Family CALWELLIIDAE MacGillivray, 1887

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Family CALWELLIIDAE MacGillivray, 1887

Compiler and date details

July 2001 - Dr Philip Bock

Calwelliidae MacGillivray, 1887.
Onchoporidae Busk, 1884.

Introduction

The family Calwelliidae was introduced by MacGillivray (1887) for the genus Calwellia, which had first been described for Calwellia bicornis by Wyville Thomson in 1858. Gordon (1989) gave notes on the publication history of this name. C. bicornis was from Bass Strait. A second species, C. gracilis was illustrated from off Portland, Victoria, by Maplestone (1882). This paper consists of notes on living bryozoan species, but, apart from one small sketch purporting to be of C. gracilis, no description, nor any notes on living colonies of the species was given. Gordon (1989) discussed both species and gave a full description of material from New Zealand which he identified with C. gracilis. MacGillivray (1880) had described Victorian specimens of C. bicornis and remarked 'there may be more than one species'. Elucidation of the problem has to await further collection and examination of Victorian specimens.

The distinctive characters of Calwellia are the erect branches of alternating pairs of zooids, which consist of a dilated distal part and a long, tubular proximal part which is inserted between the distal portions of the two more proximal autozooids. The orifice is almost straight proximally and is flanked by hollow spinous processes. There is a small proximal ascopore.

The Calwelliidae includes five genera, three of which occur in Australia. All are closely similar to each other, and are separated principally by details of the mode of growth. All have flexible colonies, with thinly calcified autozooids which have an ascopore.

C. bicornis occurs in bushy tufts 'half an inch high' according to Wyville Thomson (1858). The branches have no joints, the proximal parts of the zooids being deficient in calcification which allows flexibility. C. bicornis was also reported to be associated with catenicellid bryozoans as a substratum.

C. gracilis has a similar growth form, but the autozooids are more slender. They have a rounded ascopore, flanked by a pair of large frontal pores and spinous processes. In both species the ovicells are large, globular and prominent. They have a membranous ectooecium and calcified entooecium, are ridged laterally and basally and are not closed by the operculum.

The genus Malakosaria was introduced by Goldstein (1882) for Challenger material he called M. pholarhamphos. This species is identical with Onchopora sinclairii, described earlier by Busk (1857). The name Onchopora is a junior synonym of Margaretta, and is not available for Busk's species (Harmer 1957). M. sinclairii has branches of biserial to quadriserial autozooids unlike those of Calwellia. The frontal shield of the autozooids has a curved ascopore and paired frontal pores. There are also frontal pores distal to the orifice. The ovicell has a membranous ectooecium and ridged calcified entooecium. Malakosaria dentata was originally referred to Urceolipora by MacGillivray (1885) and was illustrated as U. nana on the plate. Specimens were from Port Phillip 'forming small tufts about an inch high'. It is not related to the genus Urceolipora, but has a similar growth form (Gordon 1989).

Malakosaria has been reported from Australia, New Zealand, Marion, Heard and Kerguelen Islands ( Busk 1879 and Gordon 1989) from a depth range of 64-3600 metres.

The genus Ichthyaria was introduced by Busk (1884) for specimens from the Falkland Islands. I. oculata has biserial branches of zooids facing the same way, the basal walls of which are only partially calcified. The frontal wall is smooth, with an asymmetrically placed ascopore and paired frontal pores. The ovicells are smooth, prominent and not closed by the operculum. I. oculata thus resembles other genera and species of Calwelliidae, differing in the mode of growth. Harmer (1902) illustrated C. gracilis, M. sinclairii and I. oculata when discussing the morphology and development of the ascus.

Diagnosis

Colony flexible, thinly calcified, erect, bushy, anchored by rhizoids. Zooids paired, back-to-back, expanded distally, tubular proximally, and inserted between previously budded zooids. Orifice large, with spinous processes and a proximal ascopore. Avicularia absent; ovicell large, prominent, with a calcified entooecium and membranous ectooecium.