Discodoris ketos
Creators: name: Valdés, Ángel
Publisher: name: Zenodo
Year: 2002
Subjects: Biodiversity
Taxonomy
Animalia
Mollusca
Gastropoda
Nudibranchia
Discodorididae
Discodoris
Discodoris ketos

description: DISCODORIS KETOS(EV. MARCUS & ER. MARCUS,
1967) (FIGS 4E, 19, 20)
Tayuva ketos Marcus & Marcus, 1967b: 192–194, figs 52-56.
Type material
LECTOTYPE (here designated): Playa Norse, Puerto Peñasco, Sonora, Mexico, 2 November 1963, 28 mm preserved length, leg. P. Pickens (USNM 678409).
Additional material
North of Gauiola, Mazatlán, Sinaloa, Mexico, 1 December 1953, one specimen, 42 mm preserved length, leg. L. O. Miles (CASIZ 081808). Las Cruces, Baja California Sur, Mexico, 25 January 1984, one specimen, 30 mm preserved length, leg. T. M. Gosliner (CASIZ 072843).
External morphology
The background colour of the living animals is pale grey (Fig. 4E). The dorsum is covered with numerous rounded or oval dark brown patches, which are larger in the centre of the dorsum. There are a few darker patches, almost black, situated in two rows on both sides of the visceral hump and several opaque white spots irregularly distributed. The rhinophoral and branchial sheaths are low and surrounded by several white spots. The rhinophores are grey, with a number of small dark brown spots. The branchial leaves are also grey, having dark grey spots and white patches. The whole dorsum is covered with small, conical tubercles (Fig. 19D). The largest tubercles are situated in the central region of the body. The rhinophoral and branchial sheaths have tubercles similar to those on the rest of the dorsum. There are six tripinnate branchial leaves. The anal papilla is situated in the centre of the branchial circle of leaves. The rhinophores are elongate, having 21 lamellae in a 30-mm preserved length specimen.
Ventrally the anterior border of the foot is grooved and notched (Fig. 20E). The oral tentacles are short and conical.
Anatomy
The posterior end of the glandular portion of the oral tube has six strong retractor muscles (Fig. 20C) which attach to the body wall. The oval, muscular buccal bulb has two large additional muscles attached; two long salivary glands connect with it at each side of the oesophageal junction. The buccal bulb is longer than the glandular portion of the oral tube. The labial cuticle is armed with a number of small rodlets (Fig. 19E). The radular formula is 23 ¥ 32.0. 32 in a 42-mm long specimen. Rachidian teeth are absent. The lateral teeth are hamate and lack denticles (Fig. 19A). The teeth from the middle portion of the half-row are larger than those closer to the medial portion of the radula (Fig. 19B). The outermost teeth are smaller and also lack denticles (Fig. 19C). The oesophagus is short and connects directly to the stomach.
The ampulla is very long and convoluted (Fig. 20B). It branches into a short oviduct and the prostate. The oviduct enters the female gland mass near to its centre. The prostate is large and flattened. It has two different portions that are clearly distinguishable in colour and texture. The prostate connects with a long duct that narrows and expands again into the large ejaculatory portion of the deferent duct. The penis is unarmed. The muscular deferent duct opens into a large, common atrium with the vagina. The vagina is short. At its proximal end it joins the bursa copulatrix. From the bursa copulatrix leads another duct connecting to the uterine duct and the seminal receptacle. The bursa copulatrix is oval in shape, about three times as large as the elongate seminal receptacle.
In the central nervous system (Fig. 20D) the cerebral and pleural ganglia are fused and distinct from the pedal ganglia. There are four cerebral nerves leading from each cerebral ganglion and three pleural nerves leading from each pleural ganglion. There is no separate abdominal ganglion on the right side of the visceral loop. The buccal ganglia are near to the rest of the central nervous system, joined to the cerebral ganglia by two relatively long nerves. Gastro-oesophageal, rhinophoral and optical ganglia are present. The pedal ganglia are clearly separated, having two nerves leading from the left ganglion and three from the right one. The pedal and parapedal commissures are enveloped together with the visceral loop.
The circulatory system (Fig. 20A) consists of a large heart and two blood glands situated in front of and behind the central nervous system.
Remarks
Marcus & Marcus (1970a) described the new subspecies Tayuva ketos juva from the tropical Indo-Pacific. The description, based on a single preserved specimen, is not complete and does not include detailed anatomical information. It is very likely that this description corresponds to a tropical species of Discodoris, rather than a subspecies of Discodoris ketos, which is probably restricted to the Panamic biogeographical region of the eastern Pacific
Another subspecies of Discodoris ketos, Tayuva ketos gila, was described by Marcus & Marcus (1970b) based on material from Curaçao, Caribbean Sea. Again, it is difficult to determine the identity of the preserved animals they saw, but it is unlikely that they belong to the same species. Marcus & Marcus (1970b) mentioned the presence of denticles on the innermost teeth of the two specimens of Tayuva ketos gila; these are absent in the Panamic specimens examined here.
description: Published as part of Valdés, Ángel, 2002, A phylogenetic analysis and systematic revision of the cryptobranch dorids (Mollusca, Nudibranchia, Anthobranchia), pp. 535-636 in Zoological Journal of the Linnean Society 136 (4) on pages 569-571, DOI: 10.1046/j.1096-3642.2002.00039.x, http://zenodo.org/record/4634200