Abstract
The present study focuses on the distribution and abundance of the giant isopod community, based on specimens collected using the bottom shrimp trawling on the Amazon continental shelf during fishery surveys, at depths between 81 m and 626 m, conducted during the REVIZEE/Score-North Program between 1996 and 1998. The study area is located within the exclusive economic zone of Brazil, between the States of Amapá and Pará. In total, 170 specimens were collected, distributed in the two species Bathynomus giganteus (n = 49) and Bathynomus miyarei (n = 121), in which 54% of the material were collected in the northern and 46% in the southern sector of the study area. B. miyarei was considered to be the dominant species in both sectors, whereas B. giganteus was uncommon in the northern sector, but abundant in the southern sector. Both species preferred gravelly bottoms in the northern sector, and gravelly sand in the southern sector and were more abundant during the dry season in the northern sector, but during the rainy season in the southern sector. The smallest female B. giganteus was collected in the northern sector, and the largest in the southern sector, whereas both the largest and the smallest female B. miyarei were captured in the southern sector. All the male specimens collected in this study were captured in the northern sector.
Highlights
A basic measure of the diversity of a biological community is the number of species, known as species richness (Primack & Rodrigues, 2001)
More than two-thirds (71%) of the specimens belonged to the species B. miyarei, with the other 29% belonging to B. giganteus
While B. giganteus preferred gravel bottoms in both sectors, B. miyarei was associated with gravel in the northern sector, and gravelly sand in the southern sector (Figure 6). Both species were more abundant in the northern sector of the study area during the dry season, but were more abundant during the wet season in the southern sector (Figure 7)
Summary
A basic measure of the diversity of a biological community is the number of species, known as species richness (Primack & Rodrigues, 2001). The number of species found in a community varies according to the physical conditions of the environment, habitat heterogeneity, primary productivity, and dispersal potential (Ricklefs, 2003). The order Isopoda contains approximately 10,000 species, which are found in marine, freshwater, and terrestrial environments. The largest species belong to the genus Bathynomus A. Milne-Edwards, 1879 (Bueno, 2007). Most isopods are found in marine environments, and are well-distributed in a variety of different niches (Loyola e Silva, 1999)
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