Hypselodoris decorata, (RISBEC, 1928)

Epstein, Hannah E., Hallas, Joshua M., Johnson, Rebecca Fay, Lopez, Alessandra & Gosliner, Terrence M., 2018, Reading between the lines: revealing cryptic species diversity and colour patterns in Hypselodoris nudibranchs (Mollusca: Heterobranchia: Chromodorididae), Zoological Journal of the Linnean Society 20 (1), pp. 1-74 : 20-21

HYPSELODORIS DECORATA ( RISBEC, 1928)

(FIGS 2D, 4H, 9, 10)

Chromodoris decorata Risbec, 1928: 152 –154, fig. 43, pl. VII, fig. 4.

H y p s e l o d o r i s m a c u l o s a m i s i d e n t i f i c a t i o n, n o t H. maculosa Pease, 1871 ; Gosliner et al., 2015: 254, second photograph from top on left.

Material examined

CASIZ 191315 , subsampled for molecular study, Mizegwadan Reef , 5.16000°S, 145.82333°E, Madang, Papua New Guinea, 20 m depth, 18 November 2012, V.Knutson . CASIZ 191214 , two specimens, one dissected, south point, Pana Tibun islet, 5.196667°S, 145.806667°E, 14 November 2012, Anthony Berberian . CASIZ 190661 , one specimen, dissected, Bethlehem , 13.67°N, 120.84°E, Tingloy , Maricaban Island, Batangas, Luzon, Philippines, 17 November 2012, T. Gosliner . CASIZ 184316 , one specimen, dissected, Bethlehem , 13.67°N, 120.84°E, Tingloy , Maricaban Island, Batangas, Luzon, Philippines, 2 October 2010, T. Gosliner . CASIZ 208606 , one specimen, off Bamboo Beach 13.52°N, 120.96°E, Batangas Channel, Puerto Galera, Mindoro Oriental, Philippines, 11 April 2015, T. Gosliner . CASIZ 176776 , two specimens, West Beach , Pulau Tenggol , South China Sea, Malaysia, 29 September 2007, T. Gosliner . CASIZ 197309 , one specimen, Calatagan 13.91°N, 120.60°E, Batangas, Luzon, Philippines, 19 May 2014, C. Piotrowski . CASIZ 217267 , one specimen, Bonito ( Culebra ) Island 13.63°N, 120.95°E, Tingloy, Batangas, Luzon, Philippines, 21 April 2016, T. Gosliner . CASIZ 217358 , two specimens, Dive and Trek reef, 13.80°N, 120.91°E, Bauan, Batangas, Luzon, Philippines, 17 April 2016, Brenna Green .

Type locality

New Caledonia.

Geographical distribution

Known from the Marshall Islands, Vanuatu, New Caledonia, Indonesia, Papua New Guinea, the Philippines and Malaysia (present study).

Description

External morphology: Living animals ( Fig. 9 ) moderately large, reaching 25 mm in length. Body long, slender, translucent pink, with four thin, continuous opaque white longitudinal lines on dorsal surface of notum. Broad orange band found along lateral margins of notum, often with interior undulations and opaque white spots.Anterior and posterior ends of the animal with purple to orange areas with opaque white spots. Rows of reddish to purple spots found on notum, with more diffuse purple pigment found around periphery situated between opaque white lines. Similar pattern of lines and spots found on lateral margins of the body and foot. Seven to eight unipinnate gill branches having a translucent white base and inner margin and bright red–orange pigment on apical surfaces and outer margin. Bulb of perfoliate rhinophores opaque white with two red transverse bands and bearing ~14–16 densely arranged lamellae. Base of rhinophores translucent white with a third red transverse ring.

Mantle glands: Subcutaneous mantle glands simple and rounded in shape ( Fig. 2D ). Glands situated anteriorly and posteriorly, with no glands present in the central lateral regions of body margin. Eight to ten glands on either side of anterior end of the body, with arc of 15–20 glands situated posteriorly. Their arrangement was based upon four specimens examined.

Buccal armature: Muscular portion of buccal mass slightly longer than oral tube. Chitinous labial cuticle ( Fig. 10A ) found at anterior end of muscular portion of the buccal mass bearing numerous jaw rodlets ( Fig.10B ). Rodlets sharply angled with single, acutely pointed apex and posterolateral extensions. Radular formula of two specimens 55 × 26.0.26 (CASIZ 190661) and 48 × 26.0.26 (CASIZ 191214) ( Fig. 10C ). Rachidian row of teeth absent ( Fig. 10D ). Innermost lateral teeth having one or two large, triangular denticles on inner side of bifid primary cusp, with another one to two outer denticles. Next several laterals lacking inner triangular denticle but possessing two denticles on outer side of primary bifid cusps. Midlateral teeth ( Fig. 10E ) all lacking inner denticles but having three to four sharply pointed, triangular outer denticles. Outermost teeth having a narrower base and shorter tooth shape, with two to four rounded outer denticles ( Fig. 10F ).

