Spurilla faustina ( Bergh, 1900 )

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 : 641-645

Spurilla faustina ( Bergh, 1900)

(®gures 4, 5) Aeolidiella faustina Bergh, 1900: 235 ±236; Bergh, 1904: 2 ±3, ®gured as A. paci W ca Bergh; Suter, 1913: 582.

Morphology (®gure 4A)

Length of largest preserved specimen 18.5 mm, of the one living specimen (moribund when examined) 11 mm. Body fairly narrow and low, tail approximately onesixth length of foot. Foot slightly wider than visceral part of body, anteriorly nearly straight-sided then tapering gradually to blunt point; anterior end curved, grooved, corners produced into tapered processes approximately one-third maximum width of foot (®gure 4B). Oral tentacles short, stout tapering to a blunt tip. Rhinophores of moribund specimen similar to orals, those of larger preserved specimens contracted, distinctly and evenly folded, concertina-like, up to eight folds, in life possibly represent narrow, ring-shaped swellings (®gure 4D). Cerata slightly fusiform, apex distinctly conical. Anteriorly cerata arranged in arches, rear limb of arch reducing posteriorly to leave, after ®fth or sixth arch, a forwardly and downwardly directed row (®gure 4C). First (pre-cardiac) arch largest, with up to 22 cerata in a double row, second (post-cardiac) smaller with up to 15 cerata, double row restricted to extremity of limbs of arch, thereafter single rows; cnidosac large (®gure 4E). Anus within second right arch, renal pore immediately below end of anterior limb of the same arch; reproductive apertures immediately below middle of ®rst right arch.

Colour

In the single small specimen collected alive: body wall translucent, colourless; reddish orange triangular patches, widest sides opposed, one immediately in front of and the other behind rhinophores and joining between latter, and as an oval patch on pericardial swelling continuing rearwards mid-dorsally as a stripe and several dashes. Distal half of oral tentacles with opaque white pigment. Rhinophores speckled lightly with small particles of black, apices with opaque white. Ceratal diverticula reddish orange. Crystalline white scattered sparingly on mid-dorsal region of body and anterior face of cerata from just below cnidosac to base.

Alimentary system (®gure 4E±H)

Oral tube wide leading to fairly long, ovate (viewed from above) buccal bulb. Oral glands seven, arranged around front of buccal bulb, one mid-dorsal, one pair dorso-lateral, two pairs ventro-lateral, all opening into a deep groove at junction of oral tube and buccal bulb, upper three opening separately, lower two pairs by a common duct on each side of ventral midline. Salivary glands narrow, simply branched (®gure 4H); ducts irregularly looped, enter at sides of oesophagus. Precardiac ducts of digestive gland divide to form an arch, each limb bearing two rows of diverticula. Stomach narrows gradually into a wide median posterior duct (postcardiac) which gives rise to up to ten pairs of primary lateral ducts; ®rst pair like pre-cardiacs but ceratal diverticula arise in two rows only at tip of limbs. Posterior limb of arch of succeeding pairs of post-cardiac lateral ducts diminishes, disappearing by ®fth or sixth pair, each secondary duct (dorso-lateral) having a single row of diverticula. Intestine arises a short distance behind right pre-cardiac duct, curves gently in a semi-circle beneath anterior limb of ®rst right post-cardiac duct, then bends sharply to run laterally to anus.

Buccal armature

Radular formula of 11 mm specimen 16 (1 developing) Ö 0.1 .0 teeth. Teeth pectinate, strongly curved to each side of fairly deep median notch with a cusp at centre (®gure 5A). Up to 34 denticles on each side, longest at summit of lateral lobes. Jaws ovate, indentation at posterior end of upper margin and a beak-like extension at front, latter convex, thickened with long, curved articulatory ridge on inside of left, depression on right. Masticatory process fairly narrow with sharply pointed extension, cutting edge thickened, smooth (®gure 5B).

Kidney (®gure 4F)

Dorsoventrall y compressed, rami®ed laterally. Extends posteriorly to penultimate pair of post-cardiac lateral ducts, forwards on left side to level of origin of intestine and right side to front of pericardium. Renopericardial and renal ducts lie on right a little distance behind anterior end of kidney.

