Larval development of Pandalus gracilis Stimpson (Crustacea: Decapoda: Pandalidae) reared in the laboratory

The complete larval development of Pandalus gracilis Stimpson is described based on larvae reared in the laboratory. The species has four larval stages (stages 1–4) and one postlarval stage (stage 5). The survival rate of the postlarva stage is very high. Of the 40 larvae reared individually, 39 larvae moulted to the postlarva stage within approximately 21 days at a rearing temperature of 15°C. Larval morphological characteristics of the species are described and figured. Larval development of P. gracilis is compared with other Pandalus and Pandalopsis species. Komai (1999 Komai, T. 1999. A revision of the genus Pandalus (Crustacea: Decapoda: Caridea: Pandalidae).. Journal of Natural History, 33: 1256–1372.  [Google Scholar]) divided species of Pandalus into four species groups based on adult morphology. Pandalus gracilis belongs to the P. hypsinotus group. In this study, using larval characters, the P. hypsinotus group can be divided into two groups by the appearance of the mandibular palp and the shape of the telson: the first group contains P. hypsinotus and P. danae, and the second group contains P. gracilis, P. prensor, and P. nipponensis.     

Complete larval development of the rare porcellanid crab,Novorostrum decorocrus Osawa, 1998 (Crustacea: Decapoda: Anomura: Porcellanidae), reared under laboratory conditions

The complete larval development of Novorostrum decorocrus Osawa, , is described and illustrated on the basis of laboratory‐reared material. Two zoeal stages and one megalop stage were recorded. Zoeas of N. decorocrus closely resemble those of N. indicum in the appendage characters, including the endopod of the maxillule with only a single stout seta on the distal margin. This character is unique to Novorostrum zoeas. However, N. decorocrus is distinguished from N. indicum by the setation on the endopod of the maxilla and the basis of the second maxilliped in both zoeal stages. The megalops of N. decorocrus are characterized by having a strongly elongate carapace, and differs considerably from the adults in the structure of the carapace, rostrum and third thoracic sternite, and in the armature of the pereiopods. The larval duration of N. decorocrus suggests that this rare porcellanid is more widely distributed than currently known.     

Juvenile development and growth patterns in the mud crab Eurytium limosum (Say, 1818) (Decapoda,Brachyura, Xanthidae) under laboratory conditions

The post‐larval development of the mud crab Eurytium limosum was studied under laboratory conditions by using the offspring of ovigerous females collected at the Comprido River mangrove, SP, Brazil. The first crab stage is fully described and the juvenile development, until crab stage 10, is examined with emphasis on morphological change, sexual differentiation and growth patterns. The carapace of the first crab stage is nearly square as observed in other xanthids, becoming similar to adults only at stage 15. The sexes can be distinguished from stage four, based on the number of pleopods and their morphology. While the intermoult period increases, the moult percentage decreases at each stage. The abdominal allometric growth is sex‐dependent, with males showing a negative (b?=?0.71) and females an isometric (b?=?0.95) relative growth pattern. Male gonopods undergo a positive allometric growth, and their shape changes remarkably until sexual maturity. The cheliped dentition can be observed after stage 4. Regardless of sex, most crabs have a molariform right cheliped, which is thought to aid the handling of asymmetric prey such as gastropods.     

Abbreviated larval development of the freshwater prawn,Macrobrachium pilimanus (De Man, 1879) (Decapoda,Palaemonidae), reared in the laboratory

The larvae of the freshwater prawn, Macrobrachium pilimanus (De Man, 1879), were reared in the laboratory. Larval development was highly abbreviated, with two zoeal and one megalopal stages. Newly hatched larvae were benthic, with a tendency to cling on to roughened surfaces. All larval stages subsisted solely on endogenous yolk. Morphological and behavioural differences between the first zoea of this species and that of M. malayanum (Roux, 1934) are highlighted. The potential use of larval characters in taxonomy is also discussed.     

Studies on the provenzanoi and other pagurid groups: VI. Larval and early juvenile stages of Pagurus ochotensis Brandt (Decapoda; Anomura; Paguridae) from a northeastern Pacific population,reared under laboratory conditions

Zoeal, megalopal, and early juvenile stages of Pagurus ochotensis (Brandt, 1851) from a northeastern Pacific population are described from laboratory-reared individuals. Zoeal and megalopal development in this population is compared with that described for a population of this species from Hokkaido, Japan. First and second juvenile crab stages of this species are described for the first time. The nearly identical developmental morphology of the two populations supports the earlier synonymy of the northeastern Pacific species, Pagurus alaskensis (Benedict) with P. ochotensis.     

