Brain and sense organ anatomy and histology in hemoglobinless Antarctic icefishes (Perciformes: Notothenioidei: Channichthyidae)

• Published in: Journal of Morphology
• Main Authors: Eastman, Joseph T., Lannoo, Michael J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2004
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1002/jmor.10221; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjmor.10221; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jmor.10221

Abstract The Channichthyidae, one of five Antarctic notothenioid families, includes 16 species and 11 genera. Most live at depths of 200–800 m and are a major component of fish biomass in many shelf areas. Channichthyids are unique among adult fishes in possessing pale white blood containing a few vestigal erythrocytes and no hemoglobin. Here we describe the brains of seven species and special sense organs of eight species of channichthyids. We emphasize Chionodraco hamatus and C. myersi, compare these species to other channichthyids, and relate our findings to what is known about brains and sense organs of red‐blooded notothenioids living sympatrically on the Antarctic shelf. Brains of channichthyids generally resemble those of their bathydraconid sister group. Among channichthyids the telencephalon is slightly regressed, resulting in a stalked appearance, but the tectum, corpus cerebellum, and mechanoreceptive areas are well developed. Interspecific variation is present but slight. The most interesting features of channichthyid brains are not in the nervous tissue but in support structures: the vasculature and the subependymal expansions show considerable elaboration. Channichthyids have large accessory nasal sacs and olfactory lamellae are more numerous than in other notothenioids. The eyes are relatively large and laterally oriented with similar duplex (cone and rod) retinae in all eight species. Twin cones are the qualitatively dominant photoreceptor in histological sections and, unlike bathydraconids, there are no species with rod‐dominated retinae. Eyes possess the most extensive system of hyaloid arteries known in teleosts. Unlike the radial pattern seen in red‐blooded notothenioids and most other teleosts, channichthyid hyaloid arteries arise from four or five main branches and form a closely spaced anastomosing series of parallel channels. Cephalic lateral line canals are membranous and some exhibit extensions (canaliculi), but canals are more ossified than those of deeper‐living bathydraconids. We ...