Encephalization and Brain Organization of Mobulid Rays (Myliobatiformes, Elasmobranchii) with Ecological Perspectives (original) (raw)
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International Journal of Fisheries and Aquatic Studies, 2021
Fishes are the aquatic vertebrates inhabiting all the levels of the water column. Different species of fishes are well adapted to successfully live in all types of water bodies. They possess a well-developed nervous system to combat all the challenges they encounter in their specified habitat in the water column. Fishes that are migratory in nature are also able to overcome the problems faced by them in moving from one type of water body to the other. Although the sub divisions of the brain in different species of fish are same, there occurs a considerable variation among them owing to the whole brain size, shape and size of sub divisions etc. Studies have reported variations in whole brain size and enlargement of a particular brain subdivision that may be correlated with the body size, ecological niche or habitat of the species or cognitive ability of the species. Most of the studies performed with this objective reported interspecific variations among fishes. Fewer studies however, reported intraspecific morphological variations in brain/brain subdivisions among the fish population. Nevertheless, brains are energetically costly organs. Super class Pisces including all the fishes is a diverse group with respect to body size and habitat within water column and all such studies are so scattered that it is difficult to summarize them all. Therefore, the aim of this paper is to discuss and provide information about the variations in the brain size and in its subdivisions and unique brain structures found in fishes. Such studies were conducted in earlier times also and are gaining a great interest since past 10 years.
Morphological variations in the brain of some selected Teleosts
The Pharma Innovation Journal, 2019
Brain are the substrate for sensory perception, processing and behavioural output. Structural variation of the "command headquarter of the body" may be used to predict niches better than any other structure of an organism .The vertebrate brain is the main part of the central nervous system in vertebrates (and most other animals).The brain is at the front, in the head. It is protected by the skull and close to the main senses of vision, hearing, balance, taste, and smell. As an animal moves forward, its senses, collect data about the surroundings, and that data goes directly to the brain. Brains are extremely complex. The structure of all vertebrate brains is basically the same. There were notable differences in the rates of evolution of the different brain structures.The present study focuses on morphological variations in the brain of some teleosts: Anabas testudineus, Aplocheilus lineatus, Arius nenga, Carassius auratus and Clarius batrachus. Marked differences in the hind brain lobes of fishes were clearly reflected. The hind brain is equipped with well developed cerebellum, facial lobe, vagal lobe and somatic sensory lobes. Highly developed cerebellum is observed in Arius nenga. In Clarius batrachus, facial lobe is bilobed, in Arius nenga and Carassius auratus it is single lobed while it is absent in Anabas testudineus and Aplocheilus lineatus. Vagal lobe is bilobed in all the species studied except in Aplocheilus lineatus.Somatic sensory lobe is absent in Anabas testudineus and Aplocheilus lineatus ,bilobed in Arius nenga and Carassius auratus while well developed in Clarius batrachus. Generally the brain showed a high degree of structural diversity in fishes taken for the study.
Comparative Histological Analysis of Cerebellum of Representative Species of Elasmobranchii
International Journal of Morphology, 2023
In elasmobranch fishes, variations in gross structural organization of cerebellum has been extensively explored. The basic histological features of cerebellum although conserved in the group but the comparative account on subtle cellular variations is largely underestimated. The present study aims to explore the histological and cellular variations in different layers of cerebellar cortex of the representative elasmobranchs' species belonging to different habitat. Our findings showed that the histological architecture of cerebellar granular layer between the examined species varies noticeably. By and large increase cellular density were observed in all the layers of cerebellum in the representative species of shark compared to ray. The findings were then compared and discussed with reference to their habitat and behavior.
Brain Behavior and Evolution, 2007
The widespread variation in brain size and complexity that is evident in sharks and holocephalans is related to both phylogeny and ecology. Relative brain size (expressed as encephalization quotients) and the relative development of the five major brain areas (the telencephalon, diencephalon, mesencephalon, cerebellum, and medulla) was assessed for over 40 species from 20 families that represent a range of
Habitat dependant variations in the brain lobes in teleost
Ecological parameters have influence on the size of brains and its anatomical parts. The environmental milieu of the fish during development is important. This study establishes the effect of one ecological parameter-habitat. A surface habitat feeding fish namely Etroplus suratensis has been observed and analysed in comparison with a bottom feeding habitat fish Mystus gulio. Both fishes were the inhabitants of fresh water, habituating diverse ecological milieu. M. Gulio possessed large brains with a well developed cerebellum compared to E. Suratensis inhabiting the bottom strata possessing large eyes at the bottom to aid its feeding nature. In the present study, the variations in brain lobe during the maturing stages were more significant than in the later stages.
Acta Histochemica, 2008
This study is the third part of a comprehensive series of publications on the cytoarchitectonic organization of the brain of the European sea bass, Dicentrarchus labrax. This study provides an atlas of the brain stem based on Nissl-stained transverse sections as well as a description of cell masses and a discussion on comparative aspects of brain stem nuclei, including methodological studies in other species. By external examination, the sea bass exhibits a prominent Optic tectum and Corpus cerebelli as expected in a predator species with a highly developed visual system. However, no hypertrophy of the facial and vagal lobes was observed as reported in other non-perciform teleosts. The general organization pattern of the mesencephalon and rhombencephalon of the sea bass brain resembles that reported for other perciform teleosts. However, the Valvula cerebelli has been subdivided into anterior, central and posterior parts. In addition, the ventricular surface of the granular layer of the Valvula cerebelli appears to be in contact with those of the Torus longitudinalis. This cell apposition could be interpreted as a direct connection, but more studies demonstrating the absence of ependyma between both structures are needed. Furthermore, we have tentatively described the electro/mechano receptive pre-eminential nucleus in the rhombencephalon of the sea bass. This study completes one of the few descriptions, as well as the most complete and detailed available, of the brain of any marine perciform species.