The larval development of the mud shrimp Upogebia yokoyai Makarov, 1938 (Decapoda: Gebiidea: Upogebiidae) reared under laboratory conditions

Larval development of the mud shrimp Upogebia yokoyai Makarov, 1938 Makarov, VV. 1938. Crustacea Anomura. Fauna USSR. 10;3, Moscow, Leningrad: AN SSSR.  [Google Scholar] (Decapoda: Gebiidea: Upogebiidae) is described and illustrated for the first time from material reared in the laboratory. The development includes four zoeal stages and a megalopa. At 20–22°C the megalopa was attained 16 days after hatching. The zoeae of U. yokoyai are distinguishable from those of the sympatric species Upogebia major and Upogebia issaeffi, inhabiting Russian waters of the Sea of Japan, by the presence of two pairs of spines (posterolateral and posterodorsal), each on the fourth and fifth pleonal somites. The megalopa of U. yokoyai differs in the length of the rostral spine, shape of telson and number of antennular aesthetascs.     

Larval development of Clibanarius antillensis Stimpson, 1859 (Crustacea: Anomura: Diogenidae) reared under laboratory conditions: a comparison between Panamanian and Brazilian populations

The larval developmental sequences of Clibanarius antillensis Stimpson from first zoea through to megalopa are compared between laboratory-reared populations from Panama and Brazil. Only four zoeal stages are recorded for the Panamanian population, in contrast to four or five for the Brazilian larvae. Other differences in morphology are discussed and illustrated. Variations resulting from geographic differences and/or differing laboratory conditions raise the question of the validity of phylogenetic hypotheses based on single laboratory rearing events.     

Larval development in Phimochirus roseus (Benedict) (Decapoda: Anomura: Paguridae) reared in the laboratory

The zoeal and megalopal stages of Phimochirus roseus (Benedict, 1892) are described and illustrated from material reared under laboratory conditions. Although the vast majority of zoeae of this species pass through only four larval stages before the moult to megalopa, an occasional fifth stage has been observed. Phimochirus roseus differs in a number of morphological attributes from the only other species of Phimochirus whose larvae have been described. However, their shared features are sufficiently characteristic to confirm the distinctiveness of the genus and its general developmental homogeneity.     

The complete larval development of the crab Pilumnus spinifer (Brachyura: Xanthoidea: Pilumnidae) reared in the laboratory

The complete larval development of the crab Pilumnus spinifer from the western Mediterranean was obtained in the laboratory. All four zoeal stages and the megalopa are described and illustrated. The morphological characters of the larvae of Pilumnus spinifer are compared with those of other known larvae of the genus. The zoeae of P. spinifer show the rostral spine longer than the antennule (excluding aesthetascs); short lateral spines present on the carapace, and the mediolateral processes are present only in abdominal somites 2 and 3. The megalopa is similar to that of other Pilumnidae species. The morphology of the larval stages shows very similar characteristics to that of those of P. hirtellus and P. dasypodus, among the described stages of the family.     

Larval development of the fiddler shrimp,Metapenaeopsis stridulans (Alcock, 1905) (Decapoda: Penaeidae) reared in the laboratory

Larvae of Metapenaeopsis stridulans (Alcock, 1905) from Malaysia were successfully reared in the laboratory from the egg to the 1st post-larval stage. The larvae developed through six naupliar, three protozoeal and four mysis stages. The morphology of all these larval stages is described and figured.     

The larval development of the spider crab Rochinia gracilipes (Crustacea: Majoidea: Epialtidae: Pisinae) reared in the laboratory

The larval development of the spider crab Rochinia gracilipes Milne-Edwards, 1875 (Crustacea: Decapoda: Brachyura: Majoidea: Epialtidae: Pisinae) is described and illustrated from laboratory-reared larvae. Development consisted of two zoeal stages and one megalopa, following the typical pattern in Majoidea. Zoea I of R. gracilipes, R. debilis and R. carpenteri differed in lengths of the rostral spine of the carapace, in the number of setae and aesthetascs of several head appendages (exopods of antennules, endopods of maxillules, and endopods and scaphognathites of maxillae) and in the length of posterolateral processes of abdominal somites; lateral carapace spines were present only in R. carpenteri and pleopod buds only in R. debilis. Megalopae of Rochinia gracilipes and R. carpenteri differed in several notable characters: a dorsal spine and long rostrum of the carapace, as well as spines in coxa and ischium of pereiopods, appeared only in R. carpenteri, and podobranchiae of the 3rd maxilliped appeared only in R. gracilipes; they also differed in setation of abdomen and pleopods. The comparison of the available information on Pisinae larval development suggested that larval morphology would not help to accurately understand the phylogenetic relationships of this subfamily of spider crabs.     

