Chelidonura alisonae, Gosliner, 2011

Gosliner, Terrence, 2011, Six new species of aglajid opisthobranch mollusks from the tropical Indo-Pacific, Zootaxa 2751 (1), pp. 1-24 : 15-18

publication ID	https://doi.org/ 10.11646/zootaxa.2751.1.1
persistent identifier	https://treatment.plazi.org/id/394D87A1-FFF2-235B-FF5E-FD2AFA0D694E
treatment provided by	Felipe
scientific name	Chelidonura alisonae
status	sp. nov.

Treatment

Chelidonura alisonae View in CoL n. sp.

( Figures 1F View FIGURE 1 , 2D View FIGURE 2 , 10 View FIGURE 10 )

Chelidonura sp. 1 Gosliner et al., 2008; Pittman and Fiene, 2009.

Chelidonura sp. Hoover, 2006: 148 , inset photo; Adams, 2009.

Chelidonura hirundinina (Quoy and Gaimard) Kay, 1979: 429 View in CoL , figure 138F; Bertsch and Johnson, 1981: 19, upper figure; Rudman, 2007, misidentifications.

Material examined. Holotype: CASIZ, 174176, intertidal reef platform, Diamond Head Beach Park , Honolulu, O’ahu, Hawai’i, 21.255795° N 157.810771° W, 8 February 1986, T. M. Gosliner GoogleMaps . Paratypes: CASIZ, 073410, one specimen, intertidal reef platform, Diamond Head Beach Park , Honolulu, O’ahu, Hawai’i, 21.255795° N 157.810771° W, 8 February 1986 GoogleMaps , T.M. Gosliner . CASIZ 073408 , one specimen, dissected, intertidal reef platform, Diamond Head Beach Park , Honolulu, O’ahu Hawai’i, 21.255795° N 157.810771° W, 8 February 1986 GoogleMaps , T. M. Gosliner and Michael T. Ghiselin . CASIZ 174177 , one specimen, dissected, sea water tanks, Kewalo Marine Laboratory , Honolulu, O’ahu, Hawai’i, 25 October 1986 , T.M. Gosliner and M . T. Ghiselin . CASIZ, 088428, four specimens, fish spot, outer reef, S. side Sand Island , Midway Atoll, Hawai’ian Islands, 2 June 1993 , T. M. Gosliner and P. Fiene . CASIZ 088365 , six specimens, fish spot, outer reef, S. side Sand Island , Midway Atoll, Hawai’ian Islands, 1 June 1993 , T. M. Gosliner and P. Fiene . CASIZ 088575 , one specimen, dissected, White Cross , N. E. side Sand Island, Midway Atoll, Hawai’ian Islands, 5 June 1993 , T. M. Gosliner and P. Fiene . CASIZ 165872 , one specimen, molecular sample removed, 1 m depth, Hekili Point , Maui, Hawai’ian Islands, 5 June 2003 , C. Pittman. CASIZ 156080 , seven specimens, one dissected, 3–8 m depth, Johnston Atoll, lagoon reefs near, Johnston Island , 23 April 2001 , Phil Lobel. CASIZ 170052 , 1– 2 m depth, 1 specimen, natural tidal pool, Hotel Iorana , Easter Island, 27.15904°S, 109.442286° W, 15 December 2002 GoogleMaps , T. M. Gosliner . CASIZ 174146 , two specimens, M36 84, Easter Island , Louis de Salvo. American Museum of Natural History 319376, one specimen, Anakena Beach , Easter Island, Christopher Boyko, 1999 .

Geographic range. This species is known only from the Hawai’ian Islands (this study), Johnston Island (this study), Phoenix Island ( Adams 2009), Moorea (C. Pittman personal communication), the northern Marianas Islands ( Urasawa 2007) and Easter Island ( Gosliner et al. 2008; this study).

