Halgerda fibra, Fahey & Gosliner, 2000

Fahey, Shireen J. & Gosliner, Terrence M., 2000, New records of Halgerda Bergh, 1880 (Opisthobranchia, Nudibranchia) from the deep western Pacific Ocean, with descriptions of four new species, Zoosystema 22 (3), pp. 471-498 : 473-479

Halgerda fibra n. sp.

( Figs 1 A-C; 2-4)

HOLOTYPE. — Philippines. MUSORSTOM 3, stn CP 134, 12°01’ N, 121°57’E, 92-95 m, 5.VI. 1985, 38 mm (MNHN).

PARATYPES. — Philippines. MUSORSTOM 3, stn CP 134, 12°01’ N, 121°57’E, 92-95 m, 5.VI.1985, 2 sp., 30 mm, 44 mm (MNHN).

ETYMOLOGY. — The specific name is taken from the Latin fibra meaning thread or filament. The name refers to the many thin, dark lines on the dorsum, which radiate downward from the distinct tubercles.

OTHER MATERIAL EXAMINED. — Banc Aztèque. Sud Nouvelle-Calédonie, SMIB 8, stn DW 184, 23°18’ S, 168°05’E, 305-320 m, 31.I.1993, 1 sp., 22 mm (CASIZ 119062). — Stn DW182-184, 23º18’S, 168º05’E, 305-367 m, 31.I.1993, 1 sp., 30 mm (MNHN). — Stn DW189, 23º18’S, 168º06’E, 400- 402 m, 31.I.1993, 1 sp., 35 mm (MNHN).

Banc Jumeau ouest. Sud Nouvelle-Calédonie, SMIB 8, stn DW 174, 23º40’S, 168º01’E, 235-240 m, 29.I.1993, 3 sp., 25 mm, 35 mm, 41 mm (MNHN); 235-240 m, 29.I.1993, 2 sp., 26 mm, 23 mm (MNHN). — Stns DW170-172, 23º41’S, 168º00’E, 230-290 m, 29.I.1993, 3 sp., 26 mm, 30 mm, 37 mm (MNHN). — Stn DW173, 23º41’S, 168º00’E, 234- 242 m, 29.I.1993, 1 sp., 37 mm (MNHN). — Stn DW175, 23º41’S, 168º01’E, 235-240 m, 29.I.1993, 1 sp., 29 mm (MNHN).

Banc Kaimon Mau. Sud Nouvelle-Calédonie, SMIB 8, stn DW 158, 24º46’S, 168º08’E, 262-290 m, 28.I.1993, 1 sp., 21 mm (MNHN).

Ride de Norfolk. Nouvelle-Calédonie, BATHUS 3, stn CH 802, 23º41’S, 168º00’E, 357-550 m, 27.XI.1993, 6 sp., 14 mm, 20 mm, 22 mm, 25 mm, 28 mm, 29 mm (MNHN). — Stn CP804, 23º41’S, 168º00’E, 244-278 m, 27.XI.1993, 9 sp., 18 mm, 20 mm, 20 mm, 22 mm, 25 mm, 30 mm, 36 mm, 37 mm, 40 mm (MNHN). — Stn CH801, 23º39’S, 168º00’E, 270-300 m, 27.XI.1993, 4 sp., 26 mm, 35 mm, 38 mm, 46 mm (CASIZ 119060).

Sud Nouvelle-Calédonie. SMIB 4, stn DW 52, 23°41’ S, 168°01’E, 235-250 m, 9.III.1989, 1 sp., 33 mm (MNHN). — Stn DW53, 23°40’S, 168°00’E, 250-270 m, 9.III.1989, 1 sp., 40 mm (MNHN). — CHALCAL 2, stn CP20, 24º45’S, 168º09’E, 230 m, 27.X.1986, 1 sp., 12 mm (MNHN).

Nord Nouvelle-Calédonie. BATHUS 4, stn CP 938, 19º00’S, 163º26’E, 280-288 m, 8.IX.1994, 4 sp., 15 mm, 21 mm, 25 mm, 26 mm (MNHN). — Stn DW932, 19º08’S, 163º29’E, 170-190 m, 8.VIII.1994, 1 sp., 23 mm (MNHN). — Stn DW941, 19º02’S, 163º27’E, 270 m, 8.VIII.1994, 1 sp., 23 mm (MNHN). — Stn CP936, 19º04’S, 163º28’E, 252-258 m, 8.IX.1994, 2 sp., 18 mm, 19 mm (MNHN). — Stn DW939, 18º58’S, 163º25’E, 304-320 m, 8.IX.1994, 2 sp., 10 mm, 20 mm (CASIZ 119061).

