Hypselodoris obscura ( Stimpson, 1855 )

Johnson Aângel Valdeâs, Rebecca F., 2001, complex (Mollusca, Nudibranchia, Chromodorididae), with remarks the genus Brachychlanis Ehrenberg, 1831, Journal of Natural History 35 (9), pp. 1371-1398 : 1386-1389

Hypselodoris obscura ( Stimpson, 1855)

(®gures 1C, 10A, B, 11, 12)

Goniodoris ? obscura Stimpson, 1855: 388 ±389.

Goniodoris crossei Angas, 1864: 54 .

Chromodoris crossei (Angas) : Bergh, 1883, pl. 7, ®gures 4±8, pl. 8, ®gure 1; 1884a: 648±650.

Chromodoris runcinata Bergh : Bergh, 1884b: 76 ±78, pl. 6, ®gures 1±4.

Hypselodoris infucata (RuÈppell and Leuckart) : Thompson, 1972: 395 ±398 (in part), ®gure 2G±J, pl. 2, ®gure E.

Hypselodoris obscura (Stimpson) : Rudman, 1977: 387; 1984: 185 ±188, ®gures 48±51, 56, 58; Gosliner and R. Johnson, 1999: 61.

Additional material

Pittwater , Coaster’s retreat, New South Wales, Australia, January 1981, two specimens, 14±16 mm long, leg. W. B. Rudman ( AM C126484 ). Callala Point, Jervis Bay, New South Wales, Australia, November 1984, one specimen, 16 mm long, leg. J. Hunter and H. Woodward ( AM C144046 ) .

Distribution

This species is distributed throughout temperate south-eastern Australia (Rudman, personal communication).

External morphology

The living animals are up to 50 mm in length. The body is elongate and relatively high in pro®le, clearly higher in the middle region, where the posterior end of the foot emerges (®gure 1C). The general body colour is blue. Dark blue and yellow spots (occasionally orange) are scattered over the entire dorsum. The yellow spots are larger than the dark blue ones and may be rounded, oval or occasionally very elongate. The posterior end of the foot is long, extending far beyond the mantle.

The perfoliate rhinophores are composed of 15±18 lamellae. They are white to bluish, with red or reddish orange lamellae. Occasionally the whole rhinophore is red. The gill is composed of 12±18 unipinnate branchial leaves, which are white with a red rachis on either both sides or just the outer side. Sometimes the most distal lamellae are all red and occasionally all of the lamellae are completely red.

There are one to four mantle glands on either side of the head (®gure 10A, B). Sometimes, the number of glands on either side is asymmetrical. There are 10±26 mantle glands along the posterior edge of the mantle.

Anatomy

The buccal mass is divided evenly into an anterior glandular portion and a posterior muscular one. The jaws are composed of a number of elongate, curved, unicuspid rodlets about 10 m m in length (®gure 11D). The radular formula is 60 Ö 94.0 .94 for a 16 mm long specimen ( AM C144046). The innermost lateral teeth have two large cusps, with one shorter denticle on the inner side of the cusp (®gure 11A). The length of the inner denticle is extremely variable. The remaining lateral teeth are hook-shaped, have two cusps and lack denticles on both sides (®gure 11B). Some of the middle laterals of some specimens may have a minute, pointed denticle below the second cusp. The presence of these denticles is not consistent on one radula, much less in radulae from one locality. The outer laterals are short, having one to ®ve denticles situated under the second cusp (®gure 11C).

The reproductive system has an short, oval ampulla that divides into the oviduct and the prostate (®gure 12). The oviduct is short and enters the female glands near the centre of the mass. The prostate is long, tightly coiled with several loops. It narrows and then expands into a long, muscular vas deferens. The ejaculatory portion of the vas deferens is long and coiled, and opens into a common atrium with the vagina. The penis is unarmed. Near the exit of the female glands there is a large, rami®ed vestibular gland. The vagina is long and wide. The small and oval seminal receptacle emerges from the base of the bursa copulatrix. The very long and convoluted uterine duct connects to the vaginal duct distally to the seminal receptacle connection.

Remarks

Hypselodori s obscura is apparently endemic to temperate south-eastern Australia. It is distinguishable from H. infucata solely by the presence of a very long and coiled ejaculatory portion of the vas deferens. Other features proposed in the literature to separate both species are too variable within H. infucata and not useful for this objective (see remarks on H. infucata ).

There are some other diOEerences between H. obscura and H. infucata , but they are not always consistent. For example, in H. obscura the seminal receptacle always emerges from the base of the bursa whereas in the majority of the specimens of H. infucata it emerges from the middle of the vaginal duct. Also, specimens of H. obscura are dark in colour, but H. infucata shows a wide range of colour variation that is not consistent at any locality or consistent with any anatomical features.