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

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Reproductive period and size at the onset of sexual maturity of mottled purse crab, Persephona mediterranea (Herbst, 1794) (Brachyura, Leucosioidea) on the southeastern Brazilian coast

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Differential benthic occupation by crabs in the Ubatuba bay, São Paulo, Brazil

The goal of this work was to examine the occurrence of brachyurans in soft bottom sublittoral habitats and their association with some environmental factors. The relative abundance of crabs in two depth strata (from 4.5 to 9 m and from 9 to 18 m) was quantified. Crabs were collected with an otter-trawl with 3.7 m of mouth opening and 12-mm mesh in the cod end. Monthly sampling, consisted of a single trawl in each stratum during a 1-yr period, were carried out. Fifteen brachyuran and six anomuran species were found, including Callinectes ornatus Ordway, 1863; Callinectes danae Smith, 1869; Hepatus pudibundus (Herbst, 1785); Libinia spinosa H. Milne-Edwards, 1834; Persephona punctata (Linnaeus, 1758), and P. mediterranea (Herbst, 1794), which were the most abundant and frequent in the area. The most abundant swimming crabs in both strata were C. ornatus and C, dan(re. Size differences in C. ornatus were observed between strata, suggesting a spatial separation of juveniles and adult crabs.

Postlarval stages and growth patterns of the spider crab Pyromaia tuberculata (Brachyura, Majidae) from laboratory-reared material

The spider crab Pyromaia tuberculata was introduced into southeastern Brazil; ovigerous material was collected and reared in the laboratory. Morphologic changes and growth patterns of post-larval development are reported. Results show that within-stage size variation is lowest in mature stages, especially in the case of females in which there is an apparent size threshold for the last juvenile stages to undergo the puberty molt. A prepuberty molt taking place at the fourth crab stage is indicated by analyzing the allometric growth of the abdomen in females. In contrast, the same procedure using the allometric growth of chelae failed in detecting both the prepuberty and puberty molts in males. Conversely to females, which develop a complex brood chamber at the puberty molt, the enlargement of chelae was not consistent in all postpuberty males. The short instar sequence of this species, in no case exceeding nine stages, is marked by conspicuous morphologic alterations achieved at each molt. Almost all stages can be identified by examining diagnostic features of rostrum, abdomen, sternum, and pleopods.

Morphometric study of the ghost crab Ocypode quadrata (Fabricius, 1887) (brachyura, ocypodidae) from Ubatuba, São Paulo, Brazil

A morphometric study of the ghost crab Ocypode quadrata from Ubatuba, São Paulo, Brazil, focusing on the relationships between carapace width and carapace length, abdomen width, gonopod length and propodus length and height of the major cheliped is presented. An allometric positive growth was found for most of the analyzed relationships; however, important changes in the gonopod and abdomen were observed at the size at which sexual maturity is attained. Morphological (external) sexual maturity for both sexes is achieved at a smaller size than that at which gonad maturity is reached. Concerning heterochely, 53.3% of the analyzed specimens exhibited a longer propodus length in the right cheliped.

The megalopa and juvenile development of Pachygrapsus transversus (Gibbes, 1850) (Decapoda, Brahyura) compared with other grapsid crabs

Megalopae were reared in the laboratory to the 7(th) crab stage. The megalopa and 1(st) crab stage are described and juvenile development was studied with emphasis on pleopodal differentiation. The megalopal phase, is easily identified, and shares with those of other Grapsinae and Plagusiinae big size, the presence of many natatory setae, and a series of conspicuous teeth on the inner margin of the dactyli from the 2(nd) to 4(th) walking leg. These features are regarded as adaptive for settlement in a wave-swept environment, such as the rocky marine intertidal where most of those species live. Fast development of juvenile pleopods is another characteristic of these subfamilies. In Pachygrapsus transversus, the sexes can be distinguished from the 2(nd) crab stage. Gonopod differentiation in males and the basic segmentation of all four pleopod pairs in females are already concluded at the 5(th) instar. A review of the available information indicated that settlement of large megalopae and fast juvenile development, preceding a precocious sexual maturity, are trends in Grapsinae and Plagusiinae. on the other hand, the Sesarminae pass through a more extensive juvenile instar sequence and presumably a delayed maturity.

