Abstract
The structural organization and histo-cytochemical features of dorsal skin of Ancistrus dolichopterus (acari bodo) are the main focus of this work. The epidermis, dermis and subcutis are the principal layers of the skin. The epidermis mainly consists of epithelial and mucous cells. Interspersed between them are lymphocytes, pigment cells, eosinophilic granular cells (EGC), and the taste buds as sensory structures. The high number of EGCs is implicated in general and specific immunological defense from pathogenic bacteria and multicellular parasites. The epithelial cells and mucous cells contain glycoproteins with oxidizable vicinal diols, carboxyl groups and O-sulphate esters and their high secretory activity is correlated with the bottom dwelling habit of this species. A thick stratum laxum contains overlapping osteoderms bearing denticles, and the stratum compactum make the integument thicker to help the fish in negative buoyancy for maneuvering near the bottom and protection. The entire body surface is covered by conical, backwardly directed denticles. These are composed of a dentine cone, surrounding a pulp cavity with the top covered by mineralized cap, and are the true homologues of teeth. These structures provide effective protection from abrasion and enemies. These structural peculiarities and histochemical features indicate additional physiological role of the skin of A. dolichopterus.
Highlights
Amazonian fishes constitute the most diverse ichthyofauna on the earth; more than 3,000 fish species have been already described in the Amazon, including representatives of almost all freshwater fish groups (de Pinna, 2006)
The epidermis of A. dolichopterus is thicker than the skin of other teleosts (Banerjee & Mittal, 1975; Park et al, 2003; Lizarazo et al, 2008) ranging two to three time fold
Mucogenic cells generally provide this function by secreting their contents on the surface, but siluroids generally present a low number of mucous cells in epidermis
Summary
Amazonian fishes constitute the most diverse ichthyofauna on the earth; more than 3,000 fish species have been already described in the Amazon, including representatives of almost all freshwater fish groups (de Pinna, 2006). These fishes colonize most types of aquatic habitats in the immense basin (Val & Almeida-Val, 1995). For that they developed a suite of morpho-physiological adaptations that includes the latest frontier between internal and external media, the skin. The comparative anatomy of fish skin, especially the epidermis, has been investigated by light and electron microscopy (for reviews, see Imaki & Chavin, 1984; Whitear, 1986). Bhatti (1938) made an elaborate study of the dermal skeleton when he studied the integument of Siluroidea. Sire & Meunier (1993) described only the superficial ornamentation and structure of the dermal plates in a few armored Siluriformes
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