THE MANTLE AND SHELL OF SOLEMYA PARKINSONI (PROTOBRANCHIA: BIVALVIA)

Abstract

The shell of Solemya exhibits considerable flexibility which is further enhanced by the marked extension of the periostracum beyond the calcareous portions of the valves. This fcature, more than any other, has made possible the habit, unique among bivalves, of burrowing deep within the substrate without direct contact with the water above. The inner calcareous layer of tho valves is restricted to a small area near the umbones while the outer calcareous layer is thin and contains a high proportion of organic material. The shell conchiolin consists mainly of protein, varying in composition, but much of it strengthcned by quinone‐tanning, and in ccrtain regions probably by the presence of appreciable quantities of chitin. The ligament, although superficially resembling an amphidetic structure, is opisthodetic, the extcnsion anterior to the umbones consisting of anterior outer layer only. The mantle is characterized by an extension of the outer fold of the mantle margin which has effected equally both the inner and outer surfaces of this fold. The secretory epithelium and the modified pallial musculature, contraction of which results in the intucking and plaiting of the periostracum, is dcscribed. Simple tubular oil glands open at the mantlo margin and are responsible for the water‐repellent nature of the periostracum. The form of the mantlelshell and that of the enclosed body are discussed and compared with those of other bivalves in which elongation of the mantle/shell is achieved in a different way. It is concluded that the mantlelshell of Solemya is of little value in determining its relationships, and that the greatly elongatod ligament, the edentulous hinge and the flexible shell are all adaptations to a specialized mode of life.

Mantle margin morphogenesis in Nodipecten nodosus (Mollusca: Bivalvia): new insights into the development and the roles of bivalve pallial folds

“…Different levels of fusion during mantle margin and siphon formation are among the key features associated with the evolutionary radiation of infaunal bivalves [ 6 , 16 , 17 ]. Specialized secretory glands from the mantle margin are widespread in many groups performing a variety of roles, e.g., cleansing, adhesion, lubrication, and boring [ 18 – 20 ]. Pallial tentacular structures are also present in some families, such as Limidae, Pectinidae, and Galeommatidae, performing sensorial, defensive, and secretory functions [ 21 – 23 ].…”

The biology, functional morphology and taxonomic status of Gaimardia (Neogaimardia) finlayi (BivaMa: Gaimardiidae)

“…In comparison, the siphons of both Dreissena and Trapezium are complex, extensible structures possessing numerous papillae and, in the latter, very long tentacles. Mantle fusion, where it occurs in all three species, is simple and of the inner mantle folds only; the periostracum is similarly two layered in a11 these bivalves but this appears to be typical of most heterodont bivalves (Morton, 1969; in press) with a three-layered periostracum occurring in, for example, the Mytilacea (Beedham, 1958;Morton, 1973) and a four-layered structure in the protobranch Solemya parkinsoni (Beedham & Owen, 1965).…”

A mathematical model for the mechanical properties of scallop shells

“…(We should point out that shell compliance is, in itself, sometimes of adaptive value in the bivalves. For instance, shell flexibility in the totally infaunal Solemya facilitates burrowing (Beedham & Owen, 1965), and flexibility in the Pinnacea allows very close apposition of the valves of shells particularly prone to attack (Yonge, 1953). ) We can approach this by considering the costs and benefits involved in building shell valves to various designs.…”