Campanile symbolicum, IREDALE, 1917

Strong, Ellen E., 2011, More than a gut feeling: utility of midgut anatomy in phylogeny of the Cerithioidea (Mollusca: Caenogastropoda), Zoological Journal of the Linnean Society 162 (3), pp. 585-630 : 589-590

CAMPANILE SYMBOLICUM IREDALE, 1917

Material examined

Indian Ocean: Australia: WA: Point Peron, between Rockingham and Safety Bay ( USNM 796276).

Remarks

The midgut morphology of Campanile symbolicum was described by Houbrick (1981a: fig. 5B, 1989). Additional specimens were examined to ensure consistency among hypotheses of homology with those made herein for cerithioideans. The ‘large flat fold’ ( Houbrick, 1981a), given its position within the gastric chamber and the configuration of its anterior tip (expanded, with a weakly developed recurved segment that passes transversely anterior to the oesophageal aperture), is considered here to represent an expanded marginal fold. The marginal fold is paralleled along much of its length to the left by a parallel fold, separated by a deep intervening groove; the parallel fold and groove diminish posteriorly as the marginal fold diminishes. The parallel fold and groove have no corresponding counterpart within the Cerithioidea . The marginal fold is further unique from that of cerithioideans in that it is bisected just behind the oesophageal aperture by a deep, transverse groove. The ‘elongate, raised, muscular area’, in agreement with Houbrick (1981a), is hypothesized to be homologous with the glandular pad. The marginal fold and glandular pad diminish and eventually become indistinct posteriorly, the former extending slightly farther posteriorly than the latter; the marginal fold and glandular pad do not join posteriorly, but remain separate.

The region identified by Houbrick (1981a) as a sorting area with broad, transverse folds, was observed to consist of fine, longitudinal folds that cover the surface of the midgut wall, the latter being thrown into regular, broad, transverse undulations. The fine folds are narrow and somewhat irregular, with a corrugated appeareance, constantly anastomosing and splitting. The fine folds extend from the marginal fold, across the midgut roof, to the right margin of the glandular pad, leaving a smooth ventral channel between the marginal fold and the glandular pad to which the posterior digestive gland duct opens. As the marginal fold and glandular pad become indistinct, the fine folds also diminish, and spread across the interior surface of the gastric chamber, and from there extend to its distal tip. Given the irregular appearance of these folds, and the indistinct nature of the boundary between them and adjacent regions of the gastric chamber epithelium, these are not considered to comprise a discrete sorting area comparable with that in other cerithioideans. The distal tip of the gastric chamber lumen becomes flatter and narrower posteriorly, and was considered by Houbrick (1981a, 1988) to be a vestige of the spiral caecum (see character 21, below). There is no evidence of a ‘U-shaped fold’ similar to that seen in many cerithioideans below the style sac aperture.

bivorous caenogastropod midgut organization, viz. a ciliated fold (i.e. marginal fold) directing midgut contents posteriorly into the gastric chamber, a welldeveloped sorting area, and a large gastric shield.

In its simplicity, the midgut structure of Plesiotrochus is completely unlike that of Campanile ; however, given the range of morphologies evident in other superfamilies, this result is perhaps unsurprising. One feature that differs is the presence of a small sorting area in Plesiotrochus . However, it does not occur in a topographically similar region of the gastric chamber, as compared with other cerithioideans, and is not considered to be homologous. Houbrick (1990a) indicated the presence of a large sorting area in Plesiotrochus crinitus Thiele, 1930 (as Plesiotrochus cf. penetricinctus ); thus, this feature may be variable within the family.