Ecological distribution and population structure of Acantholobulus schmitti (Rathbun, 1930) (Crustacea, Decapoda, Xanthoidea) on the southeastern Brazilian coast

Os objetivos deste estudo foram analisar a distribuição ecológica e a estrutura populacional de A. schmitti no litoral sudeste brasileiro. Os caranguejos foram coletados, mensalmente, de janeiro de 1998 a dezembro de 1999 nas enseadas: Ubatumirim (UBM), Ubatuba (UBA) e Mar Virado (MV), onde também foram obtidas amostras de água e sedimento para análise dos fatores ambientais. A maior abundância de A. schmitti foi verificada em UBM (224), seguida por UBA (154) e MV (23) e não apresentou associação com os fatores ambientais analisados. O motivo da baixa abundância desses caranguejos em MV pode ser a alta ação de ondas que movimenta o material biodetrítico acumulado no fundo e, frequentemente, remove pequenos caranguejos de seus abrigos entre fragmentos de conchas. Os indivíduos foram 269 machos e 132 fêmeas, das quais apenas 4 eram ovígeras. O recrutamento juvenil ocorreu o ano todo, sendo menos intenso na primavera. A maior abundância de indivíduos, bem como as fêmeas ovígeras, ocorreu em 1999, quando a entrada da Água Central do Atlântico Sul (ACAS) foi mais intensa do que no ano anterior. Esta influência ambiental pode ser o principal fator modulador para esta população.This investigation analyzed the ecological distribution and population structure of A. schmitti on the southeastern coast of Brazil. Crabs were sampled monthly from January 1998 to December 1999 at the following bays: Ubatumirim (UBM), Ubatuba (UBA) and Mar Virado (MV). Water and sediment samples were also collected from all sampling sites for an analysis of environmental factors. Acantholobus schmitti was most abundant at UBM (224), followed by UBA (154) and MV (23) but its abundance showed no association with the environmental factors analyzed. The low abundance of these crabs in MV may be due to the high wave action that moved biodetritic material accumulated on the bottom and frequently removed small crabs from their sheltered positions among the shell fragments. The individuals captured included 269 males and 132 females, of which only 4 specimens were brooding females. Juvenile recruitment occurred throughout the year, but was less intense in the spring. The major abundance of individuals as well as of ovigerous females occurred during 1999, when the entrance of the South Atlantic Central Waters (SACW) was stronger than in previous year. This environmental influence could be the main factor modulating this population

Estrutura populacional do siri candeia Achelous spinicarpus (Crustacea, Portunoidea) no litoral norte paulista

The swimming crab Achelous spinicarpus is commonly captured as a “by catch” of the shrimp fishery. This study evaluated some aspects of the population structure of A. spinicarpus, such as sex-ratio and size classes’ frequency distribution. A shrimp trawler equipped with double-rig nets was used to capture the swimming crabs at Ubatuba and Caraguatatuba areas, northern coast of São Paulo state, Brazil. A total of 1,057 individuals were collected in Ubatuba, including 598 males (525 juveniles and 73 adults) and 459 females (379 juveniles and 80 adults, including 15 ovigerous crabs). In Caraguatatuba 5,112 individuals were collected, of which 3,138 males (2,638 juveniles and 500 adults) and 1,974 females (1,746 juveniles and 228 adults, including 29 ovigerous crabs). The sex-ratio favors the number of males in both regions, probably because females have the habit of occupying deeper regions. The size classes’ frequency distribution shows polymodality for both sexes, except for males in Ubatuba. This is the result of some age groups among the juveniles, which migrate to shallower areas, being affected by the fishing activity. Adults have the habit of staying in deeper areas characterized by colder waters.Keywords: Brachyura, sex-ratio, Decapoda, bycatch, size distribution.O siri candeia, Achelous spinicarpus, é comumente capturado como “by catch” da pesca camaroeira. Este estudo avaliou alguns aspectos de sua estrutura populacional, como razão sexual e distribuição de frequência em classes de tamanho. Para coletar os siris, foi utilizado um barco de pesca camaroeiro equipado com redes “double rig” nas áreas de Ubatuba e Caraguatatuba, litoral norte do estado de São Paulo, Brasil. Um total de 1.057 indivíduos foi coletado em Ubatuba, incluindo 598 machos (525 juvenis e 73 adultos) e 459 fêmeas (379 juvenis e 80 adultas, incluindo 15 ovígeras). Em Caraguatatuba, 5.112 indivíduos foram coletados, dos quais 3.138 machos (2.638 juvenis e 500 adultos) e 1.974 fêmeas (1.746 juvenis e 228 adultas, incluindo 29 ovígeras). A razão sexual favoreceu o número de machos em ambas as áreas, provavelmente devido ao hábito de as fêmeas ocuparem regiões mais profundas. A distribuição de frequência em classes de tamanho apresentou polimodalidade para ambos os sexos, exceto para machos em Ubatuba. Isso é resultado de alguns grupos etários entre os juvenis, os quais migram para áreas mais rasas, sendo afetados pela atividade pesqueira. Os adultos permanecem em áreas mais profundas, caracterizadas por águas frias.Palavras-chave: Brachyura, razão sexual, Decapoda, by catch, distribuição de tamanho

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

Using the attention cascade model to computationally account for the age differences in an Attentional Blink (AB) task

The attention cascade model (Shih, 2008) is a general, mathematical model of attention and working memory. It is applied here to characterize cognitive aging

