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Subject: LCSH

Polydora cornuta


Biology | Ecology and Evolutionary Biology | Marine Biology


A population of the polychaete Polydora ligni Webster was studied during 1982 and 1983 in Alewife Cove, Connecticut, USA, to determine seasonal changes in population characteristics. During early spring (March and April), the population was comprised of primarily large adults that had over-wintered. Females in this group exhibited the highest mean individual fecundity over the year (> 2000 larvae per brood). However, total larval production at this time was low (5200 to 208 000 larvae m-2 per 14 d) due to low densities of adults. Population density increased slowly during spring as juveniles produced by overwintering adults recruited into the population and matured into adults. While mean individual fecundity of these adults was lower (≈ 1200 larvae brood-1), larval production peaked (≈ 884000 larvae m-2) due to their high density. Population abundance peaked coincident with peaks in larval production, decreased rapidly during late summer and leveled off during fall and winter. Population density was lower and fluctuated less in the second year of the study, but general seasonal patterns were repeated. Reproductive activity was continuous over the study period. The overall female-to-male sex ratio was 2.42 : 1,and females grew to significantly larger sizes than males. Besides fecundity, there were seasonal differences in the number of gametogenic segments per female and the number of eggs per capsule; there were no seasonal differences in the number of egg capsules per brood. Temporal changes in population characteristics of P. ligni differed to various degrees from those reported for related taxa and other opportunistic polychaetes. However, the general patterns were similar. Seasonal variation in the population characteristics of opportunistic polychaetes may cause responses to disturbance to vary because of changing dynamics in populations that act as sources of larvae. Seasonally varying dynamics may also be an important evolutionary determinant of opportunistic life history traits.


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Publisher Citation

Zajac, R. (1991). Population ecology of Polydora ligni (Polychaeta: Spionidae). I. Seasonal variation in population characteristics and reproductive activity. Marine Ecology Progress Series, 77, 197-206.