Larval development and emigration behaviour during sea-to-land transition of the land hermit crab Coenobita brevimanus Dana, 1852 (Crustacea: Decapoda: Anomura: Coenobitidae) under laboratory conditions

To determine the early life history of the land hermit crab Coenobita brevimanus Dana, 1852, larvae were cultured individually in the laboratory. The zoeal and the megalopal stages are described and illustrated. The larvae developed through four planktonic zoeal stages to the megalopal stage. The major differences in the zoeal characters between C. brevimanus and other described Coenobita species were found in the armature of the pleomeres, whereas the character of pleomeres of C. brevimanus zoeae is the same as that of the coconut crab Birgus latro, a different genus in the same family. Morphological similarity was also found in segmentations of antennules and antennae in megalopae between C. brevimanus and the coconut crab. Megalopae of C. brevimanus were cultured in containers holding seawater and a hard substrate. These crabs migrate from the sea to land after developing a habit of acquiring gastropod shells.     

Larval development of Apiomithrax violaceus (A. Milne Edwards, 1868) (Decapoda: Brachyura: Majoidea: Pisidae) reared in laboratory conditions,and a review of larval characters of Pisidae

Apiomithrax violaceus (A. Milne Edwards, 1868 Milne Edwards A 1868 Observations sur la faune carcinologique des Iles du Cap-Vert Nouvelles Archives du Muséum d'Histoire Naturelle, 4, 49–68, pls 16–18  [Google Scholar]) is a pisid majoid crab occurring in tropical and subtropical coastal waters of the eastern and western South Atlantic. Larval development consists of two zoeal stages and a megalopa. Beginning with the first zoea, the duration of each larval stage at 24°C was 3–8 (5±1), 3–5 (4±0.5) and 9–15 (11±2) days, the megalopa and first crab instar appearing 9–11 (10±1) and 20–27 (23±2) days after hatching, respectively. Larval characters agree with those proposed for the Majoidea, in having nine or more setae on the scaphognathite in the first zoea and well-developed pleopods in the second zoea. However, larvae of A. violaceus do not fit larval pisid features. Zoeal stages differ from most other Pisidae in having lateral spines, a long rostral spine extending beyond the antenna, two spines per telson fork and a dorsolateral process on the third abdominal somite. The megalopa differs in having a spine dorsally on the carapace and on the basial segment of the second pereiopod. Two characters that are potentially unique to Apiomithrax include a zoeal antenna with an exopod that is much longer than the protopod, and a rostral spine that is longer than the dorsal spine. These characters should facilitate the identification of this taxon and could also be useful for phylogenetic studies. A review of larvae of 28 species among 14 genera indicated that there is no apparent single larval character that differentiates the Pisidae, with more limited phylogenetic analyses suggesting that this is a paraphyletic group. Apiomithrax, Eurynolambrus, Pisoides, Rochinia and Scyra have the most divergent morphological characters within the family. The analysis and inclusion of additional taxa is likely to shed more light on the sister-group relationships of the Pisidae. However, based on the extent of morphological interspecific variability of known larvae it is likely that the group, as presently defined by adult morphology, is not monophyletic.     

A new pontoniine shrimp (Crustacea: Decapoda: Palaemonidae) from the Ryukyu Islands,Japan

An unusual new genus and species of pontoniine shrimp, Nippontonia minirostris gen. nov., sp. nov., from a sponge host from the Ryukyu Is., Japan, is described and illustrated. The new genus appears not to be closely related to any of the previously described genera. The genus is particularly remarkable for the morphology of the fixed finger of the minor second pereiopod, which is without parallel in the Palaemonidae.     

Larval development of Maja crispata Risso 1827 (Crustacea,Decapoda, Majidae) reared in the laboratory

The morphology of the zoea and megalop of Maja crispata are described from laboratory-reared material, and compared with other two spider crabs belonging to the subfamily Majinae, Maja squinado and Maja goltziana, recorded in the same region of the eastern Atlantic. The diagnostic characters allowing the separation of these species' larvae are tabulated and discussed.     

A comparison of two methods for sampling the Gulf of California mud shrimp,Neotrypaea uncinata (Crustacea: Thalassinidea)

Methods for collecting mud shrimp are highly variable, and the efficiency of these techniques is poorly known. In October 1999, on a mud flat near Puerto Peñasco, Sonora, México, we compared the 'kiwi' method for extracting mud shrimp from their burrows, with a core sampling method designed to accomplish the same goal. The coring method involved pressing a 10 cm × 90 cm PVC pipe into the substratum, creating suction in the pipe, and withdrawing a core of mud and the shrimp within. The kiwi method required 8-10 researchers to march in a circle on the mud flat to gradually liquefy the mud, thereby forcing shrimp to the surface as the circle closed inward. Two transects of 30 cores conducted at high and at low tide yielded similar numbers of adult animals of both sexes. Previous results show that mud shrimp tend to aggregate within burrows when breeding. In this collection, the distribution of mud shrimp in cores did not differ from a Poisson distribution, suggesting that these shrimp were non-reproductive. The kiwi method provided no such information on mud shrimp distributions. Moreover, this method generated significantly fewer intact mud shrimp than were obtained in cores. Our results indicate that compared to the kiwi method, the coring method generates more animals, is less destructive of mud shrimp habitat, and provides more detailed information on mud shrimp populations.