Morphology of the first zoeal stages of eleven Sesarmidae (Crustacea,Brachyura, Thoracotremata) from the Indo-West Pacific,with a summary of familial larval characters

Summary

The first zoeal stages of eleven species of Sesarmidae from the Indo-West Pacific were obtained from ovigerous females. Those of Labuanium scandens, L. rotundatum, L. trapezoideum, L. politum, Metasesarma aubryi, Pseudosesarma crassimanum, Stelgistra stormi, and Sesarmops impressum, are described for the first time, while the first zoeal stages of Clistocoeloma merguiense, Metasesarma obesum and Sesarmops intermedium are re-described. Larval characters of all these species are compared with previously described ones for the family and morphological features are re-evaluated. Minute spines on the telson of the zoeae are described as a new larval character in Sesarmidae and their presence or absence in other grapsoid groups is discussed. The results demonstrate that a recurrent combination of reliable larval characters distinguishes zoeae and megalopae of the examined sesarmids from the rest of the Grapsoidea. This appears to be consistent with recent studies that redefine the Sesarmidae.     

Heterochrony in mandible development of larval shrimp (Decapoda: Caridea)—A comparative morphological SEM study of two carideans

Mandible development in the larval stages I–V of two palaemonid shrimp species, Palaemon elegans and Macrobrachium amazonicum, was analyzed using scanning electron microscopy, light microscopy, and confocal laser scanning microscopy. In contrast to the zoea I of P. elegans, first‐stage larvae of M. amazonicum are nonfeeding. At hatching, the morphology of the mandibles is fully expressed in P. elegans, while it appears underdeveloped in M. amazonicum, presenting only small precursors of typical caridean features. In successive zoeal stages, both species show similar developmental changes, but the mandibular characters of the larvae in M. amazonicum were delayed compared to the equivalent stages in P. elegans, especially in the development of submarginal setae and mandible size. In conclusion, our results indicate heterochrony (postdisplacement) of mandible development in M. amazonicum compared to that in P. elegans, which is related to initial lack of mandible functionality or planktivorous feeding at hatching, respectively. This conclusion is supported by comparison with other palaemonid zoeae exhibiting different feeding modes. Our data suggest that an evolutionary ground pattern of mandible morphology is present even in species with nonfeeding first‐stage larvae. J. Morphol. 275:1258–1272, 2014. © 2014 Wiley Periodicals, Inc.     

Complete larval development of the hermit crabs Clibanarius aequabilis and Clibanarius erythropus (Decapoda: Anomura: Diogenidae), under laboratory conditions, with a revision of the larval features of genus Clibanarius

The complete larval development (four zoeae and one megalopa) of Clibanarius aequabilis and C. erythropus, reared under laboratory conditions, is described and illustrated. The larval stages of the two northeastern Atlantic Clibanarius species cannot be easily differentiated. Their morphological characters are compared with those of other known Clibanarius larvae. The genus Clibanarius is very homogeneous with respect to larval characters. All Clibanarius zoeae display a broad and blunt rostrum, smooth abdominal segments and an antennal scale without a terminal spine. Beyond the second zoeal stage, the fourth telson process is present as a fused spine, and the uropods are biramous. In the fourth larval stage all species display a mandibular palp. The Clibanarius megalopa presents weakly developed or no ocular scales, symmetrical chelipeds, apically curved corneous dactylus in the second and third pereiopods, and 5–11 setae on the posterior margin of the telson. Apart from the number of zoeal stages, Clibanarius species may be separated, beyond the second zoeal stage, by the telson formula and the morphology of the fourth telson process.     

