Comparing vibrissal morphology and infraorbital foramen area in pinnipeds

Pinniped vibrissae are well-adapted to sensing in an aquatic environment, by being morphologically diverse and more sensitive than those of terrestrial species. However, it is both challenging and time-consuming to measure vibrissal sensitivity in many species. In terrestrial species, the infraorbital foramen (IOF) area is associated with vibrissal sensitivity and increases with vibrissal number. While pinnipeds are thought to have large IOF areas, this has not yet been systematically measured before. We investigated vibrissal morphology, IOF area, and skull size in 16 species of pinniped and 12 terrestrial Carnivora species. Pinnipeds had significantly larger skulls and IOF areas, longer vibrissae, and fewer vibrissae than the other Carnivora species. IOF area and vibrissal number were correlated in Pinnipeds, just as they are in terrestrial mammals. However, despite pinnipeds having significantly fewer vibrissae than other Carnivora species, their IOF area was not smaller, which might be due to pinnipeds having vibrissae that are innervated more. We propose that investigating normalized IOF area per vibrissa will offer an alternative way to approximate gross individual vibrissal sensitivity in pinnipeds and other mammalian species. Our data show that many species of pinniped, and some species of felids, are likely to have strongly innervated individual vibrissae, since they have high values of normalized IOF area per vibrissa. We suggest that species that hunt moving prey items in the dark will have more sensitive and specialized vibrissae, especially as they have to integrate between individual vibrissal signals to calculate the direction of moving prey during hunting

Chemosensitizers of the multixenobiotic resistance in amorphous aggregates (marine snow): etiology of mass killing on the benthos in the Northern Adriatic?

Periodically appearing amorphous aggregates, 'marine snow', are formed in the sea and if settled as mats on the sea bottom cause death of benthic metazoans. Especially those animals are killed which are sessile filter feeders, e.g. sponges, mussels, or Anthozoa. The etiology of the toxic principle(s) is not yet well understood. Gel-like marine snow aggregates occurred in the Northern Adriatic during summer 1997. Samples of these aggregates were collected during the period July to September and the outer as well as the inner zones were analyzed for (i) cell toxicity, and (ii) chemosensitizing activity of the multixenobiotic resistance (MXR) mechanism. Organic extracts were prepared and cell toxicity was determined using mouse lymphoma cells. The experiments revealed that the major activity is seen in the center of the mats of the gel-like aggregates; a growth inhibitory activity of up to 54% (correlated to 5 ml of snow sample) was determined. The same extracts were used to determine the inhibition of the P-glycoprotein (Pgp) extrusion pump which confers the multixenobiotic resistance. The analyses were performed with cells from the sponge Suberites domuncula and with gills from the clam Corbicula fluminea in situ. Both systems have been shown to express the Pgp extrusion pump. The data show that extracts from the outer zone of the gel-like aggregate samples display pronounced inhibitory activity on the MXR extrusion pump and hence act as chemosensitizers by reversing the MXP property. These findings indicate that gel-like aggregates contain compounds in the outer zone, chemosensitizer of the Pgp extrusion pump, which lower the level of protection of metazoan animals towards dissolved compounds in their surrounding milieu, and in the center toxic compounds which are--very likely--even in the absence of chemosensitizers hazardous for the invertebrates