The toad fly Lucilia bufonivora: its evolutionary status and molecular identification

Abstract

The blow fly genus Lucilia is composed largely of saprophages and facultative myasis agents, including the economically important species Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) and Lucilia sericata (Meigen). Only one species is generally recognized as an obligate agent of myiasis, Lucilia bufonivora Moniez, and this is an obligate parasite of toads. Lucilia silvarum (Meigen), a sister species, behaves mainly as a carrion breeder; however, it has also been reported as a facultative parasite of amphibians. Morphologically, these species are almost identical, and historically this has led to misidentification, taxonomic ambiguity and a paucity of studies of L. bufonivora. In this study, dipterous larvae were analysed from toad myiasis cases from the U.K., The Netherlands and Switzerland, together with adult specimens of fly species implicated in amphibian parasitism: L. bufonivora, L. silvarum and Lucilia elongata Shannon (from North America). Partial sequences of two genes, cox1 and ef1α, were amplified. Seven additional blow fly species were analysed as outgroups. Bayesian inference trees of cox1, ef1α and a combined-gene dataset were constructed. All larvae isolated from toads were identified as L. bufonivora and no specimens of L. silvarum were implicated in amphibian myiasis. This study confirms L. silvarum and L. bufonivora as distinct sister species and provides unambiguous molecular identification of L. bufonivora.

Ecological and geographical speciation in Lucilia bufonivora: The evolution of amphibian obligate parasitism

“…Phylogenetic resolution of the L. bufonivora species group is often poor when using nuclear DNA markers (McDonagh and Stevens, 2011; Arias-Robledo et al, 2019a). In fact, a recent study failed to differentiate L. elongata from L. silvarum using the gene EF1α , highlighting the close relationships of this species group (Arias-Robledo et al, 2019a). In the present study, single-gene phylogenies inferred from both per and ITS2 sequence data provided clearer resolution on the relationships of this species group and recovered L. elongata as being closely related to L. silvarum .…”

“…In contrast, L. silvarum is distributed throughout the Holarctic (Rognes, 1991; Tantawi and Whitworth, 2014) and this species has been reported as being involved in amphibian myiasis in Europe (Duncker, 1891; Mortensen, 1892; Linder, 1924; Stadler, 1930). Nevertheless, a recent study found that in the UK, the Netherlands and Switzerland amphibian myiasis appears to be caused only by L. bufonivora , as no specimens of L. silvarum were found to be implicated in the disease (Arias-Robledo et al, 2019a). Moreover, the saprophagous behaviour of L. silvarum has been previously well documented (Hanski and Kuusela, 1977; Hanski, 1987; Prinkkila and Hanski, 1995; Fremdt et al, 2012).…”

“…The mitochondrial gene cytochrome c oxidase subunit one ( COX1 ) has proved to be a useful molecular marker for the detection and identification of various parasites and pathogens, including, but not limited to, nematodes (Aravindan et al, 2017), trypanosomes (Rodrigues et al, 2017), ticks (Chitimia et al, 2010) and oestrid flies (Samuelsson et al, 2013). Additionally, this mtDNA marker has provided clear resolution on the relationships of the L. bufonivora species group: L. bufonivora , L. elongata and L. silvarum (McDonagh and Stevens, 2011; Arias-Robledo et al, 2019a). In contrast, the various nuclear markers used to date have yielded mixed results and some are clearly not suitable for resolving the relationships of these recently diverged taxa (McDonagh and Stevens, 2011; Arias-Robledo et al, 2019a).…”

“…Additionally, this mtDNA marker has provided clear resolution on the relationships of the L. bufonivora species group: L. bufonivora , L. elongata and L. silvarum (McDonagh and Stevens, 2011; Arias-Robledo et al, 2019a). In contrast, the various nuclear markers used to date have yielded mixed results and some are clearly not suitable for resolving the relationships of these recently diverged taxa (McDonagh and Stevens, 2011; Arias-Robledo et al, 2019a). Nonetheless, some other phylogenetic studies on Calliphoridae have shown that the use of optimised nuclear markers, such as the period gene ( per ) or the non-coding ribosomal DNA (rDNA) Internal Transcribed Spacer 2 ( ITS2 ), are suitable for phylogenetic analysis of closely related blowfly taxa (Marinho et al, 2011; Williams and Villet, 2013).…”

A case of Dipteran parasitism in Trachycephalus typhonius (Anura: Hylidae), with a summary of myiasis parasitism in anurans

“…Brumpt 1934a,b, Hendriks 1974, Garanin and Shaldybin 1976, Strijbosch 1980, Nijs 1984, Spieler 1990, Albrecht et al 1996, Zavadil 1997, Gosá et al 2009, Salazar et al 2012, Arias-Robledo et al 2019 Lucilia silvarum 1 Duncker 1891, Stadler 1930, Heim de Balsac 1933, Sandner 1955, Eaton et al 2008 Lucilia sp. 1 Gerber 1950, Janzen 1994…”