Discodoris, BERGH, 1877

Valdés, Ángel, 2002, A phylogenetic analysis and systematic revision of the cryptobranch dorids (Mollusca, Nudibranchia, Anthobranchia), Zoological Journal of the Linnean Society 136 (4), pp. 535-636 : 565-569

GENUS DISCODORIS BERGH, 1877

Discodoris Bergh, 1877a: 518 . Type species: Discodoris boholiensis Bergh, 1877 , by subsequent designation by O’Donoghue (1926).

Fracassa Bergh, 1878a: 598 . Type species: Fracassa zibethina Bergh, 1878 , by monotypy, syn. nov.

Erythrodoris Pruvot-Fol, 1933: 133 . Type species: Erythrodoris dollfusi Pruvot-Fol, 1933 , by monotypy, syn. nov.

Tayuva Marcus & Marcus, 1967b: 191–192 . Type species: Tayuva ketos Ev. Marcus & Er. Marcus, 1967 , by original designation, syn. nov.

Diagnosis

Dorsum covered with simple tubercles, stiffened by integumentary spicules, which occasionally protrude from the dorsal surface in an irregular fashion. Head with two conical oral tentacles. Anterior border of the foot grooved and notched. Labial cuticle armature with rodlets. Radula composed of simple, hamate teeth. The outermost teeth may be simple or denticulate. Reproductive system with a flattened, granular prostate, having two well differentiated regions. Penis and vagina devoid of hooks. Vestibular or accessory glands absent.

Remarks

Bergh (1877b) introduced the genus Discodoris based on Doris granulata Ehrenberg, 1831 , Doris crucis Mörch, 1863 , Doris pardalis Alder & Hancock, 1864 , Doris concinna Alder & Hancock, 1864 , Doris fragilis Alder & Hancock, 1864 , and eight hitherto undescribed species: Discodoris boholiensis , D. meta , D. cebuensis , D. notha , D. muta , D. modesta and D. schmeltziana . Bergh (1877a) described these species, and at the same time reproduced the original description of the genus Discodoris . O’Donoghue (1926) subsequently designated Discodoris boholiensis Bergh, 1877 as the type species. Bergh’s (1877a) paper was published in December 1877 (see Winckworth, 1946), whereas the date of publication of Bergh (1877b) is unspecified. According to Article 21.3 ( ICZN, 1999), as the exact day of publication is not specified for any of these papers, and one of them was published in December, the date of publication of both papers is determined to be the last day of 1877. If Bergh’s (1877b) paper is selected to be the original description of the genus, D. boholiensis is not eligible to be the type species (it was undescribed). Therefore, acting as First Reviser ( ICZN, 1999: Article 24), I select Bergh’s (1877a) paper as the original description of the genus; thus D. boholiensis becomes eligible to be the type species.

Bergh (1878a) described the genus Fracassa for Fracassa zibethina Bergh, 1878 , collected from the Philippines. According to Bergh (1878a) this genus is characterized by having a quite smooth dorsum, conical oral tentacles, tripinnate branchial leaves, wide foot with the anterior border grooved and notched, presence of jaws, radular teeth simple and hamate, large differentiated prostate and penis unarmed. Re-examination of the holotype of Fracassa zibethina revealed that the dorsum of this species is covered with small, rounded simple tubercles. All these characteristics are also present in the genus Discodoris , for which Fracassa is a synonym.

Pruvot-Fol (1933) described the genus Erythrodoris based on Erythrodoris dollfusi Pruvot-Fol, 1933 , characterized by having a labial cuticle with articulated plates, elongated body and unarmed penis. These features of Erythrodoris are also present in Discodoris , and these names are regarded as synonyms. It is impossible to determine the identity of Erythrodoris dollfusi Pruvot-Fol, 1933 based on the original description and the type material is probably lost.

