Other senses

The ears and lateral line organs of fish are sensitive to vibrations in the water, and enable fish to detect and locate objects in their vicinity. Many species have very acute hearing, and in some deep-level fish the lateral line system is very well developed, for example, in myctophids and macrourids, and this must compensate

Figure 4.12 Some bathypelagic fishes showing various adaptations for life in darkness. (a) Argyropelecus - photophores and tubular eyes. (b) Linophryne - luminous lure and elaborate barbel. (c) Eurypharynx - large mouth and distensible stomach. (d) Saccopharynx - large mouth, distensible stomach and luminous tissue at end of elongate tail. (e) Lasiognathus - luminous lure with hooks. (f) Gigantactis - luminous lure. Note the small size of most of them (approximate lengths given in cm).

Figure 4.12 Some bathypelagic fishes showing various adaptations for life in darkness. (a) Argyropelecus - photophores and tubular eyes. (b) Linophryne - luminous lure and elaborate barbel. (c) Eurypharynx - large mouth and distensible stomach. (d) Saccopharynx - large mouth, distensible stomach and luminous tissue at end of elongate tail. (e) Lasiognathus - luminous lure with hooks. (f) Gigantactis - luminous lure. Note the small size of most of them (approximate lengths given in cm).

to some extent for poor illumination and reduction or loss of vision. In some cases it appears that the swimbladder and acoustico-lateralis system function together for production and detection of vibration (Hawkins, 1973).

The olfactory organs of some species are exceptionally well developed and assist the detection and recognition of organisms and possibly also have a function in navigation. Very long tactile appendages are a frequent feature of animals that live in darkness, and are found in several forms among deep-sea creatures. Some fish have barbels of extraordinary length or elaboration (Stomias boa, Linophryne, Ultimostomias) (Figure 4.12b). Others have feeler-like fin rays (Bathpterois) or delicate, elongate tails (Stylophorus). The abundant family of deep-sea prawns, Sergestidae, have antennae of great length which are minutely hooked and possibly are used both for detecting and entangling their prey.

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