Gross brain morphology of Rhamdia quelen (Quoy & Gaimard 1824) (Ostariophysi: Siluriformes: Heptapteridae)

Abstract

The brain gross morphology of Rhamdia quelen is described and compared with seven species of six genera of Heptapteridae. Interspecific variation in shape, size, and position of brain subdivisions was observed in all examined species. The posterior position of the hypophysis on the hypothalamus and presence of a lateral subdivision on the lobus facialis are shared by all examined heptapterids. Rhamdia quelen and Pimelodella gracilis, currently considered closely related within the family Heptapteridae, exhibit the anterior and posterior area of the telencephalon with equivalent widths, and the lateral line lobe reaching the anterior area of the lobus vagi. Members of the so called Nemuroglanis sub-clade (Cetopsorhamdia iheringi, Heptapterus mustelinus, Imparfinis mirini, and Phenacorhamdia tenebrosa) share the lobus vagi proportional smaller than the lobus facialis; the lateral line lobe reaching the half length of the lobus facialis; the tectum mesencephali in contact with the telencephalon, and thinner anterior area of the telencephalon. The results reveal several features that are phylogenetically informative among the heptapterids examined, and corroborate previous hypotheses based on other non-neural anatomical characters.

Encephalon gross morphology of the cichlid Geophagus sveni (Cichlidae: Geophagini): Comparative description and ecological perspectives

“…The corpus cerebelli is posteriorly directed in G. sveni , as in other cichlid species (Huber et al ., 1997). In contrast, this structure is anteriorly directed in various Siluriformes (Abrahão et al ., 2018a; Abrahão et al ., 2018b; Angulo & Langeani, 2017; Trajano, 1994). Furthermore, females of G .…”

“…Conversely, this feature may be stalked, as found in some Ostariophysi groups. It has also been found in the base of the olfactory organ and connected to the telencephalon by the tractus olfactorius in Pseudopimelodidae (Abrahão et al ., 2018a; Abrahão & Shibatta, 2015), Loricariidae (Angulo & Langeani, 2017), Heptapteridae (Abrahão et al ., 2018b) and Bryconidae species (Pereira & Castro, 2016). The olfactory bulb receives most of the sensorial inputs from the olfactory organ through the tractus olfactorius (Meek & Nieuwenhuys, 1998).…”

“…Loricariidae (Angulo & Langeani, 2017), Heptapteridae (Abrahão et al, 2018b) and Bryconidae species (Pereira & Castro, 2016). The olfactory bulb receives most of the sensorial inputs from the olfactory organ through the tractus olfactorius (Meek & Nieuwenhuys, 1998).…”

“…The central nervous system is recognized as the main center of sensorimotor coordination, behaviour control and integration of signs from the environment through cranial and spinal nerves (Meek & Nieuwenhuys, 1998). These nerves connect several sensory organs (i. e., olfactory, gustatory, visual, acoustic, vestibular and somatosensory) with different encephalon regions (Meek & Nieuwenhuys, 1998), varying in size and shape among different species of fishes, even in related groups (Abrahão et al, 2018a(Abrahão et al, , 2018bAngulo & Langeani, 2017;Huber et al, 1997;Kotrschal et al, 1998;Meek & Nieuwenhuys, 1998;Pereira & Castro, 2016). Moreover, some species have shown a higher differential development of encephalic regions responsible for the reception of signs from specialized organs (e.g., palatal organ in cyprinids, lateral line system in mormyrids and gymnotids; see Meek & Nieuwenhuys, 1998).…”

Gross brain morphology of Hypoptopomatinae and Neoplecostominae (Siluriformes: Loricariidae): Comparative anatomy and phylogenetic implications

“…So far, few teleosts have had their brains studied in detail (Vernier, 2017) and, among the Siluriformes, the Ictaluridae has been the most explored family (Atema, 1971; Finger, 1975, 1976; Knudsen, 1976, 1977; Lee & Bullock, 1984; Meek & Nieuwenhuys, 1998; Northcutt, Holmes, & Albert, 2000; Striedter, 1990a, 1990b, 1991; Tong & Finger, 1983). Increased interest in brain evolution (Striedter, 2005) has since permitted more comparative approaches, resulting several combined investigations of neuroanatomy and systematics among Notothenioidei (e.g., Eastman & Lanoo, 1995, 2003a, 2003b, 2004, 2007, 2008, 2011), Callichthyidae (Pupo, 2011; Pupo & Britto, 2018), Pseudopimelodidae (Abrahão, 2013; Abrahão, Pupo, & Shibatta, 2018a), Bryconidae (Pereira & Castro, 2016), Heptapteridae (Abrahão, Pupo, & Shibatta, 2018b), Cetopsidae (Abrahão, 2018), and Loricariinae (Angulo, 2019). The brains of most of the fishes outside of these groups, such as Hypoptopomatinae, are like black boxes waiting to be opened.…”