Dawestrema cycloancistrium (Monogenea) from the head pores of arapaimas

Abstract

Arapaima gigas is one of the main cultured fish species in South America, and monogenean parasites of this species cause large economic losses to fish farmers. During surveys of the parasites of cultured arapaimas from Mexiana Island in the Amazon River Delta, Rio Branco, in northwestern Brazilian Amazonia, and Yurimaguas, Peru, the monogenean Dawestrema cycloancistrium was found in the gills of A. gigas as well as in previously unreported sites, i.e. the head pores and chambers. The aim of this study was to investigate the transmission route of this parasite and its geographical distribution as well as to describe its morphology as observed by light and confocal imaging. Phalloidin labeling confirmed the presence of 2 prostatic reservoirs and showed muscular branches of fibers supporting haptoral sclerites. In arapaimas, the head connects to the gill chambers via 2 perforated scales located at the dorsolateral sides of the distal part of the head. The scales connect to thin channels and chambers situated in the proximal part of the head. These chambers are filled with cephalic mucus, which flows out to the environment through terminal pores. Adults and egg masses of monogeneans were found on the gills and inside the head pores and cavities of fish along with cephalic mucus. This indicates a specialized method of parasite transmission from adult fish to fingerlings during parental care (holding offspring in the mouth) or via head secretions, providing evidence of a new adapted mechanism of dispersion.

An Annotated Checklist of Monogeneans (Platyhelminthes, Monogenea) from Aquatic Vertebrates in Peru: A Review of Diversity, Hosts and Geographical Distribution

“…Arapaima gigas ; gills; freshwater, Loreto (05°54′ S, 76°05′ W) (CHIOC 38.656 a-c, 38657 a-c) [ 78 ].…”

Bioprospection of biocompounds and dietary supplements of microalgae with immunostimulating activity: a comprehensive review

“…Similarly, studies of parasitic fauna of Tambaqui hybrids ( Colossoma macropomum × Piaractus brachypomus and Colossoma macropomum × Piaractus mesopotamicus ) under cultivation conditions were also performed (Silva et al, 2013; Dias et al, 2015; Pinheiro et al, 2015; Winckler et al, 2015), as were studies of Arapaima ( Arapaima gigas ) specimens grown in Amazonia Peruvian (Delgado, Delgado & Orbe, 2013; Mathews et al, 2014) and in the Brazilian Amazon (Araújo et al, 2009; Marinho et al, 2013; Santos, Da Silva & Moravec, 2017), including those performed in the extreme north of Brazil (Amapá State) (Dias et al, 2015; Hoshino et al, 2017). In addition, research on the use of secondary metabolites of higher plants has also been undertaken to identify important factors for the better management and maintenance of aquaculture processes in the region (Brilhante et al, 2015; Barbas et al, 2016; Barbas et al, 2017; Ribeiro et al, 2016; Soares et al, 2017; Dutra et al, 2017).…”