Sexual structure of population and reproduction cycle of Echinogammarus olivii (Crustacea, Isopoda) in the fouling community of Odessa Bay (Black Sea)

Abstract

The sexual structure of Echinogammarus olivii (Milne-Edwards, 1830) population in the fouling community of Odessa Bay ( Black Sea ) has been determined. It is shown that t he annual dynamics of sexual structure is conditioned by the peculiarities of the breeding cycle of this species in the coastal fouling community. Throughout the year quantitative pre vale nce of females over males was recorded . E. olivii breeding process takes place throughout the year. Peak of the breeding of this species falls within the early spring when the water temperature reaches 10 °C. During the period of mass reproduction of crustaceans , sex ratio in the population is aligned . In this time the number of ovigerous females reaches 96% of the total. At the end of mass reproduction process the previous generation of adults die. Males eliminate earlier than females. In this period up to six females fall on one male. In early summer, 79% of population of these crustaceans comprise young immature species . In late summer, E. olivii , avoiding overheating, migrate from the coastal zone in the deeper layers and less warmed water. In the autumn crustaceans return to the coastal zone of the sea. At the same time , they reach sexual maturity and a re ready for a new cycle of reproduction. In the Black Sea this species can produce up to four generations per year. In winter, when water temperature is lower , sex ratio in the population of crustaceans is aligned again . Maximum absolute fe rtil ity of females E. olivii in the fouling community of Odessa Bay i s equal to 31 eggs. The relationship of this parameter with length and weight of the crustaceans is shown. Coefficients of the equations of the dependence of wet to dry weights of males, oviparous and non - oviparous females of E. olivii on their length are presented. Absolute fe rtility parameters growth with increasing size of crustaceans females has been detected .