Anteaeolidiella, Miller, 2001

Miller, M. C., 2001, Aeolid nudibranchs (Gastropoda: Opisthobranchia) of the family Aeolidiidae from New Zealand waters, Journal of Natural History 35 (5), pp. 629-662 : 634-639

Genus Anteaeolidiella gen. nov.

Diagnosis

Body low, widish, pericardial swelling prominent, oral tentacles longish tapering to a rounded tip, rhinophores shorter tapering to a blunt tip, smooth; cerata clubshaped, largest approximately length of orals, in single rows arranged in clusters with up to eight rows in ®rst, ®ve in second, number decreasing posteriorly, associated lateral digestive gland ducts trace out a fork-like pattern; cleioproctic, anus between middle rows of second ceratal cluster, renal pore pre- and adanal; reproductive apertures immediately below anterior rows of ®rst ceratal cluster; foot wider than body, curved at front, corners very short triangular processes. Oral glands large, each comprising a large fusiform shaped proximal part with two opposite rows of swellings (5 giant secretory cells) and a long narrow tapered duct distally; radular tooth moderately wide, strongly bilobed, largest denticles at apex of each lobe, median cusp small yet distinct; jaw masticatory process smooth.

Type species. Aeolidiella indica Bergh, 1888 .

Etymology. The noun Aeolidiella (a combination of Greek and Latin!) is pre- ®xed with the latin adverb ante meaning`before’ to indicate a form earlier in origin.

It is my view that Aeolidiella indica does not sit easily within the genus Aeolidiella . This species stands apart by the forked arrangement of the lateral ducts of the digestive gland and cerata and clavate shape of the latter at rest, evenly tapered body, curved anterior end of the foot with very small angles, the widish high bilobed tooth with a cusp, and nodulose spindle-shaped oral glands, the lines of nodules or swellings being emergent giant secretory cells ( Williams, 1978). I believe that the diOEerence is large enough to warrant the creation of a new genus for it, and this is what I have done here. As I have signi®ed earlier, Aeolidiella indica manifests several features which represent early stages in aeolidiid evolution. Possibly other species might qualify for inclusion in this new genus. Baeolidia benteva Marcus, 1958 has the same repeated fork-like ceratal arrangement but the cerata are fusiform, the radular tooth much wider with only a small cusp, and tentaculate foot angles. Notwithstanding these particular diOEerences I would assign B. benteva to this new genus on the basis of ceratal arrangement and positions of the ori®ces. Another species, Baeolidia cryoporos Bouchet, 1972 , has the pre-cardiac part of the digestive gland forming rows of cerata, the post-cardiac two rows and then one row and the anus opens below the second group of post-cardiac or post-stomachal rows. This species with a curved bow-like radula seems better placed within the genus Aeolidia than in Baeolidia , even though the rhinophores are papillate.

Anteaeolidiella indica ( Bergh, 1888) (®gures 1±3) Aeolidiella indica Bergh, 1888: 755 .

For a full synonymy, see Gosliner and Gri ths, 1981: 119.

Morphology (®gure 1)

Extended length up to 20 mm. Body broadest just posterior to rhinophores, ¯attish with large, prominent pericardium one-third of body length from tip of head. Oral tentacles one-seventh to one-eighth of body length, stout at base tapering to a blunt apex: rhinophores one-tenth of body length, stoutish tapering to rounded tip, surface sometimes weakly wrinkled. Tail fairly short, one-seventh to one-eighth body length. Foot only slightly broader than visceral part of body: anterior end curved, corners extending sideways as short, blunt processes (®gure 2A); tapers gradually posteriorly to a sharp tip. Cerata arranged in up to eight clusters (®gure 2B), last two being di cult to separate externally; in oblique rows in ®rst three clusters, irregular thereafter becoming more so posteriorly, cerata occasionally present between upper ends of rows; disposition of ceratal rows in ®rst cluster as follows, in a 20 mm specimenÐright side 346778, left side 1344778, in a 6 mm specimenÐ right side 12344, left side 22344; cerata highly mobile, large ceras at rest clavate, tipped with minute nipple-like process bearing opening of cnidosac, cerata contracted radially become linear in outline. Anus and renal pore, latter immediately in front of former, situated almost level with centre of pericardium and half-way down side of body, i.e., immediately in front of lower half of next to last row of second cluster (®gure 2B). Reproductive apertures lie on side of body approximately one-third of distance between rhinophores and anterior end of pericardium, i.e., in a large specimen between lower halves of second and third rows of ®rst ceratal cluster (®gure 2B).

