Curculionichthys, Roxo, Fabio F., Silva, Gabriel S. C., Ochoa, Luz E. & Oliveira, Claudio, 2015

Roxo, Fabio F., Silva, Gabriel S. C., Ochoa, Luz E. & Oliveira, Claudio, 2015, Description of a new genus and three new species of Otothyrinae (Siluriformes, Loricariidae), ZooKeys 534, pp. 103-134 : 104-107

Taxon classification Animalia Siluriformes Loricariidae

Curculionichthys gen. n.

Type species.

Curculionichthys insperatus (Britski & Garavello, 2003), new combination.

Diagnosis.

The new genus can be distinguished from all other Otothyrinae species by the following combination of characters: (1) a pair of rostral plates at the tip of the snout; (2) the presence of two large pre-nasal plates just posterior to the rostral plates; (3) a supra-opercular plate that receives the laterosensory canal from the compound pterotic before the preopercle; (4) a well developed membrane at anal opening in females; and (5) the presence of a V-shaped spinelet.

Etymology.

Curculionichthys , from the Latin “curculionem” (elongated snout) and from the Greek “ichthys” (fishes) related to the relatively elongated snouts of the fish species included in this genus.

Discussion of the new genus.

Schaefer (1998a) resurrected Hisonotus using characters that were considered ambiguous by Britski and Garavello (2007) and needed to be redefined. The hypothesis of monophyly of Hisonotus was rejected by Roxo et al. (2014a) and Martins et al. (2014). Roxo et al. (2014a) found Hisonotus acuen ( Hisonotus sp. 3, Fig. 3 in Roxo et al. 2014a) closely related to Hisonotus chromodontus , Parotocinclus sp. 3 and Parotocinclus aripuanensis . The species Hisonotus vespuccii ( Hisonotus sp. 1, Fig. 3 in Roxo et al. 2014a) appeared closely related to Parotocinclus aff. spilurus and a new species of Otothyrinae ( Hisonotus sp. 2 from municipality of Jaíba, Minas Gerais State in Rio São Francisco basin). The species Hisonotus bocaiuva appeared closely related to species of Parotocinclus from Rio São Francisco (i.e. Parotocinclus prata and Parotocinclus robustus , Fig. 4 in Roxo et al. 2014a), Parotocinclus bahiensis and two new taxa (New taxon 1 and New taxon 2).

On the other hand, the species Curculionichthys insperatus , Curculionichthys luteofrenatus , Curculionichthys oliveirai , Curculionichthys paresi and Curculionichthys piracanjuba form a monophyletic group that is unrelated with the type species Hisonotus notatus , but instead with species of Corumbataia in Roxo et al. (2014a - using molecular data) and with Hypoptopoma inexspectatum , Niobichthys ferrarisi , Otocinclus affinis , Oxyropsis acutirostra and Acestridium martini in Martins et al. (2014 - using morphological data) (see Fig. 1 in the present paper for illustration of the phylogenetic position of Curculionichthys with the subfamily Otothyrinae according to Roxo et al. 2014a). In the present study, based in the information published in Roxo et al. (2014a) and in new morphological analyses, we propose the new genus, Curculionichthys , for re-allocation of five species described within Hisonotus : Curculionichthys insperatus , Curculionichthys luteofrenatus , Curculionichthys oliveirai , Curculionichthys paresi and Curculionichthys piracanjuba (see Table 2) and include three new species: Curculionichthys sabaji , Curculionichthys coxipone , and Curculionichthys sagarana . Four putative additional species are recognized in the analyzed material, but these species cannot be described yet due to the lack of sufficient specimens.

