Influence of salinity and temperature on growth and survival of the planktonic larvae of Marenzelleria viridis (Polychaeta, Spionidae)

Abstract

In a series of experiments, the planktonic larvae of MArenzelleria viridis (Verrill, 1873) were exposed to various combinations of salinity (S=0.6, 2.5, 5.0, 10 and 20‰) and temperature (T=5.10 and 20°C) from the l-setiger stage to the onset of metamorphosis (16- to 17-setiger stage). One-setiger larvae were unable to complete their development to metamorphosis at salinities below 5‰. Metamorphosis was successful at salinities of 10 and 20‰, when the animals adopted a benthic life mode. Larval development was more rapid at 10‰ that at 20‰, and was positively affected by higher temperatures. Larvae exposed to a salinity of 3.5‰ at the 4- to 5-setiger stage developed and completed metamorphosis to benthic juveniles despite the low salinity. These larvae developed most rapidly at a temperature of 10°C. The salinity tolerances (LC50) of M. viridis larvae (t=48 h), juveniles and adults (t=72 h in each case) were determined at 10°C. The results showed that all development stages can tolerate salinities < 1‰. The importance of constraints on development and tolerance to low salinities for the successful colonization of oligohaline regions is shown and discussed in connection with other brackish-water organisms.