Distinct Genetic Lineages of Bactrocera caudata (Insecta: Tephritidae) Revealed by COI and 16S DNA Sequences

The fruit fly Bactrocera caudata is a pest species of economic importance in Asia. Its larvae feed on the flowers of Cucurbitaceae such as Cucurbita moschata. To-date it is distinguished from related species based on morphological characters. Specimens of B. caudata from Peninsular Malaysia and Indonesia (Bali and Lombok) were analysed using the partial DNA sequences of cytochrome c oxidase subunit I (COI) and 16S rRNA genes. Both gene sequences revealed that B. caudata from Peninsular Malaysia was distinctly different from B. caudata of Bali and Lombok, without common haplotype between them. Phylogenetic analysis revealed two distinct clades, indicating distinct genetic lineage. The uncorrected ‘p’ distance for COI sequences between B. caudata of Malaysia-Thailand-China and B. caudata of Bali-Lombok was 5.65%, for 16S sequences from 2.76 to 2.99%, and for combined COI and 16S sequences 4.45 to 4.46%. The ‘p’ values are distinctly different from intraspecific ‘p’ distance (0–0.23%). Both the B. caudata lineages are distinctly separated from related species in the subgenus Zeugodacus – B. ascita, B. scutellata, B. ishigakiensis, B. diaphora, B. tau, B. cucurbitae, and B. depressa. Molecular phylogenetic analysis indicates that the B. caudata lineages are closely related to B. ascita sp. B, and form a clade with B. scutellata, B. ishigakiensis, B. diaphora and B. ascita sp. A. This study provides additional baseline for the phylogenetic relationships of Bactrocera fruit flies of the subgenus Zeugodacus. Both the COI and 16S genes could be useful markers for the molecular differentiation and phylogenetic analysis of tephritid fruit flies

Biochemical genetic relationship of Thailand and Hawaii isolates of Parastrongylus cantonensis (Nematoda: Angiostrongylidae)

The genetic relationship of the Thailand and Hawaii isolates (strains) of the rat lungworm Parastrongylus (=Angiostrongylus) cantonensis was investigated by gene–enzyme systems using vertical polyacrylamide slab gel electrophoresis. Six gene–enzyme systems were successfully determined, with each being represented by two presumptive loci. Glucose phosphate dehydrogenase, glucose phosphate isomerase, lactate dehydrogenase, malate dehydrogenase and malic enzyme were monomorphic at both loci, and the respective bands exhibited similar mobility in both isolates implying absence of genetic variation. Of the two phosphoglucomutase loci, the faster-moving locus (PGM-1) was polymorphic in the Hawaii isolate, represented by two alleles, the faster-moving, less common Pgm-1A (allele frequency = 0.36 ± 0.03) and the slower-moving, more common Pgm-1B (allele frequency = 0.64), with heterozygosity of 0.43. PGM-1 was monomorphic in the Thailand isolate, represented by the faster-moving Pgm-1A allele. The slower-moving PGM-2 locus was invariant, with a single band of enzyme activity, in the female worms of both the Thailand and Hawaii isolates. There was no detectable enzyme activity at this PGM-2 locus in the male worms of both isolates. The non-expression or ‘null’ PGM-2 phenotype in the male worms was presumed to be sex-limited. Based on the six gene–enzyme systems with a total of 12 presumptive loci, it can be concluded that the Thailand and Hawaii isolates of P. cantonensis are genetically very similar, with a genetic distance of D = 0.03. The very low proportion of polymorphic loci (P = 0.08) in the Hawaii isolate and its absence in the Thailand isolate may be attributed to founder effect (a special type of genetic drift)

Meiotic chromosomes and sex determination mechanism in Thailand and Hawaii isolates of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae)

Angiostrongylus cantonensis, the nematode lungworm of rats, has a XX/X0 sex-determination mechanism. The chromosome constitution consists of 10 autosomes, with 2n = 12, XX in the female and 2n = 11, X0 in the male. Meiosis-I shows five bivalents and one univalent for the male worm, and six bivalents for the female worm. The chromosome constitution of the Thailand and Hawaii isolates of A. cantonensis is similar to those reported for the taxa from Japan, Egypt and mainland China

Angiostrongylus mackerrasae and A. cantonensis (Nematoda: Metastrongyloidea) belong to same genetic lineage: evidence from mitochondrial protein-coding genes

Angiostrongylus mackerrasae is a parasitic nematode of rats found in Australia. When first reported, it was referred to as A. cantonensis. Recent molecular studies, including the mitochondrial genome, indicate that it is highly similar to A. cantonensis. These studies did not include A. malaysiensis, another member of the A. cantonensis species complex, for comparison. The present study examined the genetic distance and phylogenetic relationship between the component taxa (A. cantonensis, A. mackerrasae and A. malaysiensis) of the A. cantonensis species complex, based on the 12 protein-coding genes (PCGs) of their mitochondrial genome. Both the nucleotide and amino acid sequences were analysed. Angiostrongylus mackerrasae and A. cantonensis are members of the same genetic lineage and both are genetically distinct from A. malaysiensis. The genetic distance based on concatenated nucleotide sequences of 12 mt-PCGs between A. mackerrasae and A. cantonensis from Thailand is p = 1.73%, while that between the Thai and Chinese taxa of A. cantonensis is p = 3.52%; the genetic distance between A. mackerrasae and A. cantonensis from China is p = 3.70%. The results indicate that A. mackerrasae and A. cantonensis belong to the same genetic lineage, and that A. mackerrasae may be conspecific with A. cantonensis. It remains to be resolved whether A. mackerrasae is conspecific with A. cantonensis or undergoing incipient speciation

