FOREGUT ANATOMY OF CRASSISPIRINE GASTROPODS 



89 





In many species, there are large buccal lips, which protrude into 

 the buccal tube (eg. Fig. 33 A - Funa spp. 33 D - Crassispira 

 (Crassiclava) spp.). In several species, for example. Ptychobela 

 suturalis (Fig. 34 E) the buccal lips are able to invert inside the 

 buccal cavity. The functional significance of this feature is unknown, 

 but could perhaps be associated with the passage of food items into 

 the buccal cavity. 



In four species, the tip of the proboscis is able to invert inside itself 

 (Figs. 33 E, 34 D). In Burchia spectabilis (Fig. 33 E), the buccal 

 mass is situated at the base of the proboscis and is not protruded 

 through the mouth, when the proboscis tip is inverted. By contrast, 

 the long buccal lips of Inquisitor latifasciata and Ptychobela suturalis 

 (Fig. 34 D) are exposed through the mouth when the proboscis tip is 

 inverted. In the latter species, the foregut has a totally different 

 appearance when the proboscis is partially protracted (Fig. 34 E). 

 For one species (Fima jeffreysii - Fig. 19), it has been demonstrated 

 that the whole buccal mass can be protruded through the mouth 

 opening (Taylor, 1994, fig. 8). It is highly possible, that in other 

 crassispirines the buccal mass may also be protruded through the 

 mouth and used in prey capture. 



Many Conoidea possesses one or more sphincters in the anterior 

 part of the buccal tube, these grip the detached, marginal, radular 

 teeth at the proboscis tip (Kantor & Taylor, 1991; Taylor et al.. 

 1993). In Crassispirinae, up to two sphincters were found within the 

 buccal tube (Fig. 33 B - Crassispira dysoni, Fig. 33 D - Crassispira 

 (Crassiclava), and others). Where two sphincters were present, the 

 anterior was usually much smaller than the posterior. The positions 

 of the sphincters also vary. A sphincter(s) was defined as anterior in 

 position, if it lies at a distance of not more than 2.5 marginal tooth 

 lengths from the mouth opening. The more posterior sphincter of the 

 buccal tube is shifted backwards in some species, sometimes occu- 

 pying a position in the mid-proboscis (Fig. 34 A - Antiguraleus 

 morgani). If the sphincter lies at a distance of more than 2.5 marginal 

 tooth lengths from the mouth we classified it as intermediate (e.g. 

 Crassispira dysoni - Fig. 33 B; Crassispira (Striospira) spp. - Fig. 

 33 F, and others). An intermediate sphincter within the buccal tube 

 has previously been found only in one species of Splendrillia 

 (Drilliidae) (Sysoev & Kantor, 1989). Its function is obscure, for it 

 cannot be used for gripping teeth at the proboscis tip, but may 

 perhaps be used in transportation of the tooth from the radular sac to 

 the proboscis tip. The anterior buccal tube sphincter is often absent 

 and only the intermediate sphincter present (Nquma scalpta, 

 Naudedrillia praetermissa - Fig. 34 C; Inquisitor spp.; Crassispira 

 (Striospira) spp. - Fig. 33 F; Miraclathurella bicunalifera). Only 

 rarely are both sphincters absent and this indicates that separate 

 marginal teeth are probably not used at the proboscis tip (Burchia 

 spectabilis - Fig. 33 E. Inquisitor latifasciata - Fig. 33 D). 



As in the majority of conoideans, there is in crassispirine species 

 a more or less well-defined, sac-like enlargement of the buccal tube, 

 which is lined with a modified epithelium. The structure is associ- 

 ated with the gripping of single radular teeth at the proboscis tip 

 (Kantor & Taylor, 1991). From our sections of Crassispirinae, it 

 appears that the presence and degree of development of the sac-like 

 enlargement is not correlated with the position of the buccal tube 

 sphincters (either both anterior and intermediate, or only one may be 

 present). In three species, namely, C. turricula, C. apicata (Figs 12, 



33 D) andC. dysoni (Figs 5, 33 B), the walls of the enlargement were 

 more muscular than the rest of the buccal tube. No enlargement was 

 found in Burchia spectabilis (Fig. 33 E), Inquisitor latifasciata (Fig. 