The new genus Curculionichthys is defined by the following combination of characters: (1) a pair of rostral plates at the tip of the snout; (2) the presence of two large pre-nasal plates just posterior to the rostral plates; (3) a supra-opercular plate that receives the laterosensory canal from the compound pterotic before the preopercle; (4) a well developed sexual dimorphic membrane at anal opening in females; and (5) the presence of a V-shaped spinelet. The tip of the snout that is composed of a pair of rostral plates (Fig. 2) was first reported in species of Hisonotus by Britski and Garavello (2003) in the description of Hisonotus insperatus ( Curculionichthys insperatus ), the type species of the new genus Curculionichthys . This character state according to Martins and Langeani (2012) is shared with Corumbataia cuestae Britski, 1997, species of Microlepidogaster Eigenmann & Eigenmann, 1889 (except Microlepidogaster longicolla Calegari & Reis, 2010), Otothyris Myers, 1927, and in all genera of Hypoptopomatinae (except in Hypoptopoma Gunther, 1868). We also observed that Rhinolekos capetinga , a species recently described from the Rio Tocantins basin, also have a pair of rostral plates. However, the morphology of this character in the species of Curculionichthys is different, as described by Martins and Langeani (2012), since the rostral plates are very large, the length of each plate is greater than their width and are more conspicuous when compared with all species listed previously in which the pair of rostral plates is smaller and have a quadrangular form.

The second character used to diagnose the new genus is the presence of two large pre-nasal plates just posterior to the rostral plates (Fig. 2). The pre-nasal plates present some variation in members of Otothyrinae, with respect to their numbers and shapes. In most species of Otothyrinae the pre-nasal plates are small or very tiny, however in species of Curculionichthys we found two very large pre-nasal plates just posterior to the rostral plates. However, even in species of Curculionichthys we can find variation in pre-nasal plates contacting the frontal and the nasal plates, but the two large pre-nasal plates just posterior to the rostral plate apparently is a synapomorphic character exclusive to Curculionichthys .

The presence of a supra-opercular plate that receives the laterosensory canal from the compound pterotic before the preopercle is the third character used to diagnose the new genus. According to Martins and Langeani (2012) this character is present in a large number of species of Loricariidae , but absent in the Hypoptopomatinae and Otothyrinae, except in the new genus Curculionichthys . The fourth character is the presence of a well developed membrane at anal opening in females. Both sex of Curculionichthys species have a membrane on the anal opening, however, it is more developed in females than in males, covering almost the entire urogenital opening. This character was first reported by Roxo et al. (2014b) in the description of Curculionichthys oliveirai and Curculionichthys paresi and it is absent in all other species of Otothyrinae, in which the membrane at anal opening is poorly developed (see Fig. 4 in Roxo et al. 2014b for illustration about this character states).

The fifth character used to diagnose Curculionichthys was the presence of a V-shaped spinelet in the dorsal fin. This character was first reported by Carvalho and Datovo (2012) in the description of Hisonotus bockmanni in personal communication with Roberto E. Reis. This character is not exclusive to Curculionichthys and it is shared with Hisonotus acuen , Hisonotus chromodontus , Hisonotus vespuccii and two new species of Parotocinclus , one from Xingu basin (LBP 15894) and the other one from Barra do Garça (LBP 12274). Furthermore, the V-shaped spinelet is shared with vast majority of Hypostominae species ( Silva et al. 2014). However, within Otothyrinae it is good character that distinguishes the new genus.

In the description of Curculionichthys oliveirai and Curculionichthys paresi , Roxo et al. (2014b) found variation in head plate shape and number in the last two species and in Curculionichthys insperatus , even though osteological characters are generally conserved within Otothyrinae and Hypoptopomatinae ( Schaefer 1987, 1997, 1998b; Garavello 1977; Mo 1991; de Pinna 1998; Diogo et al. 2001; Ribeiro et al. 2005). Roxo et al. (2014b) analyzed 18 specimens of Curculionichthys insperatus from type localities in Rio Capivara and Rio Araquá, from Botucatu, São Paulo State, three individuals presented a single rostral plate, instead of a pair of rostral plates (see Fig. 8 in Roxo et al. 2014b for variation of all characters). In Curculionichthys oliveirai and Curculionichthys insperatus the authors found bilateral asymmetry in the first infraorbital and the first and second posterior rostral plates and in an extra plate is found between preopercle and compound pterotic (known in the present study as our third character: a supra-opercular plate that receives the laterosensory canal from the compound pterotic before the preopercle). Despite the variation observed among specimens of Curculionichthys , those characters appear to be conserved enough to be used as synapomorphies and delimit this new genus of all remaining Otothyrinae.