Histological Observations and Regeneration of Barbels in Juveniles of the Chinese Longsnout Catfish Leiocassis longirostris

Abstract

Barbel structure and regenerated barbel length in the juvenile Chinese longsnout catfish Leiocassis longirostris (G<TEX>$\ddot{u}$</TEX>nther), were evaluated. The barbles consisted of an epidermis, a dermis, and a central rod. The epidermis harbored taste buds, granular cells and epidermal cells. The taste buds were basophilic and situated along the distal portion of the epidermis. The dermis was composed of loose connective tissue containing blood vessels pigment cells. The innermost central region was cartilage enclosed within layers of muscle layers. After 30 days, the regenerated barbel length measured <TEX>$0.92{\pm}0.404mm$</TEX> at <TEX>$15^{\circ}C$</TEX> (regenerated growth curve: y = 0.5085x + 4.0678, <TEX>$r^2$</TEX> = 0.9654, where y is regenerated length and x is experimental period in days), <TEX>$1.88{\pm}0.521mm$</TEX> at <TEX>$20^{\circ}C$</TEX> (y = 0.1806x + 4.808, <TEX>$r^2$</TEX> = 0.9822), and <TEX>$6.44{\pm}0.751mm$</TEX> at <TEX>$25^{\circ}C$</TEX> (y = 0.0914x + 4.9918, <TEX>$r^2$</TEX> = 0.9944). Fifteen days after amputation, the regenerated length was significantly longer at <TEX>$25^{\circ}C$</TEX> than at 15 or <TEX>$20^{\circ}C$</TEX> (P < 0.05). The barbels of the Chinese longsnout catfish was the tender and flexible type, and our experimental findings provide evidence of temperature-dependent regeneration. Additional investigation of the behavior and physiology of the Chinese longsnout catfish is needed, particularly histological studies of regenerated barbels and the measurements of the numbers of taste buds per barbel under various environmental conditions.