Diaulula niƲosa, Valdés & Bertsch, 2010

Valdés, Ángel & Bertsch, Hans, 2010, Two new species of dorid nudibranchs from the Gulf of California (Mar de Cortés), Baja California, Mexico, add _ journal _ name _ here 33 (1), pp. 1-11 : 3-7

Diaulula niƲosa spec. nov.

Figs 2A , 3 , 4

Material examined. Holotype: Punta la Gringa , Bahía de los Ángeles, Gulf of California, Baja California, México (29°02.57'N; 113°32.3'W), 23 July 1995, 1.8 m depth, 17 mm long alive, leg. Hans Bertsch ( LACM 3029 ).

External morphology. The body is oval to elongate ( Fig. 2A ), with the posterior end of the foot covered by the mantle. The dorsum is covered with caryophyllidia about 150 µm long ( Fig. 3D ). Most of the caryophyllidia of the preserved holotype were partially deformed, probably due to preservation, but in some areas ciliated tubercles were clearly visible surrounded by a ring of spicules. The body is brownish orange with four black patches situated between the rhinophores and the gill, two on each side of the viscera hump. The caryophyllidia have a white apex, more conspicuous in those near the center of the dorsum. The rhinophoral sheaths are elevated and inflated. The rhinophores are the same color as the dorsum, with the apex white. The gill is composed of six tripinnate branchial leaves, which are pale gray to white.

The anterior border of the foot is grooved and notched(Fig.4B).Theoraltentaclesarelongandconical.

Anatomy. The labial cuticle is smooth. The radular formula is 16 ×27.0. 27 in the holotype ( LACM 3029). Rachidian teeth are absent ( Fig. 3A ). The lateral teeth are hamate, having a single cusp and lacking denticles ( Fig. 3B ). The teeth increase their size gradually towards the medial portion of the half-row. The outermost teeth are also hamate and lacking denticles ( Fig. 3C ).

The reproductive system is triaulic (Fig. 4A). The ampulla is very long and convoluted. It narrows into the oviduct, which enters the female glands near their nidamental opening. The prostate is large and granular. It is divided into two different portions

dd sr pr1 pr2 v bc fg a A ot

Fig. 4. Diaulula nioosa spec.nov., holotype ( LACM 3029), anatomy. A. Reproductive system; scale bar: 1 mm. B. Ventral view of the mouth area; scale bar: 2 mm. Abbreviations: a, ampulla; bc, bursa copulatrix; dd, deferent duct; fg, female glands; ot, oral tentacle; pr1, distal prostate; pr2, proximal prostate; sr, seminal receptacle; v, vagina.

B

that are clearly distinguishable by their different texture and coloration. The deferent duct is long, and expands into the muscular ejaculatory portion. The deferent duct opens into a common atrium with the vagina. There are no penial hooks. The vagina is long and narrow. At its proximal end, the vagina connects to the large, oval bursa copulatrix. Another duct, which connects to the seminal receptacle and the uterine duct, leads from the bursa copulatrix. The bursa copulatrix is about five times as large as the seminal receptacle in volume (Fig. 4A).

Etymology. The species name nioosa is Latin for snowy, in reference to the frosty-looking white pigment on the dorsum of the living animal. It also commemorates a rare climatological event along the shores of the Sea of Cortez. On 3 April 1997, while driving to Punta la Gringa with Mike Miller and Paty Beller, the junior author saw snow on top of the mountains behind (immediately west of) the town of BLA.

Remarks. Diaulula nioosa has all the features characteristic of the genus Diaulula (see Valdés 2002), so it is regarded as a member of this taxon.

Diaulula nioosa is most similar to Diaulula sandiegensis (Cooper, 1863) , which is distributed from Canada to the northern Pacific coast of Baja California (Cooper 1863; Behrens & Valdés 2001). Diaulula sandiegensis has a variable background external coloration, from white to orange (Behrens & Valdés 2001), but in all cases specimens have a series of dark rings on the dorsum. The rings may vary in number and coloration; in most specimens there are a few dorsal rings (between 4-8), which have a pale brown central area, whereas in northern specimens (from Canada) there are numerous small rings with a darker central area. In a few cases the central area of the rings is the same color as the rest of the dorsum.

The most distinctive features of D. nioosa are the presence of a number of small white spots on the dorsum that correspond to the apices of the caryophyllidia and the absence of rings. Internally, D. nioosa and D. sandiegensis differ in the absence of denticles on the outermost radular teeth in D. nioosa , but this characteristic is variable in D. sandiegensis .