Nouvelle-Calédonie. MUSORSTOM 4, stn CP 191, 19º02’S, 163º28’E, 250 m, 19.IX.1985, 1 sp., 30 mm (MNHN). — Stn DW227, 22º46’S, 167º20’E, 300 m, 30.IX.1985, 2 sp., 16 mm, 11 mm (MNHN). — Stn DW183, 19º02’S, 163º20 ’ E, 280 m, 18.IX.1985, 1 sp., 20 mm (MNHN). — BIO- CAL, stn CP84, 20º43’S, 167º01’E, 150-210 m, 6.IX.1985, 1 sp., 14 mm (MNHN).

Buccal armature

The buccal mass is not pigmented; however, there are small dark spots on the buccal opening. The radular sac is elongate, curved and lies flat on the posterior end of the buccal mass. The labial cuticle is smooth and devoid of any jaw rodlets.

The radula ( Fig. 3 ) of the holotype (MNHN MUSORSTOM 3 CP 134, 38 mm) has a formula of 51 × 65.0.65. Two paratypes (MNHN

BATHUS 3 CP 804, 22 mm & MNHN SMIB 4 DW 52, 33 mm) each had a radular formula of 41 × 51.0.51. The three outer teeth ( Fig. 3A ) are much smaller than the inner and middle lateral teeth and have no denticles. The eight or so inner lateral teeth ( Fig. 3B ) are smaller and have shorter hooks than the middle lateral teeth and the rows are arranged in a V-shaped pattern. The middle lateral teeth ( Fig. 3C, D ) are hamate with long, pointed hooks. They have a flattened flange that overlaps the adjacent tooth.

Reproductive system

The reproductive system ( Fig. 4 , MNHN BATHUS 3 CH 801) is triaulic. The ampulla is flattened, moderately elongate and lies flat on the prostate in the holotype and one paratype. In two other specimens (CASIZ 119062 SMIB 4 DW 184, 22 mm & MNHN SMIB 4 DW 52, 33 mm) the ampulla is extremely large and coiled. The ampulla narrows into the postampullary duct, which bifurcates into the vas deferens and oviduct. The short oviduct enters the female gland mass. The female gland mass is slightly larger than the prostate gland. The short vas deferens separates from the ampulla and widens into the glandular prostate. The prostate consists of two distinct glandular types and they are welldifferentiated as in most other members of Halgerda . The prostate coils behind the bursa, and in some specimens, the prostate partially covers the bursa with a thin membrane. The muscular portion of the vas deferens leaves the distal prostate in a long, thick duct, that loops twice, then enters the wide penial bulb. The short uterine duct emerges from the female gland mass and joins the oval receptaculum seminis near the last quarter of its length. The duct connecting the receptaculum and the bursa is very long and coiled. The oval receptaculum seminis is much smaller than the thin-walled spherical bursa copulatrix. The long, wide vaginal duct emerges from the base of the bursa copulatrix. Near the vagina exit there is a large muscular portion of the bulbous vagina. The common genital atrium is wide and large. The opening of the female gland mass is adjacent to the genital aperture.

DISCUSSION

The external markings on the dorsum of Halgerda fibra are unique among members of the genus. Due to some external and internal morphological similarities with Halgerda willeyi Eliot, 1904 a comparison is made between these two species. In addition, due to some external similarities with the original description of Halgerda graphica Basedow & Hedley, 1905 , and H. johnsonorum (Carlson & Hoff 2000) , a contrast is drawn between all three species.

First, in comparing the external morphology of these species, the following similarities and contrasts are noted: the general body shape of all four species is similar in that they are broad ovals; three of the species, Halgerda fibra , H. willeyi (Eliot, 1904) and H. graphica (Basedow & Hedley, 1905) , have a high body profile and a surface texture that is firm and gelatinous; Halgerda johnsonorum has a low body profile and a soft, flaccid surface texture (Carlson & Hoff 2000). Both Halgerda willeyi and H. fibra have distinct dorsal ridges that have rounded tubercles at the junctions. Although both species can have dark pigment in the depressions between the ridges, this pigment is arranged in two distinct patterns. The thick dark pigment on the dorsum of H. willeyi lies in the ridge depressions, parallel to the ridges that are also lined with orange. In H. fibra , the dark pigment is arranged as finely drawn lines that radiate down from the tubercles and gill pocket. While both species have dark pigment at the mantle border, Halgerda willeyi has distinct dark lines perpendicular to the bor- der, whereas H. fibra can have either small, distinct speckles or lines arranged both perpendicular to the border, then parallel to the border nearest to its edge.

