Abstract We determined the infestation rate of Probopyrus sp. in populations of Palaemon pandaliformis (Stimpson, 1871) and P. northropi (Rankin, 1898) in the Ubatumirim River, localized in a mangrove ecosystem on Ubatumirim Beach, northern coast of the state of São Paulo, Brazil. Samplings were carried out monthly from April 2003 to March 2004. Monthly prevalence varied from 0 to 4.94 % for P. pandaliformis, and from 0 to 4.54 % for P. northropi. This is the first record of Probopyrus sp. infesting the studied species in this region. Species of Probopyrus (Giard and Bonnier, 1888) seem to have a high plasticity with regard to palaemonid hosts, as they can be parasites of shrimps in both Palaemon (Fabricius, 1798) and Macrobrachium (Spence Bate, 1868). The linear relationships between the parasite and host sizes suggest that the parasite infests both hosts early in their development. We concluded that the infestation of Probopyrus sp. has little impact on Palaemon populations, mostly due to the low prevalence of infestation.

Abstract Aegla charon n. sp. is endemic to the “Lago Subterrâneo” cave from the Alto Ribeira karst region, southeastern Brazil. The most remarkable morphological trait observed in the new species was the presence of partially developed pair of uniramous pleopods 2‒5 in adult male specimens, whereas the absence of these pleonal appendages is the general condition in this sex in Aegla Leach, 1820. Some of the pleopods are even morphologically similar to those typically observed in adult females in that they may also be two-segmented, only shorter in size. The pigmented area of the cornea is slightly reduced, which is probably a troglomorphic adaptation to subterranean habitats. Aegla charon n. sp. is also the only obligate cave-dwelling aeglid known to inhabit lentic subterranean waters. A key to all species from the Alto Ribeira karst area is provided.

Abstract Allometric growth of chelae dimensions was analyzed to assess the average size at the onset of morphometric maturity (ASOMM) and sexual dimorphism regarding the pair of chelae in the Aegla castro. Both adult males and females are heterochelous with the most robust chela occurring predominantly on the left side. Both chelae are larger in males than they are in females of similar size, thus characterizing these structures as sexually dimorphic traits. The ASOMM estimated for males and females were 10.91 and 10.03 mm of carapace length (CL), respectively. The increase in variability of chelae dimensions in post-pubertal males led to the recognition of two morphotypes (I and II). Temporal variation in the proportions of morphotype II males in relation to females showing late ovarian development was synchronous, making the sexually functional nature of these males evident. The average size at the onset of functional maturity (ASOFM) estimated for males (based on the transition from morphotype I to morphotype II) and females (based on the detection of late ovarian development or eggs) were 17.12 and 12.59 mm of CL, respectively. Ovigerous females were sampled from April through August 2007, characterizing a marked seasonal reproductive period lasting for 5 months.

O tamanho de uma população adulta bem estabelecida da espécie exótica de lagostim cambarídeo Procambarus clarkii (Girard, 1852) em um lago artificial no Parque Municipal Alfredo Volpi, localizado na cidade de São Paulo, Brasil, foi estimada em quatro ocasiões distintas entre 1999 e 2001 através de técnica de marcação e recaptura e do método de Schumacher e Eschmeyer para estimativa da população. Os animais adultos foram marcados mediante a colocação de um pequeno anel elástico na base de cada pedúnculo ocular. O tamanho da população adulta variou de aproximadamente 269 e 273 (o último obtido pelo modelo de Tanaka) no verão de 2000 e 2001, e entre 640 e 468 durante o período de inverno de 1999 e 2000 respectivamente.

The size of a well established adult population of the exotic cambarid crayfish Procambarus clarkii (Girard, 1852) from a artificial pond at the Alfredo Volpi City Park, in the city of São Paulo, Brazil, is estimated in four different occasions between 1999 and 2001 by means of a mark-and-recapture technique and Schumacher and Eschmeyer's method for population size determination. Adults were marked by placing small elastic rings at the base of both eyestalks. Population size varied from approximately 269 and 273 adults (the latter corrected by Tanaka's model) in the summer in 2000 and 2001, and between 640 and 468 adults during the winter season of 1999 and 2000, respectively.

Este trabalho contribui para o conhecimento da riqueza de espécies de crustáceos decápodes do vale do Ribeira de Iguape, região sul do estado de São Paulo. Foram realizadas amostragens em seis Parques Estaduais (Campina do Encantado, Intervales, PETAR, Carlos Botelho, Jacupiranga e Ilha do Cardoso) e na Estação Ecológica Juréia-Itatins, abrangendo grande parte do remanescente de Mata Atlântica da região da bacia do rio Ribeira de Iguape. As coletas foram realizadas sazonalmente durante os anos 2000 e 2001, empregando dois métodos de amostragem (peneira e armadilha com isca). Foram registradas 18 espécies de crustáceos decápodes: Palaemonidae (6), Atyidae (3), Aeglidae (5), Trichodactylidae (3) e Grapsidae (1).

This paper contributes to the knowledge of the species richness and distribution of decapod crustaceans at the Ribeira de Iguape river basin, south of São Paulo State, Brazil. Seven protected areas (E.E. Juréia-Itatins, P.E. Ilha do Cardoso, P.E. Jacupiranga, P.E. Campina do Encantado, P.E. Carlos Botelho, P.E. Intervales and PETAR) were investigated, covering most of the Mata Atlântica remaining in the Ribeira de Iguape basin. Samples were taken during each season of the years 2000 and 2001 using two sampling methods (sieves and traps). Six species of palaemonid shrimps, three atyid shrimps, five aeglid anomuran crabs, and three trichodactylid and one grapsid crabs were collected.