Colour

Body transparent, colourless. Head and mid-dorsal region marked with a fairly intricate pattern of orange and opaque white pigment, so characteristic of this species. Orange pigment in two broad stripes which zigzag along body following roughly median limits of ceratal clusters; orange deepest on head, except for a postpericardial patch, becoming gradually paler posteriorly, petering out approximately three-quarters of way along body; orange stripes often conūent where cerata of two sides closest medially; on head two dorso-lateral stripes of dense orange joining immediately in front of rhinophores, a single thin stripe running between latter then spreading widely and ending abruptly immediately behind U-shaped area between orange stripes on head, sometimes ®lled, partially or completely, with same pigment. Opaque white present mid-dorsally ¯anked by orange pigmentÐdisposed as an inverted triangular or kite-shaped area immediately behind rhinophores followed by a series of kites changing to diamond-shaped areas, usually separate but sometimes continuous, ending on tail as a patch or irregular strip. Front of head speckled with crystalline white. Oral tentacles and rhinophores orange proximally, opaque white distally (orals one-half to one-®fth from tip, rhinophores one-quarter to one-®fth), upper surface only of orals pigmented, base of rhinophores colourless but orange on orals may be continuous with stripes on head. Except for apex, distal half to two-®fths of ceras encircled by a band of crystalline white, upper half commixed with a broad hoop of orange. Diverticula fawn, visible through transparent proximal section of ceras.

Alimentary system (®gure 2C±F)

Oral tube large, almost globular, highly glandular. In contrast, buccal bulb small, somewhat barrel-shaped; radular sac not obvious externally. Pair of large oral glands, each comprising a fusiform`reservoir’ with two, roughly opposite (dorsal and ventral) rows of large nodules (5 giant secretory cells) (®gure 2E): long narrow duct leaves anterior end of`reservoir’, bending twice and narrowing before opening ventrally at rear end of oral tube. Short, fairly wide oesophagus leads into large, spacious stomach. Pair of large ramose salivary glands (®gure 2F), each lying between stomach and anterior stomachal ducts of digestive gland: salivary duct fairly wide and long running forwards to enter buccal bulb at side of oesophagus. Anterior stomachal ducts of digestive gland divide, giving up to six branches running laterally and ventrally. Posteriorly stomach tapers gradually into wide, hind duct of post-cardiac part of left digestive gland giving rise to up to six pairs of lateral ducts: all but most posterior of these ducts branched, ®rst post-cardiac lateral duct having up to four simple branches, number reducing posteriorly. Each ®nal branch of digestive gland bears a single row of diverticula. Intestine issues from stomach immediately behind main duct of right digestive gland and, following a double ¯exure, runs laterally to open between middle branches of ®rst right duct of posterior digestive gland.

Buccal armature

Radular formula of an 11 mm specimen 12 Ö 0.1 .0: teeth only moderately wide, bilobed with a distinct median cusp (®gure 3A); largest teeth bear up to 22 denticles on each side, largest of these standing on summit of lobe; outermost denticles small and bent. Jaws oval in outline with a slight indentation on upper edge (®gure 3B); thick in front, particularly at hinge, and thin behind. Masticatory process approximately one-half of length of jaw, free end drawn out into a point, border smooth.

Kidney (®gure 2D)

A fairly thick sac with contiguous, rounded side branches. Narrow anterior part extending more than half way beneath right side of pericardium; renopericardial duct opens into this limb at level of anterior branch of ®rst post-cardiac part of digestive gland; renal duct arises a short distance behind renopericardial duct. Kidney reaches back to penultimate pair of branches of digestive gland.