Etymology. This species is named in honor of the late Dr. E. Alison Kay, Professor Emeritus of the University of Hawai’i. Dr. Kay was a superb mentor to many students including the author of this paper. She also pioneered the modern study of the molluscan fauna of the Hawai’ian Islands and the biogeography of the Central Pacific.

Natural history. This species is found on exposed intertidal reef platforms and shallow reefs in 1–10 m depth. It has been observed feeding on acoel flatworms of the genus Convoluta ( Pittman & Fiene 2009; present study).

Description. External morphology. The general body color of the living animal ( Fig. 1A View FIGURE 1 , 10A View FIGURE 10 ) is black to brown. The head shield has a pair of bright blue spots, each of which is surrounded by a pair of orange lines that connect anteriorly and form a loop around the blue spots. The two outer bands terminate at the outer edges of the cephalic shield after a short distance, while the two inner bands continue to the posterior end of the cephalic shield where they converge. At the posterior end of the cephalic shield a white or blue band is usually present but may be absent in some specimens. There is also a large blue pigment spot on the anterior end of the head. The margins of the parapodia are decorated with five to seven pairs of bright blue spots. A submarginal orange line extends the length of the parapodia. Additional blue pigment spots are present on the dorsal portion of the posterior shield and on the surfaces of the two posterior extensions. Additional orange lines are present on the posterior shield including the posterior extensions. The lines may coalesce forming a reticulated network. Orange lines are also present on the ventral surface of the foot where they also form a network of interconnected lines. A specimen from Easter Island (CASIZ 170052) has less orange pigment on the cephalic shield. In this instance the inner orange lines do not extend to the end of the cephalic shield. This specimen also has opaque white spots scattered on the dorsal and ventral surfaces. A network of orange lines is still present on the foot.

The anterior end of the cephalic shield is trilobate. The cephalic shield is triangular, broadest anteriorly and terminates posteriorly with a short rounded lobe. Elongate sensory bristles are visible on the anterior end of the head ( Fig. 10A View FIGURE 10 ). The posterior shield is well rounded anteriorly and terminates in two moderately elongate, broad posterior lobes that are acutely pointed at their ends. The left lobe is always longer than the right one. The parapodia are relatively wide largely covering most of the cephalic and posterior shields. The gill is plicate with 7–8 primary folds.

Shell ( Fig. 2D View FIGURE 2 ). The shell is relatively thickly calcified and is a shiny white or brown. It occupies the almost the entire area of the posterior shield. There is a broad anteriorly-directed wing and a short extension that is deeply imbedded in the posterior shield right to the end of the right posterior lobe.

Digestive system ( Fig. 10B View FIGURE 10 ). The buccal mass is small, highly muscularized, occupying the anterior two-thirds of the cephalic shield. The buccal bulb entirely lacks any vestige of a radula. There is a small dorsal oral gland and a large ventral one. At the posterior end of the buccal mass, near the junction with the crop, is a pair of elongate salivary glands. The crop is small and saccate, smaller than the buccal bulb. The crop narrows posteriorly and enters the digestive gland. The intestine emerges from the right side of the digestive gland and terminates near the posterior end of the body near the base of the gill.

Central nervous system ( Fig. 10C View FIGURE 10 ): The circumesophageal nerve ring consists of a paired cerebral, pedal and pleural ganglia and a single supraintestinal ganglion on the right side. The cerebral and pedal commissures are both short with short connectives to the adjacent ganglia. Immediately adjacent and posterior to the right pleural ganglion is the supraintestinal ganglion. From its posterior end is the right branch of the visceral loop and the osphradial nerve. The two lateral branches of the visceral loop join posteriorly at the posterior ganglia. The left visceral loop enters the subintestinal ganglion, while the right lateral nerve enters near the middle of the visceral ganglion. The visceral ganglion is larger than the subintestinal ganglion. From the visceral ganglion is the genital nerve, which lacks a distinct genital ganglion.

