Cetopsorhamdia iheringi ( Siluriformes , Heptapteridae ) : a new record for the freshwater ichthyofauna of Argentina

Cetopsorhamdia is a genus of Neotropical catfishes with a broad distribution in the main drainages of South America. Herein we report the first record of Cetopsorhamdia iheringi in Argentina and comment on the type series of the species.


INTRODUCTION
The genus Cetopsorhamdia Eigenmann & Fisher 1916, with nine species currently considered valid (Eschmeyer et al., 2017), has a broad distribution including the main Neotropical basins: Orinoco, Amazon, and Rio de La Plata.The genus is also present in the cis-Andean Magdalena River basin, as well as coastal rivers of northeastern Brazil (Bockmann & Guazzelli, 2003;Ferraris, 2007).
Cetopsorhamdia is diagnosed by the following combination of characters: first dorsal and pectoral-fin rays not spinous, anal-fin moderately developed, lower caudal-fin lobe longer than upper one, origin of pelvic-fin just below dorsalfin, adipose fin base three times longer than its depth, small frontal fontanel distant from the long parietal fontanel, skull covered with skin, minute occipital process, orbit without free margin, subconical head, projected snout, and absence of teeth in vomer and palatine.
The small catfish Cetopsorhamdia iheringi Schubart & Gomes 1959 was described with specimens from Mogi-Guaçu and Camanducaia rivers.The former is a tributary of Grande River and the latter is part of the Tocantins River basin.Subsequent studies reported its presence at headwater riffles of the São Francisco River (Casatti & Castro, 1998) as well as in many drainages of the Upper Paraná system (Pavanelli et al., 2007;da Graça & Pavanelli, 2007;Ingenito & Buckup, 2007;Cunico et al., 2009;Casarim et al., 2012;Cetra et al., 2012;Delariva & da Silva, 2013).Recent expeditions to Northeastern Argentina at Paraná River basin, in Misiones, resulted in the collection of specimens identified as C. iheringi, that represent the first records of this species from this country.These specimens extend the species known distribution about 260 km southward and are the first record of Cetopsorhamdia iheringi in the Middle Paraná system.
Along with the original diagnosis of Cetopsorhamdia iheringi, Schubart and Gomez (1959) distinguished this species only from C. insidiosa and a species currently included in genus Imparfinis Eigenmann & Norris, 1900.Herein we provide a full comparison of C. iheringi with all species of the genus and comment on the type series of the species.
Cetopsorhamdia iheringi (Fig. 1 and 3 In C. iheringi this consists of dark-brown body background, turning to pale yellow ventrally.Head dark-grey with pale lips.Five light blotches at dorsum, the first posterior to the supraoccipital, the second and third at dorsal-fin origin and end respectively, the fourth at posterior margin of adipose fin and the fifth at the caudal fin origin.Sometimes the dorsum is dark and blotches are not noticeable.This pattern is different from of C. insidiosa which has a relatively big golden-yellow spot on dorsal fin insertion and a dark brown band on the caudal-fin base; C. boquillae is distinguishable by a distinct yellow band around the head, a notorious yellow spot in front of first dorsal-fin ray and another at the end of it; C. phantasia pattern is characterized by the anterior part of the body iridescent green with snout, lips, and chin very dark and two ovate, light-colored spots on nape bracketing occipital process, body olive gray and basal portion of fins very dark, contrasting with distal tip almost unpigmented; C. molinae has a metalyellow body with four wide brown bands, first on predorsal, second at the end of dorsal fin base, third over the adipose-fin and fourth at caudal peduncle; C. picklei is characterized by the caudal fin white, sharply contrasting with blackish caudal-fin base; C. nasus has small purplish dots and a light band across the base of the occipital. Cetopsorhamdia orinoco differs from C. iheringi in morphometric characters, as body depth (14.2-14.8% vs. 18.5-21%), body width (20.6-20.8% vs. 17.5-19%),caudal peduncle depth (23.6-24% vs. 17-21.7%)and length of anal-fin base (22.6-24.3% vs. 14.7-17.5%).Cetopsorhamdia iheringi can also be distinguished from C. molinae by the length of caudal peduncle longer in C. molinae (33% vs. 17-21%).
The cranial fontanelle configuration distinguishes C. iheringi from C. insidiosa, C. filamentosa and C. boquillae (narrow fontanelles, the   lar areas that shared almost the same features (Fig. 4).The riverbed was mainly composed of basaltic bedrock with some loose stones.

