Heterorhabditis baujardi sp. n. (Rhabditida: Heterorhabditidae) from Vietnam and morphometric data for H. indica populations

Abstract

A survey of entomopathogenic nematodes in Vietnam yielded several Heterorhabditis isolates. The majority belonged to H. indica; their morphometrics are given in this paper. Three isolates collected in forests in Backan, Ninhbinh and Kontum provinces, Vietnam are here described as a new species Heterorhabditis baujardi sp. n. The new species is distinguished from the other ten valid Heterorhabditis species by a combination of morphological, morphometrical, and DNA characters. Heterorhabditis baujardi sp. n. is morphometrically similar to H. indica, but can be separated from this species by the shape of the gubernaculum and the number of normal pairs of genital papillae. The gubernaculum of H. baujardi sp. n. with the proximal end ventrally curved resembles that of H. bacteriophora. Heterorhabditis baujardi sp. n. can be separated from this latter species by a shorter body length of infective juveniles and longer spicules, longer gubernaculum, and a higher spicule length to anal body diameter ratio of males. The canonical discriminant analysis of morphometrical characters of both infective juveniles and males failed to discriminate Heterorhabditis baujardi sp. n. from H. indica. However, the new species was easily distinguished from H. downesi, H. marelatus, H. megidis and H. bacteriophora. Heterorhabditis baujardi sp. n. was slightly separated from H. bacteriophora by variables of the infective juveniles, but was clearly distinguishedby variables of the males. Cross-breeding tests using isolates of the new species and H. indica did not yield fertile progeny. Analysis of the ITS1 sequence of rDNA of H. baujardi sp. n. revealed substantial differences with other known ITS1 Heterorhabditis sequences. Phylogenetic relationships between Heterorhabditis species and the usefulness of morphological and molecular characters for identi cation of species from this group are discussed.

Variability study of entomopathogenic nematode populations (Heterorhabditidae) from Argentina

“…These nucleotide variations were not present in the rest of H. bacteriophora member of the clade B. Results obtained in our study are according to Adams et al (1998) andPhan et al (2003) who analyzing DNA sequences of the ITS1 of the Heterorhabditis genus, showed the type strain H. bacteriophora (HB1) differing from H. argentinensis in a single transversion (G vs. C) at position 620 (Adams et al, 1998;Phan et al, 2003) and in a single insertion of a C at position 348 as we mentioned (Phan et al, 2003). Therefore, by the results obtained in our study, H. argentinensis would be a sister taxa of H. bacteriophora, as was considered by Adams et al (1998).…”

“…In our study, morphometric variations were observed according to Nguyen (2016) which considered some morphological features as highly variables for Argentinian strains. The greatest differences were registered between H. argentinensis and all other H. bacteriophora populations, unlike between H. bacteriophora strains from different regions.…”

“…Morphometry of the parasites can be influenced by nutritional conditions inside the host, and environmental factors (Phan et al, 2003;Canto-Silva, et al, 2005). Stock and Mrácek (2000), mentioned that the geographical origin and habitat can influence on morphometric data, so even values obtained from a same host can change based on abiotic factors and rearing conditions.…”

“…However, Adams et al (1998) considered H. argentinensis and H. bacteriophora species as sister taxa and possibly even conspecific by PCR amplification of the ITS-1 region. Even, Nguyen (2016) mentioned the arrangement of the last three genital papillae of the bursa, as highly variable in strains of Argentina.…”

A survey of entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae (Nematoda: Rhabditida) in the north-west of Iran

“…For ML analysis, the appropriate substitution model of DNA evolution that best fitted the data set was determined by the Akaike Information Criterion with Model Test 3.06 (Posada & Crandall, 1998). Bootstrap analysis with 1000 replicates was conducted as a measure of support for individual clades for MP and ML trees (Phan et al, 2003).…”