Brain and sensory organ morphology in Antarctic eelpouts (perciformes: Zoarcidae: Lycodinae)

• Published in: Journal of Morphology
• Main Authors: Lannoo, Michael J., Eastman, Joseph T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2005
• Subjects: Antarctic; Arctic; Pacific; Southern Ocean; Antarc*; Antarctica; North Atlantic
• Online Access: http://dx.doi.org/10.1002/jmor.10391; http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjmor.10391; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmor.10391

Abstract Eelpouts of the family Zoarcidae comprise a monophyletic group of marine fishes with a worldwide distribution. Centers of high zoarcid diversity occur in the North Atlantic and North Pacific, with important radiations into the Arctic, along southern South America, and into the Southern Ocean around Antarctica. Along with snailfishes (Liparidae), zoarcids form an important component of the non‐notothenioid fauna in the subzero shelf waters of Antarctica. We document the anatomy and histology of the brains, cranial nerves, olfactory apparatus, cephalic lateral lines, taste buds, and retinas of three Antarctic zoarcid species, living at depths of 310–939 m, representing three of the nine genera from this region. The primary emphasis is on Ophthalmolycus amberensis , and we provide a detailed drawing of the brain and cranial nerves of this species. Although this brain reflects general perciform neural morphology, it exhibits a reduction of the (optic) tecta and the eminentia granulares and crista cerebellares of the lateral line system. Interspecific differences among the three species are slight. The olfactory rosette consists of three to four lamellae and the nasal sac, contrary to the claim of Fanta et al. ([2001] Antarct Rec, Natl Inst Polar Res, Tokyo 45:27–42), is not in communication with the cephalic lateral line system. Primary olfactory neurons are abundant and converge on branches of the olfactory nerve. Numerous taste buds are located in the lips. All three species lack an ocular choroid rete and have relatively thin retinas with a low cell density and a single bank of rods as the only type of photoreceptor. Neural diversification among Antarctic zoarcids has not involved the evolution of sensory specialists; brain and sensory organ morphologies do not approach the condition seen in primary deep‐sea fishes, or even that of some sympatric non‐perciform secondary deep‐sea fishes, including liparids and muraenolepidids (eel cods). There may be phylogenetic constraints on brain morphology in ...