Rostanga ghiselini Gosliner and Bertsch, 2017

Gosliner, Terrence M. & Bertsch, Hans, 2017, Two New Species of Nudibranch Mollusks from the Tropical Eastern Pacific of Mexico, Proceedings of the California Academy of Sciences 64 (6), pp. 117-130 : 119-124

Rostanga ghiselini Gosliner and Bertsch sp. nov.

urn:lsid:zoobank.org:act:A8F265B6-8E50-4E9F-8C5F-B22C35E7B147

Figures 1A,B , 2 , 3 , 4A

Reddish dorid: Bertsch, 2008:337.

Rostanga sp. : Bertsch, 2014:177; Bertsch and Aguilar Rosas, 2016:275 (photo).

MATERIAL EXAMINED.— Holotype: CASIZ 220373 , dissected and subsampled for molecular study, 10 m depth, Punta Gringa , Bahía de los Ángeles, Baja California, Gulf of California, México, 25 March 2017, Craig Hoover.

Comparative material examined: Rostanga pulchra : One specimen, CASIZ 097529 , Punta Vicente Roca , Isla Isabela , Galápagos Islands, 14 May 1994, Paul Humann .

Additional observations: One specimen, Bahía San Luis Gonzaga, Baja California, Gulf of California, México, 11 December 1962, Wesley M. Farmer (photo M321). One specimen, 5 m depth, Punta la Gringa, Bahía de los Ángeles, Baja California, Gulf of California, México, 12 mm, 24 October 1986, H. Bertsch. One specimen with egg mass, 3 m depth, Punta la Gringa, Bahía de los Ángeles, Baja California, Gulf of California, México, 20 mm, 14 March 1992 (HB photo M3895). One animal, 6 m depth, Punta la Gringa, Bahía de los Ángeles, Baja California, Gulf of California, México, 15 mm, 21 December 1994, H. Bertsch (HB photo M4639); One animal, 3 m depth, Punta la Gringa, Bahía de los Ángeles, Baja California, Gulf of California, México, 16 mm, 24 December 1995, Hans Bertsch (HB photo M4789); One specimen, Cuevitas, Bahía de los Ángeles, Baja California, Gulf of California, México, l0 mm, 6 April 1990, H. Bertsch (HB photo M3243). One specimen, 4 m depth, Cuevitas, Bahía de los Ángeles, Baja California, Gulf of California, México 10 mm, 20 March 1994, H. Bertsch. One animal, 3 m depth, Cuevitas, Bahía de los Ángeles, Baja California, Gulf of California, México, 8 mm, 20 December 1994, H. Bertsch (HB photo M4618). One specimen, 5 m depth, s. w. Isla Ventana, Bahía de los Ángeles, Baja California, Gulf of California, México, 15 mm, 24 February 1997, H. Bertsch (HB photo M5402). One specimen, Guaymas, Sonora, México, 30 November 1975, Leroy H. Poorman (photo M 2947).

GEOGRAPHICAL DISTRIBUTION.— Thus far, known only from Bahía San Luis Gonzaga and Bahía de los Ángeles, Baja California, and Guaymas, Sonora, all within the Gulf of California , México.

ETYMOLOGY.— This species is named for our colleague and mentor, Michael T. Ghiselin, a superb teacher, scientist, philosopher, historian and friend.

DESCRIPTION.— External morphology. The living (Fig. 1A – B) holotype (Fig. 1A – B) was approximately 30 mm in length and 20 mm wide. The general body color is red to reddish orange with a series of large, well-spaced black spots present on the dorsal surface. The perfoliate rhinophores are conical with a series of 10 – 14 horizontal lamellae. The gill is composed of 7 bipinnae branches. The rhinophores and gill are the same color as the rest of the body. The body shape is oval. The notum is covered with a series of densely packed caryophyllidia (Fig 2A). Each caryophyllidium bears 5 – 6 calcareous spines with a small ciliated tubercle located in its center. The anal papilla is situated within the circle of the branchial plume. The anterior border of the foot is labiate and notched. The foot is wide relative to the mantle margin. The oral tentacles are well-formed and appear conical in shape.

Buccal armature: The labial cuticle is smooth with two small rectangular areas where chitinous jaws are present. The jaws contain numerous rodlets that are elongate and have a broader apical end (Fig. 2B). The radular formula of the holotype is 73 X 67.25.1.0.1. 25.67 (Fig. 2C). The innermost lateral teeth are deeply arched and bifurcate with an inner denticulate lobe and an outer acutely pointed secondary cusp ( Figs. 2E , 3C ). The inner denticulate lobe has about 8 – 21 denticles along its inner margin. The next several inner lateral teeth are similar in shape to the innermost tooth ( Figs. 2D , 3B ), but lack denticles on the inner margin. At about tooth number 7 or 8, the bifid cusps become more elongate with the inner cusp longer than the outer one ( Fig. 2F ). At about tooth 25, the primary cusp is about ten times longer than the secondary cusp ( Figs. 2G , 3D ). The next 67 or so teeth are narrow ( Fig. 2H ) and elongate with a bifid cusp near the apex of the narrow apices ( Fig. 3A ).