The first zoeal stage of two species of Grapsidae (Decapoda, Brachyura) and a key to such larvae from the Brazilian coast

First zoeal stages of the grapsinid Goniopsis cruentata (Latreille, 1803) and the sesarminid Aratus pisonii (H. Milne Edwards, 1837), are described and illustrated. Grapsinae zoeae can be distinguished from the other grapsid larvae by the absence of lateral spines on the carapace and the reduction of the antennal exopod to a small seta. A key to the first zoeal stage of the Brazilian coast Grapsidae is provided.

Larval stages of Stenocionops furcatus (Olivier, 1791) (Decapoda : Brachyura : Majoidea) and a reappraisal of larval morphological characters for Mithracidae

Stenocionops furcatus is a spider crab found in the western Atlantic, from Georgia, USA to Rio Grande do Sul, Brazil, on sand, coral, rocks or mud bottoms from the intertidal zone to 180 m. We describe all laboratory-reared larval stages of S. furcatus obtained from the northern coast of São Paulo State, Brazil, and compare our data with existing larval descriptions for the genus and other mithracids. The larval development of S. furcatus consists of two zoeal stages and one megalopa. The durations of the first and second zoeal stage were similar to4 and 5 days respectively, the megalopa appearing 10-18 days after hatching. Our results show that the zoeae of S. furcatus differ from those of other Mithracidae by possessing four setae on the proximal lobe of the coxal endite of the maxilla, instead of five, and by the presence of mid-dorsal setae on the third abdominal somite in the second zoeal stage, which are lacking in other mithracids. Larval descriptions for Stenocionops in two previous publications were attributed to the subspecies S. furcatus coelatus from the Caribbean. Larvae from Brazilian waters closely resemble one of these accounts, suggesting that this taxon extends beyond the West Indies and that the other description represents larvae of S. furcatus furcatus. Additional morphological details, not available previously, are provided.

Larval development of Epialtus bituberculatus H. Milne Edwards, 1834 (Crustacea : Decapoda : Brachyura : Majidae) with comments on majid larvae from the southwestern Atlantic

The larval development of the spider crab Epialtus bituberculatus H. Milne Edwards which Lives on rocky shores with algae such as Sargassum and Hypneia, is described. Larvae were obtained from ovigerous females collected in Ubatuba, State of São Paulo, Brazil. Rearing was carried out at 24 +/- 1 degreesC, with an average salinity of 35 parts per thousand. Larval development consists of two zoeal stages and one megalopa. Zoeal development was completed in 9.5 days. Analysis indicated that zoeae of E. bituberculatus are very similar to those of E. brasiliensis Dana and Acanthonyx scutiformis (Dana). Differences noted between these species pertain to the setation of the carapace, maxillule and second maxilliped. The main morphological features useful for identification are presented together with a summary of features that characterize larvae of majid subfamilies in Brazil. A key for the identification of southwestern Atlantic majid zoeae to the family level is provided.

Larval stages of Paradasygyius depressus (Bell, 1835) (Crustacea : Decapoda : Brachyura : Majidae) and a phylogenetic analysis for 21 genera of Majidae

All larval stages and the first crab instar of Paradasygyius depressus (Bell) were obtained in laboratory culture. Larval development consists of two zoeal stages, followed by the megalopa. Each larval stage is described in detail. Beginning with the first zoea, the duration of each stage was 4--7 (4.5 +/- 0.7), 4-5 (4.5 +/- 0.5), and 7 days, the megalopa and first crab instar appearing 11 +/- 1 and 15 days after hatching, respectively. A phylogenetic analysis of 21 genera of Majidae is provided based on 34 zoeal and three megalopal characters. The phylogenetic analysis resulted in four equally parsimonious trees 173 steps long (CI = 0.66, RI = 0.71, and RC = 0.47) supporting the monophyly of Oregoniinae, Majinae, and Inachinae (with the exclusion of Macrocheira de Haan incertae sedis). Based on general agreement of sister-group hypotheses, we provide sets of larval characters that define Oregoniinae, Majinae, and Inachinae. Our phylogenetic hypothesis suggests that Oregoniinae is the most basal clade within the Majidae, and Majinae and the clade (Epialtus H. Milne Edwards + Inachinae [excluding Macrocheira incertae sedis]) are sister taxa. Within Inachinae, all trees suggest that Inachus Weber and Macropodia Leach are sister taxa nested as the most derived clade, followed by Achaeus Leach, Pyromaia Stimpson, Paradasygyius Garth, Anasimus A. Milne-Edwards, and the most basal Stenorhynchus Lamarck. The sister-group relationships of the clade (Pisa Leach (Taliepus A. Milne-Edwards + Libinia Leach)), Mithrax Latreille and Microphrys H. Milne Edwards remained unresolved.

