Involvement of cathepsin D during tail regression in tadpoles of the common Indian tree frog, Polypedates maculatus (Anura: Rhacophoridae)

Interspecific Variations in Duration of Tail Regression in Two Tropical Anurans

“…The melanocytes constituted about 4.25% of the surface area of the section of regressing tail of early stage XXIV of D. melanostictus (Figure 2(b)) while in P. maculatus it was found to be only 0.22% (Figure 2(a)). Similarly, in late stage XXIV tail of D. melanostictus, the melanocytes occupied 5.31% of the total section of the regressing tail (Figure 2(d)) while in P. maculatus the melanocytes occupied only 1.73% of the total area of the regressing tail (Figure 2 muscle, spinal cord, and blood vessels in the tadpoles of P. maculatus and D. melanostictus [10,11]. Melanocytes contain specialized lysosomes called melanosomes that contain a broad array of lysosomal hydrolases [23].…”

“…Release of acid hydrolases from preformed lysosomes is described to be the primary cause of tail atrophy and an increase in activity of lysosomal hydrolase is related to the progressive release of hydrolytic enzymes from preformed lysosomes [24]. Cathepsin D plays an important role in degradation of major tail tissues during tail resorption in tadpoles of P. maculatus and D. melanostictus [10,11]. The present study thus compared the localization of cathepsin D in the regressing tail tissues of P. maculatus and D. melanostictus to ascertain the involvement of cathepsin D in causing variations in the duration of tail regression.…”

“…The involution of tadpole tail is also characterized by the neosynthesis of lysosomal enzymes apparently resulting from the activation of macrophages by some primary autolytic changes in the tail tissue [8,9]. An elevation in the level of lysosomal enzymes, during tail regression, has been reported recently in the common Indian tree frog Polypedates maculatus [9,10] and common Asian toad Duttaphrynus melanostictus [9,11].…”