Basics of skin structure and function in elasmobranchs: a review

Abstract

In contrast to the bony fishes, particularly the teleosts, the integument of elasmobranchs is rather unknown. Therefore, a description of the basic structural and functional features of shark and ray skin is given, based on a review of the literature and published or unpublished findings of the authors. The latter aspect makes it possible to document in more detail the specific structure of the skin layers regarding, particularly, the epidermis and its cell spectrum, the more or less robust dermis with its specific features, the very special scales with their derivates and the sophisticated sensoric integumental equipment. As far as possible, all important structures are discussed including their typical biological functions and results from applied scientific work. To some extent the information given is evaluated as compared with the much broader knowledge from the Osteichthyes.

Confirmation of the occurrence of a second killer whale morphotype in South African waters

“…In most sharks, placoid scales cover the entire body, whereas among rays only sawfish (Pristiformes) and guitarfish (Rajiformes: Rhinobatidae) show a similar body coverage: some members of the Myliobatiformes (including whiptail stingrays and eagle rays) have very few scales or none at all (Meyer and Seegers 2012). Visser (2005) found that over 90% by number of the elasmobranchs preyed upon by New Zealand killer whales were sting or eagle rays, so although sharks were also taken, their incidence was perhaps not high enough to produce significant tooth wear.…”

Biomimetic shark skin: design, fabrication and hydrodynamic function

“…Liem et al, 2001). These denticles are composed of an outer enameloid layer and an inner bone-like layer surrounding a pulp cavity, and the denticles are sculpted into complex three-dimensional (3D) shapes (Kemp, 1999;Meyer and Seegers, 2012;Motta et al, 2012;Oeffner and Lauder, 2012). Denticles erupt through the epidermis and thus are in direct contact with the water.…”

“…This suggests that analyzing flexible shark skin models during swimming is an important prerequisite to understanding how skin functions during in vivo locomotion (Oeffner and Lauder, 2012). And as shark skin is composed of numerous hard denticles embedded within a flexible dermis (Kemp, 1999;Meyer and Seegers, 2012), from a biomimetic perspective synthetic shark skin should contain both rigid and flexible components.…”

“…The structure of shark skin denticles and their possible effect on the pattern of water flow over the body has attracted considerable interest from biologists interested in the microstructure and distribution of denticles (Kemp, 1999;Meyer and Seegers, 2012;Motta et al, 2012;Reif, 1978;Reif, 1982a;Reif, 1985), engineers focused on how the surface roughness may reduce drag forces during locomotion (Bechert et al, 1997;Bechert et al, 2000;Lang et al, 2011), and researchers interested in generating biomimetic models of shark skin to reduce locomotor drag on humans and human-designed structures (Büttner and Schulz, 2011;Mollendorf et al, 2004). Bioengineering studies of shark skin denticle function have focused on the effects of denticle-like structures using scaledup models of denticles to study how surface roughness affects drag forces (Dean and Bhushan, 2010;Lang et al, 2008;Lang et al, 2011;Luchini et al, 1991;Walsh, 1980;Walsh, 1983).…”

Quantifying ontogenetic stable isotope variation between dermis and muscle tissue of two pelagic sharks

“…This consumption would result in more consistent isotope values between tissues even with different turnover rates, but small sample sizes over ontogeny limit the conclusions that can be made. Shark placoid scales or dermal denticles form in the dermis and increase in size with increasing body surface or body growth during the lifetime of an animal (reviewed by Meyer & Seegers 2012). The growth of these placoid scales is continuous, with substitution taking place as scales shed, resulting in different growth stages of scales occurring between fully grown dermal denticles (Meyer & Seegers 2012).…”