Australian Bryozoa Volume 2: Taxonomy of Australian Families

321 Pages·2018·20.85 MB·English

by  Patricia Cook

Australian
BRYOZOA
Volume 2
Taxonomy of Australian Families
Editors: Patricia L. Cook, Philip E. Bock, Dennis P. Gordon and Haylee J. Weaver
Australian
BryozoA
Volume 2
Taxonomy of Australian Families
Editors:
Patricia L. Cook, Philip E. Bock, Dennis P. Gordon and Haylee J. Weaver
© Commonwealth of Australia 2018
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Volume 2 to be cited as:
Cook PL, Bock PE, Gordon DP and Weaver HJ (eds) (2018) Australian Bryozoa Volume 2: Taxonomy of
Australian Families. CSIRO Publishing, Melbourne.
Individual chapters cited as:
Bock PE, Taylor PD, Hayward PJ and Gordon DP (2018) Class Stenolaemata, Order Cyclostomata. In Cook
PL, Bock PE, Gordon DP and Weaver HJ (eds) Australian Bryozoa Volume 2: Taxonomy of Australian Families.
pp. xx–xx. CSIRO Publishing, Melbourne.
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Contents
List of authors v
1 Class stenolaemata, order Cyclostomata 1
Philip E. Bock, Paul D. Taylor, Peter J. Hayward and Dennis P. Gordon
1.1 Definition and general description 1
1.2 History of discovery 2
1.3 Morphology 3
1.4 Natural history 5
1.5 Classification 6
1.6 Taxonomic treatments of families of Cyclostomata 6
References 27
2 Class Gymnolaemata, order Ctenostomata 33
Patricia L. Cook, Philip E. Bock and Dennis P. Gordon
2.1 Introduction to the class Gymnolaemata 33
2.2 Order Ctenostomata 33
2.3 Classification of the Ctenostomata 37
2.4 Taxonomic treatments of families of Cyclostomata 37
References 54
3 Class Gymnolaemata, order Cheilostomata 61
Patricia L. Cook, Philip E. Bock, Peter J. Hayward and Dennis P. Gordon
3.1 Definition and general description 61
3.2 Colony morphology 63
3.3 Zooidal morphology 63
3.4 Classification of Cheilostomata 74
3.5 Relationships within the Cheilostomata and with the order Ctenostomata 79
3.6 Taxonomic treatments of the families of Australian Cheilostomata 79
3.7 Taxonomic treatments of families of Cheilostomata 81
References 251
4 Class Phylactolaemata 281
Timothy S. Wood
4.1 Definition and general description 281
4.2 History 284
4.3 Morphology and physiology 285
4.4 Natural history 289
4.5 Fossils 290
4.6 Collection and preservation 290
4.7 Taxonomy 291
References 293
Index 296
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List of authors
Philip E. Bock Paul D. Taylor
Museum Victoria, Melbourne, Victoria 3001, The Natural History Museum, Cromwell Road,
Australia. London, United Kingdom.
Patricia L. Cook (deceased) Timothy S. Wood
Glen Waverley, Victoria 3150, Australia. Department of Biological Sciences, Wright State
University, Dayton, Ohio, United States.
Dennis P. Gordon
National Institute of Water and Atmospheric
Research, Wellington 6021, New Zealand
Peter J. Hayward
Southgate, Swansea SA3 2AH, United Kingdom.
