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Pygospio elegans showed great seasonal changes in both the female to male ratio and
sexual activity on Drum Sands. The proportion of female tubes containing embryos or
larvae decreased during the summer, possibly as a result of limited sexual
reproduction due to the decreased abundance of mature males. When the abundance
of ripe males increased during the winter there was a marked increase in reproductive
activity. This suggests that sexual reproduction was probably the primary method of
propagation at Drum Sands, which is in agreement with previous studies elsewhere
(Thorson, 1946; Smidt, 1951; Rasmussen, 1973; Anger, 1984). It is likely that the
majority of the adult males at Drum Sands began to show sex reversal in May after the
main breeding season as a result of a slight increase in water temperature. Sex
reversal continues during the summer, resulting in a high female : male ratio
(Rasmussen, 1973). In late autumn the immature individuals develop into sexually
mature males and females according to their original sex, probably due to a decrease
in water temperature (Rasmussen, 1973). This corresponded to the sudden increase in
the number of males sampled in the population at Drum Sands and the consequent
decrease in the female : male sex ratio. This was also observed in the study by Wilson
(1985) who found that during November the males, which were indistinguishable
from the females during the summer, developed secondary sexual structures and
became ripe. Since sexual reproduction was the primary method of propogation with
the population at Drum Sands, the availability of males, and the spatial distribution of
males relative to the females, were likely to be major factors governing the
reproductive output of the population as a whole.
Anger (1984) suggested that P. elegans was unique among spionids in being able to
reproduce at the low temperatures encountered during the winters at high latitudes.
The presence of juvenile worms, i.e., those