Rostanga australis
- Radula
PHOTO
From Figure 19. Rostanga australis, radular morphology of South Australian specimens. A-D,Juvenile specimen, AM C145127. A, Central region; B, outermost lateral teeth; C, jaw plates on roof of buccal cavity; D, jaw plate, A, C, D, scale bar = 100 µm, B = 20 µm. Photo G.J. Avern. [Rudman, W.B. & Avern, G.J. (1989). The genus Rostanga Bergh, 1879 (Nudibranchia: Dorididae) in the Indo-West Pacific. Zoological Journal of the Linnean Society 96: 281-338.]
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In the largest adult specimen the innermost lateral tooth has a broad base and a recurved hook-like pointed cusp without denticulation. The adjacent lateral teeth are similar in shape and size but gradually lengthen towards the outside. A maximum size is reached about ten teeth from the outside, from where they rapidly reduce in size. The outermost two teeth show some denticulation, with one or two rounded bumps on the outside just below the tip. The teeth of the two smallest specimens are similar in general morphology to those of the adults but have a much higher degree of denticulation (Figs A, D). The basal half of the inside edge of the innermost lateral tooth is fringed with approximately twelve short denticles and the ten outer lateral teeth have up to ten long bluntly rounded outer denticles reminiscent of the radular teeth of the chromodorid genus Digidentis (Rudman, 1984). Intermediate sized specimens show no signs of denticulation on the innermost tooth of each row but the ten outer laterals show stages in the loss of denticulation, some teeth having no denticles, some having eight or nine denticles and others having an intermediate arrangement). The jaw plates are small consisting of a fringe of two to three rows of chitinous rodlets at the anterior end of the buccal cavity (Figs C, D).
The radular formulae of two specimens from South Australia are:
83.0.83 x 56 (+ 1) - 31 mm alive (AM C145182)
35.0.35 x 41 (+ 2) - 15 mm alive (AM C145127)
The formulae of three specimens from the Portsea Pier, Victoria, population (AM C149545) are:
28.0.28 x 36 (+ 1) - 5 mm preserved
50.0.50 x 40 (+ 2) - 14 mm preserved
50.0.50 x 53 (+ 1) - 17 mm preserved
Rudman, W.B., 2002 (February 5) Rostanga australis - Radula. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/rostaustrad
