Description of Dendrorchis Retrobiloba N. Sp. (Digenea: Gorgoderidae) From Astyanax Fasciatus (Teleostei: Characidae) From Southern Uruguay, With an Emended Diagnosis of the Genus Dendrorchis

Abstract

To date, the monospecific Dendrorchis is represented by D. neivai, reported from Brazil and parasitizing Brycon lundi. Dendrorchis retrobiloba n. sp. is described from the swim bladder of Astyanax fasciatus from Cañada del Dragón stream in Montevideo, southern Uruguay (34 degrees 47'S, 56 degrees 14'W), and the emended diagnosis of Dendrorchis is given. The diagnosis of Dendrorchis has been modified to include the following characters: Phyllodistominae with flattened body, wider in the region posterior to acetabulum. Intestinal ceca sinuous or not. Testes branched or with superficial lobes. Ovary with deep or superficial lobes. Seminal receptacle present or absent. Vitellaria ellongate or pyriform. Uterus extends to posterior region and to portion of body anterior to acetabulum. Eggs oval, variable size, thin-shelled, without opercula. Dendrorchis retrobiloba n. sp. differs from D. neivai by having pyriform vitellaria, ovary larger than the testes and not deeply lobed, wider distribution of the uterus, smaller egg size, testes with superficial lobes, oral sucker wider than the acetabulum, shorter esophagus, 2 terminal lobes at the posterior end of the body, and much smaller body length. Despite being found in different hosts, both species of Dendrorchis parasitize the swim bladder of freshwater Characidae.

First report of Dendrorchis retrobiloba Volonterio & Ponce de León, 2005 (Digenea, Gorgoderidae) in Astyanax aff. fasciatus (Cuvier, 1819) (Characiformes, Characidae) from southern Brazil

“…The specimens of D. retrobiloba are easily distinguished from the congeners D. neivai, D. ritata, and D. pampae based on morphological traits such as body shape, the size and shape of the suckers, testes, ovary and, the extension of the uterus (Travassos 1926, Volonterio and Ponce de León 2005, Soofi et al 2016, Monteiro et al 2018. The bodies of D. neivai, D. ritata, and D. pampae are pyriform, whereas D. retrobiloba has an elongated body.…”

“…The oral sucker of D. retrobiloba is larger than its ventral sucker, whereas in all the other species, these 2 suckers are of similar size. In addition, D. retrobiloba is the only Dendrorchis species that has 2 posterior lobes, with a posterior cleft (Volonterio and Ponce de León 2005).…”

“…The diagnosis of the genus Dendrorchis provided by Travassos (1926) was amended recently by Volonterio and Ponce de León (2005), Campbell (2008), andMonteiro et al (2018). Travassos (1926) recognized specimens with a pyriform body, small cirrus sac, branched testes, deeply lobed ovary, and vitellaria occupying all body fields, except for the intercaecal field above the vitellaria.…”

“…Travassos (1926) recognized specimens with a pyriform body, small cirrus sac, branched testes, deeply lobed ovary, and vitellaria occupying all body fields, except for the intercaecal field above the vitellaria. Volonterio and Ponce de León (2005) added the following diagnostic traits: body wider posterior to the ventral sucker, testes branched or with superficial lobes, seminal receptacle present or absent, vitellaria elongate or pyriform, uterus extending to anterior portion and posterior region of the body, eggs thin-shelled without opercula. Brooks and MacDonald (1986) examined 2 syntypes of D. neivai deposited in the Helminthological Collection of the Oswaldo Cruz Institute and noted the absence of a cirrus sac, which was the principal reason for Campbell's (2008) proposal for a new amendment of the diagnosis of Dendrorchis.…”

“…The genus Dendrorchis was proposed by Travassos (1926) to accommodate Dendrorchis neivai Travassos, 1926, a parasite of the swim bladder of Brycon lundii (= Brycon orthotaenia Günther, 1864) from São Paulo state, Brazil. Subsequently, several other Dendrorchis species have been described in fish hosts, including Dendrorchis retrobiloba Volonterio & Ponce de León, 2005 in Astyanax fasciatus (Cuvier, 1819) from Montevideo, Uruguay (Volonterio and Ponce de León 2005), Dendrorchis ritata Soofi, Birmani & Dharejo, 2016 in Rita rita (Hamilton, 1822) from Jamshoro, Pakistan (Soofi et al 2016), and Dendrorchis pampae Monteiro, Wendt & Zebral, 2018in Cynopoecilus melanotaenia (Regan, 1912 from Rio Grande do Sul state, Brazil (Monteiro et al 2018).…”