Reproductive system ( Fig. 10D, E–H View FIGURE 10 ). The arrangement of reproductive organs is a modified monaulic system ( Fig. 10D View FIGURE 10 ). From the large ovotestis, which is intermingled with the digestive gland, emerges the slightly convoluted ampulla. The ampulla narrows into the hermaphroditic duct, which curves around the receptaculum seminis and enters short, coiled albumen and membrane glands with a single duct. The hermaphroditic duct may have a portion that widens that may function as a proximal receptaculum seminis. The larger mucous gland is straight or curved with a massive primary lobe. The hermaphroditic duct then joins the duct of the elongate receptaculum seminis and continues to the genital atrium where it joins the duct of the bursa copulatrix. The bursa is large and spherical. Its duct is narrow and elongate and does not widen at the genital atrium. From the genital atrium the open, ciliated sperm groove leads to the cephalic penis. The penis is somewhat variable in shape ( Fig. 10E–H View FIGURE 10 ), but consists of a penial sac and a lobate prostate gland that is joined to the penial sac by a wide duct. Within the penial sac is a large penial papilla that is smooth and conical. The penial papilla is devoid of any armature.

Remarks. Chelidonura alisonae is externally similar to the sympatric Chelidonura hirundinina ( Quoy and Gaimard, 1832) and has often been misidentified with this species ( Kay 1979; Bertsch and Johnson 1981; Rudman, 2007). Despite this similarity, there are consistent differences in external anatomy, which clearly distinguish these species. Both species have a black to brown body. Chelidonura hirundinina is quite variable in color but has a broad horizontal anterior yellowish or orange band. Behind this band is another blue or whitish transverse band that has a perpendicular connection to a mid-dorsal band of the same color that may extend to the posterior end of the cephalic shield or may run just to its midsection. Most often there is a transverse opaque white crescent-shaped patch across the posterior shield, but this is occasionally absent. Generally, the parapodial margins are ornamented with a bright blue line, but occasionally this line is more greenish in color. There is a variable arrangement of orange lines on the cephalic shield, parapodia and posterior shield, but these lines never form a reticulating network as in C. alisonae . In contrast, C. alisonae always has a pair of blue spots on the head that is each surrounded by orange lines. No T-shaped opaque white or blue lines are present on the cephalic shield. An anterior blue patch rather than a yellow or orange one is present at the anterior end of the head. Chelidonura alisonae always has orange lines that form a reticulated network on the foot, but occasionally also on the posterior shield. The parapodial margins are ornamented with isolated blue spots rather than a continuous blue line. The posterior extensions of the posterior shield of C. hirundinina are always more elongate and finely tapered than those of C. alisonae .

There are also internal features that consistently separate the two species. In C. hirundinina , the right posterior end of the shell is slightly more elaborated than that of C. alisonae and it appears that the protoconch of the former is larger than that of the later. The central nervous system of C. hirundinina has a distinct genital ganglion ( Gosliner 1988; present study) that is absent in C. alisonae . The mucous gland of C. hirundinina is tightly coiled, while that of C. alisonae is straight or curves only at the apex.

Pittman and Fiene (2009) have never observed copulation between specimens of C. hirundinina and C. alisonae .

We have conducted preliminary molecular studies (Camacho-Garcia, Gatdula & Gosliner personal communication.), using H3 nuclear and COI mitochondrial genes. In these studies, Caribbean and Indo-Pacific specimens of C. hirundinina cluster together, while a specimen of C. alisonae (CASIZ 165872) clusters with Navanax sp. ( Gosliner et al. 2008: 48, bottom photo) and members of the Chelidonura inornata complex. Chelidonura alisonae differs from Caribbean and Australian specimens of C. hirundinina in its COI gene by 23% of its base-pairs.

Independent lines of evidence from external and internal morphology, species mate recognition systems and molecular markers clearly support the distinctness of C. alisonae from C. hirundinina and all other described species of Chelidonura .