Family CRISIIDAE Johnston, 1838

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Family CRISIIDAE Johnston, 1838

Compiler and date details

July 2001 - Dr Philip Bock

Crisiidae Johnston, 1838.

Introduction

The family was introduced by Johnston in 1838 for the genus Crisia. It includes all Recent cyclostomes with articulated colonies.

The colonies are erect, anchored by rootlets, multi-branched, and are composed of calcified internodes of from 1 to more than 30 zooids, which are articulated at cuticular joints. (Crisiona is a Cretaceous to Recent non-articulated form Canu & Bassler 1927).

Colonies are anchored by rhizoids; the proximal part of the colony may be constructed of kenozooidal stem segments. The internodes may be uniserial or biserial. The autozooids are tubular, but may have confluent external surfaces in their proximal portions, forming a flattened branch; the zooids terminate in a circular orifice. Articulated hollow spines may be present; in some cases these are jointed and multizooidal. The gonozooids are bulbous and inflated, with a circular opening (the ooeciostome) at the end of a short tube. Both the zooids and the gonozooids have closely spaced pseudopores on the surface.

Several species from the genera Crisia Lamouroux (1812) and Bicrisia d'Orbigny (1853) have been recorded from Australian waters; in addition, Filicrisia geniculata was recorded from Torres Strait by Harmer (1915). Crisia species are composed of internodes with more than three zooids, in some cases more than 30. Internodes of Bicrisia are usually of two or three zooids, with pairs of jointed curved spines. Filicrisia geniculata (Milne Edwards 1838) has sterile internodes of one, or, more rarely, two or three zooids; spines are not present. It is present in Europe; according to Hayward & Ryland (1985) 'records from other parts of the world are best treated with some suspicion'. Australian specimens are known with internodes composed of a single zooid and a pair of spines, which seem referable to the genus Crisidia, but the lack of gonozooids has not permitted further identification.

The European Crisia eburnea is a Linnaean species, originally described as a species of Sertularia. The most common species in Australian waters is Crisia acropora Busk (1852), which has colonies with dark cuticular joints and nine to thirteen zooids in an internode. It was also figured by Bock (1982), who stated that it is a common shallow-water species. C. setosa was described by MacGillivray (1869, 1879), and C. tenuis by MacGillivray in 1879. Maplestone (1905) described C. cuneata and C. howensis from Lord Howe Island. Bicrisia edwardsiana d'Orbigny (1847) has been recorded, as for example by MacGillivray (1879), but the wide distribution suggests that this group needs closer examination. B. biciliata was described by MacGillivray from Victoria, and Stach (1935) described B. warrnamboolensis, but this may be a synonym of B. biciliata (Borg 1944).

Crisia, Bicrisia, and Filicrisia have been recorded from Antarctic and subantarctic waters, for example by Borg (1944).

No observations of live Australian crisiids are recorded. No information exists on tentacle number of local species, nor the internal biology and the reproductive behaviour and life cycle. Polyembryony is recorded for overseas species, as with other cyclostome bryozoans.

Crisiids have been recorded from shallow coastal waters, attached to algae or to other bryozoans, mainly from depths less than 100 m, although this may reflect sampling frequency. Unpublished data show that crisiids extend to at least 1200 m. They appear to be eurythermal, and are distributed over wide regions. However, the widely distributed records of species such as Crisia acropora and Bicrisia edwardsiana may prove, after detailed comparative study, to have been made of distinct species with similar characters. Estimates of the number of endemic species, or of the total species diversity, would be premature.

The degree of relationship with other suborders of the cyclostome bryozoans is unknown.

The earliest fossil crisiids are described from the Upper Valanginian and Lower Hauterivian of Europe (Voigt & Walter 1991). Internodes of Crisia species are recorded from the Miocene of southeastern Australia (MacGillivray, 1895). Other genera, such as Bicrisia, form much smaller fragments when the cuticular joints decay, and are less likely to be preserved as fossils.
The Crisiidae include cyclostome bryozans with colonies which are erect and branching, or low growing, and jointed. The calcified internodes are joined by cuticular tubes, and are composed of one, two or many zooids. Gonozooids develop from a modified autozooid, and are typically pyriform with a small and inconspicuous ooeciostome. Crisiids are often found as part of a bushy thicket, together with other bryozoans, and algae or hydroids. They are more frequently found in shallow water, but extend to water depths greater than 1200 m.

Diagnosis

Colony lightly calcified, erect, nodal, anchored by rhizoids, with cuticular joints. Autozooids forming uniserial or biserial internodes, tubular, free terminally. All zooids with numerous pseudopores. Articulated spines also present. Gonozooids bulbous and often very inflated, ooeciostome terminal, usually on a short tube.