Heterorhabditis amazonensis n. sp. (Rhabditida: Heterorhabditidae) from Amazonas, Brazil

Abstract

In a survey of entomopathogenic nematodes in Brazil, a nematode isolate of the genus Heterorhabditis was found. The nematode was collected from soil by the insect-baiting technique and maintained in the laboratory on last instar Galleria mellonella (L.) larvae. Morphological and molecular studies of the isolate showed that the nematode is a new species. Light and scanning electron microscopy, DNA characterisation and phylogeny were used for this description. Heterorhabditis amazonensis n. sp. is morphologically similar to H. baujardi, H. floridensis, H. mexicana and H. indica, and can be distinguished from these species mainly by male and female characters. Fifty percent of Heterorhabditis amazonensis n. sp. males have two pairs of bursal papillae in the terminal group; 25% with two papillae on one side and one papilla on the other side and 25% with one pair of papillae. Twenty percent of the population has a curved gubernaculum. The percentage of the gubernaculum to spicule length (GS%) is lower than that of H. mexicana (50 vs 56), and the length of the spicule relative to anal body diam. (SW%) is lower than that of H. mexicana (152 vs 167) and H. baujardi (152 vs 182). The female can be differentiated from related species by its unique vulva pattern. In a phylogenetic tree, the new species, H. floridensis, H. baujardi and H. mexicana form a monophyletic group, a sister group to H. indica. The new species has evolved three autapomorphic nucleotide character states, differing from its sister taxa H. mexicana at 22, and H. baujardi at 15, aligned positions.

Host-seeking behavior of the Heterorhabditis amazonensis nematode in response to stimulant sources1

“…Heterorhabditis amazonensis RSC5 was isolated from soil in Benjamin Constant, Amazonas state, Brazil (Andaló et al 2006), and maintained in Erlenmeyer flasks containing 500-1,000 infective juveniles mL -1 , in an aqueous suspension, and then placed in an incubator at 16 ± 1 ºC, for at most two months. For use in the experiments, the infective juveniles were multiplied in Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae), which was reared at the Universidade Federal de Lavras, using an artificial diet modified by Parra (1998).…”

“…The same methodology was used to evaluate the infective juveniles displacement direction, with respect to garlic seedlings, S. frugiperda larvae, garlic plant root exudates and S. frugiperda larvae feeding on garlic seedlings (based on the results of previous tests) (Andaló et al 2014). The S. frugiperda larvae were buried in the sand at 24 h after the seedlings were transplanted, allowing them to be established.…”

Studies on entomopathogenic nematodes in Brazil: past and future

“…Machado et al isolated H. indica IBCB-n5 in Itapetininga, São Paulo and tested against M. fryanus [12] . Andaló et al [50] collected soil samples from the region of Benjamin Constant, Amazonas, and isolated a new entomopathogenic nematode species of the genus Heterorhabditis. The nematode was baited using Galleria mellonella L. larvae and was named Heterorhabditis amazonensis.…”

“…In a survey performed in Lavras, Minas Gerais state, Andaló et al [53] isolated two populations of the genus Heterorhabditis that were obtained from the soil through the insect-bait technique in areas cultivated with sorghum (Sorghum sp.) and garlic (Allium sativum).…”

“…Moino et al [50] H. amazonensis IBCB n10, IBCB n24, IBCB n40, IBCB n44, IBCB n46 Dell'Acqua et al [56] H. indica IBCB n5 Dell'Acqua et al [56] H. indica LPP30 Minas [55] H. baujardi LPP22 Matos [61] H. amazonensis FCA07 Brida et al [58] S. rarum RS4, RS55, RS70, RS89, RS90, RS102, RS106 Barbosa-Negrisoli et al [54] Steinernema feltiae RS76 Barbosa-Negrisoli et al [54] Steinernema glaseri RS38 Barbosa-Negrisoli et al [54] Steinernema riobrave RS59 Barbosa-Negrisoli et al [54] Steinernema sp. RS69, RS92 Barbosa-Negrisoli et al [54] Steinernema brazilense n. sp.…”