Halgerda azteca, 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 : 482-485

Halgerda azteca n. sp.

( Figs 8-10 )

HOLOTYPE. — Banc Aztèque. Sud Nouvelle- Calédonie, SMIB 8 , stns DW182-184, 23º18’S, 168º05’E, 314-367 m, 31.I.1993, 1 sp., 10 mm ( MNHN).

PARATYPES. — Banc Aztèque. Sud Nouvelle- Calédonie, SMIB 8, stns DW182-184, 23º18’S, 168º05’E, 314-367 m, 31.I.1993, 1 sp., 15 mm ( MNHN).

Banc Jumeau east. Sud Nouvelle-Calédonie, SMIB 8, stns DW170-172, 23º41’S, 168º00’E, 230-290 m, 29.I.1993, 3 sp., 28 mm, 16 mm, 12 mm (CASIZ 119059).

ETYMOLOGY. — The specific name refers to the locality, banc Aztèque, where the type specimens were collected near New Caledonia.

DISTRIBUTION. — This species is found at Norfolk Ridge near the southern end of New Caledonia (present study) at depths from 230 to 367 m.

DESCRIPTION

External morphology

The preserved animals studied have a firm, smooth body. The body profile is high and the dorsum has ridges arranged in a reticulate pattern ( Fig. 8 ). There are pronounced tubercles at the ridge junctions. The gill and rhinophoral pockets are smooth. The ground color of the dorsum and foot is white. There are spots of dark pigment on the dorsum and along the mantle edge. Along the mantle edge of the preserved animal there are also perpendicular dark lines that extend nearly to the mid dorsum. The rhinophores are tapered towards the tips. No pigmentation is present on the preserved animals.

The bipinnate gill has two main branches, each divided into two secondary branches and sparsely pinnate. There is dark stripe on the anterior side of each branch. The anal papilla is white.

Buccal armature

The buccal mass is not pigmented. The radular sac is elongate and protrudes from the buccal mass. The labial cuticle is smooth and devoid of any jaw rodlets. The radular formula of the animal examined (MNHN SMIB 8 DW182-184) is 27 × 43.0.43. The four outer teeth ( Fig. 9A ) are much smaller than the inner and middle lateral teeth and have no denticles. The middle lateral teeth ( Fig. 9C, D ) are hamate with long, pointed hooks. They have a flattened base that overlaps the adjacent tooth. The seven or eight inner lateral teeth ( Fig. 9B ) are smaller than the middle lateral teeth and are arranged in V-shaped rows.

Reproductive morphology

The reproductive system ( Fig. 10 ) is triaulic. The ampulla is tubular, rather short and lies flat against the female gland mass. 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 about the same size as 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 not as well differentiated as in most other members of Halgerda . The muscular portion of the vas deferens leaves the distal prostate in a long, convoluted duct, that loops several times into a tall, twisted mass over the wide penial bulb. The short uterine duct emerges from the female gland mass and joins the spherical receptaculum seminis near its base. The duct connecting the receptaculum and the bursa is very long, thick and coiled. The spherical receptaculum seminis is much smaller than the large, thin-walled spherical bursa copulatrix. The prostate does not cover the bursa copulatrix, but wraps around it as is common in other species of Halgerda . The vaginal duct that emerges from the base of the bursa copulatrix is very long and convoluted. At its exit is a sphincter at the top of a glandular portion of the bulbous vagina. The glands are isolated on either side of the vagina. The common genital atrium is wide and large.

DISCUSSION

Although this species has some similar external characters to other Halgerda species , no photo or description was available to confirm its color characters. The dark pigmentation that remains on the animal through preservation is most similar to Halgerda willeyi and H. johnsonorum (Carlson & Hoff 2000) . For this reason, these animals are compared.

First, in comparing the external morphology of these species, the following similarities and contrasts are noted.

