On the validity and distribution of Myxobolus curemae Vieira, Agostinho, Negrelli, Silva, Azevedo and Abdallah, 2022 (Myxozoa: Bivalvulida) from a new record on the coast of southeastern Brazil.

Myxobolus spp. are parasites of wide diversity and distribution in fish, both in the natural environment and in freshwater or marine farming systems around the world and are sometimes associated with severe disease in their hosts (Schmahl et al. 1989; Lom and Dyková, 1995; Eiras et al. 2021). The white mullet Mugil curema Valenciennes, 1836 is a pelagic fish of the Mugilidae family widely distributed in the Atlantic Ocean (Froese & Pauly 2022). Recently, Myxobolus curemae Vieira, Agostinho, Negrelli, Silva, Azevedo and Abdallah, 2022 was described from white mullets Mugil curema Valenciennes, 1836 in Brazil (Vieira et al. 2022). In the current work, Myxobolus sp. was identified with the same biological and morphological characteristic features of M. curemae from white mullets from the Jacarepaguá Lagoon Complex in the State of Rio de Janeiro, Brazil, in addition to being 100% identical for a genic region of the nuclear small subunit ribosomal DNA. However, this Myxobolus sp. was also similar to Myxobolus hani Faye, Kpatcha, Diebakate, Fall and Toguebaye, 1999, which was described from white mullets in Senegal, Africa, without molecular identification (Faye et al. 1999). Therefore, this current work makes observations on these Myxobolus spp. which are morphologically and biologically similar, and that could establish M. curemae as a junior synonymy of M. hani.

Metazoan endoparasites of Hoplias malabaricus (Bloch, 1794) (Actinopterygii: Erythrinidae) from upper and middle São Francisco river basin, Minas Gerais State, Brazil.

The endoparasitic fauna of Hoplias malabaricus (which is a species of paramount importance in the fishing and human food sectors) from Três Marias reservoir, São Francisco river, and from eleven marginal lagoons in the upper and middle São Francisco river basin, Brazil, was herein recorded for the first time. In total, 13 endoparasite species belonging to ten different families were found in 147 analyzed H. malabaricus specimens. The identified taxa comprised individuals belonging to phyla Apicomplexa-Calyptosporidae-Caplyptospora sp. (oocysts); Platyhelminthes-Trematoda-Diplostomidae (metacercariae)-Austrodiplostomum sp. and Sphincterodiplostomum musculosum, Clinostomidae (metacercariae)-Clinostomum sp., Gorgoderidae (adults)-Phyllodistomum spatula, and Eucestoda-Proteocephalidae gen. sp. (plerocercoids larvae); and Nematoda-Anisakidae (larvae)-Contracaecum sp. Types 1 and 2 and Hysterothylacium sp., Gnathostomatidae (larvae)-Spiroxys sp., Camallanidae (juveniles/adults)-Procamallanus (Spirocamallanus) inopinatus, Guyanemidae (juveniles/adults)-Guyanema baudi, and Cystidicolidae (juveniles/adults)-Cystidicoloides fischeri. Proteocephalidae gen. sp. and Contracaecum sp. Type 1 were the species presenting expressive parasitic indexes in the reservoir, in the river, and in nine of the eleven lagoons. Cystidicoloides fischeri was recorded for the first time in H. malabaricus. Guyanema baudi and S. musculosum had their geographic distribution expanded to São Francisco river basin.

Sebekia sp. (Eupentastomida, Sebekidae) in Pygocentrus piraya (Actinopterygii: Serrasalmidae) from marginal lagoons of the middle São Francisco River basin, Brazil.

Pygocentrus piraya is an endemic species of the São Francisco River basin. In this study, 342 carnivorous fish were examined, nymphs specimens of Sebekia sp. and its ecological indexes are recorded only in piranhas, of the total of 53 collected from three marginal lagoons of the middle São Francisco River basin: 17 specimens from Curral de Varas lagoon; 15 from Maris lagoon, both of state of Minas Gerais; and 21 specimens from Mocambo lagoon, state of Bahia. The prevalence (P) and mean abundance (MA) of Sebekia sp. nymphs in intermediate hosts were as follows: in Curral de Varas lagoon, P = 11.8%, MA = 0.18; in Maris lagoon, P = 46.6%, MA = 0.47; and in Mocambo lagoon, P = 14.3%, MA = 1.05. Despite the lower number of fish examined from Maris lagoon, this lagoon had the highest number of piranhas (seven) parasitized by Sebekia sp. Pentastomids have zoonotic importance and evaluation of the indirect life cycle of sebekids in lagoons is necessary for defining the intermediate and final hosts involved. This record is novel and stems from collection of piranhas in the marginal lagoons of the São Francisco River, in the states of Minas Gerais and Bahia, Brazil.

Helminth endoparasites of endemic fish Pygocentrus piraya (Characiformes, Serrasalmidae) from Três Marias reservoir, Minas Gerais, Brazil.