Reproductive System ( Fig. 4A ): Reproductive organs of the holotype fully mature. Ampulla thin, tubular, and strongly curved, narrowing somewhat before bifurcating into oviduct and vas deferens. Short oviduct entering female gland mass near albumen gland. Prostatic portion of vas deferens wide, curved and thin, partially enveloping bursa copulatrix. Prostatic portion narrowing abruptly as it transitions into muscular, ejaculatory portion. Ejaculatory portion long curved, narrow, entering short, narrow, slightly wider, penial bulb. Penial bulb adjacent to straight, narrow vaginal duct at common gonopore. Female gland mass consisting of large mucous gland and small membrane and albumen glands. Small, lobate vestibular gland situated near exit of mucous gland. Moderately long vagina leading to large spherical, thin-walled bursa copulatrix. Adjacent to vagina, long narrow uterine duct leading to smaller receptaculum seminis. Receptaculum seminis pyriform with short duct entering the female gland mass.

REMARKS.— Rostanga ghiselini differs from all other 23 described members of the genus. Most species of Rostanga , as in R. ghiselini , have a reddish or orange body color, except for R. setidens (Odhner, 1939) (whitish), R. phepha Garovoy, Valdés and Gosliner, 2001 (white), R. risbeci Baba, 1991 (dark gray to black), R. ankyra Valdés, 2001 (white) and R. crocea Edmunds 2011 (yellow). Species of Rostanga have rhinophores of two basic forms, either conical with a series of transverse lamellae, as in most other dorid nudibranchs, including R. ghiselini , or broader rhinophores with nearly vertical lamellae ( Table 1 ). Twelve species have transverse lamellae while 11 have vertical ones.

The buccal armature, both the jaws and radula, of most Rostanga species is distinctive. In six species, R. ankyra , R. aureommala Garovoy, Valdés and Gosliner, 2001 , R. crocea , R. elandsi Garovoy, Valdés and Gosliner, 2001 , R. rosi (Ortea, 1979) and R. setidens lack any trace of jaw rodlets, while the remaining species, including R. ghiselini , either have small areas of the labial cuticle with jaw rodlets or well developed rodlets. The inner lateral tooth of many species of Rostanga often contains a series of distinct denticles. This arrangement is found in 16 species of Rostanga , while five species have a bifid or simply hamate inner tooth. In R. crawfordi (as R. australis ), Rudman and Avern (1989) noted that small specimens have a denticulate inner lateral whereas medium-sized or large specimens have an entirely smooth inner lateral. Of the species with a denticulate inner lateral tooth, only R. ghiselini and R. rubra have a secondary triangular cusp below the inner margin bearing numerous denticles. In R. ghiselini this cusp is far more pronounced than in R. rubra ( Valdés and Gosliner, 2001; Edmunds, 2011). Also, in R. rubra , some of the middle lateral teeth near the point where the hamate teeth become more elongate, lack a secondary denticle, whereas all of them in R. ghiselini have a secondary denticle.

Rostanga ghiselini can be compared in detail with the only other species found in the eastern Pacific, R. pulchra MacFarland 1905 . Both species are reddish orange in color, but R. ghiselini also has large black spots present on the notum. The rhinophores of R. ghiselini are conical with transverse lamellae, whereas those of R. pulchra are broad with vertical lamellae. There are 6 – 7 bipinnate gill branches in R. ghiselini and 8 – 12 unipinnate branches in R. pulchra . Internally, the radular morphology of the two species differs. The innermost radula tooth is denticulate in both species but in R. ghiselini the tooth bears 8 – 21 denticles whereas in R. pulchra there are 7 – 9 denticles ( Fig. 5E, F ). In R. ghiselini all of the hamate teeth are strongly bifid whereas only the second tooth is bifid in R. pulchra . The 67 elongate outer teeth of R. ghiselini have bifid apices whereas the 25 elongate teeth have 3 – 6 fine apices in R. pulchra ( Fig. 5H ). The reproductive system is similar in both species with the exception that the vagina of R. pulchra is more elongate.

Valdés and Gosliner (2001) included Boreodoris Odhner, 1939 as a synonym of Rostanga , noting that the absence of jaws and a denticulate inner lateral tooth was not sufficient to warrant generic separation. Subsequently, Garavoy, Valdés and Gosliner (2001) described three new South African species of Rostanga that all had a bifid inner lateral tooth. Two of these species, R. aureomala and R. elandsia , lacked jaws, whereas R. phepha had distinctive jaw rodlets. Martynov (2003), stating that Boreodoris lacking jaws and lacking an innermost lateral tooth with denticulate flange, is sufficiently distinct from Rostanga and should be considered as a distinct genus. Based on this distinction, he considered R. aureomala , R. elandsia , R. phepha and R. ankyra Valdés, 2001 , together with R. setidens (Odhner, 1939) , as members of Boreodoris . This distinction is not consistent since Rostanga phepha has well developed jaws with rodlets (as in Rostanga ) but lacks an inner lateral tooth without a denticulate flange (as in Boreodoris ). Two other species have radular morphology that is intermediate between the two forms. In Rostanga crawfordi (as R. australis ) ( Rudman and Avern, 1989), the inner radular in small specimens may have a denticulate flange but in larger specimens the inner lateral tooth is entirely smooth. This variability was also confirmed by Dayrat (2010). Similarly, in Rostanga lutescens (Bergh, 1905) , the inner lateral tooth lacks a denticulate flange but the tooth has 1-5 denticles on the inner side and may have additional outer denticles ( Johnson and Bertsch, 1985; Dayrat, 2010). Therefore, there are no consistent features that distinguish Rostanga and Boreodori s and they should, once again, be regarded as synonyms.