Marcus & Marcus (1967b) introduced the new genus Tayuva for Tayuva ketos Ev. Marcus & Er. Marcus, 1967 . The diagnosis of Tayuva included the following characteristics: pointed tentacles, labial plates with rodlets, hook-shaped radular teeth, stout penial papilla, large vestibule (atrium) stiffened by spicules and lodging the penial papilla and the vaginal aperture, nidamental opening independent from that of the atrium. This structure of the genital opening was considered ‘aberrant’ by Marcus & Marcus (1967b) and they could not find another genus that could ‘receive’ that species. In fact, this anatomical arrangement is present in all species of cryptobranch dorids. The combination of the characters described above and simple dorsal tubercles indicates that Tayuva ketos clearly belongs to the genus Discodoris ; thus Tayuva is a junior synonym of Discodoris .

DISCODORIS BOHOLIENSIS BERGH, 1877

( FIGS 4D , 15 , 16 )

Discodoris boholiensis Bergh, 1877a: 519–522 , pl. 60, fig. 23, pl. 61, figs 6–12.

Discodoris meta Bergh, 1877a: 522–526 , pl. 60, figs 24, 25, pl. 61, figs 25–28.

Type material

SYNTYPES of Discodoris boholiensis : Bohol, Aibukit , Philippines, date unknown, three specimens, 45 mm (decapitated) 70 mm preserved length, leg. C. Semper

( ZMUC GAS-2122 ). HOLOTYPE (by monotypy) of Discodoris meta : Cebu, Ubay, Philippines, leg. C. Semper ( ZMUC).

Additional material

North side of Sombrero Island, Batangas, Luzon, Philippines, 19 February 1992, three specimens, 20– 49 mm preserved length, leg. T . M. Gosliner ( CASIZ 083654 ) .

External morphology

The background colour of the living animals varies from pale cream in the centre of the dorsum to pale ochre near to the mantle edge ( Fig. 4D ). The dorsum is covered with a number of rounded white spots situated on each dorsal tubercle. These white spots are more densely concentrated on the mantle margin, forming several radial white lines. There is an irregular pattern of dark brown patches and lines on the centre of the dorsum, from behind the rhinophores to the gill. A similar pattern also occurs near to the mantle edge. Both areas are connected by irregular, faded pale brown lines forming a broken network. The rhinophoral and branchial sheaths are elevated and surrounded by a dark brown line, which in the case of the branchial sheath is interrupted by several white spots. The rhinophores are dark brown to black, with several irregular white lines. The branchial leaves are also dark brown, almost black, with dark grey rachises. The whole dorsum is covered with small, conical tubercles, which have spicules protruding on their dorsal surface ( Fig. 15E ). 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 26 lamellae in a 49-mm preserved length specimen.

Ventrally the anterior border of the foot is grooved and notched ( Fig. 16F ). The oral tentacles are elongate, with a blunt apex.

Anatomy

The posterior end of the glandular portion of the oral tube has six strong retractor muscles ( Fig. 16E ) 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 shorter than the glandular portion of the oral tube. The labial cuticle is armed with a number of small, simple rodlets ( Fig. 15D ). The radular formula is 29 ¥ 35.0. 35 in a 49- mm long specimen. Rachidian teeth are absent. The lateral teeth are hamate and lack denticles ( Fig. 15A ). The teeth from the middle portion of the half-row are larger than those closer to the medial portion of the radula ( Fig. 15B ). The outermost teeth are smaller and also lack denticles ( Fig. 15C ). The oesophagus is short and connects directly to the stomach ( Fig. 16A ).

The ampulla is long and simple ( Fig. 16C ). 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 ( Fig. 16B ). The prostate connects with a very long and convoluted 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 common atrium with the vagina. The vagina is long. 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 rounded in shape, about three times as large as the seminal receptacle.

In the central nervous system ( Fig. 16D ) the cerebral and pleural ganglia are fused and distinct from the pedal ganglia. There are three cerebral nerves leading from each cerebral ganglion and two pleural nerves leading from each pleural ganglion. There is a 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 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. 16A ) consists of a large heart and two blood glands situated in front of and behind the central nervous system.

