Elysia hamanni, Krug, Patrick J., Vendetti, Jann E. & Valdés, Ángel, 2016

Krug, Patrick J., Vendetti, Jann E. & Valdés, Ángel, 2016, Molecular and morphological systematics of Elysia Risso, 1818 (Heterobranchia: Sacoglossa) from the Caribbean region, Zootaxa 4148 (1), pp. 1-137 : 112-114

Elysia hamanni new species

( Figs. 56 H, 67–69)

Elysia sp. 5 — Valdé s et al. 2006: 76–77.

Type material. Banana River , Florida, USA, May 1988, (Holotype LACM 3310 ) collected by Jeff Hamann ; True Blue Point , True Blue Bay, Grenada, December, 1987, (Paratype LACM 3311 [8 in lot]), collected by Jeff Hamann .

Type locality. Banana River , Florida, USA

Material examined. Banana River , Florida, USA, May 1988, 5 specimens (Holotype LACM 3310 , LACM 178668 [1 in lot], LACM 178669 [3 in lot]) ; Grenada: September, 1981, 3 specimens ( LACM 178671 ), True Blue Point, True Blue Bay, December , 1987, 8 specimens (Paratype LACM 3311 ) ; Isla Mujeres, Mexico, December, 1993, 8 specimens ( LACM 178670 [5 in lot], LACM 178673 [3 in lot]); Ranguana Caye , Belize, 31 March 1992, 1 specimen ( LACM 178667 ) ; Port Antonio , Jamaica, August 1990, 5 specimens ( LACM 178672 ) .

Live animal. Resting slugs held their parapodia apart, forming a series of irregular openings ( Fig. 67 A–B). The animals leave characteristic circular feeding marks on their algal host, Caulerpa prolifera . When stressed the animals release a milky white substance.

External anatomy. Holotype (LACM 3310) measuring 21 mm long, 10 mm wide at widest point with parapodia flattened; paratype (LACM 3311) 17 mm long, 6 mm wide. Other examined specimens: LACM 178672, 19 mm long × 10 mm wide; LACM 178667, 18 mm long.

Background coloration pale green with a pinkish tinge on external side of parapodia. Epidermis of head and body covered by small dark purple to black spots. Body elongate when parapodia contracted over dorsum. Head pale green with pinkish pigment dorsally, and elongate lighter area on each side running from eyes into base of rhinophores. Rhinophores elongate, rolled, with flat tips. Body covered with numerous conical papillae of various sizes, larger papillae occur mainly on external sides of parapodia. Parapodia margins lighter, with faint, thin, dark grey line, also covered with papillae.

Pericardium small and oval, pale green, dotted with few white spots. Renopericardial extension runs almost entire length of body, pale green. Extension narrows immediate upon exiting pericardium and expands again. Numerous very thin dorsal vessels, opaque white. One vessel extending out of pericardium and running along dorsal surface of renal extension ( Fig. 68 ). Two dorsal vessels emerging from pericardium on each side, numerous remaining vessels emerging from renopericardial extension at regular intervals along whole body length. Vessels symmetrical, with most paired with a vessel on opposing side of body. Most vessels bifurcating about halfway up inner parapodial surface margin and then forking again near parapodial margin; vessels anastomosing into complex network ( Fig. 68 ).

Internal anatomy. Radula with 28 teeth (LACM 3311), 6 teeth in ascending limb and 22 in descending limb ( Fig. 69 A). Leading tooth wide and robust with a parallelogram-like shape and lacking denticles. Housing depression for interlocking teeth extending ⅔ the tooth length ( Fig. 69 B). Base of tooth approximately ⅓ of total tooth length. Ascus with 16 teeth, becoming progressively smaller in size, in a spiral or whorl ( Fig. 69 C).

Penis broad, and relatively large with rigid musculature resistant to desiccation ( Fig. 56 H), tapering distally into a conical apex lacking armature ( Fig. 69 D–E). Deferent duct long, narrow, and highly convoluted.

Reproduction and development. Egg masses were photographed in the field along with the specimens. The egg strand formed a tight elysiid spiral, with one egg per capsule. Within the strand, capsules alternated on either side of a continuous ribbon of bright orange ECY ( Fig. 67 C). The egg ribbon was flat. Development mode could not be determined from the photographs.