Reproductive system (®gure 3C)

Gonad a large, compact body extending between heart and penultimate lateral ducts of digestive gland. Lobules large, each comprising a large central male follicle completely invested by small spherical to ovoid female follicles; lobules join hermaphrodite duct separately, or in twos and threes by a short common duct. Hermaphrodite duct wide and straight in region of gonad, but narrow and looped as it runs forwards for a short distance, then widening into a convoluted tube, the ampulla, on reaching female glands. From anterior end of ampulla a long, fairly straight duct extends forwards to reach almost anterior border of female glands where it forks: one branch, the vas deferens, enlarging almost immediately into swollen prostate, long, looped, gradually tapering running diagonally to penis, elongate, conical, unarmed (®gure 3D); other branch runs backwards widening into fertilization chamber, then leading posteriorly to large, saccate bursa copulatrix, and laterally to albumen part of female glands.

Localities and habitat

New Zealand, the North Island, East Coast: Parengarenga Harbour , Dog Island , one specimen under a rock at low tide, 21 March 1996 (collected by M. S. Morley); Whangarei Heads , Smuggler’s Bay , one specimen on side of rock in small pool at MTL, 4 April 1999 (collected by Rhys Hodson); Leigh near Warkworth , Goat Island Bay , one specimen on the underside of a stone in a shallow pool on Echinoderm Reef ¯at, 18 May 1974 (collected by R. C. Willan) ; Whangaparoa Peninsula, Army Bay , two specimens together under a stone, January 1968 (collected by P. Parkinson), and two specimens under a stone, in a mid tidal sandy pool, 31 December 1973 (collected by R. C. Willan) ; Auckland, Milford , one specimen under a stone lying on ®ne sand in the eulittoral zone, 17 July 1962 ; Narrow Neck reef, on the undersurface of a rock in the lower eulittoral zone, one specimen 11 July 1960 and one 11 July 1960; Devonport , one specimen on ¯oating seaweed, 26 June 1962 ; West Tamaki Head reef, one on a settlement plate in the Corallina zone, 8 December 1962 (collected by Penelope Luckens) and eight specimens under stones in a pool in the eulittoral zone, 8 June 1963 .

Breeding

The specimens collected at Army Bay, 31 December 1973 spawned in captivity (R. C. Willan).

Types

Not designated: three specimens on a sandy bottom in 2±3 fathoms, Grand Baie , Mauritius, 24 December 1874 ( Bergh, 1888) .

Remarks

The New Zealand specimens examined in this study fall well within the description of Aeolidiella indica which is now much broader than when the species was ®rst recognized. Gosliner and Gri ths (1981), as part of their work on South African aeolids, described specimens of A. indica and examined thoroughly the descriptions of six other Aeolidiella species which possess more than ®ve rows in the anterior digestive system. They were unable to separate clearly any of these species from A. indica as well as from each other, and thus concluded that all of them should be united as this species. Within the wide variation created by the amalgamation of the seven species, the New Zealand specimens are very similar to A. takanosimensis Baba, 1930 (see Baba, 1949, 1979 a,b) and have been named as such since discovery here (Gordon and Ballantine, 1976; Williams, 1978; Willan and Morton, 1984). Some of the specimens show the very distinctive (`classic’) dorsal pattern of red or orange comprising a U on the head, an incomplete kite immediately behind, followed by an ellipse around the pericardial swelling, then kites gradually becoming diamonds, the space within this pattern being ®lled with crystalline white pigment which continues as an irregular streak on the tail; the two pairs of the tentacles and cerata are marked with orange and white. There is no blue on the cerata which is present in Aeolidiella multicolor Macnae, 1954 , a species (now a colour form) close to A. takanosimensis . Baba (1979a,b) has shown that the`classic’ pattern does vary; parts may be missing, others added, though the basic pattern is still recognizable. Striking variations are the U-shaped head marking continuing across the front to form an O or completely ®lled, or ¯anked by parallel lines of red or orange which continues on to the oral tentacles. The red or orange band below the ceratal tip may be broad, narrow or absent. In some New Zealand specimens the reddish orange or orange pigment does not join in the mid line and the white is continuous down the length of the body: this pattern occurs in Japanese specimens ( Abe, 1964). Also like A. takanosimensis , the radular teeth are narrowish with a high rounded lobe on each side of the median gap and the cerata are arranged in up to seven multi-rowed posterior clusters.