Family CANDIDAE Busk, 1852

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Family CANDIDAE Busk, 1852

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The family name Candidae d'Orbigny has priority over the previously used names Scrupocellariidae and Cabereidae. The family is a large one, including at least 25 genera, most of which have a world-wide distribution. Twelve genera are known from Australia and the Antarctic region.

Colonies have in common an erect growth form arising from a single, semi-erect ancestrula (Ryland & Hayward 1977), and supported by rhizoids. They are most often biserial, with all the autozooids facing in one direction. Branches are usually formed into zooidal internodes, connected by thick, tubular, cuticular joints. Internodes are thinly to well calcified and may include multiserial rows of 50 zooid generations or more ( eg. Caberea), or only 1 to 3 zooids (eg. Monartron). The complex patterns of branch bifurcations were described by Harmer (1923), Ryland & Hayward (1977), and Hayward (1995), for most of the genera included here. Autozooids have a distinct, often tubular gymnocyst and a well-developed cryptocyst. Oral and other spines are often present, one lateral spine, in particular, being enlarged, flattened and branched, overarching the frontal area as a protective scutum. Ovicells are usually large, globular and frontally fenestrate. Avicularia are typically present, frontally, laterally and basally. They are sessile, and the mandibles of the basal members are usually long, setiform and often toothed. These 'vibracula' have subrostral chambers which cover the basal surface in conspicuous series in the genera Caberea and Amastigia. Rhizoids arise laterally and basally and pass downward to the colony origins, anchoring it to the surrounding substrata. Rhizoids frequently form thick lateral or basal ropes, and may produce a massive stalk at the base of the colony.

The genus Canda Lamouroux is represented by four Australian species, the commonest being C. arachnoides (sensu Busk 1852), which has bright orange colonies illustrated by Bock (1982), and Gordon (1986), who noted that the zooids had 16 tentacles. The biserial branches are sporadically united by calcified tubular connections, forming a reticulated, flexible erect sheet. Colonies may reach a height of 100 mm.

The genus Caberea also has robust colonies and enormous basal 'vibracula'. The mandibles of these may move in concert. At least 6 species have been reported from Australia, including C. glabra, which has biserial branches, and the much larger, multiserial C. texta Lamouroux (often described as C. grandis), which forms orange-brown colonies 50 mm high. Both species are described by Bock (1982). Gordon (1984, 1986) has described several southern ocean species, but only C. darwinii is certainly known to extend to the Antarctic. It is a very variable species, and Hayward (1995) noted that Antarctic specimens were more robust than those from adjacent waters.

Amastigia is represented by at least three species from Australia. A. rudis Busk (1852b) has a wide distribution and was figured by Bock (1982). A. funiculata (MacGillivray) has been described by Harmer (1923) and by Gordon (1986), and A. harmeri was discussed by Hastings (1943). Seven species were described from the Antarctic and subantarctic by Hayward (1995).

The genus Scrupocellaria has a world-wide distribution, and is represented in Australia by at least 9 species. Colonies form small, straggling tufts, usually anchored to other bryozoans, algae, shell or coral in shallow waters. Many species have frontal, lateral and basal avicularia. The basal vibracular mandible can be seen in living specimens to move constantly over both surfaces of the colony (Cook, 1985; Winston, 1984). Many species have a very wide distribution: for example, S. maderensis, illustrated from the Great Barrier Reef by Ryland & Hayward (1992), is known from the tropical and subtropical Atlantic and Pacific, and S. diadema extends from the Indian Ocean to Japan. S. bertholettii is another cosmopolitan species known as part of the fouling fauna of South Australia (Bock 1982; Brock 1985). S. ornithorhynchus, also described by Bock (1982), has a more restricted distribution, from New South Wales to Bass Strait.

The closely similar genus Notoplites is known only from New Caledonia (d'Hondt & Gordon, 1996) in Australasian waters, and is often abyssal in occurrence. In the Antarctic, the genus is found in shallower water and Hayward (1995) described a diverse fauna of nine species from the shelf region. Colonies are not usually large, and tend to be diffuse, although N. drygalskii grows in dense tufts exceeding 150 mm in height.

In contrast, the genus Tricellaria has only one Antarctic representative, T. aculeata, where it forms 'dense, feathery tufts' (Hayward, 1995). Three species have been confused in the past: T. porteri, T. occidentalis, and T. inopinata (Dyrynda et al., 2000). These require a reassessment of distribution. In Australia, T. porteri was described by Bock (1982) and Brock (1985) as fouling species from South Australia, and was figured by Dakin & Bennett (1987). The invasive species T. inopinata may be present in Australia (Dyrynda et al., 2000).

Bugulopsis is a genus that has been placed in synonymy with Tricellaria, but is likely to be a valid genus. The species B. monotrypa is common in southern Australia. Colonies are of biserial branches without avicularia; branching is symmetrical. Ovicells are located in the axils of branch bifurcations.

The genus Menipea has no scutum and the rhizoids form large lateral bundles (Gordon, 1986). The branches are biserial or multiserial, and may be bilaminar or unilaminar. Three species have been described from Victoria (Hincks, 1881, as Membranipora; MacGillivray, 1886, as Craspedozoum).

The genus Emma is represented by six Australian species, most from New South Wales and Victoria. They have been described by Hastings (1939), Bock (1982) and Gordon (1984, 1986). Bock described E. rotunda as a tangled network about 30 mm in diameter. It has small internodes of two to three zooids and immersed ovicells.

Eupaxia is known as a single species, E. quadrata, recorded from the Heard Island region (Busk, 1884).

The genus Monartron was described from southern Australia by Canu & Bassler (1929). It has small internodes of 1-3 zooids only, and large, curved jointed spines. Internodes are similar in general appearance to those in Emma, but the internodes are connected by a single tube, rather than a double tube. The ovicell is hyperstomial.

The genus Maplestonia is thinly calcified and includes two Victorian species which require further investigation. The zooids lack avicularia, and ovicells have not been seen (MacGillivray 1885, 1885b). The absence of any of the characteristic structures seen in other genera of the family leaves the family placement of the genus open to question.

The family is known from the Late Cretaceous (Taylor, 1993). Fossils of the thinly calcified internodes of genera such as Canda and Amastigia are known in the Tertiary sediments of Victoria.

Diagnosis

Colony erect, branching; branches unilaminar or bilaminar, biserial or multiserial, attached by rootlet system. Most are articulated, with internodes ranging from paired zooids to extensive lengths. Frotnal with extensive gymnocyst, and a narrow border of cryptocyst. Opesia elongate, with a modified spine (scutum) arching over the frontal membrane in many species. Distal spines present in many species. Avicularia frequent, adventitious; setiform avicularia (vibracula) on the basal side in several species. Avicularia absent in some species. Ovicells hyperstomial.