Marisa cornuarietis, (LINNAEUS 1758)

Strong, Ellen E., 2003, Refining molluscan characters: morphology, character coding and a phylogeny of the Caenogastropoda, Zoological Journal of the Linnean Society 137 (4), pp. 447-554 : 456-458

MARISA CORNUARIETIS (LINNAEUS 1758)

Material Examined

Ft. Meyers, Florida ( USNM 890932); San Juan, Puerto Rico ( USNM 795555); Charlotteville, St. John, Tobago ( USNM 836135).

External anatomy and mantle cavity

Mantle roof forming well vascularized lung with pneumostome opening alongside ctenidium. Pedal gland opening to anterior margin of propodium. Operculum present. Anterior kidney chamber extending into pallial roof.

Reproductive system

Gonopericardial connection absent. Seminal receptacle with orientated sperm formed by distal oviduct, embedded in glandular oviduct. Proximal tip of glandular oviduct invading viscera.

Seminal vesicle derived from vas deferens absent. Pallial vas deferens closed along entire length, opening to mantle cavity via small aperture at distal end of prostate. Penis present on edge of pallial skirt with vas deferens opening at tip.

Alimentary system

Foregut. Radula taenioglossate. Single pair of odontophoral cartilages present. Large, complexly folded subradular organ present ( Fig. 4C ). Paired jaws composed of outer homogeneous layer and inner rodlet layer ( Fig. 5B, j ). Anterior salivary gland ducts lying under circum-oesophageal nerve ring. Buccal pouches opening to posterior buccal cavity and anterior most oesophagus. Mid-ventral fold beginning in buccal cavity and continuing into anterior oesophagus. Two ventro-lateral folds present, bounding inner buccal pouch ducts. Mid-ventral fold diminishing after separation of buccal pouches. Mid-oesophagus uniformly folded, lacking septate oesophageal gland.

Midgut. Oesophagus opening broadly to S-shaped gastric chamber. Epithelium of gastric chamber coarsely folded and cuticularized. Gastric cuticle thickened to right of oesophageal aperture. Sorting areas absent. Three digestive gland ducts opening to vestibule at proximal end of style sac. Paired gastric pouches present, adjacent to lip of style sac, bordering extension of intestinal groove into gastric chamber. Ciliary currents flowing clockwise around lip of style sac. Currents flowing from digestive gland vestibule into intestinal groove. Paired typhlosoles running length of style sac. Style sac epithelium transversely folded bearing differentiated cilia. Pyloric caecae present at distal end of style sac.

Hindgut. Intestine exiting style sac, curving a short distance posteriorly alongside distal style sac, and completing approximately three loops below kidney lumen.

Reno-pericardial system

Kidney comprising posterior, visceral lobe and anterior lobe within pallial roof. Kidney communicating with auricle; nephridial gland absent at site of connection.

Nervous system and sensory structures

Nervous system hypoathroid, left and right zygoneurous. Nerve ring lying anteriorly, with buccal connectives passing posteriorly to buccal ganglia lying near emergence of buccal pouches. Single pedal and pleural commissure present, with single anastomosis between pedal nerves. Single visceral ganglion present. Statocysts with numerous statoconia present dorso-laterally on pedal ganglia. Osphradium bipectinate. Eyes on tips of ocular peduncles. Tentacular nerve single.

Remarks

The anatomy of this species is well documented in several publications, most notably a detailed study on ampullariids ( Berthold, 1991), as well as several papers on the reproductive system ( Mello, 1988; Schulte-Oehlmann et al. 1994), digestive system ( Demian, 1964) and a series on organogenesis ( Demian & Yousif, 1973a,b, 1975). Minor omissions from existing descriptions include precise descriptions of ventral folding within the anterior oesophagus, the ciliary currents within the midugt and the branching patterns of the tentacular nerve. Berthold (1991) did not describe the presence of the subradular organ in his morphological investigations of ampullariids, including Marisa cornuarietis ; the structure was thoroughly described by Demian (1964) and Lufty & Demian (1967).