The general body shape of all three species is similar in that they are broadly ovate. Two of the species, Halgerda azteca and H. willeyi , have both a high body profile and a surface texture that is firm and gelatinous. Halgerda johnsonorum has a low body profile and a softer, more flaccid surface texture.

Both Halgerda willeyi and H. azteca have distinct dorsal ridges that have rounded tubercles at the junctions. Although both species 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 Halgerda willeyi lies in a complex pattern in the depressions along with orange lines. In Halgerda azteca the dark pigment remains as finely drawn lines that radiate down the sides of the dorsum to the mantle edge in no particular pattern. Both species have these distinct dark lines perpendicular to the mantle border. Halgerdajohnsonorum has very low-lying ridges with no noticeable tubercles on the dorsum. The dark pigment on this animal 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 underside of Halgerda azteca are irregularly spaced dark spots. Eliot (1904) described black spots on the genital orifices, but no other pigment on the underside of H. willeyi . Halgerda johnsonorum has dark spots on the foot, and a few leading into the genital pore.

There are differences among the rhinophores of the three species. No pigmentation is present on the preserved specimens of Halgerda azteca . Halgerda willeyi has a dark line on the posterior side of the rhinophores, and in addition, there is dark pigment covering the club. Halgerda johnsonorum has dark spots randomly scattered over the entire rhinophoral stalk.

The gill of Halgerda azteca has two main branches each divided into two secondary branches. Halgerda willeyi has two main plumes that each divide into three subdivisions. Halgerda johnsonorum has four main plumes with the posterior two being secondarily divided. The gill coloration differs among the three species. The gill of both H. azteca and H. willeyi has a black stripe on the anterior side of each plume. Halgerda johnsonorum has dark spots all over the gill. The radular differences among the three species are as follows: Halgerda azteca has four outer teeth reduced, simple with no trace of denticles; the three outer lateral teeth of H. willeyi 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.

There are significant differences among the reproductive morphologies of three species. Firstly, the ampulla of each of the three species differs in length and in placement on the reproductive system. Halgerda azteca has a flattened ampulla that is intermediate in length to that of H. willeyi and H. johnsonorum , and rests against the female gland mass. Halgerda 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 azteca is long, convoluted and is not embedded under 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 surrounded by the glandular prostate in H. azteca . The bursa in H.johnsonorum is entirely covered by the prostate and mostly covered in H. willeyi . The ejaculatory duct of H. azteca is distinct. It is extremely long, coiled and protrudes from the genital mass. In contrast, the ejaculatory ducts of both H. willeyi and H. johnsonorum are thin and extremely short in comparison, and tucked against the genital mass. The penial sheath of the three species differs in length and width. The sheath is wide and bulbous in H. azteca and in H. johnsonorum , whereas the penial sheath of H. willeyi is short, then it widens before it enters the common genital vestibule. The vaginal duct of H. azteca 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 . Halgerda azteca also has a glandular portion of the vagina, which is not present in either of the other two species. There is a common genital atrium in all three species.

The unusual reproductive morphology combined with the radular differences and dark external pigmentation clearly separate Halgerda azteca as a new species.

Figures

FIG. 8. — Halgerda azteca n. sp., preserved specimen (MNHN SMIB 8 DW182-184); A, dorsal view; B, ventral view. Scale bar: 3 mm.

FIG. 9. — Electron micrographs of H. azteca n. sp. (MNHN SMIB 8 DW182-184), radular morphology; A, outer lateral teeth; B, inner lateral teeth; C, middle lateral teeth; D, middle lateral teeth. Scale bars: A, B, 60 µm; C, D, 150 µm.

FIG. 10. — Drawing of H. azteca n. sp. reproductive morphology. Abbreviations: am, ampulla; bc, bursa copulatrix; ej, ejaculatory duct; fgm, female gland mass; ga, genital atrium; p, penis; pr, prostate; rs, receptaculum seminis; v, vagina; vs, vaginal sphincter. Scale: 10 ×.