Cyerce elegans Bergh, 1870

Moreno, Karina, Medrano, Sabrina, Gosliner, Terrence M., Wilson, Nerida G., Krug, Patrick J. & Valdés, Ángel, 2025, Phylogenetic systematics of the genus Cyerce Bergh, 1870 (Mollusca: Heterobranchia: Sacoglossa: Caliphyllidae) from the Pacific and Indian oceans with descriptions of nine new species, Zoological Journal of the Linnean Society 204 (1) : -

Cyerce elegans Bergh, 1870

( Figs 15A, 16, 17A)

Cyerce elegans Bergh, 1870 : pl. 1, fig. 9; 1871: 99–113, pl. 9, figs 13–17, pls. 13–15, pl. 16, figs 23–25. Type locality: Palau.? Cyerce elegans var. Bergh 1888: 769–771, pl. 77, figs 6, 7, pl. 78, figs 8, 9.

Cyerce sp. 3 Gosliner et al. 2018: 402 middle left photo.

Type material

Cyerce elegans — one syntype at NHMD (GAS-002149), Palau, Sep 1859, not examined .

Material examined

Riwo Island, Madang Province, Papua New Guinea, 27 Nov 2012, leg. T.M. Gosliner, 1 specimen 6.5 mm preserved length, dissected (isolate MM89 , CASIZ 191446 ). Verde Island Passage, Luzon Island , Batangas Province, Philippines, 12 May 2014, leg. T.M. Gosliner, 1 specimen 18 mm preserved length, dissected (isolate MM20 , CASIZ 199264 ). Maricaban Strait , Mabini (Calumpan Peninsula), Luzon Island , Philippines, 2.5 m depth, 30 Mar 2017, leg. T.M. Gosliner, 1 specimen, dissected (isolate KM27 , CASIZ 222101 ). Bohol Island, Philippines, 0–5 m depth, Sept. 2003, leg., J. Hinterkircher, 1 specimen ( CASIZ 173751 ) .

Range

Widespread in the Indo-West Pacific, from the Maldives to the Hawaiian Isl. (Rudman 1999 a, Gosliner et al. 2018; present paper).

Description

External morphology: Body colour pale green to cream, with white speckling ( Fig. 15A). Pericardium elevated, smooth, oval, cream; clear tubules extending from pericardium throughout body; tubules do not enter cerata. Anal papillae anterior to pericardium, cream. Head cream. Rhinophores, tentacles elongated, translucent white. Cerata inflated, obovate, translucent white, with minute white speckling throughout. Cerata peduncle cream to pink. One to two fluorescent blue to green spots on each ceras, one spot nearer to base and second above. Ceratal margin outlined by reddish-brown band; triangular clusters of white specks distributed throughout. Foot colour pale yellowish-cream, greyish hue.

Internal morphology: Radula from an 18 mm (preserved length) specimen ( CASIZ 199264) with 11 teeth, 6 on descending limb, 5 on ascending limb ( Fig. 16A). Teeth narrow, slightly bent, elongate, about 700 µm in length; tips concave, blunt ( Fig. 16B). Two rows of ~23 triangular denticles along either side; denticles smaller near base and tip. Ascus with about 15 used teeth ( Fig. 16C). Penis with no stylet visible ( Fig. 17A) in several specimens examined.

Ecology

Diet unknown.

