Fecundity and Reproductive Output of Pisidia Longicornis (Decapoda, Anomura) in the Ría De Arousa (Galicia, Nw Spain)

Abstract

[Pisidia longicornis is a small anomuran crab that constitutes the dominant component of the epifauna of mussel rafts in the Ria de Arousa (NW Spain). This species forms isolated post-larval populations on the ropes used in the culture, experiencing a wide range of environmental conditions, both spatially and seasonally. This paper studies the fecundity (egg size and number per brood) of P. longicornis in the inner and outer areas of the ria at 5 and 10 m depth over a yearly cycle. The fecundity of this species is highly variable (ranging from 10 to over 1443 eggs per brood), and it is primarily determined by carapace width, CW (P 3 in most of cases). Spatial differences were due partially to changes in body size; in the outer area (mean CW 4.9 mm), the number of eggs per brood was 265 ± 225 (mean ± SD), and in the inner area with larger specimens (mean CW 6.1 mm), fecundity was higher (600 ± 373 eggs). Egg volume in the outer station (0.025 mm3± 0.005) was higher than in the inner station (0.023 mm3± 0.005) and slightly larger at 10 m deep (0.025 mm3 ± 0.005) than at 5 m (0.023 mm3 ± 0.004). In the outer ria area, where the food availability, density and growth are higher, the reproductive output (defined as number of eggs x egg size) corrected for body size, was higher than in the inner station. Both parameters related to reproductive output exhibited significant temporal variability. During the main breeding period there was an increase in number of eggs per brood and a decrease in egg volume from January to March-April. This seasonal change in the reproductive strategy is associated with the increase in planktonic production in spring. P. longicornis shows a great plasticity in reproductive output, both seasonally (within a population) as well as spatially (between populations), that is hypothesized as an adaptative strategy to the spatial and temporal variations in the environment, and especially food abundance for planktonic larvae., Pisidia longicornis is a small anomuran crab that constitutes the dominant component of the epifauna of mussel rafts in the Ria de Arousa (NW Spain). This species forms isolated post-larval populations on the ropes used in the culture, experiencing a wide range of environmental conditions, both spatially and seasonally. This paper studies the fecundity (egg size and number per brood) of P. longicornis in the inner and outer areas of the ria at 5 and 10 m depth over a yearly cycle. The fecundity of this species is highly variable (ranging from 10 to over 1443 eggs per brood), and it is primarily determined by carapace width, CW (P 3 in most of cases). Spatial differences were due partially to changes in body size; in the outer area (mean CW 4.9 mm), the number of eggs per brood was 265 ± 225 (mean ± SD), and in the inner area with larger specimens (mean CW 6.1 mm), fecundity was higher (600 ± 373 eggs). Egg volume in the outer station (0.025 mm3± 0.005) was higher than in the inner station (0.023 mm3± 0.005) and slightly larger at 10 m deep (0.025 mm3 ± 0.005) than at 5 m (0.023 mm3 ± 0.004). In the outer ria area, where the food availability, density and growth are higher, the reproductive output (defined as number of eggs x egg size) corrected for body size, was higher than in the inner station. Both parameters related to reproductive output exhibited significant temporal variability. During the main breeding period there was an increase in number of eggs per brood and a decrease in egg volume from January to March-April. This seasonal change in the reproductive strategy is associated with the increase in planktonic production in spring. P. longicornis shows a great plasticity in reproductive output, both seasonally (within a population) as well as spatially (between populations), that is hypothesized as an adaptative strategy to the spatial and temporal variations in the environment, and especially food abundance for planktonic larvae.]