Register of bivalves Cyclinella subquadrata (Hanley, 1844) and Raeta undulata (Gould, 1851) on the coast of the Ancash Region, Peru

Abstract

The species Cyclinella subquadrata and Raeta undulata were registered for the first time in the Ancash Region-Peru and the taxonomic characteristics that identify them were described. Factors analyzed were: size structure, relative density, and some oceanographic variables such as temperature (°C), dissolved oxygen (mL/L), and salinity (ups) in the Canaco (9.85°S/78.24°W), El Dorado (9.18°S/78.56°W), and El Agua Fría (9.15°S/78.57°W) geographical areas. 49 live individuals of C. subquadrata and 11 specimens of R. undulata (4 live and 7 single valves) were analyzed, with sizes ranging from 6 to 95 mm and 60 to 119 mm, respectively; in the first species, an important fraction of juveniles (<22 mm), about 51%, stood out as an indicator that the species under study would be reproducing at discrete levels. Their relative densities were low, which is characteristic of rare species, with values of 1 to 18 ind./m2 for C. subquadrata and 1 ind./m2 for R. undulata. 73% of the stations presented 1 ind./m2 for C. subquadrata. The length-to-weight ratio showed a good fit for the potential model with the determination coefficient (r2) of 0.99 and positive allometric type growth (b >3.0). The location of both species in intermediate localities of the Peruvian coast (9°S) would confirm that there is no interruption in their distribution.