PYURIDAE Hartmeyer, 1908

Kott, Patricia, 2009, Taxonomic revision of Ascidiacea (Tunicata) from the upper continental slope off north-western Australia, Journal of Natural History 43 (31 - 32), pp. 1947-1986 : 1979-1980

Family PYURIDAE Hartmeyer, 1908

Type genus: Pyura Molina 1782 .

The family is one of the most speciose of the Stolidobranchia . Also, pyurid individuals are specially resilient with tough fibrous tests that often are hard and almost impreg- nable. In many species the test is covered with epibionts and sometimes has scales and/ or pointed papillae or tubercles on the surface; and as a result of its strong adhesive properties a range of stalks, roots and hairs enhance its attachment to the substrate or attach a covering of sand or other particles. Body muscles also are strong; longitudinal bands from the each of the apertures cross one another on the sides of the body and the creases, wrinkles, folds and furrows that form on the surface when the organism is contracted further increase the strength of the test. The test of pyurid ascidians also appears to accommodate changes in external morphology (such as changes in body shape and orientation of apertures) in response to environmental pressures. Branched branchial tentacles and overlapping scales or spines in the siphonal linings of Pyuridae probably prevent the entry of foreign organisms with the incurrent feeding stream. The branchial sacs of species in this family are large and the filtering area vastly increased from the flat branchial sac of phlebobranch ascidians; and it is in this group of genera that arborescent or elaborate sessile glandular diverticula of the gut develop in the pyloric region replacing the simple gastric folds of genera of the Styelidae . It appears that species of the stolidobranch family Pyuridae have physical attributes of the test that provide protection for these large individuals and support their occupation of shallow water habitats. Species of this family have long gut loops, distinctive digestive diverticula and large, folded, branchial walls and may be among the most efficient filter-feeding species of solitary Ascidiacea. However, despite the adaptive advantages associated with the mechanical efficiency of their morphology, this group appears to be more diverse in temperate Australian shallow water habitats (where a range of indigenous species has been observed) than it is in the tropics where species tend to have vast geographic ranges ( Kott 1985). Species of this family have large hermaphrodite gonads on both sides of the body and fertilization is external, possibly both advantageous to dispersal and geneflow in species with a wide geographic range.

The Pyuridae also have radiated in deeper water habitats where a filter feeding capacity appears to be of less significance. A number of genera have been reported (see listing in Kott (1985)), including Hemistyela Millar, 1955 , which has transversely oriented stigmata in a folded branchial wall ( Sanamyan KE and Sanamyan NP 2006).

In the present collection, the family is represented by a single specimen of Culeolus herdmani , a common component of waters of the continental slope 400 m to 1000 m.