Family AETEIDAE Smitt, 1868

Museums

Museum list

Regional Maps

Family AETEIDAE Smitt, 1868

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The suborder Inovaticellina includes only one family and one genus. The Aeteidae was introduced for Aetea by Smitt (1867). It is characterized by its adnate, bipartite autozooids, which lack spines, avicularia and ovicells. The genus Aetea includes a large number of nominal species, such as A. anguina, several of which are reported to have a world-wide range. However, it appears more probable that many more species than those currently named are in existence, and that separate populations of these widespread species are in fact, distinct taxa. For example, all populations of any Aetea in which the erect part of the autozooid is curved tend to be identified as A. anguina without further investigation.

Colonies are composed of uniserial chains of encrusting autozooids. From each proximal encrusting part, a tubular erect part of the zooid arises and bears a frontal membrane and opesia. This is directed towards the origin of the colony. Zooids are thinly calcified, with virtually no interior walls. Species have 10 to 12 tentacles, which, when extended, have a circlet of fine teeth round the base of the tentacle sheath, which have been regarded as a homologue of the ctenostome setigerous collar (Harmer 1926; Banta et al. 1995). The lophophore is withdrawn by an extremely long retractor muscle, which is inserted at the proximal end of the adnate part of the zooid.

Embryos are brooded in ovisacs which are almost entirely cuticular, and may be intussusceptively developed (Cook, 1977). Ovisacs have been described on the dorsal and the frontal sides of zooids, attached by a small distal area and adpressed to the zooid wall or frontal membrane over the rest of their basal wall. The ovisacs do not seem to have an orifice and the covering membrane is ruptured on release of the larva. The ancestrula buds a distal zooid, followed by a triad and a proximal zooid (Cook 1977, Ryland & Hayward, 1977).

Aetea also shares with the Ctenostomata the ability to produce hibernacula asexually. These 'sacculi' are of several different types (Simma-Krieg 1968; Balduzzi et al. 1991).

McKinney (1988) described a case of exploitation of colonies of Cornucopina by epizoic Aetea from Australia.

Colonies are usually inconspicuous, and encrust algae, shells, hydroids, and erect bryozoans, often being part of a fauna forming a 'turf' of species. Records are from the sublittoral to about 50 m depth (Bock. 1982). Australian records of four nominal species, including 'A. anguina' are from Bass Strait, Torres Strait, South Australia, Victoria, Tasmania, New South Wales and Western Australia. Two species were recorded from Queensland by Hastings (1932) and one by Ryland (1974). Hayward & Ryland (1995) reported A. anguina as abundant on Sargassum from Heron Island.

Hastings (1943) described frontal ovisacs in colonies of 'A. anguina' from the southern oceans, and Hayward (1995) has reviewed the records of these species, remarking that 'their extreme southern limits have still to be determined'.

Diagnosis

Colonies are runners (or chains) of single zooids, with each zooid composed of an adnate portion and an erect portion. The erect part is tubular, terminating with a frontal membrane and terminal operculum. Brooding of larvae is in membranous sacs attached to the erect part of the zooid, but are ephemeral and are rarely seen.