Oil gland and oil pores in billfishes: in search of a function

Type Article
Date 2020-10
Language English
Author(s) Dhellemmes F.1, 2, Hansen M. J.1, Bouet S. D.1, 2, Videler J. J.3, Domenici P.4, Steffensen J. F.5, Hildebrandt T.6, 7, Fritsch G.6, Bach Pascal8, 9, Sabarros Philippe8, 9, Krüger A.1, Kurvers R. H. J. M.10, Krause J.1, 2
Affiliation(s) 1 : Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587 Berlin, Germany
2 : Faculty of Life Sciences, Humboldt-Universität zu Berlin, Invalidenstrasse 42, 10115 Berlin, Germany
3 : Groningen & Leiden University, Zuidlaarderweg 57, Noordlaren, The Netherlands
4 : IAS-CNR, Istituto per lo studio degli impatti Antropici e Sostenibilità in ambiente marino, Consiglio Nazionale delle Ricerche, Località Sa Mardini, 09170, Torregrande, Oristano, Italy
5 : Marine Biological Section, University of Copenhagen, Strandpromenaden 5, DK-3000 Helsingør, Denmark
6 : Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Straße 17, 10315 Berlin, Germany
7 : Freie Universität Berlin, 14195 Berlin, Germany
8 : MARBEC, Université de Montpellier, CNRS, Ifremer, IRD, 34203 Sète, France
9 : Institut de Recherche pour le Développement, Ob7, 34203 Sète, France
10 : Centre for Adaptive Rationality, Max Planck Institute for Human Development, Lentzeallee 94, 14195 Berlin, Germany
Source Journal Of Experimental Biology (0022-0949) (The Company of Biologists), 2020-10 , Vol. 223 , N. 19 , P. jeb224956 (7p.)
DOI 10.1242/jeb.224956
Keyword(s) Comparative method, Functional morphology, Rostrum, Glandula oleofera, Rete lubricans, Fatty acids, Co-evolution
Abstract

Billfishes are well known for their distinctive elongated rostra, i.e. bills. The functional significance of billfish rostra has been frequently discussed and the recent discovery of an oil gland (glandula oleofera) at the base of the rostrum in swordfish, Xiphias gladius, has added an interesting facet to this discussion regarding the potential co-evolution of gland and rostra. Here, we investigated the oil gland and oil pores (through which the oil is brought to the skin surface) of four billfish species – swordfish, Atlantic blue marlin (Makaira nigricans), Indo-Pacific sailfish (Istiophorus platypterus) and striped marlin (Kajikia audax) – and provide detailed evidence for the presence of an oil gland in the last three. All four species had a high density of oil pores on the forehead which is consistent with the hypothesis of hydrodynamic benefits of the oil. The extension of the pores onto the front half of the rostrum in sailfish and striped marlin, but not in swordfish or blue marlin, suggests that the oil may have additional functions. One such function could be linked to the antibacterial and anti-inflammatory properties of the oil. However, the available evidence on predatory rostrum use (and hence the likelihood of tissue damage) is only partly consistent with the extension of pores on rostra across species. We conclude that the oil gland probably serves multiple, non-mutually exclusive functions. More detailed information on rostrum use in blue marlin and swordfish is needed to better link behavioural and morphological data with the aim of accomplishing a full comparative analysis.

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Dhellemmes F., Hansen M. J., Bouet S. D., Videler J. J., Domenici P., Steffensen J. F., Hildebrandt T., Fritsch G., Bach Pascal, Sabarros Philippe, Krüger A., Kurvers R. H. J. M., Krause J. (2020). Oil gland and oil pores in billfishes: in search of a function. Journal Of Experimental Biology, 223(19), jeb224956 (7p.). Publisher's official version : https://doi.org/10.1242/jeb.224956 , Open Access version : https://archimer.ifremer.fr/doc/00656/76805/