Fernando L. Mantelatto

Fecundity of the crab Callinectes ornatus Ordway, 1863 (Decapoda, Brachyura, Portunidae) from the Ubatuba region, São Paulo, Brazil

[The objective of the present study was to characterize the fecundity of Callinectes ornatus from the northern coast of Sao Paulo, Brazil. To study the fecundity and its relationships to size, brood weight, and egg size, the ovigerous females were collected at 2-month intervals for two consecutive years (January, 1991 to November, 1992) in the Ubatuba region using a fishing boat equipped with an otter-trawl type of net. After collecting, the animals were screened, bagged, labeled, and stored frozen. Only data from 38 females carrying early stage eggs were considered. In the laboratory, the specimens were thawed at room temperature, the pleopod structure with the egg mass was removed and the eggs were carefully removed from the pleopods. The samples were then fixed in 10% formalin and stored in 70% ethanol, until the time for processing. Processing followed the method of Hines (1982, 1988). Following the frequency determination of carapace width and fecundity, mean egg number, mean volume and mean dry weight of brooded egg mass were determined for each class obtained. Data were analyzed by regressions of log-log transformations for allometric plots (Y = aXb) of reproductive variables versus carapace width. Carapace width was one of the main factors for the determination of fecundity, which ranged 171 570 ± 94 634 eggs, with females of the same size class presenting a wide amplitude of variation. This supports the hypothesis that portunid females present staggered spawning, possibly presenting more than one period of reproduction within one year. The present species showed lower fecundity than the remaining portunids studied, but they did show a rapid and efficient embryonic development, presumably capable of assuring reproductive success., The objective of the present study was to characterize the fecundity of Callinectes ornatus from the northern coast of Sao Paulo, Brazil. To study the fecundity and its relationships to size, brood weight, and egg size, the ovigerous females were collected at 2-month intervals for two consecutive years (January, 1991 to November, 1992) in the Ubatuba region using a fishing boat equipped with an otter-trawl type of net. After collecting, the animals were screened, bagged, labeled, and stored frozen. Only data from 38 females carrying early stage eggs were considered. In the laboratory, the specimens were thawed at room temperature, the pleopod structure with the egg mass was removed and the eggs were carefully removed from the pleopods. The samples were then fixed in 10% formalin and stored in 70% ethanol, until the time for processing. Processing followed the method of Hines (1982, 1988). Following the frequency determination of carapace width and fecundity, mean egg number, mean volume and mean dry weight of brooded egg mass were determined for each class obtained. Data were analyzed by regressions of log-log transformations for allometric plots (Y = aXb) of reproductive variables versus carapace width. Carapace width was one of the main factors for the determination of fecundity, which ranged 171 570 ± 94 634 eggs, with females of the same size class presenting a wide amplitude of variation. This supports the hypothesis that portunid females present staggered spawning, possibly presenting more than one period of reproduction within one year. The present species showed lower fecundity than the remaining portunids studied, but they did show a rapid and efficient embryonic development, presumably capable of assuring reproductive success.]

Reproductive biology and moulting cycle of the crab Callinectes ornatus (Decapoda, Portunidae) from the Ubatuba region, Sao Paulo, Brazil

Departamento de Biologia Faculdade de Filosofia Universidade de Sao Paulo, Av. Bandeirantes, 3900, CEP 14040-901, Ribeirao Preto, SP

Molecular phylogeny of the freshwater prawn genus Macrobrachium (Decapoda, Palaemonidae), with emphasis on the relationships among selected American species

The genus Macrobrachium Bate, 1868 is one of the best examples of widespread crustacean genera distributed globally throughout tropical and subtropical waters. Previous investigators have noted the systematic complexity of the group, and have suggested rearrangements within the family Palaemonidae. Our phylogenetic analysis of new mitochondrial DNA sequences of 58 species of Macrobrachium distributed mainly in America support the hypothesis of monophyly of this genus, if Cryphiops Dana, 1852 is accepted as a generic synonym. We concluded that the independent evolution of different types of life cycle (abbreviated larval development – ALD and extended larval development – ELD) must have occurred more than once in the history of the group. Similarly, we also concluded that the current type species of the genus, Macrobrachium americanum Bate, 1868, should not be considered valid, as previously proposed. The synonymy of two members of the ‘olfersi’ species complex (M. birai Lobao, Melo & Fernandes, 1986 and M. holthuisi Genofre & Lobao, 1978) with M. olfersi (Wiegmann, 1836) was confirmed. Similar results were found in comparing M. petronioi Melo, Lobao & Fernandes, 1986 and M. potiuna (Muller, 1880), in which the genetic divergence placed M. petronioi within the level of intraspecific variation of M. potiuna. The taxonomic status of the genus Cryphiops, as well as theories on the origin of Macrobrachium, is also called into question.