Reproductive system: Reproductive organs ( Fig. 4H ) fully mature in two specimens examined (CASIZ 1908661, CASIZ 184316). Ampulla thick, tubular, narrowing somewhat before bifurcating into oviduct and vas deferens. Short oviduct entering female gland mass near albumen gland. Prostatic proximal portion of vas deferens convoluted, curved and thick and narrowing slightly as it transitions into short, narrow, muscular ejaculatory portion. Ejaculatory portion widening into penial bulb. Penial bulb adjacent to curved, slightly wider vaginal duct at common gonopore. Distal end of vas deferens devoid of penial hooks. Female gland mass consisting of large mucous gland and small membrane and albumen glands. Large, lobate vestibular gland situated near exit of mucous gland. Relatively long vagina leading to minute receptaculum seminis and larger spherical, thin-walled receptaculum seminis. Receptaculum situated near base of bursa. Moderately long uterine duct emerging from vagina close to base of bursa and female gland mass, near albumen gland.

Remarks

Hypselodoris decorata is very similar to H. maculosa ( Pease, 1871) and was regarded as a synonym of this species by Rudman (1986). Johnson (2005) suggested that H. decorata has several distinguishing attributes of its colour pattern that separate it from H. maculosa , including the presence of three rather than two red rhinophoral rings. Owing to this confusion, we have provided a complete description of H. decorata for purposes of comparison with that described for H. maculosa ( Rudman, 1986; Gosliner & Johnson, 1999). The fact that specimens identified here as H. maculosa , with two rhinophoral rings, cluster together with species separate from H. decorata (with three rhinophoral rings) in our molecular phylogeny gives credence to the observation by Johnson (2005) that these represent distinct species. Hypselodoris decorata is sister to H. juniperae sp. nov., described later in this study, and H. maculosa . In addition to the colour differences noted by Johnson (2005), there appear to be distinct anatomical differences between the two species. In H. decorata , posterior glands are present, but there are no anterolateral mantle glands, and anterior mantle glands may be present or absent. In H. maculosa , posterior mantle glands are present, as are anterolateral and anterior glands. In H. decorata , the middle lateral teeth possess fewer denticles (three or four), whereas those of H. maculosa have four or five denticles ( Fig. 11 ). The reproductive system of H. decorata has a very short ejaculatory segment of the vas deferens, whereas that of H. maculosa has a much more elongate ejaculatory segment ( Fig. 4B ). Also, the receptaculum seminis of H. decorata is situated immediately below the bursa, whereas it is much closer to the uterine duct in H. maculosa . Both species appear to be sympatric in the Marshall Islands, Papua New Guinea and the Philippines. Differences between this species and H. alburtuqali and other members of H. maculosa are detailed in the remarks section of H. alburtuqali .

Figures

Figure 2. Mantle glands. A, Hypselodoris alburtuqali Gosliner & Johnson sp. nov., CASIZ 192295, holotype. B, Hypselodoris cerisae Gosliner & Johnson sp. nov., holotype, CASIZ 178350. C, Hypselodoris confetti Gosliner & Johnson sp. nov., CASIZ 191070. D, Hypselodoris decorata (Risbec, 1928), CASIZ 184316. E, Hypselodoris ghardaqana (Gohar & Abu-Ela, 1957), CASIZ 192282. F, Hypselodoris iba Gosliner & Johnson sp. nov., holotype, NMP 041279.

Figure 4. Reproductive systems A, Hypselodoris alburtuqali Gosliner & Johnson sp. nov., holotype, CASIZ19229, scale bar: 0.5 mm. B, Hypselodoris maculosa (Pease, 1871), CASIZ 139595, scale bar: 0.75 mm. C, Hypselodoris brycei Gosliner & Johnson sp. nov., paratype, WAM S12628, scale bar: 3.0 mm. D, Hypselodoris apolegma (Yonow, 2001), CASIZ 083743, scale bar: 2.0 mm. E, Hypselodoris cerisae Gosliner & Johnson sp. nov., holotype CASIZ 178350, scale bar: 0.85 mm. F, Hypselodoris krakatoa Gosliner & Johnson, 1999, CASIZ 206801, Philippines, scale bar: 1.0 mm. G, Hypselodoris confetti Gosliner & Johnson sp. nov., holotype, CASIZ 191070, scale bar: 0.60 mm. H, Hypselodoris decorata (Risbec, 1928), CASIZ 184316, scale bar: 0.60 mm. am, ampulla; bc, bursa copulatrix; ej, ejaculatory portion of the vas deferens; fgm, female gland mass; p, penis; pr, prostatic portion of vas deferens; rs, receptaculum seminis; ud, uterine duct; v, vagina; vg, vestibular gland.

Figure 9. Hypselodoris decorata (Risbec, 1928), living animals. A, CASIZ 191315, Madang, Papua New Guinea, photograph by Vanessa Knutson. B, CASIZ 217614, Mabini, Batangas, Philippines. C, CASIZ 184316, Tingloy, Batangas, Philippines. D, CASIZ 190661, Tingloy, Batangas, Philippines. E, CASIZ 217358, Bauan, Batangas, Philippines. F, CASIZ 191214, Madang, Papua New Guinea, photograph by Vanessa Knutson. G, living animal from Risbec (1928), New Caledonia.

Figure 10. Hypselodoris decorata (Risbec, 1928). A, entire jaw, CASIZ 190661. B, jaw rodlets, CASIZ 191214. C, entire radula, CASIZ 190661. D, inner lateral teeth, CASIZ 190661. E, middle lateral teeth, CASIZ 190661. F, outer lateral teeth, CASIZ 190661.

Figure 11. Hypselodoris maculosa (Pease, 1871), CASIZ 139545. A, entire jaw. B, jaw rodlets. C, entire radula. D, inner lateral teeth. E, middle lateral teeth. F, outer lateral teeth.