Anatomical Correlates of Venom Production inConus californicus

Abstract

Like all members of the genus, Conus californicus has a specialized venom apparatus, including a modified radular tooth, with which it injects paralyzing venom into its prey. In this paper the venom duct and its connection to the pharynx, along with the radular sac and teeth, were examined using light and transmission electron microscopy. The general anatomy of the venom apparatus resembles that in other members of the genus, but several features are described that have not been previously reported for other species. The proximal (posterior) quarter of the venom duct is composed of a complex epithelium that may be specialized for active transport rather than secretion. The distal portion of the duct is composed of a different type of epithelium, suggestive of holocrine secretion, and the cells display prominent intracellular granules of at least two types. Similar granules fill the lumen of the duct. The passageway between the lumen of the venom duct and pharynx is a flattened branching channel that narrows to a width of 10 micro m and is lined by a unique cell type of unknown function. Granular material similar to that in the venom duct was also found in the lumen of individual teeth within the radular sac. Mass spectrometry (MALDI-TOF) demonstrated the presence of putative peptides in material derived from the tooth lumen, and all of the more prominent species were also evident in the anterior venom duct. Radular teeth thus appear to be loaded with peptide toxins while they are still in the radular sac.

Intraspecific variation of venom injected by fish-hunting Conussnails

“…Similar observations were reported in C. californicus (Marshall et al, 2002). In order to further assess differences in DV and IV, IV samples from three C. striatus individuals with the most common venom profile (mainly s4a and s4b) were analyzed by HPLC-ESI-MS (Fig.·3A,C,E), and these data were compared to the profiles of the water-soluble peptides in the DV from the same individuals (Fig.·3B,D,F).…”

“…Mechanisms underlying the evident simplification of DV for injection are unknown, although anatomical studies of C. californicus suggest that a specialized epithelial zone connecting the venom duct to the pharynx may be the site of such processing (Marshall et al, 2002). Additionally, the pronounced intraspecific variation observed in IV peptide profiles of both C. striatus and C. catus suggests that selection and delivery processes, which ultimately yield the biologically relevant venom used in prey capture, are likely to be complex and specifically utilized by individual snails to varying degrees.…”

“…Another possibility is that certain peptides may be synthesized in some component of the venom apparatus other than the venom duct, for example in the radular sac where the teeth are stored prior to use. Previous work on C. californicus revealed peptides inside the lumen of stored teeth (Marshall et al, 2002), but neither the identity of those peptides nor their route of delivery is known. Similar studies have not been performed for any other species.…”

“…Venom is ultimately discharged into prey by injection through a highly modified radular tooth, resembling a barbed hypodermic needle, which is gripped near the tip of an extensible proboscis. Mechanisms for transferring toxins from the venom duct into the proboscis for injection are not well understood, but in at least one species, C. californicus, peptides appear to be packaged into the radular teeth themselves (Marshall et al, 2002). In the fish-hunting species C. catus, and presumably in other species as well, the radular tooth is explosively propelled in a ballistic fashion into the prey prior to venom expulsion through the tooth (Schulz et al, 2004).…”

Optimized deep-targeted proteotranscriptomic profiling reveals unexplored Conus toxin diversity and novel cysteine frameworks

“…Nevertheless, epithelial cells bordering the venom duct (VD) are most likely the site of conotoxin production, which may then be released into the duct's lumen through a holocrine secretion process (Fig. 1B) (7). The muscular venom bulb triggers burst contractions for the circulation of the venom inside the duct up to the pharynx, where conotoxins may undergo sorting and maturation (8).…”