You are correct alright. There is not much on chemoreception in marine
mammals. One reference in my library is Cetacean Behavior (1980) ed. Louis
Herman. The subject has less than two pages devoted to it, but the
references are as follows pp.152-153:
"Waterborne chemicals, detectable by taste, can provide a rich source of
social and environmental information for cetaceans, but little is known about
central or peripheral taste structures in cetaceans. Yablokov et al. (1972),
based in part on work of Kruger (1959), noted that gustatory sensibility can
reside in the thalamus and nearby areas of the brain, which are well
represented in the cetaceans, and that the distinctive fossae, or small pits,
on the root of the tongue of some odontocete cetaceans might contain
chemoreceptors. Berzin (1972) observed specialized epithelial cells near the
root of the tongue of sperm whales, which he thought were chemoreceptors.
Suchowskaja (1972) examined the pits in the tongue of the bottlenose dolphin
and the common dolphin and reported small "buds" and gustatory papillae of
typical mammalian form. Arvey and Pilleri (1970, 1972) also observed
gustatory papillae in the common dolphin and additionally, in the harbor
porpoise, beluga, and Chilean dolphin. These structures were not seen in the
white-beaked dolphin, the Ganges susu, nor, unlike data of Suchowskaja (1972)
or Donaldson (1977), in botlenose dolphins, Caldwell and Caldwell (1972)
cited a histological report suggesting that pits in the tongue were probably
lingual salivary glands and not sensory organs. Hence, existing anatomical
reports are contradictory for the bottle nose dolphin but suggest a gustatory
capability for some species."
I have not been able to locate much else that is different. You might try
the International Whaling Commission for recent papers on tactile
capabilities. I've done a quick search of some journals that I have here and
have turned up no recent work on your topic.
Hope the above is helpful at least. Good luck.
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