FOREGUT ANATOMY AND CLASSIFICATION OF CONOIDEA 



Fig. 25 Diagram (with Fig. 26) summarizing some of the major 

 types of foregut morphology found amongst the Conoidea, with 

 radulae, where present, illustrated alongside. Not to scale. A. 

 Clavus unizonalis; B. Clionella sinuata; C. Turricula nelliae 

 spurius; D. Mangelia nebula; E. Ophiodermella biennis; F. 

 Daphnella reeveana. Abbreviations: asg, accessory salivary 

 glands; sg, salivary glands; rs, radular sac; vg, venom gland; black 

 dots are sphincters. 



radular sac is located far behind the base of the proboscis. 

 Therefore, it is doubtful that the buccal mass can be everted 

 through the mouth opening. This species probably catches 

 prey using the proboscis tip. Envenomation could occur 

 either by the squirting of venom through the mouth, when the 

 proboscis is in contact with the prey, or in the anterior part of 

 the proboscis, when the prey is partly swallowed. In either 

 case the radula is not used to envenomate the prey and is 

 either used for further transportation in the oesophagus of for 

 partial tearing of prey tissue. 



The second sub-type is found in Toxiclionella tumida and 

 differs from the first in that the buccal mass is located near 

 the proboscis tip (Kantor, 1990, fig. 4), which has no distal 

 sphincter. This species is characterized by a radula formed of 

 hollow, and barbed marginal teeth (Kilburn, 1985, fig. 14), 

 which are attached all along their length to the radular 

 membrane. The hollow radular teeth are similar in morphol- 

 ogy to those of higher conoideans. The gastropod has a long 

 venom gland and in the posterior part of the proboscis there 

 is a single salivary gland with paired ducts. The radular teeth 

 are sufficiently long, that during protraction of the odonto- 



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147 



H 



Fig. 26 Further types of foregut morphology found in the 

 Conoidea. G. Gymnobela emertoni; H. Philbertia linearis; I. 

 Conus ventricosus; J. Duplicaria spectabilis; K. Terebra subulata; 

 L. Terebra maadata. 



phore, the tips would protrude through the oral opening, and 

 thereby stab the prey. 



A comparable mechanism may occur in Turricula nelliae 

 spurius (Taylor, 1985), which has the buccal mass located in a 

 similar distal position in the proboscis to that of T. tumida, 

 and during feeding can protrude the odontophore through 

 the mouth opening (Miller, 1990). But T. nelliae possesses a 

 sphincter in the anterior part of the buccal tube, and this 

 feature usually correlates with the use of separate marginal 

 teeth for stabbing (Kantor & Taylor, 1991). 



In conclusion, we suggest that a similar type of feeding 

 mechanism evolved independently in Pseudomelatoma and 

 Toxiclionella. In the former, the primitive character of the 

 radula suggests that the feeding mechanism is primary; 

 whilst in Toxiclionella it is probably a secondary feeding 

 mode when compared with other members of the subfam- 

 ily. It is possible that with the shift of the buccal mass to the 

 proboscis tip, Toxiclionella lost the mechanism of stabbing 

 the prey with single marginal teeth and instead prafrjudes 

 the radula through the mouth and uses the hollow. teeth 

 which remain firmly anchored to the radular membrane. ' 