Relative growth of Petrochirus diogenes (Linnaeus, 1758) (Crustacea, Anomura, Diogenidae) in the Ubatuba region, São Paulo, Brazil

O presente trabalho tem por objetivo investigar o crescimento relativo e a heteroquelia de Petrochirus diogenes. Os indivíduos foram coletados com um barco de pesca comercial, equipado com duas redes do tipo double-rig, durante o período de 1993 a 1996, na região de Ubatuba, SP. Os indivíduos foram pesados e mensurados na região do escudo cefalotorácico e dos própodos quelares. Os dados foram plotados em função do comprimento do escudo e ajustados na equação y = a.x b. Foram obtidos 479 exemplares (307 machos e 172 fêmeas). Nas relações do escudo, obteve-se um crescimento isométrico para ambos os sexos. As relações do quelípodo direito mostraram diferentes padrões de crescimento, enquanto o esquerdo apresentou uma alometria positiva para ambos os sexos. Para os ermitões, as mudanças em relação as partes ou apêndices não são tão visíveis como nos braquiúros, impossibilitando a detecção das alterações alométricas com precisão. Na análise da heteroquelia, observou-se que P. diogenes apresenta o quelípodo direito maior em ambos os sexos, no entanto, os machos atingem tamanhos superiores. A presença de heteroquelia pode beneficiar o ermitão durante as interações agonísticas e nos comportamentos pré-copulatórios.The purpose of this paper is to investigate the relative growth and heterochely in the hermit crab Petrochirus diogenes. Hermit crabs were collected in the Ubatuba region, SP, from 1993 to 1996; using a commercial fishing boat equipped with two double-rig nets. Body mass of each individual was weighed and their cephalothoracic shield and chelar propodus size were measured. Body mass and chelar propodus size were regarded as dependent variables and plotted against length of cephalothoracic shield according to the allometric equation y = a.x b. A total of 479 individuals were obtained being 307 males and 172 females. Cephalothoracic shield width follows an isometric growth for both sexes. Otherwise, right cheliped dimensions show different relative growth patterns and left cheliped ones present a positive allometry in males and females. Unlike brachyurans, ontogenetic changes in the growth rate of chelar propodus are not clearly discernible, which prevents the accurate detection of allometric variations. In both sexes, the right cheliped is larger than the right one. Cheliped size is a sexual dimorphic feature with males bearing larger chelipeds than females. Heterochely may be particularly adaptive in agonistic interactions and precopulatory behaviour in P. diogenes.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Fecundity and fertility in a freshwater population of the neotropical amphidromous shrimp Macrobrachium acanthurus from the southeastern Atlantic

The neotropical amphidromous shrimp Macrobrachium acanthurus is one of various freshwater crustaceans heavily exploited in the southwestern Atlantic. Fecundity (n degrees early embryos female(-1)) was examined during 2007 at four different localities (Iguape, Registro, Sete Barras, and Eldorado) along a stretch of river extending over 85 km (Ribeira de Iguape, Sao Paulo State, Brazil). Also, fertility (n degrees hatched larvae female(-1)) was examined at one locality (Registro) during 2009-2010. Fecundity (mean +/- SD: 5191 +/- 2635; range: 1086-13,014 embryos female(-1)) did not vary throughout the segment of river studied. Fecundity increased with female body size (carapace length, CL). However, fecundity scaled negatively with shrimp body size; females produce disproportionably fewer eggs with a unit increase in CL. The conditions explaining the negative allometric relationship between fecundity and female body size in M. acanthurus remain to be addressed. Nevertheless, natural food constraints limiting the ability of large but not small females to acquire enough resources to produce and fill their gonads with oocytes represents a plausible explanation for the negative scaling of fecundity with body size. Fertility varied between 545 and 12,465 hatched larvae female(-1) with an average (+/- SD) of 3981 (+/- 2693) and increased isometrically with a unit increase in female body size. M. acanthurus has an average fecundity and fertility that represents one of the extremes regarding the trade-off between fecundity/fertility and egg-size reported for caridean shrimps. All of this information needs to be considered in assessing shrimp stocks and establishing a sustainable management plan for this exploited species in the southwestern Atlantic.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

First reported occurrence of a heteromorph antennule in the freshwater prawn Macrobrachium acanthurus (Wiegmann, 1836) (Decapoda, Caridea)

In contrast with holometabolous insects, crustaceans undergo periodic shedding of the old exoskeleton (ecdysis) throughout their adult life. The occurrence of successive moultings indicates that crustaceans can regenerate lost or damaged limbs, including the eye (Ventura et al., 2018), through the moulting cycle (Chang & Mykles, 2011). The eyes, however, are not always perfectly regenerated, resulting in an anomaly known as heteromorphosis, which is the regeneration of an appendage in a foreign location, generally as a response to a natural injury or artificial ablation (Bliss, 1960; Nevin & Malecha, 1991). Heteromorphic development, although considered rare, has been acknowledged since 1864 (Milne-Edwards, 1864), and was summarized for decapods by Von Buddenbrock (1954), who states that the most striking type of heteromorphosis was the growth of an appendage similar to an antenna or antennule in the expected position of one or both eyes.Fil: Rodrigues, Maria M.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil. Federal Institute of Education, Science, and Technology of Espírito Santo State; BrasilFil: Lopez, Laura Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Bertini, Giovana. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi