Histological and Histochemical Dynamism of Oogenesis in the Cinnamon River Prawn Macrobrachium acanthurus (Caridea: Palaemonidae) Induced by Eyestalk Ablation.

Macrobrachium acanthurus is a caridean prawn native to Brazil, and studying techniques to assist in its cultivation is important due to economic interest in it. Eyestalk ablation is commonly used to promote ovarian development and maturation of captive crustaceans, but it can have possible consequences on fertility and brood quality. Histological and histochemical dynamism of oogenesis was analyzed under control (non-ablated females) and unilateral eyestalk ablated females. Females with ovaries in the spent stage of gonadal development were divided into two treatments: unilaterally ablated and non-ablated. A second experiment with the same treatments was conducted using females with mature gonads. Histological and histochemical analyses of the ovaries indicated that the ablation did not affect oogenesis based on ovarian structure, oocyte size, histochemical properties, and atretic oocytes. Ovarian maturation was not accelerated by ablation, either. Survival, nuptial molting, and spawning were also unaffected. From an applied point of view, unilateral eyestalk ablation is not needed in M. acanthurus farming because it does not improve reproductive performance.

Effect of environmental factors on the abundance of decapod crustaceans from soft bottoms off southeastern Brazil.

This study investigated the importance of variations in environmental factors affecting the abundance patterns of decapods on the southeastern Brazilian coast. Sampling was carried out monthly from January 1998 through December 1999 in Ubatumirim and Mar Virado, Ubatuba region, using a commercial shrimp fishing boat equipped with double-rig nets. Six areas adjacent to rocky shores were chosen. Bottom-water samples were collected using a Nansen bottle, to measure the temperature and salinity. Sediment samples were also obtained by means of a Van Veen grab, for determination of texture and organic-matter content. The association of environmental factors with species abundance was evaluated by Canonical Correspondence Analysis (α = 0.05). Forty-one species of Decapoda were used in the multivariate analysis. The analysis indicated that sediment texture (phi) and bottom temperature were the main factors correlated (p < 0.05) with the spatial and temporal abundance of the species. Considering the study region as faunal transition zone, including a mixture of species of both tropical and subantarctic origin, the species responded differently to environmental factors, mainly temperature. It is conceivable that the decapods adjust their distribution according to their intrinsic physiological limitations, possibly as a result of the available resources.

A new species of Macrothrix (Crustacea, Branchiopoda, Macrothricidae) from the Neotropics with description of the marthae-group.

Publications of the last three decades demonstrated the existence of some compact species groups within the Macrothrix Baird genus (Cladocera: Macrothricidae). Many species were included in hirsuticornis-group, laticornis-group, rosea-triserialis-group and paulensis-group, but not in Macrothrix marthae group. It has a peculiar set of morphological traits not observed in any other species, so far. Studying material from Ribeira de Iguape River, Brazil, we found some individuals that resemble M. marthae, which represent a new species described herein. Macrothrix lourdesae sp. nov shares with M. marthae similar morphology of Inner Distal Lobe setae and the same modifications on the fourth and fifth limbs. The main difference between them is related to the number of setae in the exopodite of the third limb. Observing the high number of morphological traits shared, it is possible to indicate that M. lourdesae sp. nov and M. marthae form a separate species group within the genus.

Is Potimirim potimirim (Crustacea, Decapoda, Atyidae) a protandric hermaphrodite species? Behavioral and morphological aspects of the reproductive system.

We evaluated the mating behavior of Potimirim potimirim in the laboratory based on the assumption that this caridean might be hermaphroditic. We also performed histology and scanning electron microscopy analyses of the reproductive system of females, males, and differentiated individuals. The mating experiments produced three behavioral stages, namely, interaction, lateral positioning, and copulation (which did not necessarily occur in this sequence). The hypothesis of a random pure searching mating was corroborated by the lack of male courtship, postcopulatory guarding, and the high aggregation of individuals. Three macroscopic ovarian stages were recorded in adult females: rudimentary, developing and mature. Secondary vitellogenesis begins at the developing stage, producing mature yolk. The male reproductive system is formed by testes and the vasa deferentia (VD), that is divided into three regions: proximal, middle, and distal. The proximal VD has a typhlosole that produces a thin layer of type II secretion around the central spermatozoa mass immersed in a type I secretion. External and adherent type III secretion is produced from the MVD to DVD, and both compound the primordial spermatophore. Potimirim potimirim has a gonochoric reproductive system and mating behavior and its sexual system does not fit into any of the previously described protandric systems.

Modulating factors of the abundance and distribution of Achelous spinimanus (Latreille, 1819) (Decapoda, Portunoidea), a fishery resource, in Southeastern Brazil.

This is the first study to examine how different environmental factors may influence the distribution of swimming crab Achelous spinimanus across geographically distant and distinct habitats. We analyzed the influence of bottom water temperature and salinity, sediment texture and organic matter content on the spatiotemporal distribution of A. spinimanus. The crabs were collected from January 1998 until December 1999 by trawling with a shrimp fishing boat outfitted with double-rig nets. The sampling took place in Ubatumirim (UBM), Ubatuba (UBA) and Mar Virado (MV) bays, located in the northern coast of São Paulo State (Brazil). These three bays were chosen as they differed in many physiographic features. We captured 1,911 crabs (UBM = 351; UBA = 1,509; MV = 51), and there were significant differences in abundance between bays and between stations. The distribution of A. spinimanus was primarily associated with sediment features: abundance was higher in stations with sandy sediments classified as gravel, very coarse sand, and intermediate sand. Portunoidea usually burrow in the sediment for protection against predators and to facilitate the capture of fast prey. In addition, the station with the highest abundance of A. spinimanus was also naturally protected from fishing activities, and composed of heterogeneous sediment, in terms of grain size. Hence, the combination of a favorable sediment heterogeneity and protection from fishery activities seemed to be effective modulators of the abundance and distribution of A. spinimanus in these bays.

Morphometry of the crab Hexapanopeus schmitti (Decapoda: Xanthoidea) on the northern coast of the state of São Paulo, Brazil

A morphometric study of the xanthoid crab Hexapanopeus schmitti was carried out, using the allometric method. Samples were taken monthly for two years (1998-1999) in the Ubatuba region, northern coast of São Paulo, Brazil. Sex and size were assessed for each specimen, and all crabs were measured to obtain their carapace width (CW) and length (CL), abdomen width (AW) of females, major cheliped propodus length and height (PL and PH), and gonopod length (GL) of males. A total of 301 crabs were analyzed, 209 males and 92 females. The CWs of the crabs ranged from 2.5 to 9.8 mm for males and from 2.8 to 9.4 mm for females. The relative growth equation (y=axb) based on the relationship between GL and CW suggested that males reach their morphological sexual maturity near 6.1 mm CW. In females, the estimated size at 50 % maturity was 4.8 mm CW, based on the relationship of AW vs. CW. Males reach larger sizes than females, which probably favors their ability to guard the females during courtship. In approximately 83 % of the crabs (n= 371), disregarding sex, theright cheliped was larger.

Estudiamos la alometría en el cangrejo Hexapanopeus schmitti. Los ejemplares (209 machos y 92 hembras) fueron recolectados mensualmente, durante dos años en Ubatuba, al norte de São Paulo, Brasil. Medimos ancho (CW) y largo del caparazón (CL), ancho del abdomen (AW) de las hembras, largo y alto de los quelípedos (PL y PH) y longitud del gonopodio de los machos (GL). Los CWs tuvieron un ámbito de 2.5-9.8 mm para los machos y 2.8-9.4 mm para las hembras. La ecuación de crecimiento relativo (y=axb) basada en la relación GL vs. CW, sugirió que los machos alcanzan su madurez sexual morfológica aproximadamente a los 6.1 mm CW. En las hembras, la talla estimada al alcanzar un 50 % de madurez fue 4.8 mm CW, según la relación AW vs. CW. Los machos alcanzan tallas mayores, lo cual probablemente permite una mayor habilidad para defender a la hembra durante el cortejo. Laheteroquelia fue evidente (incidencia del 83 %), siendo el quelípedo derecho más grande en ambos sexos.