Occurrence of additional Zoea-VI larvae in the mud crab, Scylla paramamosain (Estampador), reared in the laboratory

Mud crabs, Scylla spp. , are commercially important in many Indo-Pacific countries. The larval development of mud crabs has been reported previously as five zoeal and one megalopal stages. This paper reports larval rearing experiments that revealed variability in larval developmental stages in the mud crab Scylla paramamosain, one of four mud crab species. In addition to normal five zoeal stages, an alternative pathway of developing through six zoeal stages was observed for the crab. There were evidences suggested that the appearance of the additional Zoea-VI larvae was associated with unfavourable dietary conditions, including poor quality of diet, inadequate quantity of dietary supply and a period of starvation for newly hatched larvae. Based on exuviae and larval specimens, the morphology of the additional Zoea-VI larvae was described.     

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

Larvae 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.     

Foregut morphology and ontogeny of the spider crab Maja brachydactyla (Brachyura,Majoidea, Majidae)

We describe the morphology of the foregut of the spider crab Maja brachydactyla Balss, 1922, from first larval stage to adult, with detailed stage‐specific documentation using light and scanning electron microscopy. A total of 40 ossicles have been identified in the foregut of adults of M. brachydactyla using Alizarin‐Red staining. The morphological pattern of the ossicles and gastric mill is very similar to other Majoidea species with only a few variations. The foregut of the zoeae stages appeared as a small and simple cavity, with a cardio‐pyloric valve that separates the stomach into cardiac and pyloric regions. The pyloric filter is present from the first zoea, in contrast to the brachyuran species which have an extended larval development. Calcified structures have been identified in the cardio‐pyloric valve and pyloric region of the zoeal stages. The most significant changes in foregut morphology take place after the metamorphosis from ZII to megalopa, including the occurrence of the gastric mill. In the megalopa stage, the foregut ossicles are recognizable by their organization and general morphology, but are different from the adult phase in shape and number. Moreover, the gastric teeth show important differences: the cusps of the lateral teeth are sharp (no molariform); the dorsal tooth have a small, dentate cusp (not a well‐developed quadrangular cusp); and the accessory teeth are composed of one sharp peak (instead of four sharp peaks). The gastric mill ontogeny from megalopa to adult reveals intermediate morphologies during the earlier juvenile stages. The relationship between gastric mill structures with food preferences and their contribution to the brachyuran phylogeny are briefly discussed. J. Morphol. 276:1109–1122, 2015. © 2015 Wiley Periodicals, Inc.     

Description, seasonal morphological variation, and molecular identification of Paraxanthus barbiger megalopae obtained from the natural environment

Larval identification represents a powerful tool for detailed studies on recruitment and population dynamics in marine invertebrates. However, intra-specific morphological variation can become a serious limitation for the correct identification at species level. High morphological variation can be expected in species with continuous breeding periods because larvae are exposed to seasonal fluctuations in physical and biological factors during their development in the plankton. We describe, for the first time, the megalopae of Paraxanthus barbiger, one of the most common and abundant brachyuran crabs along the coast of Chile. To validate larvae identification, the 16S rRNA gene was sequenced from both megalopae and adults, and was compared with sequences of three sympatric species. In addition, size, body shape, and appendage setation pattern variations were analyzed with a year-round sampling scheme. The results demonstrated high seasonal phenotypic plasticity in size. Despite these differences, certain conservative characteristics exist which can be very useful for identification at species level.     

Morphological features of the larvae of spider crab <Emphasis Type="Italic">Pugettia quadridens</Emphasis> (Decapoda: Majidae) from the Northwestern Sea of Japan

The entire cycle of larval development of the spider crab Pugettia quadridens (de Haan, 1850) (Decapoda: Majidae), widespread in Peter the Great Bay (Sea of Japan) is studied under the laboratory conditions. The development cycle of this species comprises prezoea, zoea I, zoea II, and megalopa. At a temperature of 18–20° C larval development took from 11 to 15 days. Zoea II is described in detail for the first time. Many morphological characters are found distinguishing zoea and megalopa of P. Quadridens in Russian waters from the larvae of this species in Japanese and Korean waters. Some characters of larvae are similar in P. Quadridens and the related species of the genus Pugettia. The larvae of P. Quadridens occur in the plankton of Vostok Bay from late June to late October with a density up to 5 ind/m³ at a surface water temperature of 13–21°C. They are easily distinguished from the other brachyuran larvae of this region by the absence of lateral spines on the carapace.Original Russian Text Copyright © 2004 by Biologiya Morya, Kornienko, Korn.     