Discussion

Available descriptions provide a rather conservative picture of ampullariid morphology. Ampullariids are the only gastropods to possess a well-developed lung in conjunction with a ctenidium (e.g. Bouvier, 1888; Scott, 1943; Starmühlner, 1969; Demian & Yousif, 1973c).

All described ampullariids possess a glandular oviduct comprising a closed tube that lies partially behind the base of the mantle cavity; the distal oviduct forms a receptaculum seminis, bearing orientated sperm, just prior to the junction with the albumen gland ( Berthold, 1991). A bursa copulatrix may be present or absent; a ‘pseudo bursa copulatrix’ may be present, comprising the efferent duct of the receptaculum seminis ( Berthold, 1991). The penis lies within the mantle roof and is equipped with a diverse and variable array of accessory glands ( Bouvier, 1888; Scott, 1943; Starmühlner, 1969; Berthold, 1991).

The glandular apparatus of the foregut comprises massive salivary glands, buccal pouches, and a subradular organ; the jaws are large ( Scott, 1943; Starmühlner, 1969; Berthold, 1991). The voluminous mid-oesophagus forms a crop. The midgut is Ushaped, highly muscular and cuticularized ( Graham, 1939); the digestive gland ducts open to a common vestibule, a pyloric caecum is present and the gastric pouches may be single or paired ( Starmühlner, 1969; Berthold, 1991).

The kidney of ampullariids comprises two distinct chambers, with the anterior chamber, or ‘ureter’, lying within the pallial roof and bearing the nephropore ( Bouvier, 1888; Prashad, 1925; Fretter & Graham, 1962; Hägler, 1963; Andrews, 1965b; Starmühlner, 1969); the homologies of these two chambers and their precise connection with each other and the mantle cavity was historically a source of confusion (see Demian & Yousif, 1973b for review). The relative sizes of the chambers varies considerably within the family (e.g. Berthold, 1991).

The Ampullariidae are characterized by a nerve ring that is hypoathroid, left zygoneurous, with a single visceral ganglion and fused right pleural and suboesophageal ganglia, rendering the identity of the latter virtually undistinguishable; a labial commissure is present ( Bouvier, 1887; Prashad, 1925; Ranjah, 1942; Scott, 1943; Starmühlner, 1969). Pedal ganglia with one commissure, two cross connections between the pedal nerves, and a pleural commissure are also present ( Berthold, 1991), but the latter is commonly identified as a pedal commissure (e.g. Starmühlner, 1969).

For an analysis of ampullariid morphology, phylogeny and biogeography, see Berthold (1991), and Bieler (1993) for a cladistic reanalysis and critique.

Figures

Figure 4. Morphology of odontophore; subradular organ (indicated by arrows). Except when noted, view is from the side and ventral is to the right. (A) Theodoxus fluviatilis, ventral view. Subradular organ absent. Scale bar = 100 Mm. (B) Neocyclotus dysoni ambiguum. Scale bar = 1 mm. (C) Marisa cornuarietis. Scale bar = 1 mm. (D) Lampanella minima. Scale bar = 100 Mm. (E) Littorina littorea. Scale bar = 100 Mm. (F) Neverita duplicata. Scale bar = 100 Mm. (G) Cypraea robertsi. Subradular organ absent. Scale bar = 1 mm. (H) Panarona clavatula. Ventral is down. Scale bar = 100 Mm.

Figure 5. Histology of subradular organ. (A) Neocyclotus dysoni ambiguum. Transverse section. Note bi-layered jaw. Scale bar = 0.5 mm. (B) Marisa cornuarietis. Sagittal section. Note bi-layered jaw. Scale bar = 0.5 mm. (C) Lampanella minima. Transverse section. Note jaw with exposed rods. Scale bar = 1 mm. (D) Strombus mutabilis. Transverse section. Scale bar = 0.5 mm. (E) Crepidula plana. Transverse section. Scale bar = 1 mm. (F) Littorina littorea. Sagittal section. Scale bar = 1 mm. (G) Neverita duplicata. Transverse section. Scale bar = 0.5 mm. (H) Panarona clavatula. Transverse section. Scale bar = 1 mm. Abbreviations: c., radular cartilage; j, jaw; mo, mouth; r, radula; srm, subradular membrane; sro, subradular organ.