RESUMO

Considering the importance of establishing different approaches to the early detection of invasive species, the present study aimed to describe and illustrate the morphology of the early larval stages of the shrimp Lysmata lipkei, an invasive species in the Western Atlantic. Additionally, we did a morphological comparison and a review of the other Lysmata species from the Western Atlantic Ocean with a known larvae description. The larvae used in this study were obtained by the maintenance, under laboratory conditions, of ovigerous hermaphrodites of L. lipkei, collected in the wild. Then, larvae were dissected under a stereo microscope and illustrated using a microscope equipped with a camera lucida. The first three larval stages (zoeae) of L. lipkei were illustrated, described, and compared to other species of Lysmata previously described of the Western Atlantic. Some features of the larval morphology of L. lipkei are very similar when compared to other Lysmata species with previous larval descriptions, such as a rostrum long and simple, the eyes stalked with a long peduncle from the second zoeae, one pterygostomian spine and several denticles along the anterior ventral margin of the carapace, similarities in the segmentation of the maxillipeds, and the presence of dorsolateral spines on the posterior margin of the 5th pleomere, among other features. Also, unique features were observed for L. lipkei, such as differences in the setation of some structures, including the antennule, antenna, maxillule, and maxillipeds. Using the morphological descriptions, we expect to identify species from the plankton, especially invaders, that might be present in the Western Atlantic, as well as assist in several areas in which the larval morphology is relevant.

Assuntos

Decápodes , Animais , Espécies Introduzidas , Larva , Plâncton

RESUMO

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.