(Aspidobothrea: Aspidogastridae) in Pogonias cromis (Linnaeus, 1766) (Perciformes: Sciaenidae): first report from Brazil

Up until now, there have been few studies of the helminth fauna of Brazilian populations of Pogonias cromis. In North America, P. cromis is known to be a definitive host of Cotylogaster basiri, although there have been no reports of any species of Cotylogaster infecting fish in Brazil. During necropsies of marine fish obtained from professional fisherman in the state of Rio Grande do Sul, Brazil, specimens of C. basiri were found in the intestine and rectum of P. cromis. In comparison with previous studies, differences were found in relation to the number of lobes in the buccal disc and the development of the biocellate larvae in the eggs of C. basiri. This is the first report of C. basiri in P. cromis from Brazil, contributing to the understanding of the helminth fauna of this fish from the coastal zone of Brazil.

Cotylogaster basiri was described from specimens found in Calamus calamus (Valenciennes, 1830) captured at Cabo Rojo, Puerto Rico (Siddiqi and Cable, 1960), and subsequently in hosts collected at a number of different localities in North America (Nahhas and Cable, 1964;Hendrix andOverstreet, 1977, 1983;Simpson and McGraw Junior, 1979).This parasite has been recorded in South Africa (Bray, 1984) and Venezuela (Chinchilla et al., 2000), but prior to the present study, there were no reports of any Cotylogaster from Brazil (Kohn et al., 2007;Alves et al., 2015).
The black drum, Pogonias cromis (Linnaeus, 1766), is found in the western Atlantic Ocean between southern Florida and Argentina (Menezes et al., 2003).This fish is found in coastal waters influenced by large rivers, or sand and mud banks, where it feeds on bottom organisms, such as crustaceans, mollusks and other fish (Menezes and Figueiredo, 1980).Prior to the present study, two species of aspidobothreans -C.basiri and C. dinosoides -had only been reported in P. cromis from the Gulf of Mexico (Hendrix and Overstreet, 1977;Simpson and McGraw Junior, 1979).

Material and Methods
Specimens of P. cromis (n = 6) were obtained between July and August 2014 from professional fisherman in the municipality of Rio Grande (32° 11' 06" S, 052° 06' 32" W), State of Rio Grande do Sul, Brazil.The aspidobothreans found infecting these specimens were compressed and fixed in A.F.A., stained with Delafield's hematoxylin, and mounted in Canada balsam (Amato and Pereira Junior, 1995;Humason, 1979).
The measurements are presented in micrometers (μm), unless otherwise indicated.The values are presented as the range followed by the mean, standard deviation (±), with the number of specimens measured in parentheses.Ecological terminology was based on Bush et al. (1997).The drawings were produced using a drawing tube attached to a microscope, then scanned and prepared using CorelDraw X4  and Adobes Photoshop  CS2.Voucher specimens of the helminths were deposited in the 'Coleção Helmintológica do Museu de Ciências Naturais da ULBRA' (CHMU), in Canoas, Rio Grande do Sul, Brazil.

Discussion
The C. basiri specimens collected in the present study presented morphometry similar to those reported by Siddiqi and Cable (1960), Simpson and McGraw Junior (1979) and Chinchilla et al. (2000), but smaller than the specimens measured by Hendrix and Overstreet (1977).This difference may be related to the relatively long specimens (1.55-7.34mm) collected by Hendrix and Overstreet (1977) in comparison with all other studies: 2.43-4.97mm (Siddiqi and Cable, 1960), 0.99-3.97mm (Simpson and McGraw Junior, 1979), 4.26 mm (Chinchilla et al., 2000) and 2.12-3.38 mm (present study).Siddiqi and Cable (1960), Hendrix and Overstreet (1977) and Chinchilla et al. (2000) observed five lobes (two ventral, two lateroventral and one dorsal) in the buccal disc of C. basiri, whereas the specimens examined by Simpson and McGraw Junior (1979) had three lobes, with the dorsal one larger than the ventral ones.Siddiqi and Cable (1960) examined only three specimens of C. basiri, which may mean there was an error due the difficulty of visualizing the lobes.In the present study, three lobes were observed in the buccal disc, as described by Simpson and McGraw Junior (1979).Bray (1984) reported a distinctly trilobated ovary in C. basiri, although the ovaries observed in the present study were smooth in form, as observed in all other studies (Siddiqi and Cable, 1960;Hendrix and Overstreet, 1977;Simpson and McGraw Junior, 1979;Chinchilla et al., 2000).Siddiqi and Cable (1960) described a cirrus pouch in their specimens of C. basiri, although this organ was considered absent by Fredericksen (1972), Hendrix and Overstreet (1977), and in the present study.The cirrus pouch described by Siddiqi and Cable (1960) possibly represents the seminal vesicle or the prostatic vesicle as identified in the redescription of C. basiri by Hendrix and Overstreet (1977).Siddiqi and Cable (1960), Hendrix and Overstreet (1977), Bray (1984) and Chinchilla et al. (2000) observed numerous eggs in the uterus of C. basiri, as found in the specimens examined in the present study.Here, however, only the eggs near the metraterm contained biocellate larvae, in contrast with the illustrations presented in the previous studies (Siddiqi and Cable, 1960;Hendrix and Overstreet, 1977;Bray, 1984), which depicted most of the eggs containing biocellate larvae.This different may be related to factors such as the age of the adults and the development of the eggs in the specimens observed in the present study.
A recent study recorded the occurrence of 61 species of aspidobothreans in invertebrate and vertebrate hosts around the world (Alves et al., 2015).In 70.5% of these cases, the parasite infects freshwater hosts, and the other 29.5%, marine hosts.More than half (60%) of the host-parasite associations recorded in marine species were observed in the northern Atlantic Ocean.This is the first report of C. basiri in P. cromis from the coastal zone of South America, contributing to the understanding of the biodiversity of aspidobothreans in marine hosts in the Neotropical Region.