Ontogeny of the jaw and maxillary barbel musculature in the armoured catfish families Loricariidae and Callichthyidae (Loricarioidea, Siluriformes), with a discussion on muscle homologies

Abstract

The neotropical loricarioid catfishes include six families, the most species-rich of which are the Callichthyidae and the Loricariidae. Loricariidae (suckermouth armoured catfishes) have a highly specialized head morphology, including an exceptionally large number of muscles derived from the adductor mandibulae complex and the adductor arcus palatini. Terminology of these muscles varies among the literature, and no data exist on their ontogenetic origin. A detailed examination of the ontogeny of both a callichthyid and a loricariid representative now reveals the identity of the jaw and maxillary barbel musculature, and supports new hypotheses concerning homologies. The adductor mandibulae muscle itself is homologous to the A1-OST and A3′ of basal catfishes, and the A3′ has given rise to the newly evolved loricariid retractor veli as well. The A2 and A3″ have resulted in the retractor tentaculi of Callichthyidae and the retractor premaxillae of Loricariidae. Thus, these two muscles are shown to be homologous. In Loricariidae, the extensor tentaculi consists of two separate muscles inserting on the autopalatine, and evidence is given on the evolutionary origin of the loricariid levator tentaculi (previously and erroneously known as retractor tentaculi) from the extensor tentaculi, and not the adductor mandibulae complex.

Dorsolateral head muscles of the catfish families Nematogenyidae and Trichomycteridae (Siluriformes: Loricarioidei): comparative anatomy and phylogenetic analysis

“…A similar condition to that of the vandelliines Paravandellia and Vandellia also occurs in the loricarioid clade Scoloplacidae + Astroblepidae + Loricariidae, which also possesses a division of adductor mandibulae, the retractor premaxillae muscle, inserting onto the premaxilla (Howes, 1983b;Schaefer & Lauder, 1986;Schaefer, 1990;Schaefer & Provenzano, 2008;Geerinckx et al, 2009). This muscle, however, is probably derived from A3" or A2"+A3" (as demonstrated by Geerinckx et al, 2009) whereas in the Vandelliinae it is derived from part of the A2'.…”

“…This muscle, however, is probably derived from A3" or A2"+A3" (as demonstrated by Geerinckx et al, 2009) whereas in the Vandelliinae it is derived from part of the A2'. In nematogenyids (Fig.…”

“…As clearly demonstrated by Geerinckx et al (2009), the "retractor tentaculi" of loricariids (Howes, 1983a;Schaefer & Lauder, 1986Schaefer, 1997;Diogo & Vandewalle, 2003;Geerinckx et al, 2007) is actually derived from the extensor tentaculi, what lead them to rename it as the levator tentaculi. Within the Loricarioidea a retractor tentaculi derived from the adductor mandibulae complex is also reported in the Callichthyidae (Howes, 1983b;Schaefer & Lauder, 1986;Huysentruyt et al, 2007;Geerinckx et al, 2009). The retractor tentaculi of this family, however, seems to be a compound muscle derived from both the A2" (the "A2" of Geerinckx et al, 2009) and A3" (Geerinckx et al, 2009) whereas in the Copionodontinae it is derived solely from the A3".…”

“…The insertion of parts of the A3 onto the maxilla, thereby forming the so-called retractor tentaculi, apparently evolved independently in several other catfish lineages (Alexander, 1965;Howes, 1983a;Adriaens & Verraes, 1996;Diogo & Chardon, 2000;Geerinckx et al, 2009). As clearly demonstrated by Geerinckx et al (2009), the "retractor tentaculi" of loricariids (Howes, 1983a;Schaefer & Lauder, 1986Schaefer, 1997;Diogo & Vandewalle, 2003;Geerinckx et al, 2007) is actually derived from the extensor tentaculi, what lead them to rename it as the levator tentaculi.…”

Redescription of the endangered hypoptopomatine catfish Parotocinclus spilurus (Fowler, 1941) (Siluriformes: Loricariidae) from the upper rio Jaguaribe basin, northeastern Brazil

“…3). Ontogenetic shape changes were already observed in loricariids, including hypoptopomatine catfishes (Aquino & Miquelarena, 2001;Rosa et al, 2014) and must be related to allometric development of bones, muscles and plates structures (Geerinckx et al, 2008(Geerinckx et al, , 2009.…”