External Morphology of Lophiosilurus alexandri Steindachner, 1876 during Early Stages of Development, and Its Implications for the Evolution of Pseudopimelodidae (Siluriformes)

Abstract

Pseudopimelodidae are Neotropical catfishes characterized by having slightly to strongly depressed body in fully developed specimens. The largest species of the family with 500 mm SL, Lophiosilurus alexandri, experiences impressive changes in body shape during development, becoming extremely depressed when fully developed. Accordingly, Lophiosilurus alexandri is an ideal species to observe the morphological changes during ontogeny, and to seek solid interpretations on the polarity of characters. Specimens of distinct larval periods (yolk sac, flexion and postflexion; n = 186 specimens) and juvenile stages (n = 20) were analyzed. Changes in body shape, position of mouth and eye, morphology of fins and pigmentation were observed during the development of Lophiosilurus. Larvae (5.7–11.2 mm standard length) had pigmentation concentrated on the head and parts of body, eyes small and pigmented, short barbels, and well-developed finfold. Juveniles (15.9–28.1 mm standard length) had body shape similar to adult, with head depressed and bearing bony ridges, large mouth, dorsally-oriented eyes, small barbels and well-developed shoulder bulges (cleithral width). The greatest morphological changes in the development of L. alexandri occurred during the postflexion larval stage. Relative to standard length, measurements of snout length, head depth and body depth are smaller in juveniles than in larvae, but body width is larger. New interpretations on the phylogenetic characters related to these changes are provided in view of the two alternative hypotheses of the evolution of Pseudopimelodidae.

Early ontogeny of yellowtail tetra fish Astyanax lacustris (Characiformes: Characidae)

“…Studies of small species are still poorly known (Anjos & Anjos, 2006; Çelik, Celik, Cirik, Gurkan, & Hayretdag, 2012; Ferreira‐Marinho, 2017; Galuch, Suiberto, Nakatani, Bialetzki, & Baumgartner, 2003; Mattox, Hoffmann, & Hoffmann, 2014; Park et al., 2014; Santos et al, 2017; Walter, 2012). However, it is an important tool for a better understanding of biology (Nakatani et al., 2001) and systematic and/or phylogenetic position of species (Assega, Birindelli, Bialetzki, & Shibatta, 2016; Ferreira Marinho, 2017; Mattox et al, 2014), as well as for studies of identification and evaluation of fishing resources (Nakatani et al., 2001) and in aquaculture production systems (Bialetzki, Garcia, & Orsi, 2016; Martinez & Bolker, 2003).…”

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

“…According to the IUCN () list, its conservation status is vulnerable. It reproduces naturally in captivity, does not migrate for reproduction, builds nests on a sandy bottom, exhibits parental care and has high commercial value (Assega, Birindelli, Bialetzki, & Shibatta, ; Barros, Guimarães‐Cruz, Veloso‐Júnior, & Santos, ; Godinho, ; Melillo Filho et al., ). It is a carnivorous fish with piscivorous tendencies, lurking on the sandy substrate to catch other fish.…”

The light intensity in growth, behavior and skin pigmentation of juvenile catfish Lophiosilurus alexandri (Steindachner)

“…This increase in food conversion may be related to the feeding habits of the bottom species, which take advantage of food in dark environments since this condition resembles its natural habitat (Veras et al, 2013). Pedreira et al (2012) described that dark environments are suitable for larviculture success of L. alexandri species with a benthic habit, also observed in other catfish (Jauro & Usman, 2015;Assega et al, 2016).…”

“…For the catfish, Wallago attu (Bleeker, 1851), the low incidence of light also decreased food consumption (Giri et al, 2002). Similarly, feed consumption of Clarias gariepinus catfish increased with increasing light intensity, over time, indicating that the species can detect food in the absence of light; this occurs because a mechanism (barbels) that are very sensitive in detecting any material that enters your environment (Jauro & Usman, 2015), as L. alexandri (Assega et al, 2016).…”