Association between Ichthyocladius (Diptera: Chironomidae) and armored catfi shes in the Guareí River basin, São Paulo State, Brazil

: Ichthyocladius is a genus of chironomid (Diptera, Insecta) whose immature forms live attached to the bodies of some species of freshwater fi shes. Here we investigate the association between Ichthyocladius spp. and armored catfi sh in streams of the Guareí River basin, Paraná River system, Brazil. We provide the fi rst record of I. lilianae associated with fi sh in the São Paulo State and the Paraná River basin. In addition, this is the fi rst report of Ichthyocladius associated with the armored catfi shes Hypostomus iheringii and H. tietensis . Lastly, we record two undescribed species of Chironomidae (i

Currently, Ichthyocladius is represented by three species, Ichthyocladius neotropicus Fittkau, 1974, the type species of the genus, I. kronichticola Mendes, Andersen & Saether, 2004, and I. lilianae Mendes, Andersen & Saether, 2004(Mendes et al. 2004, as well as several additional species awaiting formal description. Individuals of I. kronichticola and I. lilianae have been reported to live in association with armored catfi sh (Mendes et al. 2004, Roque et al. 2004. Ichthyocladius lilianae has been recorded in waterbodies of three Brazilian States: Rio Grande do Sul (Sydow et al. 2008, Dala-Corte & Melo 2018

MATERIALS AND METHODS
Fish specimens were collected in the Guareí River basin, located in the upper reaches of the Paranapanema River (Paraná River system), São Paulo, Brazil. Armored catfishes were sampled in two tributaries of the right bank of the Guareí River during June and August 2017. Fish sampling is described in Azevedo-Santos et al. (2020). Sampling sites were designated as R1 (-23.434932°S -48.388695°W) and R2 (-23.460077°S -48.414122°W) ( Figure 1).
We searched for chironomids on the exterior surfaces of captured loricariids. All larvae and prepupae were removed and mounted on slides with Euparal ® . Chironomidae species were identified according to Fittkau (1974) and Mendes et al. (2004) and by comparison with type specimens deposited at the Museu de Zoologia da Universidade de São Paulo (hereafter MZ), São Paulo, Brazil. Immature individuals (at least one for each species of Ichthyocladius) were deposited as vouchers at the MZ. Standard Length (SL) of all hosts was measured with a digital caliper (in millimeters -mm). Classification of the catfishes (see Table SI

RESULTS
We examined nine armored catfishes, of which six served as hosts for Ichthyocladius. We recorded 13 larvae and one prepupa of the genus Ichthyocladius, including I. lilianae and two taxa identified at the morphospecies level (Ichthyocladius sp. 1 and Ichthyocladius sp. 2). This is the first record of I. lilianae for the Paraná River basin and for the State of São Paulo. The catfish An Acad Bras Cienc (2022) 94(4) e20201829 3 | 6 hosts were individuals of Hypostomus iheringii (Regan, 1908) and H. tietensis (Ihering, 1905) (28.6 -95.2 mm of SL). We found larvae attached to different regions of the body -including the eyes and fins (Table I;  These authors reported its association with two loricariid fishes, Harttia sp. and Hypostomus cf. Table I. Chironomids associated with armored catfishes from the Guareí River basin, São Paulo, Brazil. Classifications and voucher numbers can be found in Table SI.

Reach
Hosts Associated species (local in the fish)

R2
One Hypostomus iheringi (Regan, 1908) Two larvae of Ichthyocladius sp. 2 (both on the lateral of the adipose fin); two larvae of I. lilianae (near to the adipose fin and other between the adipose fin and caudal fin); and one prepupa of I. lilianae (near to the adipose fin basin). garmani (Regan, 1904). This species of chironomid has since been recorded in four Brazilian states and in different hydrographic basins, including São Francisco and Paraíba do Sul (Sydow et al. 2008, Mendes et al. 2004, Dala-Corte & Melo 2018, Henriques-Oliveira & Nessimian 2009; see details in Table II). Our work expanded its recorded range to include São Paulo State and the Paraná River basin.
We recorded two undescribed Chironomidae species (e.g., Ichthyocladius sp. 1 and Ichthyocladius sp. 2) associated with catfishes in the Guareí River system. Ichthyocladius sp. 1 is the only one without anal seta among the known species. The procersus is also absent in this species. Ichthyocladius sp. 2 differs from other species of Ichthyocladius by presenting the mentum with more than 24 median teeth and the premandible with pale teeth. In addition to these two, three additional species of the genus await formal description, being one from Ecuador (Fittkau 1974), other from Marauiá River, and the last from Argentina (Mendes et al. 2004). Therefore, the diversity of Chironomidae associated with catfishes is certainly underestimated.
Only two previous studies have reported an association between Ichthyocladius and Hypostomus Lacepède, 1803. Mendes et al. (2004 mentioned the presence of Ichthyocladius on H. cf. garmani while Roque et al. (2004) reported the interaction with Hypostomus species. Our work is the first to report Ichthyocladius on H. iheringii and H. tietensis. All hosts had at least one chironomid in the region close to the adipose fin. In the studied streams, the hosts were captured in rocky streambeds with moderate water flow, or with some turbulence. It is likely that the adipose fin, because of its particular position, is less disturbed by water turbulence, providing greater opportunities for adherence by Ichthyocladius. Individuals were also found in the eye, sometimes within the orbit (e.g., Figure 2b), possibly because it provides a more stable environment.
We finalize by emphasizing the need for more studies on the taxonomy, biogeography and ecology of Ichthyocladius -including field surveys and laboratory investigations. These organisms and their ecological interactions are poorly understood, and their possible effects on fish ecology and behavior remain largely unknown.