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.     

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.     

Occurrence of an alternative pathway in the larval development of the crab Chasmagnathus granulata Dana, 1851 under laboratory conditions

Larvae of the crab Chasmagnathus granulata were collected in a salt marsh located in the Lagoa dos Patos, Brazil and reared from eclosion to metamorphosis under different dietary regimes. Larvae reared individually in beakers of 40 ml and fed Tetraselmis chuii (zoea III and zoea IV), showed a supplementary stage, here designated as zoea V, with morphological characteristics intermediary between zoea IV and megalopa. No zoeae V molted to megalopa stage. To confirm the occurrence of the supplementary stage, mass cultures of larvae of C. granulata were fed Artemia sp. at high densities, we again detected the fifth zoeal instar. However, when zoeae V were individually placed in beakers and fed Artemia nauplii, they succeeded in molting into megalopae. We observed the occurrence of two types of zoeae IV — a smaller type (from which originated the zoeae V) and a larger type (which directly developed into megalopae). We conclude that stressful nutritional/environmental conditions were responsible for the occurrence of this alternative path of development.     

The zoeal stages and megalopa of Portunus rubromarginatus (Lanchester) (Decapoda: Portnnidae), reared in the laboratory

The present state of knowledge concerning Portunus larvae isreviewed, and the three zoeal and the megalopa stages of P.rubromarginatus are described and figured. Details of appendagesetation are tabulated. This species is unusual amongst knownPortunus spp. in having only three zoeal stages and, like otherPortunus spp. but in contrast with other Portuninae, it has4 + 4, or 4 + 1 + 4, setae on the posterior telson border. When compared with larvae of the five other Indo-West PacificPortunus species whose larvae are known P. rubromarginatus zoeaeare readily distinguished from all, except P. hastatoides, usingthe key features given by Kurata (1975). Comparison was madebetween first zoeae of these two species, and also of P. pelagicusand P. sanguinolentus, using larvae reared by the authors. Itwas found telson characters alone allow distinction betweenlarvae of these four species. These characters are tabulated. P. rubromarginatus megalopae differ from those known for congenitorsin having a large spine on the uchium of the first pereiopod,but not on the carpus, and in having relatively very small sternalcornuae. Several of these features disagree with those previously thoughtto characterise larval Portuninae or Portunus species.     

Partitioning and utilization of energy during the larval development of the xanthid crab, Rhithropanopeus harrisii (Gould)

An energy budget is constructed for the larval development of the crab Rhithropanopeus harrisii (Gould) fed nauplii of the brine shrimp Artemia salina (L.). Between the first zoeal instar and the megalopa, there is a 5.4-fold increase in caloric consumption and a 13.2-fold increase in dry weight. Weight specific energy content increases through the zoeal stages and drops at the megalopa. Rate of oxygen consumption increases steadily throughout development. Assimilation, gross growth, and net growth efficiencies increase steadily through zoeal development and drop at the megalopa. Calories put into tissue production exceed those expended via respiration in zoeal stages II–IV; the reverse is true in zoeal stage I and the megalopa.

A total energy budget has been calculated and the partitioning of energy is discussed in relation to other physiological studies on this species.     

Studies on the larval development of northeastern Atlantic and Mediterranean Procellanidae (Decapoda,Anomura). I — Redescription of the larval stages ofPorcellana platycheles (Pennant, 1777) reared under laboratory conditions

The complete larval development is described forPorcellana platycheles (Pennant) reared under laboratory conditions. The development consists of two zoeal stages and one megalopa. At 20°C and 35‰ salinity, the megalopa appeared 17–18 days after hatching. Survival was 56% from hatching to the megalopa stage. The morphological features of the zoeal and megalopa stages ofP. platycheles are compared with those of other species ofPorcellana, and a key of the known zoeal stages of the genus is given.     

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.     

The larval development of Petrolisthes politus (Gray, 1831) (Crustacea: Decapoda: Porcellanidae) under laboratory conditions

The complete larval development of the shallow-water Caribbean porcellanid crab, Petrolisthes politus (Gray, 1831), is described and illustrated from specimens reared in the laboratory. Petrolisthes politus hatches as a prezoea, which persist for less than 90 minutes, and then molts through two subsequent zoeal stages, which are completed in 6 to 7 and 14 to 16 days, respectively, before the megalopal stage is reached. From a total of about 2000 zoeae that were cultured, only two reached the megalopal stage. The two megalopae survived for up to 5 days but did not molt to the first crab stage. The zoeae of P. politus are compared with those of Petrolisthes rufescens (Heller, 1861), Petrolisthes lamarckii (Leach, 1820), Petrolisthes carinipes (Heller, 1861), Petrolisthes coccineus (Owen 1839) and Petrolisthes pubescens (Stimpson, 1858), which were hitherto the only species having bifid lateral spines on the telson of the first zoeal stage.     

