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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Microscopic aspects of the nictitating membrane in Carcharhinidae and Sphyrnidae sharks: a preliminary study

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Author(s):
Poscai, Aline Nayara ; Rangel, Bianca de Sousa ; da Silva Casas, Andre Luis ; Wosnick, Natascha ; Rodrigues, Alexandre ; Grassi Rici, Rose Eli ; Kfoury Junior, Jose Roberto
Total Authors: 7
Document type: Journal article
Source: ZOOMORPHOLOGY; v. 136, n. 3, p. 359-364, SEP 2017.
Web of Science Citations: 2
Abstract

The nictitating membrane is an anatomic structure exclusively exhibited by Carcharhiniformes, the largest order among sharks. Here we present a detailed description of morphological characteristics of the nictitating membrane through light microscopy (LM) and scanning electron microscopy (SEM) in the following shark species: Carcharhinus limbatus, Galeocerdo cuvier, Prionace glauca, Rhizoprionodon lalandii, R. porosus, Sphyrna lewini and S. zygaena. Differences in the microscopic aspects of dermal denticles from the species studied were observed. P. glauca, a pelagic shark, showed a well-developed protection apparatus when compared with other pelagic species, while coastal sharks showed even higher structural complexity. In the blue shark the denticles are enameled, presenting an extensive pulp cavity and a base inserted in a connective tissue. Moreover, the species exhibits the higher number of ridges (up to nine) of varied size and shape and the muscular tissue is inserted in the ventral region of the connective tissue. Dermal denticles from C. limbatus, R. lalandii, R. porosus, S. zygaena and G. cuvier exhibit up to five ridges with hexagonal ornamentations in the crown. In S. lewini and S. zygaena, the denticles are rounded shaped and glandular cells are present. The patterns observed in the present study suggest a high level of specialization and evolutionary conservation shaped by the function of the structure. In addition, we hypothesize that the morphological simplification observed in the membrane when compared to the dermal denticles from the skin, is an evolutionary trait that evolved to improve the dynamic and biomechanics of this highly mobile structure allowing this way, a rapid and efficient protection against abrasion, mainly during predation events. (AU)

FAPESP's process: 16/09095-2 - Lipids and stable isotopes as maternal investment and neonatal nutritional strategies indicators in histotrophic stingrays
Grantee:Bianca de Sousa Rangel
Support Opportunities: Scholarships in Brazil - Master