History Of Collecting And Taxonomic Diversity Of Great Barrier Reef Bryozoa

As the British biologist John Ryland noted, the most outstanding thing that can be said about research on GBR Bryozoa is its paucity, given the undoubted richness of the fauna, although the number of studies on particular taxa have been increasing in recent years. Ryland summarised the history of collecting from the 1840s to the 1970s and wrote a short account of the Bryozoa of the GBR for the 1984 Coral Reef Handbook based on his personal collecting. This collection, mostly from Heron Island, formed the basis of two important papers published by him and another British colleague in the 1990s. (For information on collecting bryozoans, see Box 25.3.)

Current known bryozoan diversity in the Great Barrier Reef Province from Torres Strait to the southernmost section is based on distributional information, species lists, and descriptions provided by 20 bryozo-ologists and two ecologists from 1852 to 2006. The tally from all sources, after accounting for synonyms, is 319 species for the entire Great Barrier Reef Province (see Table 25.1).

This figure for the number of species is probably extremely conservative, especially given the geographic area covered by the GBR, as well as the wide variety of habitats and niches that can be occupied by the range of colony form that bryozoans can exhibit (see below). The neighbouring New Caledonian bryofauna comprises 407 species, of which 178 species are found in the first 100 metres and 232 species range into or are found only at depths greater than 100 m. Some 178 species were recently reported in the Solomon Islands fauna, of

BOX 25.2 REPRODUCTION

Usually zooids are hermaphroditic, their sperm maturing before their ova. Some bryo-zoan species have separate female and male zooids that differ in shape, size, and anatomy. Purely reproductive zooids may lack a gut and have a few tiny non-ciliated tentacles whose sole function is to release sperm. This surprising use of tentacles as vasa deferen-tia (sperm ducts) appears to be true for all bryozoans. Since the lophophore also serves as a gill for respiration, it is a truly a multipurpose structure.

Fertilisation in bryozoans is internal. Sperm from one colony are captured by a recipient colony's tentacles, to which they first adhere then move downwards towards a duct (intertentacular organ) or, more commonly, a pore that allows entry into the body cavity. Fertilised eggs may be incubated in a special sac within the zooid, within a modified zooid (gonozooid or brood chamber), or, as in the majority of species, in a hood-like ovicell distal to the maternal orifice.

BOX 25.3 COLLECTING

Erect bushy, stick-like, and lace-like bryozoans can easily be detached from their substratum. Encrusting bryozoans are harder to collect unless they are on pieces of shell, seaweed, or coral. A thin blade can be used to lift or scrape some off the substratum. Details regarding permits required for collecting in the various zones of the GBR are provided in Chapter 12.

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