Larval salinity tolerance of the South American salt-marsh crab, Neohelice (Chasmagnathus) granulata: physiological constraints to estuarine retention, export and reimmigration

The semiterrestrial crab Neohelice (=Chasmagnathus) granulata (Dana 1851) is a predominant species in brackish salt marshes, mangroves and estuaries. Its larvae are exported towards coastal marine waters. In order to estimate the limits of salinity tolerance constraining larval retention in estuarine habitats, we exposed in laboratory experiments freshly hatched zoeae to six different salinities (5–32‰). At 5‰, the larvae survived for a maximum of 2 weeks, reaching only exceptionally the second zoeal stage, while 38% survived to the megalopa stage at 10‰. Shortest development and negligible mortality occurred at all higher salt concentrations. These observations show that the larvae of N. granulata can tolerate a retention in the mesohaline reaches of estuaries, with a lower limit of ca. 10–15‰. Maximum survival at 25‰ suggests that polyhaline conditions rather than an export to oceanic waters are optimal for successful larval development of this species. In another experiment, we tested the capability of the last zoeal stage (IV) for reimmigration from coastal marine into brackish waters. Stepwise reductions of salinity during this stage allowed for moulting to the megalopa at 4–10‰. Although survival was at these conditions reduced and development delayed, these results suggest that already the zoea-IV stage is able to initiate the reimmigration into estuaries. After further salinity reduction, megalopae survived in this experiment for up to >3 weeks in freshwater, without moulting to juvenile crabs. In a similar experiment starting from the megalopa stage, successful metamorphosis occurred at 4–10‰, and juvenile growth continued in freshwater. Although these juvenile crabs showed significantly enhanced mortality and smaller carapace width compared to a seawater control, our results show that the late larval and early juvenile stages of N. granulata are well adapted for successful recruitment in brackish and even limnetic habitats.     

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.     

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.     

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.     

The larval development of an Australian limnadiid clam shrimp (Crustacea, Branchiopoda, Spinicaudata), and a comparison with other Limnadiidae

The adult morphology of the Australian Limnadopsis shows some remarkable differences to that of other Limnadiidae. These differences are not reflected in its larval development. In Limnadopsis parvispinus, larval development comprises six stages. In stages I and II only the three naupliar appendages are present: the antennule as a small bud, the biramous antenna as the main swimming organ, and the mandible. The antennal protopod bears two endites, the proximal naupliar process and a more distal endite. In stage III a bifid naupliar process (in earlier stages not bifid) and the first signs of the carapace and trunk limb anlagen (undifferentiated rudiments) appear. In stage IV the carapace anlagen become more pronounced. The number of trunk limb anlagens increases to five, and differentiation has commenced. In stage V the first five pairs of trunk limbs are differentiated to varying degrees. The anterior-most four pairs of trunk limbs are subdivided into five endites, a small endopod, an exopod and an epipod. The bivalved carapace covers the anterior-most limbs. In larval stage VI the carapace is larger and the trunk limbs are further differentiated. A general pattern in the sequence of larval stages is the increasing number of sensilla on the antennules. From the last larval to the first postlarval stage, a significant change in morphology takes place. The trunk limbs are now used for swimming. Typical larval organs are much smaller than in the last larval stage. A comparison with other representatives of the Limnadiidae shows a high degree of correspondence, with most differences explained by the heterochronous appearance of characters during development. Five to seven stages are described for all studied Limnadiidae, including one particular stage in which four fully developed setae, a bifid naupliar process and the first signs of carapace anlagen are present. These characters are found in stage III in L. parvispinus, Limnadia stanleyana, Eulimnadia texana, and Imnadia yeyetta but in stage IV in E. braueriana and L. lenticularis. Based on a comparison of the larval stages of six limnadiid and one cyzicid species, we conclude that at least six naupliar stages belong to the limnadiid ground pattern.     

Morphology of the first zoeal stage of the commensal southwestern Atlantic crab Austinixa aidae (Righi 1967) (Brachyura: Pinnotheridae), hatched in the laboratory

The first zoeal stage of the endemic southern Atlantic pinnotherid crab Austinixa aidae is described and illustrated based on laboratory-hatched material from ovigerous females collected from the upper burrows of the thalassinidean shrimp Callichirus major at Ubatuba, São Paulo, Brazil. The zoeae of Austinixa species can be distinguished from other pinnotherids and especially from zoeae of the closely related species of Pinnixa by the telson structure.