Modulation by ammonium ions of gill microsomal (Na+,K+)-ATPase in the swimming crab Callinectes danae: a possible mechanism for regulation of ammonia excretion.

The modulation by Na(+), K(+), NH(4)(+) and ATP of the (Na(+),K(+))-ATPase in a microsomal fraction from Callinectes danae gills was analyzed. ATP was hydrolyzed at high-affinity binding sites at a maximal rate of V=35.4+/-2.1 Umg(-1) and K(0.5)=54.0+/-3.6 nM, obeying cooperative kinetics (n(H)=3.6). At low-affinity sites, the enzyme hydrolyzed ATP obeying Michaelis-Menten kinetics with K(M)=55.0+/-3.0 microM and V=271.5+/-17.2 Umg(-1). This is the first demonstration of a crustacean (Na(+),K(+))-ATPase with two ATP hydrolyzing sites. Stimulation by sodium (K(0.5)=5.80+/-0.30 mM), magnesium (K(0.5)=0.48+/-0.02 mM) and potassium ions (K(0.5)=1.61+/-0.06 mM) exhibited site-site interactions, while that by ammonium ions obeyed Michaelis-Menten kinetics (K(M)=4.61+/-0.27 mM). Ouabain (K(I)=147.2+/-7.microM) and orthovanadate (K(I)=11.2+/-0.6 microM) completely inhibited ATPase activity, indicating the absence of contaminating ATPase and/or neutral phosphatase activities. Ammonium and potassium ions synergistically stimulated the enzyme, increasing specific activities up to 90%, suggesting that these ions bind to different sites on the molecule. The presence of each ion modulates enzyme stimulation by the other. The modulation of (Na(+),K(+))-ATPase activity by ammonium ions, and the excretion of NH(4)(+) in benthic crabs are discussed.

Population structure and reproductive period of the tropical hermit crab Calcinus tibicen (Decapoda : Diogenidae) in the region of Ubatuba, São Paulo, Brazil

ABSTRACT The population of the hermit crab Calcinus tibicen in the Ubatuba region was studied with emphasis on seasonal abundance, seasonal size-frequency distribution, sex-ratio, and reproductive period based on the percentage of ovigerous females. The animals were collected at 2-month intervals for 2 consecutive years (from January 1993 to November 1994). Total mean animal size in shield length was 5.14 ± 1.23 mm for males, 4.23 ± 0.79 mm for females, and 4.53 ± 0.60 for ovigerous females. A discontinuity in reproduction was observed, with an absence of ovigerous females in July (winter) and a high incidence from September to May (spring to autumn). Calcinus tibicen is sexually dimorphic in relation to size, with a higher growth rate in males. The sex-ratio pattern changes with season, indicating that it is more a function of season or habitat than of size.

Reproductive Potential of the Hermit Crab Calcinus Tibicen (Anomura) From Ubatuba, Sao Paulo, Brazil

The purpose of this study was to determine egg production by Calcinus tibicen, as well as the influence of shell type on fecundity using morphometric relationships. Ovigerous females were collected at 2-month intervals for 2 consecutive years (from January 1993 to November 1994) along the rocky shore of Ubatuba. The number of eggs carried by individuals of several sizes (shield length), condition of development, and egg size were determined. A total of 89 specimens were analyzed. Individual fecundity ranged from 193 (SL = 5.12 mm) to 6,785 eggs (SL = 4.25 mm) and mean fecundity was 1,719.25 ? 1,199.43 eggs. The lowest mean fecundity values were observed during the spring. The number of eggs produced per female was large and varied widely among size classes. This fact may probably be attributed to multiple or fragmented spawnings and primiparous or multiparous females during the reproductive cycle. Shells of 5 gastropod species were occupied by ovigerous females of C. tibicen. Stramonita haemastoma was the most occupied shell, although Tegula viridula presented the best associations, calculated by regression analysis between the dimensions of the shell and of ovigerous females and fecundity. This shows that shell type can influence the reproductive potential of ovigerous females, but not to the point of interrupting it.

