Osteological Description of the Cranial Region and Pectoral Girdle of Pseudoscopelus scriptus Lütken, 1892 (Teleostei: Chiasmodontidae), Using Computed Microtomography (Micro-CT)

• Ano de defesa: 2023
• Autor(a) principal: Caiero, Andreza Caroline
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Deep-Ocean; Dentição; Dentition; Mar-profundo; Morfologia; Morphology; Osteologia; Osteology; Raios-x; X-rays
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21134/tde-23052023-134958/

The deep ocean is the largest environment on planet Earth and host some of the least unknown ecosystems. It is characterized by having extreme abiotic conditions, such as high hydrostatic pressure and partial or complete absence of and inhabited by a highly specialized fauna, such as the fishes of the family Chiasmodontidae. The species of the family, classified in four genera, Chiasmodon, Dysalotus, Kali, and Pseudoscopelus, are popularly known as swallowers, because some species have a distensible stomach that allows them to swallow prey larger than their own body. In addition, osteological modifications in the neurocranium, jaws, hyoid and gill arches, and dentition constitute key mechanisms for the capture and ingestion of such prey. The x-ray computed microtomography (micro-CT) is a non-destructive technique that allows precise virtual reconstructions of skeletal structures, therefore, it can be used to study the cranial morphology and dentition of these fishes. Therefore, the goal of this work is to apply micro-CT to describe the cranial osteology and dentition of the chiasmodontidae Pseudoscopelus scriptus Lütken, 1892, and to evaluate the use of this technique for deep-sea fishes, that usually have low-density bones. The analyzed specimen was wrapped in a plastic bag and soaked in ethanol to avoid desiccation, and was scanned in a micro-CT equipment. Herein, the micro-CT is being used for the first time in an osteological description of a deep-sea fish, which is characterized by having low-density or low-calcified bones. Bones of the neurocranium, hyoid and gill arches, suspensorium, pectoral and pelvic girdle, anterior vertebrae, otoliths, and the dentition were virtually reconstructed in full details and are described in relation to size, position and shape. The heterodonty and different types of tooth attachments in the premaxilla and dentary of P. scriptus, in combination with palatine and branchial teeth enhance prey capture and swallowing. The heterodonty may represent a specialization of deep-sea fishes, associated with their success in this habitat.