Family FARCIMINARIIDAE Busk, 1852

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Family FARCIMINARIIDAE Busk, 1852

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The family Farciminariidae was introduced, as Farciminariadae, by Busk (1852) for the genus Farciminaria, and its type species, F. aculeata, alone. Later, in the Challenger Report (1884), Busk added another eight species, which were all included in a new genus, Columnaria, by Levinsen (1909). This name being preoccupied, Levinsen (1914) emended it to Columnella, which is a senior synonym of Levinsenella Harmer (1926). One of Busk's Challenger species was made the type of the genus Farciminellum by Harmer (1926), who also included his genus Didymozoum, introduced in 1923, for Didymia simplex (Busk 1852), in the family Farciminariidae. Levinsen (1909) erected the genus Kenella for Farciminaria biseriata Waters (1889), from the Challenger collections, and Silén (1941) added Farciminellopsis for F. gracilis from the northwest Pacific.

Although many species of Farciminariidae are from considerable, even abyssal depths, with a world-wide distribution, Farciminaria and Didymozoum are both from shallow-shelf, Australian waters. Antarctic species referred to the family have been assigned to the Flustridae by Hayward (1995).

Species are all erect, bilaminar to quadriserial, often with opposing faces composed of either autozooids or kenozooids. Autozooids are elongated with a proximal gymnocyst, but often no cryptocyst; kenozooids, however, may develop a marginal cryptocyst (Hayward 1981).

When present, avicularia are all small and sessile, arising from the gymnocyst. Embryos are either brooded in interior ovisacs, sometimes of enlarged autozooids, or in very large ovicells. The ovicells are closed by the operculum and may be regarded as endozooidal, even though they are prominent. The outer, cuticular layer is part of the frontal membrane of the distal zooid, either an autozooid or kenozooid, and the inner, calcareous layer is immersed in the distal zooid. Alternatively, the ovicells have been regarded as hyperstomial, with a membranous ectooecium, continuous with the frontal membrane of the distal zooid, and a calcareous endooecium (compare Harmer 1926 and Hayward 1981).

Farciminaria has cylindrical, 4-6 serial branches, which are flexible, but unjointed. The autozooids are thinly calcified with little or no gymnocyst and cryptocyst, but sometimes with marginal cuticular spinous processes, which also occur on the outside of the ovicells. Avicularia are absent.

There are three Australian species. F. aculeata was described by Busk (1852b) from Tasmania, from material collected by Hooker. F. uncinata was described from Port Phillip, Victoria by Hincks (1884), as was F. simplex MacGillivray (1886). MacGillivray figured all three species in 1888; they grow in tufts, anchored by rhizoids in shallow water less than 30 meters deep.

The genus Didymozoum Harmer (1923) includes Didymia simplex Busk (1852b) from Bass Strait, and D. triseriale Phillips (1900), originally described from New Caledonia, but also reported from the Great Barrier Reef by Hastings (1932). Species form tufts of thinly calcified, biserial, jointed branches, the zooids budded in pairs both facing the same way. Ovicells are very large, and occur at branch bifurcations, immersed in a membranous kenozooid in D. simplex, but not in D. triseriale. Avicularia are absent. D. simplex forms loosely branched colonies 'several inches' high, according to Busk (1852b), and Harmer (1926) noted that the branches of D. triseriale arose from a creeping stolon of elongated kenozooids.

The genus Farciminellum is represented in Australian waters by two, very deep records of F. hexagonum, the type species, from the central Tasman Sea (Hayward 1981). Colonies are bilaminar, one face being almost entirely composed of kenozooids, the opposing face of 4-8 series of thinly calcified, very elongated autozooids. Avicularia are small, and sporadically developed on marginal zooids. Embryos are brooded in interior ovisacs of enlarged autozooids, and ovicells are absent. The ancestrula is an enlarged, cuticular sac, with numerous, blister-like kenozooids at its basal end, each of which gives rise to a rhizoid. F. hexagonum was first described from Marion Island in the southern Indian Ocean and has been reported from widely distributed localities from South Africa (its deepest record at 5110-5340 m) to Indonesia Celebes and the Philippines, and from the Kermadec Trench and Tasman Sea (at 4410-4670 m).

Diagnosis

Colonies erect, weakly calcified, rooted. Branches may be 4-6- serial, bilaminar with zooids on one surface only, or unilaminar. Little or no gymnocyst or cryptocyst. Avicularia absent or adventitious and small. Ovicells endozooidal, closed by zooidal operculum, but may be inflated on external surface of the branch.