Novel mitochondrial gene content and gene arrangement indicate illegitimate inter-mtDNA recombination in the chigger mite, Leptotrombidium pallidum

To better understand the evolution of mitochondrial (mt) genomes in the Acari (mites and ticks), we sequenced the mt genome of the chigger mite, Leptotrombidium pallidum (Arthropoda: Acari: Acariformes). This genome is highly rearranged relative to that of the hypothetical ancestor of the arthropods and the other species of Acari studied. The mt genome of L. pallidum has two genes for large subunit rRNA, a pseudogene for small subunit rRNA, and four nearly identical large noncoding regions. Nineteen of the 22 tRNAs encoded by this genome apparently lack either a T-arm or a D-arm. Further, the mt genome of L. pallidum has two distantly separated sections with identical sequences but opposite orientations of transcription. This arrangement cannot be accounted for by homologous recombination or by previously known mechanisms of mt gene rearrangement. The most plausible explanation for the origin of this arrangement is illegitimate inter-mtDNA recombination, which has not been reported previously in animals. In light of the evidence from previous experiments on recombination in nuclear and mt genomes of animals, we propose a model of illegitimate inter-mtDNA recombination to account for the novel gene content and gene arrangement in the mt genome of L. pallidum.

The head and body lice of humans are genetically distinct (Insecta : Phthiraptera, Pediculidae): evidence from double infestations

Little is known about the population genetics of the louse infestations of humans. We used microsatellite DNA to study 11 double infestations, that is, hosts infested with head lice and body lice simultaneously. We tested for population structure on a host, and for population structure among seven hosts that shared sleeping quarters. We also sought evidence of migration among louse populations. Our results showed that: (i) the head and body lice on these individual hosts were two genetically distinct populations; (ii) each host had their own populations of head and body lice that were genetically distinct to those on other hosts; and (iii) lice had migrated from head to head, and from body to body, but not between heads and bodies. Our results indicate that head and body lice are separate species.

Two new hemiurine species (Digenea : Hemiuridae) from Spratelloides robustus Ogilby (Clupeiformes : Clupeidae) off south-western Australia and records of Parahemiurus merus (Linton, 1910) from Australian and New Caledonian waters

Two new species of hemiurine hemiurid are described from Spratelloides robustus off Woodman Point in southern Western Australia. Hemiurus lignator n. sp. differs from its congeners by a combination of similar-sized suckers, long sinus-sac, tandem testes, relatively elongate shape and unthickened seminal vesicle wall. Parahemiurus xylokopos n. sp. differs from its congeners in a combination of its squat form, its distinctly lobed vitellarium and the proximity of the gonads to the ventral sucker. P. merus (Linton, 1910) is reported from Acanthopagrus australis, Pomatomus saltatrix and Trachinotus coppingeri off northern New South Wales, Caranx sexfasciatus, Scorpis lineolata, Siganus nebulosus, Thunnus tonggol and T. coppingeri off southern Queensland, Cephalopholis boenak and Euthynnus affinis off Heron Island, southern Great Barrier Reef, P. saltatrix off southern Western Australia and Priacanthus hamrur off New Caledonia.

Investigation into the ability of Gluconacetobacter sacchari to live as an endophyte in sugarcane

The relatively low numbers and sporadic pattern of incidence of the acetic acid bacterium Gluconacetobacter sacchari with the pink sugarcane mealybug (PSMB) Saccharicoccus sacchari Cockerell (Homoptera: Pseudococcidae) over time and from different sugarcane-growing regions do not indicate that Glac. sacchari is a significant commensal of the PSMB, as has been previously proposed. This study was conducted to investigate the hypothesis that Glac. sacchari is, like its closest relative Glac. diazotrophicus, an endophyte of sugarcane (Saccharum officinarium L.). In this study, both Glac. sacchari and Glac. diazotrophicus were isolated from internal sugarcane tissue, although the detection of both species was sporadic in all sugarcane-growing regions of Queensland tested. To confirm the ability of Glac. sacchari to live endophytically, an experiment was conducted in which the roots of micropropagated sugarcane plantlets were inoculated with Glac. sacchari, and the plantlets were subsequently examined for the presence of the bacterium in the stem cells. Pure cultures of Glac. sacchari were grown from homogenized surface sterilized sugarcane stems inoculated with Glac. sacchari. Electron microscopy was used to provide further conclusive evidence that Glac. sacchari lives as an endophyte in sugarcane. Scanning electron microscopy of (SEM) sugarcane plantlet stems revealed rod-shaped cells of Glac. sacchari within a transverse section of the plantlet stem cells. The numbers of bacterial cells inside the plant cell indicated a successful infection and colonization of the plant tissue. Using transmission electron microscopy, (TEM) bacterial cells were more difficult to find, due to their spatial separation. In our study, bacteria were mostly found singularly, or in groups of up to four cells inside intercellular spaces, although bacterial cells were occasionally found inside other cells.

