Predation by larvae of Sepedon ruficeps (Diptera: Sciomyzidae) and population dynamics of the adult flies and their freshwater prey

Abstract

Predation by larvae of Sepedon ruficeps (Diptera: Sciomyzidae) and population dynamics of the adult flies and their freshwater prey. -The biology, phenology, and population dynamics of the adults of Sepedon ruficeps, the most widely distributed species of Sciomyzidae in Africa, were studied in Benin in permanent and temporary freshwater habitats. The feeding behavior of the larvae, expressed as the number of snails consumed, varies as a function of the species of prey utilized (Bulinus forskalii or Biomphalaria pfeifferi), as a function of the sizes of the predator/prey, and as a function of the stages of development of the larvae. In relation to the snail-prey, the second-and third instar-larvae show a food choice varying according to the specific ethology of the prey attacked. In all cases, the third-instar larvae always consume the largest number of snails and indifferently attack all of the species of snails utilized in laboratory rearings. The larvae consume, equally well, B. forskalii that are healthy or parasitized by the larvae of trematodes. Curiously, in laboratory rearings, in the absence of snails, the larvae of S. ruficeps are equally capable of attacking and developing at the expense of Aulophorus furcatus, a small, freshwater, oligochaete annelid (Naididae).

Key Aspects of the Biology of Snail-Killing Sciomyzidae Flies

“…Although the latter estimates are 6-12 times higher than the former estimates, they are consistent with a wider study in Irish turloughs (133,135). In a study of an assemblage of sciomyzids (three Sepedon and one Sepedonella species), with emphasis on Sepedon ruficeps (42), in temporary and permanent freshwater habitats in Bénin, West Africa, the population of S. ruficeps in both habitats peaked three months after maximal rainfall, but adults were present continually in the permanently wet habitat. This was one of the few studies, in addition to those by Eckblad & Berg (32) and Arnold (2), in which snail and sciomyzid populations were studied simultaneously.…”

“…For strict parasitoids, the larval stage tends to be completed on one host, whatever its size; such larvae rarely forage for additional hosts. For predators attacking aquatic snails, the relationship tends to be size dependent, with neonate larvae killing smaller snails and later instars killing larger snails (42). In terms of prey density, a strong functional response has been reported, ranging from Type I (second-and third-instar S. senex; 17) to Type II (second-and third-instar S. sphegea; 50) to Type III (third-instar S. senex; 17).…”

Life-cycle of the Afrotropical snail-killing flySepedon (Parasepedon) ruficepsBecker, 1923

“…In addition, larval feeding descriptions have been given for S. scapularis by Maharaj (1991) and Maharaj et al (1992), particularly concerning re lationships be tween the sizes of the larvae and the molluscs/prey during progression of larval feeding in South Africa. Likewise, Gbedjissi et al (2003) provided information for S. ruficeps in Benin. Knutson (2008) added some larval feeding behaviour aspects for S. trichrooscelis and S. h. hispanica.…”

Sexual dimorphism and the impact of temperature on the pupal and adult stages of Sepedon spinipes spinipes, a potential biological control agent of fascioliasis

“…One such option is biological control (Gormally, 1987(Gormally, , 1988McDonnell & Gormally, 2003). Since then, numerous studies world-wide have investigated their biological control potential of snail hosts of trematode diseases of humans and livestock (Chock et al, 1961;Bhuangprakone & Areekul, 1973;Barraclough, 1983;Beaver, 1989;Maharaj et al, 1992;Appleton et al, 1993;Gbedjissi et al, 2003). Since then, numerous studies world-wide have investigated their biological control potential of snail hosts of trematode diseases of humans and livestock (Chock et al, 1961;Bhuangprakone & Areekul, 1973;Barraclough, 1983;Beaver, 1989;Maharaj et al, 1992;Appleton et al, 1993;Gbedjissi et al, 2003).…”

“…Berg (1953) first conclusively proved that larvae within the family Sciomyzidae (Diptera) feed on snails. Since then, numerous studies world-wide have investigated their biological control potential of snail hosts of trematode diseases of humans and livestock (Chock et al, 1961;Bhuangprakone & Areekul, 1973;Barraclough, 1983;Beaver, 1989;Maharaj et al, 1992;Appleton et al, 1993;Gbedjissi et al, 2003). In Ireland, where fascioliasis cost the agricultural sector $25 million in 2001 (O'Brien & Scully, 2002), the possible control of the disease by sciomyzids was first assessed by Hope Cawdery & Lindsay (1977).…”