Laboratory studies on larval growth ofPolydora ligni, Polydora ciliata, andPygospio elegans (Polychaeta, Spionidae)

Abstract

The spionid polychaete species Polydora ligni, P. cfliata, and Pygospio elegans were cultivated in the laboratory over several successive generations. A flow-through cultivation system for Polydora spp. is described. Duration of life cycles (time from hatching of the larva to first reproduction) and life spans (hatching to death) of these species were not significantly influenced by the degree of inbreeding nor by individual age of the parents. Minimum time from metamorphosis (15-setiger stage) to first hatching of offspring larvae (in the 3-setiger stage) at 18 °C was 33 days in Polydora spp. and 81 days in Pygospio elegans. Larval growth patterns are described in terms of number of setigers, body length, and biomass (dry weight, carbon, nitrogen, hydrogen), in relation to time after hatching. Regression models are proposed which link these measures of larval growth and, thus, may be used for conversions. Rates of development and growth show a high degree of variability in all three species, not only caused by variation in environmental factors such as temperature or food, but also among and within single hatches of larvae reared under identical conditions. Larvae were reared at constant temperatures (6 °, 12 °, and 18 °C). Temperature affected larval growth in Polydora ligni more than in P. ciliata, and least of all in l~,gospio elegans. Only the latter species was able to develop at 6 °C from hatching to metamorphosis. This differential response may be explained by differences in the natural spawning season of these species. Eleven phytoplankton species were tested as to their food values. A "relative index of growth" is proposed which compares the slopes of two growth curves (one standard and one test condition). The flagellate Dunatiella tertiolecta was used as a standard food in these experiments. Most algal species were less suitable, and only the diatom Thalassiosira rotula was consistently better food for spionid larvae than D. tertiolecta.

Population ecology of Polydora ligni (Polychaeta: Spionidae). I. Seasonal variation in population characteristics and reproductive activity

“…Larvae metamorphosed at 18 d, reached sexual maturity at 37 d, and formed egg capsules by ca 53 d ( h c e 1975). These results agree with studies by Anger et al (1986) who found that at 12 and 18°C Polydora development from hatching to metamorphosis took 16 to 28 d and 9 to 11 d, respectively, while first reproduction occurred about 33 d after settlement at 18OC. Anger et al (1986) found that the average life span of P. ligniin the laboratory was 13 mo.…”

Seasonal changes of planktonic polychaete larvae and chlorophyll a concentration in Onagawa Bay, northeastern Japan

“…Anger et al (1986) fed 11 species of phytoplankton (including diatom, dinoflagellates, Haptophyceae and Chlorophyceae) to the three spionid polychaete species, and revealed that T. rotula led to a relatively high growth rate of spionid larvae. Diatoms are a major component of spring phytoplankton blooms and it is reported that T. nordenskioeldii and Chaetoceros debilis are major components of spring phytoplankton blooms in Onagawa Bay (Inoue 1995;Sato 1996;Nakamura 2007).…”

Evidence for poecilogony in Pygospio elegans (Polychaeta:Spionidae)

“…Rogers et al 1995). Anger et al (1986) determined the mean planktonic period of larval developnlent in Pygospio elegans larvae, hatched at 3 setigers in the laboratory, at 20 to 30 d at 1B0C, and 60 to 70 d at 6OC. There is therefore potential for planktonic larval mediated dispersal in this species.…”