Allometric growth pattern and morphological changes of green terror Andinoacara rivulatus (Günther, 1860) (Cichlidae) during early development: Comparison of geometric morphometric and traditional methods

Abstract

Allometric growth pattern and body shape changes of the Green terror (Andinoacara rivulatus)(Cichlidae) were studied using landmark-based geometric morphometric (GM) and traditional methods, from hatching up to 1266 Hours Post Hatching (HPH) under culture conditions. The left side of specimens were photographed using digital camera and morphometric characters, including total length, head length, tail length, trunk length, eye diameter, snout length and body depth were measured using ImageJ software. In GM method, ten landmark-points were digitized on 2D pictures. Allometric growth patterns were calculated as a power function of total length and described by the growth coefficient to reveal important steps in the species' early life history. The scores of relative warp analysis (RW) were used as descriptors for the variation in shape. The growth patterns obtained by both traditional morphometric (TM) and GM methods showed similar patterns, but GM showed effective results to interpret the morphological changes and revealing larval stages based on the body shape change. The results also showed higher growth rate of head and tail regions up to yolk sac absorption following by isometric patterns, after begin of exogenous feeding. Based on the findings, the early development of this species can be divided into five stages based on its morphology, including newly hatching larvae (up to 48 HPH), younger larvae (156 HPH), older larvae (426 HPH), younger juvenile (666 HPH) and juveniles. The results confirmed this fact that morphological development and growth patterns during early life stages in A. rivulatus closely match its immediate required function.