Family WATERSIPORIDAE Vigneaux, 1949

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Family WATERSIPORIDAE Vigneaux, 1949

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The family Watersiporidae was introduced by Vigneaux (1949) for Watersipora Neviani (1896). Neviani misidentified his type species, which he gave as Lepralia cucullata Busk (1854), a Recent form from the Aegean. The resulting nomenclatorial problems have been discussed and summarised by Gordon (1989). Busk's type material of L. cucullata was described by Hastings (1930), and the three taxa which occur in Australia were distinguished by Ryland (1974). The family includes Watersipora, Uscia and perhaps Pachycleithonia (Canu & Bassler 1930), which possesses ovicells (Cook 1985). Watersipora is a worldwide fouling form and several different but similar taxa may occur together. Molecular studies may be needed to determine species boundaries. Watersipora is characterised by dark grey or black, usually encrusting colonies which have been figured by Dakin (1987). The autozooids have a finely porous frontal shield, with a few marginal septular pores. The species are usually distinguished by the orifice characters, which may be variously sinuate, or arcuate with a convex proximal rim. The opercula have well-developed black sclerites, which are also used in species determination. Avicularia are absent, and the bright orange-red embryos are brooded in interior ovisacs. The large, orange, bell-shaped tentacle crowns have been figured by Cook (1985) and Gordon & Mawatari (1992). Species of Watersipora are among the best-known and successful fouling bryozoans. Three species have been reported from Australia and were described by Ryland (1974). Gordon (1989) revised the names of the species, which may be called W. cucullata and W. subtorquata, which have sinuate orifices, together with W. arcuata, which has orifices with a convex proximal margin. Brock (1985) has monitored occurrences from South Australia, and Bock (1982) illustrated W. arcuata, which also occurs from New South Wales. W. subtorquata was recorded from the Great Barrier Reef by Hastings (1930) and Ryland (1974).

Undescribed material from Bass Strait of a species very close to the Indo-Pacific Pachycleithonia mutabilis (Canu & Bassler 1929; Cook 1985) is in the collections of the Museum of Victoria.

Larval morphology was described by Zimmer & Woollacott (1989), and references to the large volume of anti-fouling studies involving Watersipora were given by Gordon & Mawatari (1992). These authors noted that populations of W. subtorquata and W. arcuata from New Zealand appeared to be in competition, and that their various fortunes appeared to be temperature controlled. Cook (1985) noted that West African populations were capable of withstanding high temperatures and salinities, and even brief periods of dessication.

A Pliocene fossil species of Watersipora is recorded from Algeria; earlier records are dubious (Taylor 1993).

Diagnosis

Colony usually encrusting, forming sheets, thinly calcified, often deeply pigmented. Zooids monomorphic, frontal shields lepralioid (cryptocystidean), with numerous pseudopores. Orifice with condyles and denticles defining a proximal sinus, proximal peristome sometimes raised, with a spiramen. Operculum with well- marked, pigmented sclerites. Avicularia absent. Brooding in interior ovisacs of undifferentiated zooids, or in small, porous, hyperstomial ovicells. Some species can withstand desiccation, and form world-wide fouling complexes.