterus sp 41g, squid 24g, and 35g RFO. The measured parameters are achievement of a mature ovary, the egg incubation period, the diameter of the eggs, and protein and fat content of larvae. Data were analyzed by ANOVA. The results showed that brood crabs fed with supplementation RFO has the quality of the eggs and larvae are higher than brood crabs that fed without RFO.

Larval development of the crab Amphithrax hemphilli (Rathbun, 1892) (Decapoda, Brachyura, Mithracidae) described from laboratory-reared material

The complete larval development of Amphithrax hemphilli was described, illustrated, and compared with that of the previously described larvae of the genus Mithrax sensu lato. Specimens of A. hemphilli were sampled from the northeastern Brazilian coast. The larval development of A. hemphilli consisted of two zoeal stages and one megalopa. Amphithrax hemphilli shows morphological features in all stages of larval development that differ from those observed in other species of Amphithrax, Mithrax, and Maguimithrax. In the first larval stage, A. hemphilli was the only species with two aesthetascs on the antennule and the coxal endite of the maxillule with five setae. In the second larval stage, A. hemphilli was distinguished from the other species of the genus Mithrax sensu lato by the presence of five setae on the basial endite of the maxilla and 26 setae in the scaphognathite of the maxilla. Finally, the megalopa stage of A. hemphilli is characterized by the number of aesthetascs on the three-segmented exopod of the antennule, the setation of both the endopod of the third maxilliped, and pleonites 1-6. Based on the results obtained in the present study, we verified that the more advanced the larval stage, the more distinct characteristics are observed among species of the genus Mithrax sensu lato, facilitating the identification of species through later larval stages.

Larvae of Stilbognathus cervicornis (Herbst, 1803) (Decapoda, Epialtidae, Tychinae) reared in the laboratory, from Gulf of Mannar, India

The complete larval development of Stilbognathus cervicornis (Herbst, 1803) from hatching to the megalopa stage was obtained by culture in the laboratory. Two zoeal and one megalopa stages are described and figured. Morphological characters of zoea larvae of Stilbognathus cervicornis of the subfamily Tychinae are compared with those of Epialtinae and Pisinae.

Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming

Coastal habitats are experiencing decreases in seawater pH and increases in temperature due to anthropogenic climate change. The Caribbean king crab, Maguimithrax spinosissimus, plays a vital role on Western Atlantic reefs by grazing macroalgae that competes for space with coral recruits. Therefore, identifying its tolerance to anthropogenic stressors is critically needed if this species is to be considered as a potential restoration management strategy in coral reef environments. We examined the effects of temperature (control: 28 °C and elevated: 31 °C) and pH (control: 8.0 and reduced pH: 7.7) on the king crab’s larval and early juvenile survival, molt-stage duration, and morphology in a fully crossed laboratory experiment. Survival to the megalopal stage was reduced (13.5% lower) in the combined reduced pH and elevated temperature treatment relative to the control. First-stage (J1) juveniles delayed molting by 1.5 days in the reduced pH treatment, while second-stage (J2) crabs molted 3 days earlier when exposed to elevated temperature. Juvenile morphology did not differ among treatments. These results suggests that juvenile king crabs are tolerant to changes associated with climate change. Given the important role of the king crab as a grazer of macroalgae, its tolerance to climate stressors suggests that it could benefit restoration efforts aimed at making coral reefs more resilient to increasingly warm and acidic oceans into the future.