1 Class Stenolaemata Order Cyclostomata Philip E. Bock, Paul D. Taylor, Peter J. Hayward and Dennis P. Gordon 1.1 Definition and general description may be encrusting or erect and branching or foli- Stenolaemata is the most ancient bryozoan class, ose. They are typically dense, opaque white in with a fossil record beginning in the earliest Ordo- colour, occasionally flushed pink or purple, and vician, ~500 million years ago (Taylor and Ernst the calcification can appear speckled because of the 2004; Ma et al. 2015). Seven orders are recognised presence of numerous tissue-plugged pseudopores. currently (Taylor and Waeschenbach 2015), of In the Crisiidae, exemplifying the erect, branching which only Cyclostomata survives and includes all Articulata, the zooids are arranged in narrow rows living stenolaemate species. Globally, the order with openings on only one side of the slender, flex- Cyclostomata includes some 543 species assigned ible colony of branches linked by cuticular joints to 98 genera and 23 families (Bock and Gordon (nodes). Erect colonies of species of Tubuliporina, 2013). The group comprises, on average, ~11% of Cancellata and Cerioporina are unjointed (with the the species in any Recent bryozoan fauna (range single exception of the tubuliporine genus Crisuli- 0–24%, Banta 1991) and only rarely dominates in pora), gracile to robust, and have zooids arranged terms of numbers of colonies or biomass. evenly, in clusters or in ordered transverse rows. Stenolaemates are commonly termed ‘tubular Many species of Tubuliporina have encrusting col- bryozoans’, in reference to their elongate, slender, onies, occasionally taking the form of simple, uni- usually cylindrical zooids. The basal and vertical serial chains, but more often narrow, oligoserial walls of the zooid are heavily calcified, and the lobes or circular to irregular, flat disks or low small terminal membrane at the distal tip of the domes. Colony form may be diagnostic for a given tube represents the only area of flexible, uncalci- cyclostome species, or may show extraordinary fied body wall. Colonies grow through the exten- variation apparently in response to environmental sion and sequential division of a multizooidal influences. Homeomorphy in colony form between budding zone, termed by Borg (1926) the ‘common species, genera and even families has been a con- bud’, which in some groups persists in later ontog- siderable source of taxonomic confusion. eny as an extrazooidal, hypostegal body cavity. Fundamental morphological differences exist Living Cyclostomata are important as models between cyclostome zooids and those of other for reconstructing the anatomy, biology and ecol- extant bryozoans. The orifice, medially situated in ogy of extinct stenolaemates, but their classification the terminal membrane, can be closed by a sphinc- remains a problem at all taxonomic levels, and ter muscle; below it, the body wall is introverted to especially at family level. Colony form varies – they form a tentacle sheath enclosing the lophophore, Chapter 01.indd 1 23-01-2018 16:26:12 2 AUSTRALIAN BRYOZOA and the entire polypide is enclosed within a fur- Bryozoa collected during the H.M.S Challenger ther envelope of mesodermal tissue (= the mem- Expedition (Busk 1886). Kirkpatrick (1888b) branous sac). The entosaccal cavity within the described five species (two of them new) from Port membranous sac is considered to be a coelom, but Phillip, Victoria, and later listed four from the the exosaccal cavity surrounding the sac is proba- Torres Straits (Kirkpatrick 1890a). Although addi- bly a pseudocoel (Nielsen and Pedersen 1979). Basic tional species were described, or recorded from zooid form varies little throughout the order, and Australia by early writers, they have attracted very polymorphism is limited. The hollow spines of little specialist interest. Indeed, apart from minor some species, and the tubular units comprising the taxonomic contributions, often appended to more anchoring rootlets in Crisiidae, are coelomic cham- detailed accounts of cheilostome-dominated bers, with a lining peritoneum but no polypide, faunas, present knowledge of the Recent Cyclosto- and can be considered kenozooids. Other types of mata is due entirely to the research of very few kenozooids include the cancelli of Cancellata and authors. the alveoli of Rectangulata. Species of Plagioeciidae S.F. Harmer made some of the earliest signifi- may have distinctive, dwarf zooids, termed nano- cant contributions with his work on the embryol- zooids, each equipped with a minute lophophore ogy of Crisia, Lichenopora and Tubulipora (see comprising a single tentacle that appears to serve a Harmer 1890, 1893, 1894, 1896, 1898). His first cleaning function (Silén and Harmelin 1974). The report