Ten endoparasite species found in Pygocentrus piraya, which is a piranha species native to São Francisco river, were collected from 108 fish caught in Três Marias reservoir in 2004 and 2005, namely: Digenea - Austrodiplostomum sp. (metacercariae); Eucestoda - Proteocephalidae gen. sp. (plerocercoids); and Nematoda - Procamallanus (Spirocamallanus) inopinatus, Cystidicoloides fischeri and Capillostrongyloides sentinosa (adults); Spinitectus rodolphiheringi (juvenile); Hysterothylacium sp., Contracaecum sp. Type 1, Spiroxys sp. and Goezia sp. (larvae). In helminth fauna, P. (S.) inopinatus has shown higher prevalence and dominance. Fish sex has influenced the prevalence of Hysterothylacium sp., which was higher in female specimens. Longer total length of fish has positively influenced the abundance of C. sentinosa and Hysterothylacium sp.. The rainy season has favored parasitic indices, mainly P. (S.) inopinatus abundance, as well C. sentinosa and Hysterothylacium sp. prevalence and abundance. There were co-occurrences between adult and some larval nematodes. Endemic piranhas, as well as final hosts, are important intermediate and/or paratenic hosts, given the relevant number of larvae (proteocephalideans and nematodes) of heteroxene cycle found in them. Proteocephalidae gen. sp., C. sentinosa, Hysterothylacium sp., Contracaecum sp. Type 1, Goezia sp. and S. rodolphiheringi are new records parasitizing P. piraya in São Francisco basin.

Metazoan endoparasites of Acestrorhynchus lacustris (Actinopterygii: Acestrorhynchidae) from lagoons bordering the upper and middle São Francisco river basin, Brazil.

The endoparasitic fauna of Acestrorhynchus lacustris from eight marginal lagoons of the upper and middle São Francisco river basin, Brazil, is recorded here for the first time. For this, a total of 106 specimens of A. lacustris were collected. Eighteen helminth species were found. The taxa recorded were phylum Platyhelminthes: one metacercaria of Clinostomum sp. (Trematoda: Clinostomidae) and plerocercoid larvae of unidentified species (Eucestoda: Proteocephalidae gen. sp.); phylum Acanthocephala: juvenile of Quadrigyrus sp.; and phylum Nematoda: larvae of Brevimulticaecum sp., Contracaecum sp. Type1, Contracaecum sp. Type2, Hysterothylacium sp., Gnathostoma sp., Spiroxys sp., juvenile and adult specimens of Freitascapillaria sp., Paracapillaria piscicola, Capillariidae gen. sp., Procamallanus (Spirocamallanus) hilarii, Procamallanus (S.) inopinatus, Procamallanus (S.) saofranciscencis, Travassosnema travassosi paranaensis, Cystidicoloides fischeri and Spinitectus rodolphiheringi. Proteocephalidae gen. sp., Contracaecum sp. Type1 and Travassosnema t. paranaensis were present in all eight lagoons with high parasitic indexes. Proteocephalidae gen. sp., Brevimulticaecum sp., Gnathostoma sp., Freitascapillaria sp., P. piscicola, Capillariidae gen. sp., Procamallanus (S.) hilarii, C. fischeri and S. rodolphiheringi are new records for A. lacustris. The known geographical distribution of Gnathostoma sp., Freitascapillaria sp., P. piscicola, Capillariidae gen. sp., Procamallanus (S.) hilarii and Travassosnema t. paranaensis has now been extended to the São Francisco river basin.

First report of Myxobolus episquamalis Egusa, Maeno & Sorimachi, 1990 (Myxozoa: Bivalvulida) in Lebranche mullet Mugil liza Valenciennes, 1836 (Teleostei: Mugiliformes) from Neotropical region.

In the current study, Myxobolus episquamalis Egusa, Maeno & Sorimachi, 1990 (Myxozoa: Bivalvulida) is reported from the Lebranche mullet Mugil liza Valenciennes, 1836 in the estuarine region of the Maricá Lagoon, State of the Rio de Janeiro, southeastern Brazil. To date, this myxozoan species was reported in mullets from Asia, Africa, Europe, and Oceania. The characteristics of M. episquamalis previously reported are similar to the findings of the present study. DNA sequences of the nuclear small subunit ribosomal DNA (SSU rDNA) had 99.7-100% similarity with the sequences of M. episquamalis from North Africa and Asia. Therefore, strong morphological and molecular similarities ensure the identification of M. episquamalis in the current study. Finally, this finding records a new host and locality, revealing the worldwide distribution of this myxozoan species.

Argulus elongatus (Branchiura, Argulidae) in fish in the upper São Francisco river, Brazil.

Among 164 fish from the upper São Francisco river, caught in the Três Marias reservoir (18º 12' 59" S; 45º 17' 34" W) or downstream from this reservoir (18º 12' 32" S; 45º 15' 41" W) in 2007, 2008, 2016 and 2017, four specimens of Argulus elongatus Heller, 1857 were found, one specimen per fish, in the following host species: Brycon orthotaenia Günther (two fish parasitized out of 38 examined) and Salminus hilarii Valenciennes (one fish parasitized out of 45 examined) (both in Bryconidae); and Metynnis lippincottianus (Cope) (one fish parasitized out of 81 examined) (Serrasalmidae). This opportunistic ectoparasite deserves attention even in the case of low infestation in fish in a natural water system. This is the first record of a branchiuran species in B.orthotaenia; the host list of A.elongatus is extended through addition of the three fish species examined in this study, and the known Brazilian geographical distribution of this argulid is enlarged to the São Francisco river basin.