Host ecology. All specimens were found on the alga Caulerpa prolifera , on which they leave a characteristic round feeding scar ( Fig. 67 A–B).

Phylogenetic relationships. No specimens of E. hamanni n. sp. were available for molecular work, so the phylogenetic relationships of this species are unknown. Based on its diet, radula, and elongated renopericardial complex, we hypothesize this species belongs to subclade 4, the E. tomentosa complex.

Range. Ranguana Caye, Belize (present study), Banana River, Florida, USA (present study), Grenada (Valdés et al. 2006), Jamaica (present study), Isla Mujeres, Mexico (present study).

Etymology. Named in honor of Jeff Hamann, who over several years compiled a comprehensive collection of sea slugs from the Caribbean, including numerous new species such as this one.

Remarks. Elysia hamanni n. sp. is clearly different from other species of Elysia described to date in the Caribbean region. Morphologically, the most similar species may be E. subornata , which also has a body covered with conical papillae, similar dorsal vessels, and wide parapodia with a marginal line. Although the dorsal vessel pattern is similar in these two species, E. hamanni n. sp. has comparatively more vessels. Both species also feed on Caulerpa . However, the radular morphology of these two species is somewhat different: E. subornata has narrower, more elongate radular teeth and the ascus is highly disorganized. The radular teeth of Elysia hamanni n. sp. are proportionally shorter and wider and the ascus forms a highly organized spiral or whorl. Radular morphology of E. hamanni n. sp. is also similar to E. pawliki n. sp. and E. zemi n. sp., although teeth are more pointed and blade-like in E. hamanni n. sp. The tightly spiraled ascus is a notable similarity between E. hamanni n. sp. ( Fig. 69 C) and E. zemi n. sp. ( Fig. 63 H).

An unusual feature shared between E. hamanni n. sp. and the Indo-Pacific species Elysia (= Pattyclaya ) brycei is a single dorsal vessel extending out from the pericardium and running along the dorsal surface of the elongated renal gland (fig. 20 in Jensen & Wells 1990). As both species feed on Caulerpa , it is possible this may be a synapomorphy, and that “ Pattyclaya ” spp. are derived members of subclade 4 with lateral lammellae. Molecular data are needed to resolve the phylogenetic placement of both E. hamanni n. sp. and Pattyclaya spp. to assess homology versus convergence in characters such as the ascus and dorsal vessel patterns.

Figures

FIGURE 56. Penial morphology of some species examined. A, Elysia buonoi n. sp. (LACM 178675) B, Elysia orientalis (CPIC 00842). C, Elysia ellenae (LACM 178663). D, Elysia pawliki n. sp. (LACM 3303). E, Elysia christinae n. sp. (LACM 3309). F, Elysia zemi n. sp. (LACM 3307). G, Elysia taino n. sp. (LACM 178607). H, Elysia hamanni n. sp. (LACM 178667). Abbreviations: dd, deferent duct; pe, penis; s, stylet.

FIGURE 63. Elysia zemi n. sp., SEM of the radula and penis. A, Complete radula (LACM 178666). B, Leading tooth (LACM 178666). C, Ascus (LACM 178666). D – E, Penis and detail of penis tip showing stylet (LACM 178666). F, Radula (LACM 3306). G, Leading tooth (LACM 3306). H, Ascus (LACM 3306).

FIGURE 67. Elysia hamanni n. sp., external morphology and egg mass. Characteristic round feeding scars on host alga Caulerpa prolifera visible in all panels. A – B Live specimens from Grenada. C, Egg mass showing orange ECY ribbon.

FIGURE 68. Elysia hamanni n. sp., drawing of renopericardial complex and dorsal vessel network traced from preserved specimen from Florida (LACM 178668, 5 cm long × 3 cm width).

FIGURE 69. Elysia hamanni n. sp., SEM of the radula and penis. B, Complete radula (LACM 3311). B, Leading tooth (LACM 3311). C, Ascus (LACM 3311), D, Penis (LACM 178668), E, Penis tip (LACM 178668).