Larger context for LACK in Corpus USbrown_UKbncw/UK_bncw.txt
This is not the case In at least one species of the related genus Thais which has shifted position after injecting the narcotic and feeds at the gaping edge of the victim's shell (Carriker, 1981).
It is obviously impractical to have bulky salivary glands in the slender retractile proboscis and they lie at its inner end, anterior of the cerebral commissure.
In most prosobranchs, the saliva lacks any digestive function, being predominantly mucous and functioning as a lubricant for the food collecting and swallowing activities of the animal.
The carnivorous whelks, however, secrete several proteolytic enzymes (Fretter and Graham, 1962).
Prey Selection Throughout its geographical range, Nucella lapillus has a choice of prey species.
It follows that the snails show a pattern of prey selection.
Such patterns might be based on prey size, prey distribution, prey abundance or prey value.
In reality, it is probably a combination of two or more of these and doubtless changes as the animal grows, for a wider choice is available to larger individuals.
Nucella might be expected to select its prey in a frequency dependent manner; that is, to feed indiscriminately upon the various potential prey species, taking them in their order of occurrence.
Very few animals actually do this. 1.