The use and implications of ribosomal DNA sequencing for the discrimination of digenean species

In just over a decade, the use of molecular approaches for the recognition of parasites has become commonplace. For trematodes, the internal transcribed spacer region of ribosomal DNA (ITS rDNA) has become the default region of choice. Here, we review the findings of 63 studies that report ITS rDNA sequence data for about 155 digenean species from 19 families, and then review the levels of variation that have been reported and how the variation has been interpreted. Overall, complete ITS sequences (or ITS1 or ITS2 regions alone) usually distinguish trematode species clearly, including combinations for which morphology gives ambiguous results. Closely related species may have few base differences and in at least one convincing case the ITS2 sequences of two good species are identical. In some cases, the ITS1 region gives greater resolution than the ITS2 because of the presence of variable repeat units that are generally lacking in the ITS2. Intraspecific variation is usually low and frequently apparently absent. Information on geographical variation of digeneans is limited but at least some of the reported variation probably reflects the presence of multiple species. Despite the accepted dogma that concerted evolution makes the individual representative of the entire species, a significant number of studies have reported at least some intraspecific variation. The significance of such variation is difficult to assess a posteriori, but it seems likely that identification and sequencing errors account for some of it and failure to recognise separate species may also be significant. Some reported variation clearly requires further analysis. The use of a yardstick to determine when separate species should be recognised is flawed. Instead, we argue that consistent genetic differences that are associated with consistent morphological or biological traits should be considered the marker for separate species. We propose a generalised approach to the use of rDNA to distinguish trematode species.

Relationships of sauries and needlefishes (Teleostei : Scomberesocoidea) to the internally fertilizing halfbeaks (Zenarchopteridae) based on the pharyngeal jaw apparatus

The 40 life history, myological, and osteological characters that Tibbetts (1992) used in his study of the hemiramphids are evaluated for both saury genera (Cololabis and Scomberesox) to determine if the Scomberesocidae are more closely related to the Zenarchopteridae, to the needlefishes (Belonidae), or to the halfbeaks (Hemiramphidae) and flyingfishes (Exocoetidae). Data were analyzed using PAUP*, and eight equally parsimonious trees were found (70 steps, CI 0.814, RI 0.938). This analysis indicates that sauries are most closely related to needlefishes, supporting the historical concept of the superfamily Scomberesocoidea as a monophyletic assemblage. A caudal displacement of the origin of the retractor dorsalis muscle is a tentative additional synapomorphy for all four saury species. Zenarchopteridae is strongly supported as a valid family sister to the Scomberesocoidea (decay index = 19, bootstrap = 100). Resolution of the internal structure of the Belonidae and the Hemiramphidae requires the identification of additional characters and examination of a greater number of taxa.

An exceptionally rich complex of Sanguinicolidae von Graff, 1907 (Platyhelminthes : Trematoda) from Siganidae, Labridae and Mullidae (Teleostei : Perciformes) from the Indo-West Pacific Region

