Programa de Pós-graduação em Oceanografia Biológica (PPBGO), Instituto de Ocenografia, Universidade Federal do Rio Grande (FURG), Rio Grande, Brazil.
Instituto de Ciências Biológicas, Sector Morfologia-Pesquisa em Chondrichthyes, Universidade Federal do Rio Grande, Rio Grande, Brazil.
J Morphol. 2022 Aug;283(8):1120-1134. doi: 10.1002/jmor.21493. Epub 2022 Jul 6.
Dermal denticles cover the skin of sharks for protection and may have additional functions, depending on the environment. The aim of the present study was to analyze the morphological pattern of dermal denticles across the body of the poorly known deep-water catshark Galeus mincaronei, which is endemic to Southern Brazil. Additionally, we aimed to identify differences between sexes and stages of sexual maturity. For this purpose, we analyzed patches of eight skin samples from body regions, that is, the head, body, and tail. Dermal denticles were imaged using scanning electron microscopy. Measurements of crown morphological variations (length and width) and density of dermal denticles were performed. Nine characters of dermal denticle morphology were selected to describe a morphological pattern using principal component analysis (PCA). The first PCA axis explained 45.2% of the variation, the second explained 33%, and the third explained 14.3%, together explaining 92.5% of the total variation in denticle morphology. We identified three groups of dermal denticle crown morphologies and their possible functions. The first was composed of nostril and snout denticles, which might suggest abrasion strength functions; the second was composed of most body denticles, such as those in the cranium, on the left side of the body, and on the pectoral, dorsal, and caudal fins, which might be related to generalized functions; and the third was composed of only caudal crest denticles, which might indicate defense functions with hydrodynamic properties in G. mincaronei. Likewise, our results reveal variations in dermal denticle morphology and arrangement along the three maturity stages considered in both sexes. Similarly, sexual dimorphism in the crown width and morphology of dermal denticles was observed in developing and mature individuals. Our results are the first to reveal the morphological variation of dermal denticles in relation to function, sex, and ontogeny of individual G. mincaronei.
皮肤齿突覆盖鲨鱼的皮肤以提供保护，并且可能具有取决于环境的其他功能。本研究的目的是分析南里奥格兰德州特有的深海猫鲨 Galeus mincaronei 体躯上的皮肤齿突的形态模式，该鲨鱼的形态学特征鲜为人知。此外，我们旨在识别性别和性成熟阶段之间的差异。为此，我们分析了来自身体区域（即头部、身体和尾部）的八个皮肤样本的斑块。使用扫描电子显微镜对皮肤齿突进行成像。对齿突冠形态变异（长度和宽度）和密度进行了测量。选择了 9 个齿突形态特征，使用主成分分析（PCA）来描述形态模式。第一主成分轴解释了 45.2%的变异，第二主成分解释了 33%，第三主成分解释了 14.3%，三者共同解释了齿突形态总变异的 92.5%。我们确定了三组齿突冠形态及其可能的功能。第一组由鼻孔和吻突齿突组成，可能具有抗磨损强度功能；第二组由大多数体躯齿突组成，例如颅骨、体躯左侧、胸鳍、背鳍和尾鳍上的齿突，可能具有一般功能；第三组仅由尾嵴齿突组成，可能具有防御功能和 G. mincaronei 的流体动力特性。同样，我们的结果表明，在两性中，考虑到三个成熟阶段，皮肤齿突的形态和排列都存在变化。同样，在发育和成熟个体中观察到齿突冠的宽度和形态的性二型性。我们的结果首次揭示了与功能、性别和个体发育相关的 G. mincaronei 皮肤齿突的形态变异。
