Description, morphology and distribution of the Caulolatilus chrysops (Malacanthidae) larvae in Southeastern Brazilian Bight.

Abstract:

Caulolatilus chrysops is a Malacanthidae species, common in the continental shelf of the Western Atlantic where it has an important role in artisanal fishery. The adults are of demersal habits, but the larval stages are planktonic. Information about the early life stage of C. chrysops, including description and illustration of the larval development, are scarce in the literature. The aim of the present study is to describe and illustrate the larval development of this species and investigate the larval distribution in Southeastern Brazilian Bight. The larvae were collected during 20 oceanographic cruises, from 1974 to 2002, using a bongo net. Samples were fixed in 4% buffered formalin and were sorted in the laboratory using a stereomicroscope. All the material belongs to the Biological Collection of Oceanographic Institute of University of São Paulo (ColBIO). The illustrations were made with a camera lucida attached to a stereomicroscope and the final art was done digitally. C. chrysops larvae have an elongate body with a large head and isometric growth. The head spination increases with larval growth and represents an important character for species identification. A total of 85 specimens were analyzed. Most larvae were in pre-flexion stage (61%). The larval abundance was higher during summer and spring (mean= 0.425 larvae*m^-2; sd= 0.62) compared to autumn and winter (mean= 0.39 larvae*m^-2; sd= 0.19) considering only the positive stations. The distribution of the larvae of the earliest stages of development (pre-flexion) was wide over the continental shelf, but as growth to flexion and post-flexion stages apparently began to prefer shallower areas (<100m). The average temperature and the average salinity obtained at 10 m of depth in the positive stations for larval C. chrysops were, respectively, 23.47ºC and 36.08. The low relative abundance on the samples (0.04-3.85%) and frequency of occurrence considering all cruises suggest that larvae of C. chrysops are rare in the region.