34 D), C. tepocana and C. kluthi (Fig. 33 F). In the two former 

 species, the proboscis tip is able to invert and the separate teeth are 

 not gripped at the proboscis tip, whilst we have no other information 

 about C. tepocana and C. kluthi. 



An unusual character, previously found only in Splendrillia 

 (Sysoev & Kantor, 1989), is the presence of an epithelial pad in the 

 anterior portion of the buccal tube. For some species, marginal teeth 

 were seen adhering to this pad, probably for more secure fixation. 

 The epithelial pad was found in several crassispirine species, for 

 example, Crassispira (Crassiclava) species (Fig. 33 D) and 

 Crassispira dysoni (Fig. 33 B). 



Salivary glands differ greatly in size and histology. Before this 

 study, only two types of salivary glands were recognised amongst 

 the Conoidea -acinous and simple tubular (Taylor et al., 1993). The 

 structure of the glands was thought to be a character useful at 

 subfamilial level, for instance, differentiating the Mangeliinae and 

 Raphitominae. However, amongst the crassispirines we were able to 

 recognise four types of salivary gland. Besides the acinous salivary 

 glands (found in majority of species) and simple tubular glands 

 (Haedropleura septangularis - Fig. 34 F; Naudedrillia praetermissa 

 - Fig. 34 C), we found anastomosing tubular (Figs 33 D, F; 34 C,G) 

 and glands consisting of a simple tube surrounded by acinous cells 

 {Funa spp. - Fig. 33 A; Antiguraleus morganus — Fig. 34 A). Some- 

 times, species attributed to the same genus and even subgenus 

 possess different types of glands. For example, in Crassispira 

 (Striospira) tepocana. the glands are anastomosing tubular, while in 

 C. (S. ) kluthi and C.(S.) xanthi they are acinous. Moreover, it should 

 be emphasised, that there were no correlations between the structure 

 of the glands and the foregut anatomy. Sometimes in species pos- 

 sessing the same type of foregut, the glands were of different 

 histology (eg. Nquma scalpta and Naudedrillia praetermissa - Fig. 

 34 C; and Crassispira (Crassispira) spp. and Fhh« spp. -Fig. 33 A). 



The Crassispirinae is the only subfamily of the Conoidea, in 

 which a variety of salivary glands has so far been recorded. It is still 

 unclear whether the simple tubular salivary glands can be derived 

 from the acinous type. However, recently, it has been demonstrated 

 (Ball, Taylor & Andrews, in press) that in the embryonic develop- 

 ment of Nucella, the salivary ducts are formed first, and the salivary 

 gland itself appears later at the tip of the duct. From this, it can be 

 suggested that the simple tubular glands may represent the enlarged 

 ducts, while the gland itself was not developed. Thus, the simple 

 tubular salivary glands may originate from the acinous by 

 paedomorphosis. This may also explain the origin of the anastomo- 

 sing tubular glands, which could possibly be the result of extensive 

 coiling of the initial duct. 



Shell and radular characters 



Radula 



Radular morphology has been used extensively to recognise and 

 classify suprageneric categories within the Conoidea (e.g. Powell, 

 1966; McLean, 1971; Kilburn, 1 988, Taylor et al., 1993). However, 

 this study has demonstrated that within the Crassispirinae, there is 

 no great congruence between radular and anatomical characters. 



Many crassispirine taxa have quite similar radular teeth (e.g. Figs 

 4, 1 1 ) with the wishbone tooth formed by a robust, pointed, major 

 element and a smaller, more slender, secondary element. However, 

 this similarity of radula morphology is not reflected in foregut 

 anatomy and taxa with the same type of teeth often have widely 

 different arrangements of the foregut; for example Inquisitor 

 latifasciata (Figs 17b, 20) and Crassispira harfordiana flucki (Figs 

 4d, 6). In other cases, some gastropods possess rather similar and 

 distinctive foregut anatomies, as for example, Inquisitor latifasciata 

 and Ptychobela suturalis. However, they have very different radular 

 morphologies, with /. latifasciata having the rather standard crassi- 

 spirine wishbone form, but P. suturalis has the autapomorphic, 

 awl-shaped, hollow teeth (Fig. 23a). 



