Morphogenesis during Asexual Reproduction in Pygospio elegans Claparede (Annelida, Polychaeta)

The spionid Pygospio elegans reproduces both asexually and sexually. Using scanning electron and bright field microscopy, we examined morphogenesis following asexual reproduction to determine how "lost" body regions were regenerated after a worm spontaneously divided. Asexual reproduction...

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Bibliographic Details
Published in:The Biological bulletin (Lancaster) 2000-08, Vol.199 (1), p.41-49
Main Authors: Gibson, Glenys D., Jennifer M. L. Harvey
Format: Article
Language:English
Subjects:
Abdomen
Animal reproduction
Animals
Annelida
Annelids
Asexual reproduction
Body regions
Cilia
Claparede
Development and Reproduction
Larval development
Marine
Morphogenesis
Mortality
Palps
Physiological aspects
Polychaeta
Polychaeta - growth & development
Polychaeta - ultrastructure
Pygospio elegans
Regeneration (Biology)
Reproduction, Asexual
Thorax
Worms
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Description
Summary:The spionid Pygospio elegans reproduces both asexually and sexually. Using scanning electron and bright field microscopy, we examined morphogenesis following asexual reproduction to determine how "lost" body regions were regenerated after a worm spontaneously divided. Asexual reproduction occurred through transverse fission and divided the parent worm into 2 to 6 fragments (architomy). All fragments retained their original anterior-posterior polarity. Regeneration in all fragments followed a specific series of events: wound healing (day 1); extension of the blastema to generate lost body regions-specifically, the head and thorax for posterior fragments and the tail and pygidium for anterior fragments (days 2-3); segmentation (days 3-6); and differentiation of segment- or region-specific structures (days 4-8). This pattern occurred regardless of where the original division took place. Subsequent growth occurred through addition of terminal setigers anterior to the pygidium followed by differentiation of tail setigers into abdominal setigers, leaving the tail region about 6 to 10 setigers in size. Division rates were compared in worms from three populations in Nova Scotia, Canada. Worms from two populations (Conrad's Beach, Starr's Point) divided more frequently (about 1.2 and 1.3 weeks between divisions, respectively) than worms from Bon Portage Island (3.5 weeks between divisions). Fragments containing the original head (original mouth intact, generally much larger fragment) had a higher survivorship than fragments containing the original tail.
ISSN:0006-3185
1939-8697
DOI:10.2307/1542705