on the Bryozoa of the Siboga Expedition conspicuous brood chambers seen in most cyclos- (Harmer 1915) was an important contribution to tome species are highly modified zooidal poly- the study of Indo-West-Pacific cyclostome faunas. morphs, termed gonozooids, that sometimes However, the work of F. Borg provides the base- expand into space that would otherwise have been line for all modern studies of the Cyclostomata, in occupied by autozooids or kenozooids. particular his morphological and systematic stud- The reproductive cycle of cyclostomes is pro- ies (Borg 1926, 1933), together with his monograph foundly different from that of the other bryozoan on the Antarctic cyclostome Bryozoa (Borg 1944). classes and involves polyembryony. In all living Significant subsequent publications include: cyclostomes, the fertilised ovum undergoes several Nielsen (1970) on metamorphosis and develop- cleavages to form a primary embryo. Blastomeres ment of the ancestrular zooid; Nielsen and Ped- separate from the primary embryo, singly or in ersen (1979) on zooid wall structure and groups, and undergo further cleavage to form sec- lophophore eversion in Crisia; a monographic sys- ondary embryos. The secondary embryos may tematic and ecological survey of Mediterranean then fragment and continue cleavage to form ter- tubuliporines by Harmelin (1976); research on tiary embryos, so that the gonozooid becomes skeletal ultrastructure, organisation and its rele- packed with large numbers of clonal offspring vance to cyclostome phylogeny (Taylor 2000; (Hughes et al. 2005). Taylor and Weedon 2000, and references therein); and Waeschenbach et al. (2009) on the molecular phylogeny of cyclostomes (see also Taylor et al. 1.2 History of discovery 2011; Waeschenbach et al. 2012). The ecology and Busk (1852) first distinguished Cyclostomata from morphology of living cyclostomes has attracted Cheilostomata, because of the round, non-opercu- some recent research interest (e.g. McKinney 1988, late openings of the zooids, and recorded five spe- 1993), but taxonomic and faunistic studies on cies from Australian seas. Further Australian regions other than the NE Atlantic (e.g. Hayward records were provided in the cyclostome volume of and Ryland 1985; Ramalho et al. 2009) and Medi- Busk’s (1875) catalogue of the British Museum bry- terranean (e.g. Hayward and McKinney 2002) are ozoan collections, and in the second report of the still relatively few (e.g. Brood 1976). Chapter 01.indd 2 23-01-2018 16:26:12 14 AUSTRALIAN BRYOZOA 1882, and currently is considered to comprise only (Idmidronea and Exidmonea) colonies. Of the 11 Tervia with three species worldwide (Bock and genera and 105 species attributed to the family by Gordon 2013). The most distinctive feature of this Bock and Gordon (2013), only two genera and nine genus is the presence of gonozooids on the dorsal species are currently recorded for Australia, surfaces of the erect branches, rather than their excluding the Australian Antarctic Territory. more usual location on the frontal surface among the autozooids. Morphology The genus Nevianipora is assigned to the family Autozooids are commonly, but not always, grouped Terviidae in some references (e.g. Bassler 1953), but into longitudinal or oblique connate rows. Peri- is here included in Diaperoeciidae based on the stomes tend to be long and delicate, diverging dis- morphology and frontal location of the tally from those of adjacent connate zooids as they gonozooids. grow. Gonozooids open on the frontal surface of branches as large inflated expansions, usually Morphology growing around several series of autozooids. The Colonies are erect with narrow, bifurcating ooeciostome is either adnate to an autozooidal per- branches typically ovate in cross section. Autozoo- istome or separate, and has a simple circular or ids open on the branch frontal surface only, often in flanged ooeciostome. The surfaces of both the auto- rows of three to four apertures diverging from the zooids and gonozooids are pierced by numerous branch mid-line. The dorsal surface of branches is pseudopores. Kenozooids are often present, flank- formed from the basal exterior walls of autozooids. ing the edges of the branches in encrusting colonies Gonozooids are situated on the dorsal surface of or reinforcing the dorsal sides of the branches in branches and are elongate with a terminal erect colonies. ooeciopore. Colonies of Tubulipora are encrusting, and typi- cally spread from the ancestrula as one or several Australian diversity elongate or rounded lobes. In Idmidronea Canu and Tervia jellyae was described by Harmer (1915), with Bassler, 1920, the colonies have encrusting bases a distribution including North Queensland, Torres from which arise narrow branches, with the auto-