Conualevia marcusi COLLIER & FARMER 1964

CONUALEVIA MARCUSI COLLIER & FARMER, 1964

(FIGS 34D, 44-46)

Conualevia marcusi Collier & Farmer, 1964: 381–383, fig. 1C- H, pl. 2.

Type material

HOLOTYPE (by original designation): 6 km south of Puertecitos, Baja California, Mexico 1963, 15 mm preserved length, leg. C. L. Collier (CASIZ 018370). PARATYPES: 6 km south of Puertecitos, Baja California, Mexico 1963, one specimen, 10 mm preserved length, leg. C. L. Collier (CASIZ 018371).

Additional material

Puerto Refugio, Isla Ángel de la Guarda, Baja California, Mexico 1963, one specimen, 18 mm preserved length, leg. C. L. Collier (CASIZ 018372). Centro de Aquicultura, Bahía Tortugas, Baja California Sur, 1 July 1984, one specimen, 10 mm preserved length, leg. T. M. Gosliner (CASIZ 071531). 80 km south of Puertecitos, Baja California, Mexico, 10 April 1973, two specimens, 8–9 mm preserved length, leg. G. McDonald (CASIZ 069116).

External morphology

The general colour of the living animals is uniformly cream or pale yellow (Fig. 34D). The rhinophores and gill are yellow or cream, somewhat darker than the dorsum. The viscera are visible through the dorsal skin. The whole dorsum is covered with small, rounded tubercles (Fig. 44D). The largest tubercles are situated in the central region of the body. The rhinophoral and branchial sheaths have tubercles similar to those on the rest of the dorsum. There are seven unipinnate branchial leaves, forming a circle. The anal papilla is situated in the centre of the branchial circle of leaves. The rhinophores are elongate and almost smooth, with several irregular and inconspicuous lamellae (Fig. 45A).

Ventrally the anterior border of the foot is grooved but not notched (Fig. 45E). There are no oral tentacles, but two blunt prolongations on both sides of the mouth area.

Anatomy

The posterior end of the glandular portion of the oral tube has six strong retractor muscles (Fig. 46C) which attach to the body wall. The oval, muscular buccal bulb has two large additional muscles attached; two short salivary glands connect with it at each side of the oesophageal junction. The buccal bulb is longer than the glandular portion of the oral tube. The labial cuticle is smooth. The radular formula is 33 ¥ 51.0. 51 in a 10-mm long specimen. Rachidian teeth are absent. The lateral teeth are hamate and lack denticles (Fig. 44A). The teeth from the middle portion of the half-row are larger than those closer to the medial portion of the radula (Fig. 44B). The outermost teeth are smaller and also lack denticles (Fig. 44C). The oesophagus is short and connects directly to the stomach (Fig. 46A).

The ampulla is very long and folded (Fig. 46B). It branches into a short oviduct and the prostate. The oviduct enters the female gland mass near to its centre. The prostate is tubular and connects with a short duct that narrows and expands again into the large ejaculatory portion of the deferent duct. The penis is unarmed (Fig. 45B). The muscular deferent duct opens into a common atrium with the vagina. The vagina is long. At its proximal end it joins the bursa copulatrix. From the bursa copulatrix leads another duct connecting to the uterine duct and the seminal receptacle. The bursa copulatrix is oval in shape, about twice as large as the seminal receptacle.

In the central nervous system (Fig. 46D) the cerebral and pleural ganglia are fused and distinct from the pedal ganglia. There are three cerebral nerves leading from each cerebral ganglion and three pleural nerves leading from each pleural ganglion. There is no separate abdominal ganglion on the right side of the visceral loop. The buccal ganglia are near to the rest of the central nervous system, joined to the cerebral ganglia by two relatively short nerves. Gastrooesophageal, rhinophoral and optical ganglia are present. The pedal ganglia are clearly separated, having two nerves leading from the left ganglion and three from the right one. The pedal and parapedal commissures are enveloped together with the visceral loop.

The circulatory system (Fig. 46A) consists of a large heart and a blood gland situated in front of the central nervous system.

Remarks

Conualevia marcusi appears to be different from Conualevia alba, the other member of the genus, by its external morphology and anatomy. According to Collier & Farmer (1964), C. alba is a much thinner animal than C. marcusi, and more delicate in appearance and the mantle glands of C. alba are more evident. In addition, the rhinophores of C. alba are longer relative to their width than those of C. marcusi, and C. alba has half as many branchial leaves as C. marcusi. Anatomically, the main difference between these two species is the arrangement of the bursa copulatrix and the seminal receptacle, which are on opposing sides in C. marcusi and on the same side in C. alba.