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Title: Reproductive biology of Alcyonidium mytili Dalyell, 1948
Author: Cadman, P. S.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1995
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Abstract:
The reproductive biology of Alcyonidium mytili Dalyell, 1848 was studied over two years, revealing confusion in the literature as to its identity and reproductive mode. A. mytili is comprehensively redescribed from an approximate type locality in the Firth of Forth, Scotland and from the Daugleddau Estuary, Pembrokeshire. Zooid and polypide dimensions and modal tentacle number (16) have been determined. A. mytili is an oviparous, iteroparous, non-epidemic spawning species with a peak reproductive period between October and February. The ovary is large in comparison to the size of the zooid and contains oocytes with a wide size distribution. When the oocytes reach 40 μm in diameter, they are ovulated into the coelom and increase to 60 - 70 μm. The ova more freely within the coelom and are frequently manoeuvred towards the base of the intertentacular organ, a structure only present in reproductive zooids. The intertentacular organ develops on existent zooids and acts as a conduit for sperm entry into, and egg release from reproductive zooids. Spermatogenesis begins slightly later than oogenesis, although, after the early stages of ovarian differentiation, sperm was always present in zooids with ovulated ova. All stages of spermatogenesis are usually present within reproductive zooids, but are synchronised in individual cytophores. Sperm does not accumulate within the coelom and is shed throughout the reproductive period. Gametogenesis is not fuelled by the breakdown of the polypide, which remains functional throughout the reproductive period, but appears to gain nutrients from lipid reserves accumulated and stored during the non-reproductive period in the spring and summer. The spawned ova develop into shelled cyphonautes larvae which, when settling on Mytilus edulis shell valves, show a preference for the posterior and mid-dorsal regions. A. mytili is not as substrate-specific as the name might suggest, being found on a wide range of animate and inanimate substrata.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636194  DOI: Not available
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