Redescription of Alcyonidium mytili Dalyell, 1848 (Bryozoa: Ctenostomatida)

Abstract

Reproduction in the ctenostomate bryozoan Alqonidium mytili Dalyell, 1848, was studied over 2 years, revealing confusion in the literature over the diagnostic characters of the species and incorrect assumptions about the mode of reproduction. The literature is briefly reviewed and an approximate type locality from the Firth of Forth, Scotland, is identified. Alqonidium mytili is comprehensively redescribed from material collected in the Firth of Forth and from 2 years' collections in the Daugleddau estuary, near Pembroke Dock, South Wales. Zooid and polypide dimensions and modal tentacle number (16) have been determined from large samples. Most importantly A. mytili possesses a conspicuous intertentacular organ when reproductive; is oviparous, with eggs discharged through the intertentacular organ developing into cyphonautes larvae; and has a prolonged winter reproductive period. The contrary indications in the literature are a consequence of confusion with a superficially similar but larviparous species.

The identity of Alcyonidium diaphanum (Bryozoa: Ctenostomatida)

“…Budding and colony growth have not been investigated in A. diaphanum, and are beyond the scope of this paper but sections through the distal tip of an actively growing juvenile colony show closely packed autozooids, and neither enclosed space nor epithelium-lined axial spaces ( Figure 4C). However, the periphery of the colony is ringed with what appear to be autozooid buds ( Figure 4D), suggesting that growth proceeds through intercalary budding, as described in A. mytili by Cadman & Ryland (1996b). Longitudinal sections of another juvenile colony demonstrate enclosure of exterior space by apparent fusion of epicuticular folds ( Figure 5A^D).…”

Pattern of occurrence of supraneural coelomopores and intertentacular organs in Gymnolaemata (Bryozoa) and its evolutionary implications

“…The internal cells of the ITO differentiate from lateral cells of the tentacles which lose the cilia and later on develop a new ciliation (Hageman 1981). The differentiation of the ITO is not connected with polypide replacement (Cori 1941;Jebram 1975;Reed 1991;see also Cook 1962;Silén 1966;Jebram 1973a;Cadman and Ryland 1996). It is not yet known whether a supraneural pore is present before the formation of the ITO or whether it is found in non-fertile zooids.…”

Structure and occurrence of cyphonautes larvae (bryozoa, ectoprocta)

“…Within the Ctenostomata , cyphonautes larvae have been reported from a number of species scattered through most of the major groups. This classification follows Bock (2008): Suborder Alcyonidiina Family Alcyoniidae Genus Alcyonidium A. albidum : Prouho (1892) A. cellarioides : Calvet (1900; free spawning of small eggs, larva not described) A. mytili : Prouho (1892), Cadman and Ryland (1996) …”

“…Family Alcyoniidae Genus Alcyonidium A. albidum : Prouho (1892) A. cellarioides : Calvet (1900; free spawning of small eggs, larva not described) A. mytili : Prouho (1892), Cadman and Ryland (1996) …”