Diversity of Monogenoidea parasitizing scombrid fishes from Rio de Janeiro coast , Brazil

Eleven known species of Monogenoidea were found parasitizing six different species of scombrid fishes collected from Rio de Janeiro coast, Southwestern Atlantic Ocean: Capsala biparasitica, Capsala katsuwoni, Capsala notosinense, Nasicola brasiliensis, Nasicola klawei, Allopseudaxinoides euthynni, Sibitrema poonui, Hexostoma albsmithi, Hexostoma euthynni, Hexostoma keokeo and Hexostoma sibi. Katsuwonus pelamis is reported as a new host to A. euthynni and Thunnus obesus to H. albsmithi. Capsala notosinense, A. euthynni, H. albsmithi and H. sibi are referred for the first time in Brazil, Southwestern Atlantic Ocean. Morphological and morphometric features are presented for each species.

In South America monogenean parasites of scombrid fishes are represented by 16 genera (see Cohen et al. 2013).Research on monogenoidean parasites of scombrid fishes from Brazil had been conducted by Abdallah et al. (2002), Alves and Luque (2006), Kohn and Justo (2006), Kohn et al. (2003), Kohn et al. (2004), Mogrovejo and Santos (2002), Mogrovejo et al. (2004), Oliva et al. (2008), Price (1938), Rego and Santos (1983), Rohde (1986), Rohde and Hayward (1999) and Rohde and Watson (1985).The aim of this study is to contribute to the increase of the knowledge and expansion of the geographical distribution of monogenoidean parasites in different species of Scombridae in the area of the Southwestern Atlantic Ocean.
The fishes were obtained by local fishermen from the coastal zone of the state of Rio de Janeiro, Brazil (22°52′46″ S, 042°01′07″ W).The parasites collected were fixed under light cover-glass pressure in 5% formaldehyde, stained with Langeron's alcoholic-acid carmine, dehydrated in an ethyl alcohol series, cleared in beechwood creosote and mounted in Canada balsam as permanent slides.Measurements are in micrometers, unless otherwise specified, with the mean in parentheses followed by the number of specimens measured in brackets, where applicable.The material studied was deposited in the Helminthological Collection of the "Instituto Oswaldo Cruz" (CHIOC), Rio de Janeiro, Brazil.

RESULTS AND DISCUSSION
Eleven cosmopolitan species of four families of monogenoideans, already referred in different fish and oceans were found.Allopseudaxinoides euthynni  Yamaguti (1968) described and figured this species as Capsala (Caballerocotyla) biparasitica.Also from the Pacific, Egorova (2000) referred it as Caballerocotyla neothunni.From the Atlantic Ocean, Capsala biparasitica was described as Caballerocotyla abidjani by Bussiéras and Baudin-Laurencin (1970) and by Bussiéras (1972) and as Caballerocotyla neothunni by Kohn and Justo (2006).

Lists of parasite species
Justo and Kohn | Diversity of Monogenoidea from Brazil same author in 1960, but not recognized by Chisholm and Whittington (2007).Kohn and Justo (2006) described the new species Caballerocotyla llewelyni from the Atlantic Ocean, which was considered as synonym of Capsala katsuwoni by Chisholm and Whittington (2007).We present only the main measurements of the specimen from T. atlanticus, which is comparative larger than those found in K. pelamis reported by Ishii (1936), Murugesh (1995) and Kohn and Justo (2006).
Remarks: This species was originally described by Kohn et al. (2004) from the nasal cavity of T. obesus from Rio de Janeiro coast.The specimens recovered from the new host T. atlanticus, are morphometrically similar to those from the type host.
Remarks: Allopseudaxinoides euthynni was described by Yamaguti (1965) from gills of Euthynnus affinis (as Euthynnus yaito) from Hawaii and redescribed in 1968 in the same host and locality.In this opportunity, it is referred for the first time in Southwestern Atlantic Ocean and in a new host, K. pelamis.

LISTS OF SPECIES Justo
and Kohn | Diversity of Monogenoidea from Brazil filaments.Immature specimen: Body elongate, 4.2 mm × 1.3 mm, with two pairs of eye spots; single longitudinal row of dorsolateral spines, 57 on right side and 62 on left side in number, with 9-12 cuspids each.Cephalic sucker 480 × 580, concave ventrally.Haptor sessile measuring 1.2 mm × 1.1 mm.One pair of anchors measuring 85 long.Pharynx muscular, composed of two unequal bulbs, the posterior smaller than anterior, 440 total length by 420 largest wide.Testes rounded, 75 × 65 confined to the intercaecal field.Seminal receptacle 170 × 95.Ovary 240 × 150, immediately pretesticular.Remarks: Chisholm and Whittington (2007) published a revision of the subfamily Capsalinae Baird, 1853 based on literature and examination of type-material and considered only 36 valid species.These authors proposed Caballerocotyla Price, 1960 as synonymous of Capsala Bosc, 1811 and considered Caballerocotyla abidjani and Caballerocotyla neothunni synonymous of Capsala biparasitica.Capsala biparasitica was originally described from a copepod parasitizing T. albacares from Pacific Ocean.In 1960, Price revised Capsalinae and proposed Caballerocotyla for the type species C. biparasitica.
Testes rounded, about 70 in number.Vas deferens strongly winding.Muscular genital atrium with single circle of curved terminally bifurcated spines.Ovary tubular.Vitelline follicles small, co-extensive with intestinal branches.Vitelline reservoir Y-shaped.Egg fusiform, 210 × 90, with one filament at each pole.