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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-
ose. They are typically dense, opaque white in
Stenolaemata is the most ancient bryozoan class,
colour, occasionally flushed pink or purple, and
with a fossil record beginning in the earliest Ordo-
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 tentacle crown
2 AustrAliAn BryozoA
(= lophophore) and the entire polypide is enclosed bryozoan collections, and in the second report of
within a further envelope of mesodermal tissue (= the Bryozoa collected during the H.M.S Challenger
the membranous sac). The entosaccal cavity within Expedition (Busk 1886). Kirkpatrick (1888b)
the membranous sac is considered to be a coelom, described five species (two of them new) from Port
but the exosaccal cavity surrounding the sac is Phillip, Victoria, and later listed four from Torres
probably a pseudocoel (Nielsen and Pedersen Strait (Kirkpatrick 1890a). Although additional spe-
1979). Basic zooid form varies little throughout the cies were described, or recorded from Australia by
order, and polymorphism is limited. The hollow early writers, they have attracted very little special-
spines of some species, and the tubular units com- ist interest. Indeed, apart from minor taxonomic
prising the anchoring rootlets in Crisiidae, are coe- contributions, often appended to more detailed
lomic chambers, with a lining peritoneum but no accounts of cheilostome-dominated faunas, present
polypide, and can be considered kenozooids. knowledge of the Recent Cyclostomata is due
Other types of kenozooids include the cancelli of entirely to the research of very few authors.
Cancellata and the alveoli of Rectangulata. Species S.F. Harmer made some of the earliest signifi-
of Plagioeciidae may have distinctive, dwarf cant contributions with his work on the embryo-
zooids, termed nanozooids, each equipped with a logy of Crisia, Lichenopora and Tubulipora (see
minute lophophore comprising a single tentacle Harmer 1890, 1893, 1894, 1896, 1898). His first
that appears to serve a cleaning function (Silén and report on the Bryozoa of the Siboga Expedition
Harmelin 1974). The conspicuous brood chambers (Harmer 1915) was an important contribution to
seen in most cyclostome species are highly modi- the study of Indo-West-Pacific cyclostome faunas.
fied zooidal polymorphs, termed gonozooids, that However, the work of F. Borg provides the base-
sometimes expand into space that would other- line for all modern studies of the Cyclostomata, in
wise have been occupied by autozooids or particular his morphological and systematic stud-
kenozooids. ies (Borg 1926, 1933), together with his monograph
The reproductive cycle of cyclostomes is pro- on the Antarctic cyclostome Bryozoa (Borg 1944).
foundly different from that of the other bryozoan Significant subsequent publications include:
classes and involves polyembryony. In all living Nielsen (1970) on metamorphosis and develop-
cyclostomes, the fertilised ovum undergoes several ment of the ancestrular zooid; Nielsen and Ped-
cleavages to form a primary embryo. Blastomeres ersen (1979) on zooid wall structure and
separate from the primary embryo, singly or in lophophore eversion in Crisia; a monographic sys-
groups, and undergo further cleavage to form sec- tematic and ecological survey of Mediterranean
ondary embryos. The secondary embryos may tubuliporines by Harmelin (1976); research on
then fragment and continue cleavage to form ter- skeletal ultrastructure, organisation and its rele-
tiary embryos, so that the gonozooid becomes vance to cyclostome phylogeny (Taylor 2000;
packed with large numbers of clonal offspring Taylor and Weedon 2000, and references therein);
(Hughes et al. 2005). and Waeschenbach et al. (2009) on the molecular
phylogeny of cyclostomes (see also Taylor et al.
2011; Waeschenbach et al. 2012). The ecology and
1.2 History of discovery
morphology of living cyclostomes has attracted
Busk (1852) first distinguished Cyclostomata from some recent research interest (e.g. McKinney 1988,
Cheilostomata, because of the round, non-opercu- 1993), but taxonomic and faunistic studies on
late openings of the zooids, and recorded five spe- regions other than the Atlantic (e.g. Hayward and
cies from Australian seas. Further Australian Ryland 1985; Ramalho et al. 2009) and Mediterra-
records were provided in the cyclostome volume of nean (e.g. Hayward and McKinney 2002) are still
Busk’s (1875) catalogue of the British Museum relatively few (e.g. Brood 1976).