Remarks

Discodoris boholiensis is a well-known Indo-Pacific species characterized by having a background brown colour with black and white spots and lines on the body, and a relatively flat dorsum with undulating margins and a prominent central hump. Examination of the type material of Discodoris meta Bergh, 1877 confirmed that it is a synonym of D. boholiensis .

DISCODORIS ZIBETHINA (BERGH 1878)

( FIGS 17 , 18 )

Fracassa zibethina Bergh, 1878a: 598–601 , pl. 66, figs 21–26, pl. 67, figs 1, 2.

Type material

HOLOTYPE (by monotypy): Canal at Lapinig, Philippines, March 1865, 54 mm preserved length, leg. C. Semper ( ZMUC GAS-2112 ).

Description

The colour of the living animal is unknown ( Fig. 17 ). The body is very elongate and narrow, with a very reduced mantle margin, which is completely absent in some areas. The gill is situated on the posterior border of the body. The dorsum is covered with a number of small, rounded tubercles ( Fig. 18E ). 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. Ventrally the anterior border of the foot is grooved and notched.

The labial cuticle is armed with a number of small, simple rodlets ( Fig. 18D ). The observed radular formula is n ¥ 83.0.83. Rachidian teeth are absent. The lateral teeth are hamate and lack denticles ( Fig. 18A ). The teeth from the middle portion of the half-row are larger than those closer to the medial portion of the radula ( Fig. 18B ). The outermost teeth are smaller and also lack denticles ( Fig. 18C ).

Remarks

The holotype of Discodoris zibethina is the only known specimen of this species. The specimen was studied and dissected by Bergh (1878a), and only the skin and some internal organs, including the radula, remain. The description of the species was based on preserved material and there is no information on the features of the living animal. With the preserved holotype it is not possible a positive identification of this species. Therefore this name is here regarded as nomen dubium.

The shape of the animal strongly resembles the remains of some species of Discodoris or Sebadoris after the autotomization of the notum ( Gohar & Soliman, 1967; Soliman, 1980; pers. obs.).

Figures

Figure 4. Living animals. A, Doris pseudoargus (CASIZ 121105). B, Doris immonda (CASIZ 089023), photo by T. M. Gosliner. C, Doris granulosa (CASIZ 073536), photo by T. M. Gosliner. D, Discodoris boholiensis (CASIZ 083654), photo by T. M. Gosliner. E, Discodoris ketos, San Pedrillo, Puntarenas, Costa Rica, photo by T. M. Gosliner. F, Thordisa rubescens (CASIZ 015860), photo by T. M. Gosliner. G, Aphelodoris antillensis (CASIZ 077289), photo by T. M. Gosliner. H, Peltodoris atromaculata (CASIZ 119474). I, Peltodoris nobilis, Monterey Bay, California, photo by A. Smith.

Figure 15. Discodoris boholiensis (CASIZ 083654), SEM images of the radula, jaws and dorsal tubercles. A, inner lateral teeth; scale bar = 75 Mm. B, mid-lateral teeth; scale bar = 75 Mm. C, outer lateral teeth; scale bar = 75 Mm. D, jaw elements; scale bar = 20 Mm. E, dorsal tubercles; scale bar = 150 Mm.

Figure 16. Discodoris boholiensis (CASIZ 083654). A, general view of the anatomy; scale bar = 1 mm. B, reproductive system; scale bar = 1 mm. C, detail of several reproductive organs; scale bar = 1 mm. D, central nervous system; scale bar = 0.5 mm. E, lateral view of the buccal bulb; scale bar = 1 mm. F, ventral view of the mouth area; scale bar = 2 mm.

Figure 17. Discodoris zibethina (ZMUC GAS-2112). dorsal view of the preserved holotype.

Figure 18. Discodoris zibethina (ZMUC GAS-2112), SEM images of the radula, jaws and dorsal tubercles. A, inner lateral teeth; scale bar = 100 Mm. B, mid-lateral teeth; scale bar = 150 Mm. C, outer lateral teeth; scale bar = 100 Mm. D, jaw elements; scale bar = 30 Mm. E, dorsal tubercles; scale bar = 430 Mm.