The sensory epithelium of the tentacles and the rhinophore of Nautilus pompilius L. (cephalopoda, nautiloidea)

Abstract

Nine intraepithelial ciliated cell types that are presumed to be sensory cells were identified in the epithelium of the pre- and postocular tentacles, the digital tentacles, and the rhinophore of the juvenile tetrabranchiate cephalopod Nautilus pompilius L. The morphological diversity and specialization in distribution of the different ciliated cell types analyzed by SEM methods suggest that these cells include receptors of several sensory functions. Ciliated cell types in different organs that show similar surface features were combined in named groups. The most striking cell, type I, is characterized by a tuft of long and numerous cilia. The highest density of this cell type occurs in ciliary fields in the epithelium of the lamellae of the pre- and postocular tentacles, in the olfactory pits of the rhinophores, and in the lamellae of four pairs of lateral digital tentacles, but not in the epithelium of the medial digital tentacles. The similar morphological data, together with behavioral observations on feeding habits, suggest that this cell type may serve in long-distance chemosensory function. The other ciliated cell types are solitary cells with specific spatial distributions in the various organs. Cell types with tufts of relatively short, stiff cilia (types III, IV, VIII), which are distributed in the lateral and aboral areas of the tentacles and at the base of the tentacle-like process of the rhinophore, are considered to be employed in mechanosensory transduction, while the solitary cells with bristle-like cilia at the margin of the ciliary fields (type II) and at the base of the rhinophore (type IX) may be involved in chemoreception. Histological investigation of the epithelium and the nerve structures of the different organs shows the proportion and distribution of the sensory pathways. Two different types of digital tentacles can be distinguished according to their putative functions: lateral slender digital tentacles in four pairs, of which the lowermost are the so-called long digital tentacles, participate in distance chemoreception, and the medial digital tentacles, whose terminal axial nerve cord may represent a specialized neuromechanosensory structure, appear to have contact chemoreceptive abilities.

Adhesive mechanisms in cephalopods: a review

“…The epidermis of the cirri has transverse ridges and grooves surrounding the trunk like sickle-shaped lamellae. They are pronounced on the oral side of the cirri (Ruth et al 2002), whilst they are low and relatively flat on the aboral surface (Fukuda, 1987). In the transverse ridges on the oral side, two zones can be distinguished morphologically and by their secretory products ( Figure 2).…”

Meissner corpuscles and somatosensory acuity: The prehensile appendages of primates and elephants

“…Predictions were tested on the assumption that receptor density parallels sensitivity (Meisami, 1989;Catania, 1999;Ruth et al, 2002;Martin et al, 2004). Predictions were derived from the above hypotheses regarding the functional similarities between the prehensile appendages of anthropoids and one African elephant.…”

One rhinophore likely provides sufficient sensory input for odour-based navigation by the nudibranch mollusc,Tritonia diomedea

“…Finally, because odour-gated rheotaxis relies on detecting the direction of flow carrying odours, little or no spatial separation between the two modalities may well be adaptive. Although information on sense organs used specifically during odour-gated rheotaxis is limited, there is evidence for the detection of both flow and chemicals by a single sense organ from a range of other taxa (Basil et al, 2005;Bicker et al, 1982;Mellon, 2007;Ruth et al, 2002). Moreover, when T. diomedea crawl, the dorsally extended rhinophores are probably better placed for detecting cues associated with odour plumes, rather than the oral veil which is held close to the substrate (and therefore more strongly affected by substrate boundary layers).…”