Charitodoron veneris (Barnard, 1964)

Charitodoron veneris View in CoL

Foregut anatomy based on NMSA D4172 (off Durban, 29°50.4′ S, 31°14.0′E, 150 m, sandstone gravel, 14.1 mm); radula based on NMSA E9237 ( northern Natal , off Shellfield Beach, 29°39.8′S, 31°30.16′E, 150 m) GoogleMaps .

Although the specimen had been positioned for obtaining sagittal sections, the proboscis was diverted and sectioned nearly in frontal plane ( Fig. 6A, D). Proboscis moderately long, broad, conical, strongly contracted, so that its wall forms several telescopic folds ( Fig. 6A, C, D). Mouth opening into medium long buccal tube, spanning around 1/3 of proboscis length and leading into broad buccal cavity. Buccal cavity subdivided into two chambers by the large circular fold of its wall ( Fig. 6D, arrow); both chambers lined with tall, densely ciliated epithelium, epithelial cells with large basal or central nuclei. Wall of the posterior chamber bearing very tall longitudinal folds ( Fig. 6D–F). Wide anterior oesophagus leaving buccal cavity dorsally, forming rather long loop within proboscis, leaving proboscis and narrowing before passing through the nerve ring and then widening before transition to the posterior oesophagus ( Fig. 6D). Distinct valve-like structure, identifiable as a valve of Leiblein although lacking a ciliary cone, delimiting an anterior and a posterior oesophagus ( Fig. 6G, vl). Anterior oesophagus empty in sectioned specimen, posterior oesophagus filled with food material ( Fig. 6D, G) in which, however, no detectable remnants were found. After the oesophageal valve, tall and lightly stained epithelium of anterior oesophagus changing to low epithelium formed by small cubic cells. Anterior oesophagus lined with thin layer of muscular fibres, which become notably stronger in posterior oesophagus ( Fig. 6G).

Thin and strongly convoluted salivary ducts adjoining anterior oesophagus in front of passage through nerve ring and passing forward being embedded into its muscular wall, leaving oesophageal wall closer to the proboscis tip and entering buccal mass. Paired odontophore cartilages well developed, not fusing with strong lateral odontophore protractor muscles attached to odontophore ventrally ( Fig. 6D). Strong and massive odontophore retractor adjoining the columellar muscle shortly behind the nerve ring. Radular diverticulum opening into buccal cavity ventrally in posterior position, behind thick circular fold of the buccal cavity

BI, Bayesian inference; ML, maximum likelihood; n/a, not applicable. *Taxa represented by single specimen.

wall, forming massive ‘lip’, longer dorsally ( Fig. 6D, E, bl). After entering buccal cavity wall, distal salivary ducts passing inside that lip laterally on both sides of radular diverticulum opening ( Fig. 6D, E), and opening in the buccal cavity ventrally, underneath the semi-circular fold ( Fig. 6F). Epiproboscis absent.

Salivary gland large, unpaired, situated to the left of posterior oesophagus and dorsally to the nerve ring, histologically represented by a compactly packed, strongly convoluted tube with one layer of tall highly vacuolar, obviously glandular, cells and thin outer connective tissue layer ( Fig. 6A, B).

Condylomitra tuberosa (PANGLAO 2004, Stn B5) Proboscis moderately long, leaf-shaped, anteriorly flattened dorso-ventrally ( Fig. 7A–H) and cylindrical at its base ( Fig. 7I). On transversal sections, proboscis with two lateral lobes at mid-length and ventral part with rounded axial keel. Proboscis wall with thick cuticle and nearly cubic epithelium, with large basal nuclei; epithelium underlined by a layer of circular muscle fibres ( Fig. 7C, E, H). Lateral lobes occupied by complex interlacement of dorso-ventral, oblique and longitudinal muscular fibres; two blood vessels ( Fig. 7F, bv) running along margins of proboscis ( Fig. 7B, D, F, G). Central part of proboscis occupied with oesophagus, anterior buccal mass and epiproboscis complex forming a single stem.

Mouth opening anteriorly on the dorsal side of the proboscis in short dorsal groove; mouth surrounded by small peristome rim ( Fig. 7A). Compact buccal mass situated shortly after mouth, furnished with thick muscular walls and triangular lumen; radular diverticulum opening ventrally into buccal cavity ( Fig. 7B, C). Anterior oesophagus quadrangular on transversal sections, lying dorsally in the anterior part of the proboscis, attached to proboscis wall by thin muscular fibres ( Fig. 7D–H). Dorsal and ventral walls of oesophagus very thin, lateral walls with two large longitudinal folds jutting out into the lumen of oesophagus. Lateral folds of oesophagus disappearing at mid-proboscis height and thick layer of muscular fibres evenly covering it ( Fig. 7I). Radular diverticulum rather short; odontophore formed by two small cartilages ( Fig. 7D, E), not fused anteriorly. Odontophore retractor very strong, lying in a muscular sheath in its anterior portion ( Fig. 7F–H), and dividing into two symmetrical branches at mid-proboscis length ( Fig. 7I).

Epiproboscis short, formed by densely packed longitudinal muscle fibres, with no epithelium. Epiproboscis lying ventrally from radular diverticulum, enclosed inside its own muscular sheath, which is attached to the radular diverticulum along most of its length ( Fig. 7D–H). Both epiproboscis and its sheath originating from the ventral part of the radular retractor sheath ( Fig. 7G, H). Epiproboscis sheath opening ventrally on the anterior border of the buccal mass.

Salivary ducts passing forward along the anterior oesophagus, embedded into lateral folds of oesophagus wall ( Fig. 7D–I); salivary gland itself not sectioned. Salivary ducts shifting ventrally in the walls of the buccal cavity adjoining the epiproboscis sheath. More distally, salivary ducts running backwards along the epiproboscis sheath to its proximal part, where they enter the epiproboscis and run through its entire length to open at its tip ( Fig. 7E).