Larval,megalopal and early juvenile development in Pagurus granosimanus (Stimpson, 1859) (Decapoda: Anomura: Paguridae) reared in the laboratory

Summary

The larval, megalopal and early juvenile stages of Pagurus granosimanus are described, illustrated and compared with other North Pacific species of the genus. Morphologically, the zoeae of P. granosimanus appear most similar to the Japanese P. brachiomastus in the majority of characters, but share the endopodal setation of the third maxilliped with a second Japanese species, P. pectinatus. The megalopae of P. granosimanus are unlike those of other North Pacific species in having 5+5 marginal setae on the telson, rather than the customary 4+4, or less frequent 3+3. Comparison of juvenile characters is limited to pleopodal changes among the regional species for which data are available. P. granosimanus is unusual in undergoing complete pleopodal loss at the second crab stage with return of left pleopods in the fourth stage.     

Morphology of the larval stages of Pitho aculeata (Gibbes, 1850) (Crustacea,Brachyura, Majoidea) and its implications on the taxonomic position of the genus

The larval development of Pitho aculeata is described and illustrated in detail. The characters described are used to discuss recent molecular phylogenetic findings suggesting that Pitho is a genus in Mithracidae sensu stricto. Based on species with known larval development, our results indicate that Pitho shares more similarities with mithracids than epialtids and therefore it should be included in the former family. Presently, there appear to be no diagnostic characteristics for the zoeal stages; however, for the megalopa the fused antennal articles 5 and 6 and the distinct number of setae on the abdominal somites 1–5 can be used to differentiate Pitho from other majoideans.     

Complete larval and early juvenile development of the mangrove crab Perisesarma fasciatum (Crustacea: Brachyura: Sesarmidae) from Singapore, with a larval comparison of Parasesarma and Perisesarma

The complete larval development of the sesarmid crab Perisesarmafasciatum (Lanchester, 1900) from Singapore was obtained fromlaboratory culture. All four zoeal stages, the megalopa andthe first crab stage are described and illustrated. The morphologicalcharacteristics of the larvae of P. fasciatum are compared withthose of other known larvae of the genera Perisesarma and Parasesarma.The larval morphology of P. fasciatum clearly presents the typicalcombination of features that characterize sesarmid larvae. Overall,larval stages are very similar in Perisesarma and Parasesarmaand it is impossible to distinguish these two genera by larvalmorphology.     

Influence of temperature on the zoeal development and elemental composition of the cancrid crab, Cancer setosus Molina, 1782 from Pacific South America

Temperature changes during ENSO cause mass mortalities of adult Cancer setosus, but the effects on early life stages are unknown. The influence of temperature on survival, development and biochemical composition was studied in larvae of the hairy crab, C. setosus, from a population off the northern Chilean coast. In rearing experiments conducted at four different temperatures (12, 16, 20, 22 °C), zoeal development was only completed at 16 and 20 °C, after 78 and 36 days, respectively. Instar duration was negatively correlated with temperature. A multiple linear model relating larval body mass (in carbon) to temperature and developmental time suggests that successful larval development is possible within a narrow temperature range only. The biochemical composition, measured as carbon, hydrogen, and nitrogen (C, H, N) content, show in general the typical oscillating changes during the moult cycle of brachyuran crab larvae. However, at high (22 °C) and low (16 °C) temperatures, CHN values show deviations from the typical pattern, indicating threshold temperatures for larval activity and survival. These findings indicate that the larval development of C. setosus is compromised under conditions of El Niño, with temperatures exceeding the upper thermal temperature tolerance threshold of larvae. Effects of El Niño on early life history stages and recruitment rates should be increasingly taken into account in fisheries management strategies.