Relative growth and sexual maturity of the stone crab Menippe nodifrons Stimpson, 1859 (Brachyura, Xanthoidea) in southeastern Brazil

The relative growth and size at onset of morphological sexual maturity of the stone crab Menippe nodifrons were investigated. A total of 399 crabs was captured on Praia Grande and Tenório beaches at Ubatuba. Carapace width (CW) and length, cheliped propodus length and height, abdomen width in females, and gonopod length in males were recorded. In females, the abdominal width showed negative allometry for juveniles and positive allometry for adults; the puberty molt occurred at 31.6 mm CW. In males, the size at onset of morphological sexual maturity was estimated as 29.7 mm CW; the gonopod growth showed positive allometry for juveniles, and an isometric relationship for adults. The gonopod length and the abdominal width were the most appropriate morphometric variables to estimate size at onset of sexual maturity in this stone crab.

O objetivo do presente estudo foi determinar o crescimento relativo e a maturidade sexual morfológica de Menippe nodifrons. As coletas foram realizadas na Praia Grande e Tenório, Ubatuba, São Paulo. Os caranguejos foram separados quanto ao sexo e mensurados na região da largura (LC) e comprimento da carapaça, comprimento e altura dos própodos quelares direito e esquerdo, largura do abdome (LA) nas fêmeas e comprimento do gonopódio (CG) nos machos. Obteve-se 399 indivíduos, sendo 195 machos e 204 fêmeas. Os machos atingiram a maturidade sexual com 29,7mm LC e as fêmeas com 31,6mm LC. Para as fêmeas a melhor relação que indicou a muda da puberdade foi LA vs. LC, sendo que o crescimento foi alométrico negativo na fase jovem e alométrico positivo após a muda da puberdade. Para os machos foi CG vs. LC evidenciando crescimento alométrico positivo na fase jovem e isométrico na fase adulta.

Composição e abundância dos caranguejos (Decapoda, Brachyura) nas regiões de Ubatuba e Caraguatatuba, litoral norte paulista, Brasil / Composition and abundance of the crabs (Decapoda, Brachyura) off Ubatuba and Caraguatatuba, northern coast of São Paulo, Brazil

O objetivo do presente estudo foi caracterizar a composição e a abundância dos caranguejos no infralitoral não-consolidado de duas regiões (Ubatuba e Caraguatatuba) do litoral norte paulista, Brasil. Em cada região foram realizadas coletas mensais em sete profundidades, durante o período de dois anos (Julho/ 2001 a Junho/ 2003), utilizando-se um barco de pesca equipado com duas redes do tipo "double-rig". Obteve-se um total de 30.231 caranguejos (13.305 em Ubatuba e 16.926 em Caraguatatuba), abrangendo nove superfamílias (Dromioidea, Homoloidea, Calappoidea, Leucosioidea, Majoidea, Parthenopoidea, Portunoidea, Xanthoidea e Pinnotheroidea), 16 famílias, 29 gêneros e 44 espécies. Do total de espécies coletadas, 31 foram comuns para as duas regiões. Dentre as duas regiões, Caraguatatuba apresentou a maior riqueza de espécies (42) e o maior índice de diversidade (2,93 bits/inds.). Para ambas regiões, Callinectes ornatus, Hepatus pudibundus e Libinia spinosa, foram os braquiúros mais abundantes. Tais resultados indicam que as duas regiões analisadas apresentam ambientes propícios para o desenvolvimento dos braquiúros, possibilitando uma alta biodiversidade.