Reproductive system (®gure 5C)

Gonad extends rearwards almost to fourth pair of lateral ducts of post-cardiac digestive gland: lobed, lobes consisting of follicles joining median hermaphrodite duct in groups of ®ve to nine, duct running forwards enlarging abruptly to form fairly long, wide ampulla lying in a single coil on posterior part of female glands. At front end ampulla gradually tapers into common duct, bifurcating, posteriorly directed branch (proximal oviduct) wide, fairly long, narrowing to form T-junction, one arm leading to a sacculate bursa copulatrix preceded by a reniform ante-chambe r (fertilization chamber?), other leads directly as vaginal channel to female aperture or by short right branch to female glands. Other branch of common duct, vas deferens, graduall y enlarges to form a fairly large, looped prostatic section continuing to base of penis. Penis unarmed (®gure 5D).

Localities and habitats

New Zealand, the North Island: Wellington, Island Bay , two specimens, 23 May 1947 (Pilgrim Collection W. 5 and 6) , one under stones, 1 August 1953 (Museum of New Zealand collection) . The South Island: Otago Peninsula, Portobello , one specimen, 8 February 1947 and one, April 1957; Portobello, Aquarium Point , one specimen on under surface of a rock at low water mark, 19 August 1962 .

Types

Not designated: one specimen collected with the specimen of Aeolidiella drusilla at French Pass , opposite d’Urville Island, the South Island, New Zealand ( Bergh, 1900) .

Remarks

As far as the previous descriptions permit, the specimens examined by me are identi®able as Aeolidiella faustina Bergh, 1900 . There are marked diOEerences in the ceratal arrangement and position of the anus between the specimens examined in this study and those described by Bergh (1900, 1904). His New Zealand specimen is reported as having two anterior arches followed by about ten oblique rows, and the anus positioned behind the innermost part of about the sixth row; the Tasmanian specimens`about’ 20 rows`seemed to be compressed into several groups’, the anus`roughly’ behind the eighth. In the specimens examined by me the cerata are arranged in up to six arches, the posterior limb (pillar) reducing in size rearwards, followed by up to six slanting rows, and the anus stands in the middle of the second right arch. It is possible to reconcile the ®rst of these diOEerences by deciding that Bergh’s distinction between rows and groups is su ciently vague that the ceratal arrangement could be like that of the specimens described here. Elsewhere Bergh (1888, p. 779) counted rows yet had them`approximating’ at the top to be bowlike, i.e., arched. The position of the anus behind the sixth row in the New Zealand specimen can be explained by counting the double rows of both limbs of the ®rst arch and the anterior limb of the second. It is more di cult to reconcile the diOEerence in the position of the anus in the Tasmanian specimens. But what does`roughly behind the eighth papillal row’ mean? It is just possible that the ®rst or second arch had an additional row. This is so in one of the specimens in the Pilgrim collection though the additional row is on the left side. Bergh does not mention the additional small upper oral glands. However, it is possible that he did not distinguish these from the much larger lowermost pair. In his description of the Tasmanian specimens he states that the ptyaline glands were quite unusual in length and markedly tortuous.

One other species must be considered, the common Australian species Spurilla macleayi (Angas, 1864) . Burn (1962) experienced some di culty with the two species S. faustina and S. macleayi , initially recognizing both as present in his collections, distinguishing them principally on diOEerences in the position of the anus and colour. Later ( Burn, 1969) he believed that the specimens he had recognized as two species really belonged to one, S. macleayi , explaining the diOEerences as intraspeci®c variation. However, he continued to accept Aeolidiella faustina as a valid species. I have found it di cult to separate the specimens described here from Spurilla macleayi except on colour. In Spurilla macleayi the head, back and upper part of the cerata are speckled with yellow and the cerata have one or two subapical bands of the same colour. Unfortunately, the colour of the New Zealand specimens is based on that of one small specimen and the anatomy of Spurilla macleayi has yet to be described. As there is such uncertainty in distinguishing between these two species I have decided to identify the New Zealand specimens as S. faustina .