The three other valid species of Diaulula found in the eastern Pacific are Diaulula punctuolata d’ Orbigny, 1837 , Diaulula hispida (d’ Orbigny, 1837) and Diaulula oariolata (d’ Orbigny, 1837) from cold waters in South America ( Chile and Argentina).

Odhner (1926) transferred Doris oestita Abraham, 1877 to the genus Diaulula . According to Schrödl (1996), this species is externally very similar to Diaulula punctuolata and only distinguishable by having a smaller prostate. The original description of D. oestita ( Abraham, 1877) contains no anatomical information. The redescription by Odhner (1926) of this species resembles Diaulula punctuolata . The drawings of the reproductive system illustrated by Odhner (1926, fig. 77) for D. oestita are very similar to those in descriptions by Valdés & Gosliner (2001, fig. 23) of D. punctuolata . Valdés & Muniain (2002) regarded Diaulula oestita as a probable synonym of D. punctuolata , which was confirmed by Schrödl’s (2003) examination of the type of D. oestita .

Diaulula punctuolata and D. hispida clearly differ from the yellow-brown Diaulula nioosa in their external coloration. Illustrations of D. punctuolata and D. hispida by Schrödl (1996), showed that both are pale in coloration, the former is pale creamish-white with light brown spots and the latter is white or brownish. Both of them typically lack white pigment on the apex of the caryophyllidia, and have a more oval (wider) body.

Additionally, D. hispida is characterized by having a dorsal longitudinal ridge, which is unique to members of the genus Atagema J. E. Gray in M. E. Gray, 1850 (Valdés & Gosliner 2001). Bergh (1898) and Odhner (1926) transferred this species to the genus Trippa Bergh, 1877 on the basis of the presence of the dorsal ridge. The original descriptions of Atagema and Trippa (J. E. Gray in M. E. Gray 1842-50 [1850], and Bergh 1877) contain limited information, but re-examination of the type species allowed Valdés & Gosliner (2001) to synonymize these two taxa, Atagema being the senior name. Marcus (1959) considered that D. hispida fits better within the genus Diaulula , because of mouth morphology differences with species of Trippa . However, the drawings by Marcus (1959), showing a tubular prostate and a clear dorsal ridge, indicate the placement of Diaulula hispida within Atagema . Schrödl (2003) argued that despite these ambiguities, until more information is available, D. hispida may be retained within Diaulula .

Diaulula punctuolata was anatomically studied and illustrated by Valdés & Gosliner (2001, figs 22-23) and a description is not repeated here. These authors concluded that this species has the same features as other members of Diaulula and it should be transferred to this genus. Since Doris punctuolata is the type species of Anisodoris , this genus name became a junior synonym of Diaulula .

Diaulula oariolata ranges in dorsal color from white to brownish (but not yellowish), often with numerous dark blotches. In further contrast to D. nioosa , it has larger-sized tubercles, white gills and rhinophores, and a pear-shaped receptaculum seminis (Schrödl 2003).

Diaulula greeleyi , originally described from Brazil (MacFarland 1909), was subsequently reported from several other Atlantic localities. Camacho-García & Valdés (2003) regarded the eastern Pacific species Peltodoris nayarita Ortea & Llera, 1981 as a synonym, based on the examination of specimens from the Pacific coast of Costa Rica and revision of the original description (Ortea & Llera 1981). Bertsch et al. (2000) reported its occurrence at Punta Eugenia, on the central Pacific coast of the Baja California peninsula. Camacho-García & Valdés (2003) also provided illustrations of the reproductive system and radula of this species based on Pacific material. Diaulula greeleyi differs from Diaulula nioosa , by having a darker background color, lacking dorsal rings on the dorsum, having unipinnate branchial leaves and having larger, more hooked-shaped outermost radular teeth.

Figures

Fig. 2. Living animals. A. Diaulula nioosa spec. nov., holotype (LACM 3029). B. Peltodoris rosae spec. nov., holotype (LACM 3030).

Fig. 3. Diaulula nioosa spec. nov., holotype (LACM 3029), Scanning Electron Micrographs of radula and dorsum. A. Innermost lateral teeth; scale bar: 100 µm. B. Mid-lateral teeth; scale bar: 100 µm. C. Outermost lateral teeth; scale bar: 50 µm. D. Caryophyllidia; scale bar: 100 µm.