We describe an unprecedented radiation of sanguinicolid blood flukes ( Digenea: Sanguinicolidae) from two species of Labridae (Choerodon venustus and C. cauteroma), seven species of Mullidae (Mulloidichthys vanicolensis, Parupeneus barberinoides, P. barberinus, P. bifasciatus, P. cyclostomus, P. indicus and P. multifasciatus) and ten species of Siganidae (Siganus argenteus, S. corallinus, S. doliatus, S. fuscescens, S. lineatus, S. margaritiferus, S. puellus, S. punctatus, S. virgatus and S. vulpinus) from sites off Australia and Palau. The flukes were morphologically similar in having the combination of a long thread-like body, tegumental spines in lateral transverse rows, a vestigial oral sucker bearing concentric rows of fine spines, an H-shaped intestine, a cirrussac, a notch level with the male genital pore, a lateral or post-ovarian uterus, a uterine chamber and separate genital pores. These species are divided into two genera on the basis of testis number. Sanguinicolids from Siganus fuscescens have a single large testis between the intestinal bifurcation and the ovary and are placed in Ankistromeces Nolan & Cribb, 2004. Species from the remaining nine species of Siganidae, Labridae and Mullidae are placed in Phthinomita n. g.; these species have two testes, the anterior testis being large and between the intestinal bifurcation and the ovary whereas the small posterior testis is at the posterior end of the body and appears rudimentary or degenerate and probably non-functional. The second internal transcribed spacer (ITS2) of ribosomal DNA ( rDNA) from 29 host/parasite/location combinations (h/p/l) was sequenced together with that of Ankistromeces mariae Nolan & Cribb, 2004 for comparison. From 135 samples we found 19 distinct genotypes which were interpreted as representing at least that many species. Replicate sequences were obtained for 25 of 30 h/p/l combinations ( including A. mariae); there was no intraspecific variation between replicates sequences for any of these. Interspecific variation ranged from 1 - 41 base differences (0.3 - 12.7% sequence divergence). The 19 putative species were difficult to recognise by morphological examination. We describe 13 new species; we do not describe (= name) six species characterised solely by molecular sequences and three putative species for which morphological data is available but for which molecular data is not. We have neither morphological nor molecular data for sanguinicolids harboured in five hosts species ( Siganus margaritiferus, S. puellus, Choerodon cauteroma, Parupeneus indicus and P. multifasciatus) in which we have seen infections. Where host species were infected in different localities they almost always harboured distinct species. Some host species ( for example, S. argenteus and S. lineatus from Lizard Island) harboured two or three species in a single geographical location. This suggests that, for parts of this system, parasite speciation has outstripped host speciation. Distance analysis of ITS2 showed species from each host family ( Siganidae, Mullidae and Labridae) did not form monophyletic clades to the exclusion of species from other host families. However, a host defined clade was formed by the sequences from sanguinicolids from S. fuscescens.

Cardicola Short, 1953 and Braya n. gen. (Digenea : Sanguinicolidae) from five families of tropical Indo-Pacific fishes

A survey of Pacific coral reef fishes for sanguinicolids revealed that two species of Lutjanidae (Lutjanus argentimaculatus, L. bohar), six species of Siganidae (Siganus corallinus, S. fuscescens, S. lineatus, S. margaritiferus, S. punctatus, S. vulpinus), seven species of Chaetodontidae (Chaetodon aureofasciatus, C. citrinellus, C. flavirostris, C. lineolatus, C. reticulatus, C. ulietensis, C. unimaculatus), three species of Scombridae (Euthynnus affinis, Scomberomorus commerson, S. munroi) and three species of Scaridae (Chlorurus microrhinos, Scarus frenatus, S. ghobban) were infected with morphologically similar sanguinicolids. These flukes have a flat elliptical body, a vestigial oral sucker, a single testis, separate genital pores and a post-ovarian uterus. However, these species clearly belong in two genera based on the position of the testis and genital pores. Sanguinicolids from Lutjanidae, Siganidae, Chaetodontidae and Scombridae belong in Cardicola Short, 1953; the testis originates anteriorly to, or at the anterior end of, the intercaecal field and does not extend posteriorly to it, the male genital pore opens laterally to the sinistral lateral nerve chord and the female pore opens near the level of the ootype ( may be anterior, lateral or posterior to it) antero-dextral to the male pore. Those from Scaridae are placed in a new genus, Braya; the testis originates near the posterior end of the intercaecal field and extends posteriorly to it, the male pore opens medially at the posterior end of the body and the female pore opens posterior to the ootype, antero-sinistral to the male pore. The second internal transcribed spacer (ITS2) of ribosomal DNA from these sanguinicolids and a known species, Cardicola forsteri Cribb, Daintith & Munday, 2000, were sequenced, aligned and analysed to test the distinctness of the putative new species. Results from morphological comparisons and molecular analyses suggest the presence of 18 putative species; 11 are described on the basis of combined morphological and molecular data and seven are not because they are characterised solely by molecular sequences or to few morphological specimens (n= one). There was usually a correlation between levels of morphological and genetic distinction in that pairs of species with the greatest genetic separation were also the least morphologically similar. The exception in this regard was the combination of Cardicola tantabiddii n. sp. from S. fuscescens from Ningaloo Reef ( Western Australia) and Cardicola sp. 2 from the same host from Heron Island ( Great Barrier Reef). These two parasite/ host/location combinations had identical ITS2 sequences but appeared to differ morphologically ( however, this could simply be due to a lack of morphological material for Cardicola sp. 2). Only one putative species ( Cardicola sp. 1) was found in more than one location; most host species harboured distinct species in each geographical location surveyed ( for example, S. corallinus from Heron and Lizard Islands) and some ( for example, S. punctatus, S. fuscescens and Chlorurus microrhinos) harboured two species at a single location. Distance analysis of ITS2 showed that nine species from siganids, three from scombrids and five from scarids formed monophyletic clades to the exclusion of sanguinicolids from the other host families. Cardicola milleri n. sp. and C. chaetodontis Yamaguti, 1970 from lutjanids and chaetodontids, respectively, were the only representatives from those families that were sequenced. Within the clade formed by sanguinicolids from Siganidae there wasa further division of species; species from the morphologically similar S. fuscescens and S. margaritiferus formed a monophyletic group to the exclusion of sanguinicolids from all other siganid species.

