Myxobolus insignis sp. n. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the Amazonian teleost fish Semaprochilodus insignis (Osteichthyes, Prochilodontidae)

Abstract

A new myxosporean species is described from the fish Semaprochilodus insignis captured from the Amazon River, near Manaus. Myxobolus insignis sp. n. was located in the gills of the host forming plasmodia inside the secondary gill lamellae. The spores had a thick wall (1.5-2 µm) all around their body, and the valves were symmetrical and smooth. The spores were a little longer than wide, with rounded extremities, in frontal view, µm long by 11.3 (11-12) µm wide and 7.8 (7-8) provided a synopsis of the species giving the full characterisation of 744 nominal species, including nearly all the species described so far in fish and amphibians. It is surprising that from such a high number of species only 21 were described for South America -2 from Argentina, 1 from Guiana, and 18 from Brazil. This is surprising because the fish diversity in Brazilian waters is very high, comprising about 8000 species representing nearly 24% of all the known fish species (Cellere et al. 2002). It is likely that the small number of Myxobolus species known so far for this region (as well as of other Myxosporea species) does not mean a scarcity of parasites in this part of the world, but a lack of research on Myxosporea (Cellere et al. 2002).In this paper we describe Myxobolus insignis sp. n. (Myxozoa, Myxosporea, Myxobolidae) from the "jaraqui", Semaprochilodus insignis Jardine & Schomburgk, 1841 (Osteichthyes, Prochilodontidae), a freshwater fish from the Amazon River, Brazil. This fish species, jointly with S. taeniurus, is most important for a large part of the Central Amazon human population once they represent its main food resource. MATERIALS AND METHODSThree specimens of S. insignis (total length: 22.3-24.5 cm) were net-fished from the Amazon river, at Manaus, and transported to the laboratory. The specimens were thoroughly dissected under a compound microscope and all the organs were inspected for the presence of parasites. Measurements were made from fresh spores (30 specimens), and spores were observed under Nomarski differential interference-contrast. For detecting the presence of an iodinophilous vacuole fresh spores were treated with Lugol's iodine solution. Spores were also stained with India ink for revealing any mucous envelope (Lom & Vávra 1961). RESULTSTwo specimens of S. insignis exhibited the gills infected by Myxobolus. The parasites formed whitish, rounded or slightly irregular plasmodia (about 0.02-0.08 mm in diameter) located intra-lamellarly within the secondary gill lamellae. Most of the plasmodia were located at the base of the lamellae, but could be present also more or less far from the base.The spores (Figs 1-3) had a valvular wall 1.5-2 µm thick all around their body, and the valves were symmetrical and smooth. The spores were a little longer than wide, with rounded extremities, in frontal view, and oval in lateral view. They were 14.5 (14-15) µm long by 11.3 (11-12) µm wide and 7.8 (7-8) µm thick. Some spores showed the presence of a triangular thickening of the internal face of the wall near the posterior...

Light and electron microscopy of Myxobolus sciades n. sp. (Myxozoa), a parasite of the gills of the Brazilian fish Sciades herzbergii (Block, 1794) (Teleostei: Ariidae)

“…Most of the Brazilian Myxobolus species have been described based on only light microscopy descriptions and diagrammatic drawings (Walliker 1969, Kent & Hoffman 1984, Molnár & Békési 1993, Gioia & Cordeiro 1996, Molnár et al 1998, Cellere et al 2002, Eiras et al 2005a, 2007, Martins & Onaka 2006; even fewer have been described using light and ultrastructural observations (Casal et al 1996, 2002, 2009, Tajdari et al 2005 In this paper, we describe light and ultrastructural data for a new myxosporidian species found in the gill of the teleost fish, Sciades herzbergii, which was collected from a river Northeast of Brazil.…”

“…In a recent synopsis, 744 Myxobolus species have been identified parasitizing fish (Eiras et al 2005b) and more recently, 792 named species of the same genus, including seven infecting amphibians, have been described (Lom & Dyková 2006). However, this number has been successively increasing over the years by the continuing description of new species in different countries, including Brazil (Casal et al 2006, Martins & Onaka 2006, Eiras et al 2007, Adriano et al 2009a, b, Azevedo et al 2009).Most of the Brazilian Myxobolus species have been described based on only light microscopy descriptions and diagrammatic drawings (Walliker 1969, Kent & Hoffman 1984, Molnár & Békési 1993, Gioia & Cordeiro 1996, Molnár et al 1998, Cellere et al 2002, Eiras et al 2005a, 2007, Martins & Onaka 2006; even fewer have been described using light and ultrastructural observations (Casal et al 1996, 2002, 2009, Tajdari et al 2005 In this paper, we describe light and ultrastructural data for a new myxosporidian species found in the gill of the teleost fish, Sciades herzbergii, which was collected from a river Northeast of Brazil. …”

“…Most of the Brazilian Myxobolus species have been described based on only light microscopy descriptions and diagrammatic drawings (Walliker 1969, Kent & Hoffman 1984, Molnár & Békési 1993, Gioia & Cordeiro 1996, Molnár et al 1998, Cellere et al 2002, Eiras et al 2005a, 2007, Martins & Onaka 2006; even fewer have been described using light and ultrastructural observations (Casal et al 1996, 2002, 2009, Tajdari et al 2005, Adriano et al 2009a) as well as molecular analyses (Adriano et al 2009b). However, some specific aspects of the histopathology have been simultaneously reported by invasion of different organs; Myxobolus spp most frequently infects the gills of fish (Molnár & Békési 1993, Molnár 2002, Eiras et al 2005a, Casal et al 2006, Lom & Dyková 2006, Adriano et al 2009a, Azevedo et al 2009.…”

“…However, some specific aspects of the histopathology have been simultaneously reported by invasion of different organs; Myxobolus spp most frequently infects the gills of fish (Molnár & Békési 1993, Molnár 2002, Eiras et al 2005a, Casal et al 2006, Lom & Dyková 2006, Adriano et al 2009a, Azevedo et al 2009.…”

Synopsis of the species of Myxobolus Bütschli, 1882 (Myxozoa: Myxosporea, Myxobolidae) described between 2005 and 2013

“…Also, molecular studies allowed the separation of morphologically indistinguishable species Molnár et al, 2010) and are extremely useful for the research on these parasites. Eiras et al (2005a, b) published a synopsis of the Myxobolus species listing the characteristics of 744 nominal species. Since then 112 new species were described within a wide geographical range, all of them infecting fish.…”