Shell selection by the tropical hermit crab Calcinus tibicen (Herbst, 1791) (Anomura, Diogenidae) from Southern Brazil

Abstract Shell preferences, as shown by laboratory choice experiments, are important determinants of shell utilization under natural conditions. Size and shell species preferences of the hermit crab Calcinus tibicen were determined for the three most occupied [ Stramonita haemastoma (Linnaeus, 1767), Leucozonia nassa (Gmelin, 1791) and Pisania auritula (Link, 1807)] shell species along the rocky shore of Grande beach, Ubatuba, Brazil, taking into account the sexual condition of the individuals. All experiments were conducted under laboratory conditions using a glass aquarium where the hermit crabs (independent on their sex condition) were placed naked with a large number of shells of appropriate sizes. The chosen shells were determined after 72 h. The preferred shell species and size were determined by regression analysis. C. tibicen showed no significant choice among the three gastropod shell species. Shell size experiments revealed that the preference of hermit crabs was strongly associated with shell weight and internal volume. The shell adequacy index (SAI) decreased with increasing crab size and showed that the population was occupying relatively adequate shells (SAI=0.99±0.19). The present data lead us to conclude that shell selection by hermit crabs involves individual and sexual preferences taking into account the shell features that best provide protection and survival, principally in the rocky intertidal studied area, characterized by intense wave action.

Population dynamics of the hermit crab Paguristes erythrops (Diogenidae) from Anchieta Island, southern Brazil

The population of Paguristes erythrops (Crustacea: Anomura) was studied based on seasonal abundance, size-frequency distribution, sex ratio and reproductive period (percentage of ovigerous females). Specimens were collected monthly by SCUBA diving in the infralittoral area of Anchieta Island, Ubatuba. A total of 543 individuals was analysed. Animal size (minimum and maximum shield length, respectively was 1.7 and 11.8 mm for males, 1.7 and 10.3 mm for non-ovigerous females, and 3.2 and 7.8 mm for ovigerous females. The sex ratio was 0.91:1. Sexual dimorphism was recorded by the presence of males in the largest size-classes. The absence of ovigerous females during winter months (June to August) and their high incidence from January to March indicated discontinuity in the reproductive cycle, suggesting that females become ovigerous and breed in the summer, with the spawning period lasting from spring to autumn. This strategy of reproduction probably was based on competition with other coexisting species in this area.

Interpopulation Comparison of Reproduction of the Atlantic Shrimp Hippolyte obliquimanus (Caridea: Hippolytidae)

Abstract The genus Hippolyte is represented by typically small shrimps with intriguing mechanisms of reproduction. In order to study possible variability in reproductive aspects among different populations, we conducted an exhaustive comparative study of H. obliquimanus from South (Brazil) and Central American (Costa Rica) waters. The study focuses on fecundity and reproductive output. Mean size of ovigerous females was significantly larger, and both mean reproductive output and mean fecundity were significantly higher in specimens from Costa Rica then in those collected in Brazil. Embryo volume was significantly smaller in the Costa Rican population, and in both populations embryos doubled their volume during embryogenesis. We discuss and compare our findings with the information available regarding H. obliquimanus and other hippolytid shrimp. The reproductive traits of both populations of H. obliquimanus show some important differences which may reflect adaptations to local environmental conditions, demonstrating a high plasticity of reproductive features of the species in Brazilian and Costa Rican waters.

Relative growth and sexual dimorphism of the South Atlantic hermit crab Loxopagurus loxochelis (Anomura, Diogenidae) from Ubatuba, Brazil

Some morphometric relationships and biometric aspects were studied in the hermit crab Loxopagurus loxochelis (Moreira, 1901) with the purpose of describing its relative growth and finding the size where sexual maturity is reached. Specimens were collected monthly from September 1995 to August 1997 in the Ubatuba region using double-rig trawl nets. A total of 1084 specimens (625 males and 459 females) was analysed. In this species, sexual dimorphism is particularly evident in chela dimensions. Differences between males and females were found in the left propodus length versus cephalothoracic shield length (CSL) and wet weight (WW) versus CSL relationships. Males showed a high positive allometry in chela growth, while females were close to isometry/negative allometry. The size at which a clear differentiation occurred in the growth of the propodus length and in the increase in weight of males and females was between 4.5 and 6.0mm CSL, suggesting that size at which sexual maturity is reached.