Remarks

Bergh (1870; 1871) described Cyerce elegans Bergh, 1870 based on 10 specimens collected in Palau. The animals were described based on an illustration by Semper [reproduced by Bergh 1870: pl. 1, fig. 9 and herein ( Fig. 5D)] as having ‘water-clear, faintly yellowish-white, translucent’ cerata with ‘one or more green dots formed by peculiar yellowish bodies’ at the base and ‘reddish-brown’ margin with large spots. All these external morphological traits were also observed in specimens from Papua New Guinea and the Philippines assigned to this species, but in the specimens examined herein there was only a single fluorescent green or blue spot at the base of each ceras. Bergh (1871) also described the presence of an ‘elongated horseshoe-shaped arch’ on the dorsum from which branches extend to the base of each ceras. Bergh (1871) was most likely describing the pericardium, with tubules extending across the body as observed in our specimens. Regarding the internal anatomy, Bergh (1871) described the radular teeth as having a blunt tip, wide base, ‘slightly bent, tapered’, and denticles ‘directed backwards’ that became smaller and ‘crowded’ at the tip. These radular traits are also observed in our specimens assigned to this species. Because of the consistencies between the characteristics of the material here examined and the original description, we confidently assigned these specimens to C. elegans . Finally, Bergh (1871) described the penis of C. elegans as having a ‘sharply curved hook, which tapers very sharply’. This was also confirmed by Yonow and Jensen (2018). Although the penis was dissected from several of our specimens, we were unable to observe any penial stylet and therefore could not verify the presence of a hookshaped stylet in the male reproductive system as described and illustrated by Bergh (1871: pl. 15, figs 12–14) and Yonow and Jensen (2018: fig. 20G, H).

Bergh (1888) reported a single specimen of a variety (or colour form) of C. elegans from Mauritius, with descriptions of the live animal based on notes and a drawing of a ceras by [Karl August] Moebius [Möbius] reproduced by Bergh (1888: pl. 77, fig. 6) and herein ( Fig. 5E). The specimen was described as light brown in colour, with white spots on the rhinophores and oral tentacles, and translucent light brown cerata with yellowish-white triangular spots along the margin; from these spots are connecting ‘white veins’ and lines throughout; green to blue ‘cells’ at the base. Our specimens assigned to C. elegans also have the triangular spots along the margin of the cerata as described by Bergh (1888) but lack the radiating ‘veins’ and lines from these spots; however, these lines are present in other species of the same clade described below, including C. sp., which is also reported from the Indian Ocean. It is, therefore, likely that the specimen described by Bergh (1888) belongs to a different species of the C. elegans species complex. Other specimens assigned to C. elegans in the literature (e.g. Rudman 1999a, Yonow 2008, Gosliner et al. 2018, Nakano 2018) probably belong to other species of the C. elegans species complex as well.

Species delimitation analyses supported specimens preliminarily identified as Cyerce elegans as four separate entities, which were also recovered in phylogenetic analyses, collectively termed here as the C. elegans complex. In addition to the material identified as C. elegans , our analyses differentiated three pseudocryptic taxa: Cyerce sp. from the Red Sea; Cyerce basi sp. nov. from Papua New Guinea, the Philippines, and New Caledonia; and Cyerce whaapi sp. nov. from the Philippines and New Caledonia ( Fig. 1B; Table 3). Members of the C. elegans complex share clear, thickened cerata with triangular clusters of small white specks along the margin and a fluorescent spot at the base of each ceras varying from green to blue or light brown. However, the specimens of C. elegans sensu stricto all exhibit a reddish-brown ceratal margin as described by Bergh (1870; 1871), a trait not observed in Cyerce sp. , Cyerce basi sp. nov., or Cyerce whaapi sp. nov. Cyerce elegans was sister to C. whaapi sp. nov., which had more inflated and translucent cerata with faint vein-like striations extending from larger, deeper triangular clusters along the margin compared to C. elegans ; additionally, the fluorescent spot at the ceratal base was green to light brown in Cyerce whaapi sp. nov. but blue to green in C. elegans . Radular morphology was similar between Cyerce whaapi sp. nov. and C. elegans ; teeth were elongate, slightly bent, with concave tips and short, conical denticles.

Cyerce basi sp. nov., which overlapped with C. elegans in Papua New Guinea, was recovered as sister to C. whaapi sp. nov. and C. elegans . Cyerce basi sp. nov. had white vein-like striations throughout the cerata, observed in Cyerce whaapi sp.nov. but not in C. elegans . The triangular clusters along the cerata margin of C. basi sp. nov. have brown specks and are much deeper and larger than in C. elegans . The cerata of C. basi sp. nov. are also more inflated and translucent than in C. elegans . The radular morphology of C. basi sp. nov. is similar to that of C. elegans but the teeth of C. basi sp. nov. have a pointed tip between the first pair of denticles, not observed in C. elegans . We could not obtain specimens of Cyerce sp. for morphological analysis; therefore, we could not compare the internal morphology to our specimens of Cyerce elegans .