Halgerda graphica has distinct ridges, but no tubercles at the junctions. The dark pigment on the dorsum is a distinct spot in the center of each ridge depression. There are no other dark lines on the dorsum. On the underside of both H. fibra and H. graphica are irregularly spaced dark spots. Eliot (1904) described black spots on the genital orifices of H. willeyi , but no other pigment on the underside. Halgerda johnsonorum has very low-lying ridges with no noticeable tubercles on the dorsum. The dark pigment is similar to H. willeyi in that it lies in the ridge depressions alongside secondary lines of yellow and perpendicular to the ridges. There are dark lines perpendicular to the mantle edge, on the foot, and a few leading into the genital pore of H. johnsonorum . The dark pigment on the rhinophores of these species also differs. Halgerda fibra has one single dark line on the posterior side of the rhinophores, extending from the base to the tip of the club. Halgerda willeyi also has a dark line on the posterior side of the rhinophores, and in addition, there is dark pigment covering the club. Halgerda graphica has dark pigmentation on the club only. Halgerda johnsonorum has dark spots randomly scattered over the entire rhinophoral stalk.

The branchial plume of three species, Halgerda fibra , H. willeyi and H. graphica , is similar in that there are six branches. In both H. fibra and H. willeyi , there are two main plumes that each divide into three subdivisions. Halgerda johnsonorum has four main plumes with the posterior two being secondarily divided (Carlson & Hoff 2000). The branchial coloration differs among the four species. The gill of H. graphica is dark, whereas the gill of both H. fibra and H. willeyi has only a dark stripe on the anterior side of each plume. Halgerda johnsonorum has dark spots all over the gill.

The radula is also different. The three outer lateral teeth of three Halgerda species , H.fibra , H.graphica and H. willeyii , are small and simple, with no denticles. The six outer teeth of H. johnsonorum are reduced with the outer three flattened and the penultimate is bifid (Carlson & Hoff 2000). The radular formulae for H. fibra is 51 × 65.0.65 (38 mm specimen) and 41 × 51.0.51 (22 and 33 mm specimens), for H. graphica the published formula is 40 × 40.0.40 (45 mm specimen), for H. johnsonorum the formula is 37 × 46.0.46 (20 mm specimen) and for H.willeyi no formula is published. There are differences between the reproductive systems of three species ( Halgerda fibra , H.willeyi and H. johnsonorum ). The reproductive system of the fourth species, Halgerda graphica , was never described by the original authors, and further specimens have not been reported in the literature since.

The ampulla of each of the three described species, Halgerda fibra , H. willeyi , and H. johnsonorum , differs in length and in placement on the reproductive system. Halgerda fibra has either a flattened ampulla that is mid-length between that of H. willeyi and H. johnsonorum , or it has a very thick, coiled ampulla. In either case, the ampulla rests against the prostate gland. H. willeyi has a large, long, convoluted ampulla that is not embedded in the prostate. The ampulla of H. johnsonorum is short, slightly coiled and mostly embedded in the prostate. The uterine duct of each of the three species also differs in length. The uterine duct of Halgerda fibra is long, convoluted and is not covered by the bursa copulatrix whereas the duct of H. willeyi is long and loops completely around the bursa. The uterine duct of H. johnsonorum has one simple loop. The bursa is entirely covered by the prostate in both H. fibra and in H. johnsonorum and mostly covered in H. willeyi . The penial sheath of the three species differs in length and width. The sheath of H. fibra is long and wide, as in H. johnsonorum , whereas the penial sheath of H. willeyi is short, then widens before it enters the common genital vestibule. The vaginal duct of H. fibra is wide and long, with a muscularized portion at its exit into the bulbous vagina. The vaginal ducts of H. willeyi and H. johnsonorum are both thin and long, with a small muscular portion at the exit of the duct of H. willeyi only. There is a common genital atrium in all three species.

The combination of the external, reproductive and radular morphology of Halgerda fibra , distinguish it as a new species.

Figures

FIG. 1. — Photos of new Halgerda species from the deep sea; A, Halgerda fibra n. sp., living animal, dorsal view (MNHN BATHUS 3); B, Halgerda fibra n. sp., preserved animal, ventral view (MNHN BATHUS 3); C, Halgerda fibra n. sp., living animal, dorsal view (MNHN CHALCAL 2 CP20); D, Halgerda abyssicola n. sp., living animal, dorsal view (MNHN MUSORSTOM 8 CP1132). Scale bar: A, B, 5 mm; C, 2 mm; D, 3 mm.

FIG. 3. — Electron micrographs of H. fibra n. sp. (MNHN MUSORSTOM 3 CP134) radular morphology; A, outer lateral teeth; B, inner lateral teeth; C, middle lateral teeth; D, middle lateral teeth. Scale bars: A, 43 µm; B, C, 100 µm; D, 150 µm.

FIG. 4. — Drawing of H. fibra n. sp., reproductive morphology. Abbreviations: am, ampulla; bc, bursa copulatrix; ej, ejaculatory duct; fgm, female gland mass; ga, genital aperture; p, penis; pr, prostate; rs, receptaculum seminis; v, vaginal sphincter. Scale: 7.5 ×.