1 – Class stenolaemata, order CyClostomata 3
1.3 Morphology distribution (Weedon 1998; Jenkins and Taylor
2017). This type of calcification, with the mineral-
Colonies of cyclostome bryozoans can be extremely
ised skeleton directly underlying an organic cuti-
plastic, with an architecture and geometry
cle, is known as an exterior wall. Growth of the
responding to environmental influences; homeo-
colony proceeds by the expansion of an uncalcified
morphy is widespread. The most regular colonies
portion of cuticle to form a multizooidal bud, the
are those of Crisiidae, the sole family of the subor-
der Articulata. Crisiid colonies are erect, unilami- ‘common bud’ of Borg (1926), which is then sequen-
nate, uniserial to biserial, and branching. Each new tially divided by interior calcified walls to partition
ramus (or internode) buds adventitiously from a off new zooids. These interior walls are lined on
single zooid at a point on the preceding ramus that both sides by epithelium, contain interzooidal
may vary in location (Ryland 2000). The proximal pores and lack a cuticular layer. Cyclostome skele-
part of the new zooid – the basis rami – is sepa- tons comprise three types of walls defined topo-
rated from its distal portion by a flexible joint, the logically: basal, vertical and frontal. Basal walls
node; the node appears to develop in place of the are generally exterior walls, except in some bifoli-
calcified body wall, which is resorbed. The number ate species where the basal walls of the back-to-
of zooids comprising a node, and the pattern of back zooids may be interior walls. Vertical walls
branching, are sometimes characteristic for a genus are interior walls, whereas frontal walls may be
or species. Colony form is more diverse in the sub- either interior or exterior walls depending on sub-
order Tubuliporina, ranging from uniserial order and zooidal polymorph type. The calcified
encrusting chains, to lobate sheets, discs or frontal walls of articulates and tubuliporines,
mounds, to erect, branching growths, which may including the tubular extensions around apertures
have a colony architecture characteristic for the called peristomes, are formed by exterior walls to
genus, or vary according to habitat. Few genera are which the soft tissues are firmly anchored, and are
recognisable from colony form alone, and in most referred to as fixed-walled. The gonozooids of
tubuliporines the morphology of the gonozooid is cerioporines, roofed by calcified exterior walls con-
a particularly significant taxonomic character. taining pseudopores, are typically subcircular in
More recently, the morphology of pseudopores overall shape, occasionally longitudinally ovoidal,
(see p. 4) has been found to be of taxonomic value or digitate and irregular. They may occupy space at
(Taylor and Zaton´ 2008). In many tubuliporines, the the expense of kenozooids and extend around and
apertures of feeding zooids are spaced evenly between the autozooids. A hypostegal pseudocoel
across the colony surface, but in others they are normally links the autozooids and kenozooids
grouped into connate rows or subcircular fascicles. above the ends of their vertical walls, an organisa-
Species with apertures in clusters have been sepa- tion called free-walled. Frontal walls in cancellates
rated by some bryozoologists into a distinct subor- when developed are interior walls lying beneath
der, Fasciculina, but this is probably not a natural the hypostegal pseudocoel. The gonozooids in this
group (Taylor 2000). All Cancellata and most Cerio- suborder and in rectangulates are roofed by inte-
porina develop erect colonies, often robust, and rior walls, making the skeletal organisation of
richly branched or capitate, but colonies of the Rec- these two suborders entirely free-walled.
tangulata are always encrusting – growing as discs, The morphology of the polypide is relatively
mounds, cups or cones. uniform throughout the Cyclostomata. The zooidal
In all living cyclostomes the larva that founds orifice lies at the centre of the terminal membrane
the colony metamorphoses to produce a hemi- and can be closed by a sphincter; between the ter-
spherical protoecium, bounded by an outer, cuticu- minal membrane and the tips of the withdrawn
lar body wall that undergoes calcification on its tentacles lies a cavity termed the atrium (or vesti-
inner surface and contains pseudopores varying in bule). In most genera, the atrium is closed just