Allometric larval growth of the bottom-dwelling catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

Abstract

We investigated the early life growth pattern of pacamã, Lophiosilurus alexandri, a catfish endemic to the rio São Francisco basin, Brazil. Pacamã larvae were kept in a galvanized trough for 29 days after hatching. We collected approximately 10 larvae daily (total number = 285). We obtained from each specimen the total length (independent variable) and 11 other body measurements (dependent variables). We performed linear regressions on the log-transformed data to determine the growth pattern of the body measurements and the respective inflexion point on the growth curves. Except for trunk length, trunk width and yolk sac volume, the remaining body measurements showed a positive allometric growth coefficient up to the respective IP followed by a decrease in the rate of relative growth afterwards. Although trunk width presented a positive allometric growth, no significant inflexion point was detected. The dorsal-ventral head flattening seen in the adult pacamã was quickly expressed in the larvae as indicated by the large allometric growth of head width. Maxillary barbels showed the highest growth rate. The exceptionally high growth rates of eyes and maxillary barbels and the acquired ability to capture prey (as suggested by mouth length growth) strengthened the hypothesis of growth priorities in which the most essential organs develop first.Investigamos o padrão de crescimento inicial do pacamã, Lophiosilurus alexandri, um bagre endêmico da bacia do rio São Francisco, Brasil. Larvas de pacamã foram mantidas numa canaleta horizontal de metal galvanizado durante 29 dias após a eclosão. Diariamente, coletamos circa 10 larvas (número total = 285) das quais obtivemos o comprimento total (variável independente) e 11 outras medidas corporais (variáveis dependentes). Fizemos regressões lineares nos dados log transformados para determinar o padrão de crescimento das medidas corporais e respectivo ponto de inflexão das curvas de crescimento. Exceto comprimento do tronco, largura do tronco e volume do saco vitelino, as demais medidas corporais apresentaram crescimento alométrico positivo até o respectivo ponto de inflexão, seguido de redução na taxa relativa de crescimento. Embora a largura do tronco apresentasse crescimento alométrico positivo, não foi detectado um ponto de inflexão significativo. O achatamento dorso-ventral da cabeça, presente nos adultos, mostrou-se evidente nas larvas com o acentuado crescimento alométrico de sua largura. Os barbilhões maxilares exibiram a maior taxa de crescimento. O extraordinário crescimento dos olhos e dos barbilhões maxilares e a habilidade adquirida para a captura de presas (como sugere o crescimento do comprimento bucal) reforçam a hipótese de prioridade de crescimento em que os órgãos essenciais são os primeiros a se desenvolverem.

Morphological characterisation of the digestive tract of the catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes, Pseudopimelodidae)

“…Lophiosilurus alexandri is interesting for aquaculture, and studies have been carried out recently aimed at the development of its conservation and commercial farming, such as Barros et al. (); Santos and Luz (); Guimarães‐Cruz, Santos, Sato, and Veloso‐Junior (); Mello, Santos, Guimarães‐Cruz, Godinho, and Godinho (); Cordeiro et al. ().…”

Larval development of mandi‐pintado Pimelodus britskii (Siluriformes: Pimelodidae)

“…and other interspecifically variable morphometric traits, such as the relative position of the anus.Emergence of tactile and chemosensitive barbels in early larval stages suggests that they have an important role in food detection during the early phases of development de Mello et al (2015). reported that barbels are important organs in early life of the pacamã catfish Lophiosilurus alexandri Steindachner 1876 and showed that barbels had the highest growth rates among all body measurements evaluated in their study.…”

“…de Mello et al . () reported that barbels are important organs in early life of the pacamã catfish Lophiosilurus alexandri Steindachner 1876 and showed that barbels had the highest growth rates among all body measurements evaluated in their study. Maintenance of the embryonic membrane until the final flexion stage could help to increase a larva's chances of survival by facilitating locomotion at low Reynolds number when the lack of fins leads an inertial swimming (Webb & Weihs, ).…”

Feeding level to pacamã fingerling (Lophiosilurus alexandri)

“…The pacamã (Lophiosilurus alexandri) is a native fish São Francisco river. This species present a very flattened head (Mello et al 2015), carnivorous feed habit, sedentary behavior, and it prefers lentic environment with sand or pebbles deep (Travassos, 1959). The interest to farming of this species is related to excellent quality flavor of flesh and spines free (Meurer et al 2010).…”