Depth dependent morphological variation in two ophidiiform fishes from the deep Red Sea: evidence for species-specific structure in vertical distribution

Uiblein F., Nielsen J.G., Klausewitz W.

Date de parution: février 1994
Volume: 18
Number: 1
Pagination: 015-023
Editeur: Société Française d'Ichtyologie
doi: https://doi.org/10.26028/cybium/1994-181-002
Résumé

Data on depth distribution and morphology of two ophidiiform fishes from the Red Sea, Oligopus robustus (Smith & Radcliff, 1913) and Neobythites stefanovi Nielsen & Uiblein, 1993, were examined for possible species-specific relationships between depth, size, and important morphological variables. In the Red Sea, both species have colonized greater depths than in the Indian Ocean, a pattern most likely related to the higher temperatures in the deep Red Sea. In contrast to N. stefanovi, O. robustus occupies a wider depth-range (434-804 vs 363-1285 m) living in habitats with and without solar illumination. Significant negative correlations between depth and orbit length and two measure of mouth size were found in specimens of O. robustus reflecting a high phenotypic plasticity. This morphological plasticity may be associated with a less visually oriented lifestyle in depths of more than 1000 m and probably with a highly size-selective foraging mode in shallower habitats. In N. stefanovi, depth was negatively correlated with standard length indicating an upwards directed, ontogenetic migration which coincides well with the development of an ocellus on the dorsal fin that may allow to adapt to increased predation pressure. The species-specific and ecophenotypic approach used in the current study provides a useful tool to determine the rules guiding the depth distribution of deep-sea fishes.

Mots-clés: Deep-sea fishes - Depth distribution - ISW - Ocellus development - Ophidiiformes - Red Sea
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