DISCUSSION
Cetopsorhamdia currently includes nine valid species that are mainly distributed at north and northeastern South-America.To date, Cetopsorhamdia iheringi is the species with the southernmost records and the only one present The record in the Iguazú River is from the stretch downstream the falls and considerably reduces the distance extension.However, the revision of that material lays beyond the object of this work.We presently just consider the published records as reliable to establish the distribution of the species.This new record increase to seven the genera and to 20 the species of the family Heptapteridae currently known from Argentina, considering the most updated checklist of Argentinean ichthyofauna (Mirande & Koerber, 2015;Koerber et al., 2016) and the recently described Heptapterus mandimbusu (Aguilera et al., 2017).The Convention on Biological Diversity (CBD) proposed that each country should have accurate and updated lists of fauna and flora (Reis et al., 2003).From this perspective, the record here in presented contributes with that recommendation and should be taken into account in managements and conservation programs in the region.
To date, the only diagnosis of Cetopsorhamdia iheringi is the one provided with its description by Schubart and Gomez (1959).They compared this species only with C. Insidiosa and C. mirini, the latter currently classified as a species of genus Imparfinis.Thus, an exhaustive revision and a full diagnosis are needed for this species.Herein we provide a comparison of C. iheringi with all the species of the genus currently considered as valid.This comparison is based on the literature and we are aware of the need to corroborate this by the examination of the type material of C. iheringi.However, the situation of the type series is uncertain and the specimens are probably lost.Schubart and Gomez (1959) deposited the holotype and paratypes at "Estação Experimental de Biologia e Piscicultura" (E.E.B.P) in Piraçununga, Brazil, currently under management of the "Instituto Chico Mendes de Conservação da Biodiversidade".Upon our request, we were informed that the type series of C. iheringi is not physically located in that collection.According to our available information, the specimens were kept by Manoel Pereira de Godoy, the collector of the type series, and now the specimens would be under the care of his family.

Fig. 1 :
Fig. 1: Cetopsorhamdia iheringi from Tabay Stream, 69.85 mm, LGE-P 544.posterior one not reaching anteriorly the posterior margin of eyes vs. reaching that margin in C. insidiosa; wide and extending until anterior margin of the eyes in C. filamentosa, and extended and narrow with absence of epiphyseal bar in C. boquillae).Cetopsorhamdia iheringi also differs from C. phantasia by the number of dorsal-fin rays (i,6 vs i,10) and the absence of contact with the dorsal skin of the neural spines of the five anterior vertebrae, as described for C. phantasia.
; Table 1) may be distinguished from C. boquillae, C. filamentosa, C. molinae, and C. phantasia by the length of its maxillary barbels that slightly surpass the origin of pectoral-fins (vs.reaching or surpassing the end of pectoral fins in C. boquillae, the base of pelvic fins in C. filamentosa and C. molinae, and extending beyond the base of anal-fin in C. phantasia).The coloration pattern allows the distinction of C. iheringi from C. insidiosa, C. molinae, C. boquillae, C. phantasia, C. picklei, and C. nasus.

Table 1 :
Morphometric data of Cetopsorhamdia iheringi(n=18).SL: standard length, HL: head length, SD: standard deviation.in the Rio de La Plata basin.In this contribution we add four new points to the distribution of C. iheringi in the Paraná River basin and also report for the first time its occurrence in Argentina and the Middle Paraná basin.