Cucuvitrum rowei O'Loughlin and O'Hara

Fissiparity by Cucuvitrum rowei O’Loughlin and O’Hara

John Eichler collected a live specimen of Cucuvitrum rowei O’Loughlin and O’Hara, 1992 from Port Phillip Bay in SE Australia on 20 April 2008 (NMV F157401; variably 19 to 30 mm long live). During subsequent days peristaltic-like body contractions were observed and photographed (fig. 1a). Between April 22 and 25 the specimen divided transversely into two individuals (smaller 7 mm long). Peristaltic-like body contractions continued in both post-fissiparity individuals. Overnight on May 1 to 2 the larger individual divided transversely again (fig. 1b). Preservation and dissection of these individuals revealed that the larger post-fissiparity oral end individual had fully developed tentacles and calcareous ring, but lacked internal organs. Detached internal organ remnants were present in the smaller anal end individuals that lacked tentacles and ring. One apparent purpose of the peristaltic movements was to push the internal organs to the anal end of the coelom to provide a nutrient source for the subsequent regeneration of tentacles, ring and internal organs.

On 3 August 2008, seven smaller specimens were collected from Port Phillip Bay (NMV F161549; up to 12 mm long). After nine days none had undergone fissiparity. On 30 August 2008, five specimens were collected from Port Phillip Bay (NMV F161500; up to 16 mm long). Overnight on September 6 to 7 one of the larger individuals divided transversely. During his fieldwork John Eichler frequently noticed individuals in close proximity on the undersurface of rocks. This clustering may be a consequence of fissiparity.

Leon Altoff and Audrey Falconer photographed a live specimen in the field that showed regeneration of the anal end (fig. 1c; 4 mm long; NMV F157419). Dissection by Emily Whitfield of a large collection of NMV preserved specimens of Cucuvitrum rowei revealed rare individuals that showed evidence of fissiparity. Post-fissiparity oral ends lacked internal organs but had withdrawn fully developed tentacles and calcareous ring (fig. 1d; NMV F161501); and post-fissiparity anal ends showed a reduced developing calcareous ring and small tentacles (fig. 1d; NMV F161501), or lacked a calcareous ring and tentacles.

O’Loughlin (1991, 1994) reported fissiparity by similar mid-body transverse constriction and division in the dendrochirotid Squamocnus aureoruber O’Loughlin and O’Hara, 1992 from the rocky shallows of southern Australia. This is the first record of fissiparity by the dendrochirotid Cucuvitrum rowei, and the first record of peristaltic body movements in a dendrochirotid holothuroid.