Sex-chromosome constitution and supernumerary chromosome in the large bandicoot rat, Bandicota indica (Rodentia, Muridae) from Peninsular Malaysia

The Peninsular Malaysia taxon of Bandicota indica has a standard complement of 44 chromosomes, with medium-sized subacrocentric X and small submetacentric Y chromosomes. The present study reveals variation in the size and morphology of the X-xhromosome in B. indica with 2n = 44. The difference in size of the X-chromosome is attributed to variation in constitutive heterochromatin. Excepting the X-chromosome, the karyotype of the Malaysian taxon is similar to the Indian B. indica nemorivaga with 2n = 44. It differs from the Thailand taxon in the number of biarmed and uniarmed autosomes. A male specimen (with 45 chrosomes) of the Malaysian taxon possessed a supernumerary (B) chromosome which is identical to that reported in B. indica nemorivaga

Immunochromatographic test for rapid serological diagnosis of human angiostrongyliasis

Objectives: The serological diagnosis of human infection with Angiostrongylus cantonensis remains problematic because there are no commercially available validated tests. Most laboratories use domestically prepared tests such as the enzyme-linked immunosorbent assay (ELISA) or immunoblotting. Since laboratory facilities are not always available in endemic areas, we developed and assessed a rapid lateral flow immunochromatographic assay (AcQuick Dx Test) to detect anti-A. cantonensis antibodies in human serum. Methods: The test device was assembled with purified 31-kDa glycoprotein as diagnostic antigen and with gold-labelled anti-human immunoglublin-G as the detector reagent. A total of 97 serum samples were tested – 19 samples from clinically diagnosed patients with detectable A. cantonensis-specific antibody in immunoblotting; 43 samples from patients with other parasitic diseases, i.e. gnathostomiasis (n = 13), toxocariasis (n = 2), trichinellosis (n = 2), hookworm infection (n = 4), filariasis (n = 5), cysticercosis (n = 9), paragonimiasis (n = 2), opisthorchiasis (n = 3), and malaria (n = 3); and 35 samples from normal healthy subjects. Results: The sensitivity, specificity, positive predictive value and negative predictive value of AcQuick Dx Test to detect anti-A. cantonensis specific antibodies in serologically confirmed angiostrongyliasis cases, were 100%, 98.72%, 95% and 100%, respectively. Positive AcQuick Dx was observed in 1 of 4 cases with hookworm infections. No positive AcQuick Dx was observed in cases with other parasitic diseases, and the individual healthy subjects. Conclusions: AcQuick Dx Test is rapid, highly sensitive and specific, and easy to perform without additional equipment or ancillary supplies. It yields results that are interpreted visually, and possesses a long shelf-life at room temperature. Thus, it can be applied as an additional test for clinical diagnostic support of angiostrongyliasis either in conventional laboratories or for remote areas where laboratory infrastructure is not available

Genetically Determined Colour Polymorphism In Larvae Of Ceriagrion Chaoi (Insecta: Odonata: Coenagrionidae)

Yong, Hoi Sen, Lim, Phaik-Eem, Tan, Ji, Eamsobhana, Praphathip (2013): Genetically Determined Colour Polymorphism In Larvae Of Ceriagrion Chaoi (Insecta: Odonata: Coenagrionidae). Raffles Bulletin of Zoology 61 (1): 47-51, DOI: http://doi.org/10.5281/zenodo.535158

Genetic differentiation of Anisakis species (Nematoda: Anisakidae) in marine fish Priacanthus tayenus from Gulf of Thailand

Members of the genus Anisakis are parasitic nematodes of the family Anisakidae. They are potential zoonotic parasites, causing anisakiasis in humans who consume raw or undercooked seafood (fish or squid) infected with the larvae of this nematode. In the present study, anisakid nematodes collected from the marine fish Priacanthus tayenus (Purple-spotted big-eye) caught from the Gulf of Thailand were examined morphologically and characterized genetically by DNA sequence analysis. Sequence data from the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2) gene were used to identify these nematodes to species level and to evaluate the phylogenetic relationship among various taxa. All the 15 third-stage larvae of Anisakis nematodes investigated in this study belonged to the same genetic lineage as the A. typica species complex (named here as A. typica sp. T – T for Thailand). Eight mtDNA cox2 haplotypes were revealed in the 15 isolates of this Anisakis from Thailand. The mtDNA cox2 haplotypes of A. typica sp. T from Thailand were genetically distinct from those of the A. typica sensu stricto. Taxonomic description of this A. typica sp. T as a distinct species however awaits the availability of adult specimens