Family LEPRALIELLIDAE Vigneaux, 1949

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Family LEPRALIELLIDAE Vigneaux, 1949

Compiler and date details

July 2001 - Dr Philip Bock

Lepraliellidae Vigneaux, 1949.
Celleporariidae Vigneaux, 1949.

Introduction

The family Lepraliellidae was introduced by Vigneaux (1949) for Lepraliella Levinsen (1916), and is reasonably well circumscribed in terms of overall morphology. The family includes a number of genera forming encrusting or erect, multilaminate colonies. The zooids have umbonuloid frontal shields, and non-sinuate, subcircular or D-shaped orifices. Frontal budding is important in most species, and the absence of differentiated lateral walls is characteristic. Colonies range from a few millimetres to 150 mm in diameter and may be massive and cemented to a substratum, or minute and globular, or discoid, anchored by turgid, extrazooidal stalks. Some larger colonies, which initially grew on small substrata, become effectively free-living. Colonies are well integrated and develop maculae or mounds of frontally budded zooids producing excurrent chimneys. In general terms, zooid frontal shields are smooth, and an umbo or avicularium is usually associated with the orifice. Ovicells tend to be hooded, smooth-walled and fairly open in front ('cucullate'), at least in the early stages of ontogeny. Larger lingulate or spatulate avicularia feature quite prominently in some genera, particularly Celleporaria.

Some 20 genera may belong to the family, including Lepraliella, Celleporaria, Sphaeropora, Buchneria, Drepanophora, Kladapheles, and the Cretaceous Frurionella (Gordon 1993). Two genera occur in Australia waters, the diverse and complex Celleporaria, with at least 30 species, and the rooted Sphaeropora, with at least five living species and an extensive fossil record.

The earliest record of lepraliellids from Australia is from the collections of Péron and Lesueur, described by Lamarck (1816), some of whose specimens may be those still housed in the Paris National Museum (Pouyet 1978). The type species of Celleporaria, C. cristata, encrusts the stems of algae in a series of crests, the whole colony resembling a screw (Bock 1982). This form is very similar to Densipora corrugata, in the cyclostome family Densiporidae. C. cristata is only one of 14 species recorded from Victorian waters, and it is expected that additional species are yet to be defined. Ryland & Hayward (1992) and Hayward & Ryland (1995) have reported 10 species from Heron Island, 3 of them new. It may be a function of collecting, but the numbers of species decline westwards and northeastwards from Victoria. Thus there are 10 species known for South Australia but only two for southwestern Australia. Eight have been recorded for New South Wales, declining to seven in Torres Strait. Off Darwin, at least five species occur together in the same general area. Two are known for northwestern Australia. Many of the early workers on Bryozoa described several species of Celleporaria, as the large colonies were easily identified in dredged material. Important contributions were made by Busk (1852a, 1854, 1881, 1884) and by MacGillivray (1886, 1887, 1888). Both in tropical and temperate waters some species are quite massive, approximating small corals in size. Although colony form (and colour, where known) can be helpful in discriminating species, they are generally most accurately discriminated on the basis of details of the orifice and avicularia. Ecologically, the large species, with considerable three-dimensional relief, provide habitat for cryptic invertebrates in their interstices. Collectively, bryozoan coral can provide nursery habitat for juveniles of commercial fish. This has been demonstrated in New Zealand waters (Bradstock & Gordon 1983) and the same is likely to be true in Australian waters. Some species ,e.g. C. oculata Lamarck, allow the occurrence of commensal or symbiotic organisms on their surface, including polychaetes and small cnidarians (Osman & Haugsness 1981).

Sphaeropora fossa Haswell (1881) is the only described Recent species of its genus, although other undescribed Recent, and several fossil Australian species are known (Cook 1979; Cook & Chimonides 1981). This genus has a colony form quite unlike that of Celleporaria, with mature colonies forming spheres, lenses or elongate ellipsoids up to 25 mm in diameter or length. The colonies are supported by one or several turgid, extrazooidal cuticular rhizoids in sandy sediment. The ancestrula of S. fossa settles several millimetres below the sediment surface where, as it grows, rootlet fibrils attach to those of other colonies. The mature colony complex is analogous to a ramifying fungal mat, with fruiting bodies (mature colonies) supported above the substratum on stalks. Presumably the larvae, like those of Parmularia, once released, are negatively phototaxic or positively geotaxic, penetrating the sediment before metamorphosing. After metamorphosis, the rootlet extends considerably and can be as much as 3 mm long while supporting only 3-4 zooids. Rootlets of mature colonies occurring in sediment are 10-15 mm long with colonies raised 5 mm above the substratum, but laboratory-cultured specimens can have rootlets up to 30 mm long. Penetrating the skeleton where the extrazooidal rhizoid originates is a conical pit, about half the diameter of the colony, communicating through pores to the surrounding zooids (Cook & Chimonides 1981). Individual zooids are Celleporaria-like in zooidal morphology, but are orientated with the distal direction towards the stalk or pit This is reversed budding with respect to the apparent colony growth (i.e., like the growth of conescharellinid bryozoans). After the first few buds have been produced from the ancestrula, subsequent budding is from the interzooidal areas or frontal. A median suboral avicularium with crossbar occurs on each zooid; the mandible is directed towards the proximal end of the zooid. Ovicells have not been described, but are peristomial and cucullate, as in Celleporaria.

Living populations of Sphaeropora species have been found from Townsville in Queensland, from New South Wales, Tasmania, Bass Strait, South Australia and Western Australia, in depths ranging from 23 m to 1264 m, in association with other rooted Bryozoa. The fossil record of Sphaeropora ranges from the Late Eocene; the restriction of the genus to Australian shelf and upper slope environments reflects the low larval dispersal distances.

Only one genus of Lepraliellidae has been recorded from Antarctica. Hayward (1993, 1995) described small encrusting colonies of Acanthophragma polaris from the Ross Sea.

The family Lepraliellidae dates from Upper Campanian (Late Cretaceous) (genus Frurionella) (Gordon 1993). The earliest Celleporaria-like colonies are those of Reptocelleporaria accumulata (von Hagenow) from a little later in the lower Maastrichtian. These are small and encrusting and very like Celleporaria, with small adventitious avicularia and large spatulate avicularia, but the ovicell tends to be partly concealed by the orificial peristome.

Diagnosis

Colony well to heavily calcified, encrusting or semi-erect, mammilliform, or small, free-living, anchored by extrazooidal peduncles or rhizoids. Zooids well integrated, often frontally budded, forming maculae associated with excurrent chimneys. Small, globular or rounded colonies often with reversed frontal budding. Zooid frontal shields umbonuloid, smooth, with marginal areolae, and oral or other adventitious avicularia. Very large, interzooidal or vicarious avicularia often present Ovicells prominent, shallow, 'cucullate'.