On the larval stages of Macrocoeloma diplacanthum (Decapoda : Brachyura : Majidae), and a review of mithracine phylogenetic aspects

Larval development of Macrocoeloma diplacanthum (Stimpson) consists of two zoeal stages, followed by the megalopa. Each larval stage is described in detail. The duration of the zoeal stages was 2-3 (2.4 +/- 0.5) and 3-4 (3.5 +/- 0.5) days for the first and second zoea, respectively, the megalopa phase appearing 6-8 (7.0 +/- 0.5) days after hatching. Unlike for other majids, zoeal stages of M. diplacanthum can be readily distinguished by their distended forehead with strong underlying muscle bands, undercut dorsal carapace spine, and spine on the terminal endopod segment of the first maxilliped. No other known mithracine or majid zoeae exhibit this combination of features. Our zoeal account of M. diplacanthum from Mexico is remarkably consistent with Floridian specimens previously described. However, we have found some differences between descriptions, which could be attributed to natural variation or inadequate description. Previous attempts to evaluate the relationships within Mithacinae have been based on larval characters widely distributed throughout Majidae and therefore are considered inadequate to infer sister-group relationships. The phylogenetic analysis of majids suggested that the position of Mithracinae is still uncertain, as is its monophyletic status. We recommend that additional characters, particularly of the megalopa phase, be sought for a better resolution of majid evolutionary history.

Searching for larval support for majoid families (Crustacea : Brachyura) with particular reference to Inachoididae Dana, 1851

We re-evaluated the larval support for families within majoids using the Wilcoxon signed-rank test with emphasis on Inachoididae. To accomplish our objectives, we added 10 new taxa, two of which are traditionally assigned to the family of special interest, to a previous larval database for majoids, and re-appraised the larval characters used in earlier studies. Phylogenetic analysis was performed with PAUP* using the heuristic search with 50 replicates or the branch-and-bound algorithm when possible. Multi-state transformation series were considered unordered; initially characters were equally weighted followed by successive weighting, and trees were rooted at the Oregoniidae node. Ten different topological constraints were enforced for families to evaluate tree length under the assumption of monophyly for each taxonomic entity. Our results showed that the tree length of most constrained topologies was not considerably greater than that of unconstrained analysis in which most families nested as paraphyletic taxa. This may indicate that the present larval database does not provide strong support for paraphyly of the taxa in question. For Inachoididae, although the Wilcoxon signed-rank test rejected a significant difference between unconstrained and constrained cladograms, we were unable to provide a single synapomorphy for this clade. Except for the conflicting position of Leurocyclus and Stenorhynchus, the two clades correspond to the traditional taxonomic arrangement. Among inachoidids, the clade (Anasimus (Paradasygyius (Collodes + Pyromaia))) is supported, whereas for inachids, the clade (Inachus (Macropodia + Achaeus)) is one of the most supported clades within majids. As often stated, only additional characters will provide a better test for the monophyly of Inachoididae and other families within Majoidea.

The first zoeal stage of the genus Cronius (Brachyura, Portunidae) from the Brazilian coast, hatched in a laboratory

This study describes the first zoeal stage of Cronius ruber and Cronius tumidulus. The zoeae can be distinguished using the setation of the cephalic appendages and the lateral process on the abdominal somite.

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 ) 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 24degreesC 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.

Bathymetric distribution of brachyuran crab (Crustacea, Decapoda) communities on coastal soft bottoms off southeastern Brazil

The communities of brachyuran crabs living on soft bottoms off Ubatuba in SE Brazil were studied with respect to their structure, bathymetric distribution, composition, diversity and indices of similarity. The data were analyzed using multivariate techniques of classification and ordination. Most of the individuals caught during summer were the swimming crab Portunas spinicarpus at the 35 m isobath, which contributed to the much-decreased diversity in this season and site. Multivariate analysis indicated that the species were distributed according to depth and also in relation to environmental gradients.