New Zealand Journal of Marine and Freshwater Research abstracts
Morphology and biology of Polydora rickettsi (Polychaeta: Spionidae)
from Chile
Vasily I. Radashevsky1,2
César A. Cárdenas2
1Institute of Marine Biology
Russian Academy of Sciences
Vladivostok 690041, Russia
email: radashevsky@mail.ru
2Instituto de Zoología
Universidad Austral de Chile
Valdivia, Chile
Abstract The spionid polychaete Polydora rickettsi
is primarily a borer in various calcareous substrata in the eastern Pacific.
Redescription of the species from the type locality in Mexico is required
to better understand its distribution. In Chile, females and males become
mature after growth to c. 60 segments. Sex allocation in the population is
close to 1:1. Gametes develop along segmental blood vessels in middle segments.
Spermatogonia proliferate in temporary testes and the rest of spermatogenesis
occurs in the coelomic cavity. On their release through metanephridial segmental
organs, long-headed spermatozoa are packed in filiform spermatophores. Females
store inactive spermatozoa in paired seminal receptacles on the dorsal side
of fertile segments. Oogenesis is mostly intraovarian. Females deposit up
to 4150 eggs into 65 capsules which are joined to each other in a string.
Each egg capsule is attached by two stalks to the inner wall of the burrow
and contains up to 65 eggs c. 95 µm in diameter. Most eggs give rise
to larvae which develop inside egg capsules until the 3-segment stage, then
hatch and continue development in sea water, feeding on plankton. Fully developed
17-18-segment larvae are able to settle and metamorphose. They have one pair
of phaosomes and three pairs of black eyes on the prostomium, provisional
protonephridia in segments 1 and 2, paired dorsal melanophores from segment
3 onwards, lateral melanophores on segment 2 and from segment 10 onwards,
yellow pigment in the wall of posterior gut, glandular pouches from segment
6 onwards, short branchiae on segments 7-11, gastrotrochs on segments 3,
5, 7, 10, 13, 15, and 17, one pair of provisional modified bristles and two
or three falcate spines of a “quasi-adult” kind in segment 5. Development
of the “quasi-adult” spines is described for the first time in polydorid
larvae.
Keywords Polychaeta; Spionidae; Polydora rickettsi;
morphology; ecology; reproduction; larval development; Chile
M03061; Received 25 September 2003; accepted 18 January 2004; Online publication
date 8 June 2004
New Zealand Journal of Marine and Freshwater Research, 2004, Vol. 38:
243-254
0028-8330/04/3802-0243 © The Royal Society of New Zealand 2004
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