Figures

FIGURE 1. Living animals. A. Rostanga ghiselini sp. nov., specimen from Punta Gringa, Bahía de los Angeles, 14 March 1992, photo by Hans Bertsch. B. Rostanga ghiselini sp. nov., holotype specimen from Punta Gringa, Bahia de los Angeles, 25 March 2017, photo by Craig Hoover. C. Tenellia ivetteae sp. nov., holotype, CASIZ 220143 (upper animal) and paratype, CASIZ (lower animal), from Punta Gringa, Bahia de los Angeles, 30 June 1992, photo by Hans Bertsch.

FIGURE 2. Scanning electron micrographs, Rostanga ghiselini sp. nov., holotype, CASIZ 220373. A. Caryophyllidia. B. Jaw rodlets. C. Entire radula. D. Inner lateral teeth and rachis. E. First and second lateral teeth. F. Middle lateral teeth. G. Elongate middle to outer lateral teeth. H. Outer lateral teeth.

FIGURE 3. Scanning electron micrographs of Rostanga ghiselini sp. nov. A. Holotype, CASIZ 220373, detail of outer lateral teeth. B–D. Specimen from Punta Gringa, Bahía de los Angeles, 14 March 1992. B. Inner and middle lateral teeth. C. First and second lateral teeth. D. Elongate middle to outer lateral teeth.

FIGURE 4. Reproductive anatomy. A. Rostanga ghiselini sp. nov., holotype, CASIZ 220373. B. Tenellia ivetteae sp. nov., paratype, CASIZ 222482. abbreviations: al-albumen gland, am ampulla, bc-bursa copulatrix, ej-ejaculatory portion of vas deferens, fg-female gland mass, me-membrane gland, mu-mucous gland, p-penis, pg-penial gland, pr-prostatic portion of vas deferens, rs-receptaculum seminis, st-penial stylet, v-vagina, vd-vas deferens, vg-vestibular gland. Scale = 1 mm.

FIGURE 5. Scanning electron micrographs, Rostanga pulchra MacFarland, 1905, CASIZ 097525, Punta Vicente Roca, Galápagos Islands. A. Jaw. B. Jaw rodlets. C. Entire radula. D. Inner and middle lateral teeth and rachis. E. Inner lateral teeth. F. First and second lateral teeth. G. Outer lateral teeth. H. Outer lateral tooth apices.

Tables

Table 1. Comparative morphology of Rostanga species.

Species	Rhinophoral lamellae	Jaw rodlets	Inner lateral	Middle lateral	Outer lateral	Vestibular gland
alisae	vertical	present	denticulate	smooth	multifid	absent
aliusrubens	vertical	present	denticulate	smooth, inners	multifid	absent
ankyra	transverse	absent	bifid	bifid	bifid	absent
anthelia	vertical	present	denticulate	smooth	multifid	?
arbutus	transverse	present	denticulate	denticulate	multifid	absent
aureomala	transverse	absent	bifid also rachidian present	bifid	bifid or trifid	absent
crawfordi	vertical	reduced	denticlulate or smooth	smooth	multifid	absent
bassia	vertical	present	denticulate	no denticles	multifid	absent
bifurcata	transverse	present	denticulate	denticulate	bifid	absent
byga	vertical	reduced	denticulate	smooth	multifid	absent
calumus	vertical	present	denticulate	no denticles	multifid	absent
crocea	transverse	absent	bifid	bifid	bifid	?
dentacus	transverse	reduced	denticulate	no denticles	undivided or bifid	absent
elandsia	transverse	absent	bifid	bifid	bifid	absent
ghiselini	transverse	reduced	denticulate	bifid	bifid	present
lutescens	transverse	present	denticulate	smooth	trifiid	present
muscula	vertical	reduced	denticulate	no denticles	multifid	present
orientalis	vertical	present	denticulate	no denticles	multifid	absent
phepha	transverse	reduced	bifid	smooth	bifid	absent
pulchra	vertical	reduced	denticulate	smooth	mutifid	absent
risbeci	transverse	reduced	denticulate	smooth	bifid	absent
rosi	transverse	absent	smooth	smooth	smooth	present
rubra	vertical	present	denticulate	bifid	bifid	absent
setidens	transverse	absent	smooth	smooth	bifid	absent