Interactions of environmental temperature with photoperiod in determining age at maturity in a semelparous polychaete Nereis (neanthes) virens sars

Influence of photoperiod and temperature on oocyte growth in the semelparous polychaete Nereis (Neanthes) virens

“…Nereidae are nlostly not short lived species, as is generally supposed to be the case for semelparous organisms (Pianka 1970, Roff 1992, Stearns 1992. Nereis (Neanthes) virens is indeed one of the largest and potentially longest lived of the marine annelids (Olive et al 1998) and, as in most Nereidae, the generation time is greater than the phase length of the breeding cycle. Therefore the proportion of sexually mature worms in the population at the time of breeding will be less than unity as observed in natural populations of N. virens (Snow & Marsden 1974, Creaser et al 1983, Olive 1993.…”

“…The mean generation time is itself a response to environmental factors and in N. virens is decreased under intensive culture. High growth rate reduces both the generation time and the mean size at maturity, consequently there is an inverse relationship between growth rate and size at maturity (Olive et al 1986(Olive et al , 1998.…”

“…In natural populations where the life cycle is longer (Olive et al 1998) it is possible that the animals proceed through a series of photoperiod induced changes in metabolic activity but that the overt oocyte growth rate response to short photoperiods is suppressed until the animals become competent to complete gametogenesis. Thus a covert annual cycle of physiological activity may underlie the once per lifetime transition to sexual maturity.…”

“…The average age at reproduction in natural populations of N. virens has been variously estimated to be between 2 and 7 or more years, according to local conditions (Bass & Brafield 1972, Creaser & Clifford 1982, Caron et al 1993, Olive 1993, Desrosiers et al 1994), yet, despite variation in the age at reproduction within and between populations, maturing individuals always breed in the spring during April or May. This pattern of synchronised spring breeding has been maintained in the UK cultured populations over a period of 12 yr although the generation tlme is reduced and may be only 1 yr (Olive et al 1986, Olive 1998.…”

Effects of diet and density on growth, survival and gametogenesis of Hediste diversicolor (O.F. Müller, 1776) (Nereididae, Polychaeta)

“…The available data for H. diversicolor have only shown that the optimization of feeding rate may determine an early sexual maturation (Batista et al, 2003), causing the production of fast growing organisms breeding at smaller size. This trade-offs between initial growth rate and size at maturity exists for many organisms (Atkinson and Sibly, 1997;Sibly and Atkinson, 1994) including nereidids polychaetes with mixed or variable age at reproduction (Desroisiers et al, 1994;Last and Olive, 1999;Olive et al, 1997;Prevedelli and Cassai, 2001).…”