Vol. 8, Issue 7 (2019)

Author(s):
Soumya Hilal and Fouzia Hilal

Abstract:
The ways in which challenging environments during development shape the brain and behaviour are increasingly being addressed. Conditions fish encounter during embryogenesis and early life history can leave lasting effects not only on morphology, but also on growth rate, life‐history and behavioural traits. Fish brains and sensory organs may vary greatly between species. With an estimated total of 25,000 species, fish represent the largest radiation of vertebrates. From the agnathans to the teleosts, they span an enormous taxonomic range and occupy virtually all aquatic habitats. This diversity offers ample opportunity to relate ecology with brains and sensory systems. In a broadly comparative approach emphasizing teleosts, we surveyed classical and more recent contributions on fish brains in search of evolutionary and ecological conditions of central nervous system diversification. This review summarizes that there is a profound effect of environmental factors on brain size and brain morphology. The size and structure of an animal's brain is typically assumed to result from either natural or artificial selection pressures over generations. However, because a fish's brain grows continuously throughout life, it may be particularly responsive to the environmental conditions the fish experiences during development. The present study was undertaken on five teleosts collected from local fish farms and aquarium of Kollam district, Kerala. This study reveals phenotypic variation in fish brain of some teleosts: Cirrhinus cirrhosus, Etroplus suratensis, Heteropneustes fossilis, Mugil cephalus and Tilapia mossambica. Within the fishes marked phenotypic variation was observed in hindbrain lobes of fishes. Well-developed cerebellum was observed in Heteropneustes fossilis. Somatic sensory lobe concerned with sense of taste and touch is found only in Heteropneustes fossilis. Vagal lobes concerned with mouth tasting nature are found in all selected fishes. Facial lobe associated with skin tasting nature was found only in Cirrhinus cirrhosus and Heteropneustes fossilis.