Cliona minuscula, sp nov (Hadromerida : Clionaidae) and other bioeroding sponges that only contain tylostyles

A new bioeroding sponge belonging to the genus Cliona is described from the Australian Great Barrier Reef, Cliona minuscula, sp. nov. As the sponge lacked microscleres, comparison with existing clionaid species was difficult. We considered 15 other species of Cliona with only tylostyles: C. alderi, C. arenosa. C. caesia nov. comb., C. californiana, C. celata, C. delitrix, C. dissimilis, C. ecaudis, C. insidiosa, C. janitrix, C. kempi, C. laticavicola, C. macgeachii, C. millepunctata and C. peponaca. Characters of all species are presented in table-form to facilitate comparison during future studies. We listed additional species of Cliona that were not directly compared to the new species, because they were either invalid, insufficiently described, or they may not be obligate bioeroders. The form and dimensions of the megascleres of C. minuscula, sp. nov. indicated that it is distinct from all considered species. Its mean tylostyle dimensions were 225.3 mu m length, 4.5 mu m shaft width and 6.8 mu m tyle width, which is comparatively small. Because other morphological features were small as well ( erosion chambers, papillar diameter), this species was named C. minuscula. The species record for sponges of the genus Cliona reported from Australia is now 11.

Diverse members of the Ralstonia solanacearum species complex cause bacterial wilts of banana

The bacterial wilts of banana known as Moko disease, Bugtok disease and blood disease are caused by members of the R. solanacearum species complex. R. solanacearum is a heterogeneous species which has been divided into 4 genetic groups known as phylotypes. Within the R. solanacearum species complex, strains that cause Moko and Bugtok diseases belong to phylotype II. The blood disease bacterium, the cause of blood disease, belongs to phylotype IV. This study employs phylogenetic analysis of partial endoglucanase gene sequences to further assess the evolutionary relationships between strains of R. solanacearum causing Moko disease and Bugtok disease and the relationship of the blood disease bacterium to other R. solanacearum strains within phylotype IV of the R. solanacearum species complex. These analyses showed that R. solanacearum Moko disease-causing strains are polyphyletic, forming four related, but distinct, clusters of strains. One of these clusters is a previously unrecognised group of R. solanacearum Moko disease-causing strains. It was also found that R. solanacearum strains that cause Bugtok disease are indistinguishable from strains causing Moko disease in the Philippines. Phylogenetic analysis of partial endoglucanase gene sequences of the strains of the blood disease confirms a close relationship of these strains to R. solanacearum strains within phylotype IV of the R. solanacearum species complex.

Hematozoa of teleosts from Lizard Island, Australia with some comments on their possible mode of transmission and the description of a new hemogregarine species

Little is known of the blood parasites of coral reef fishes and nothing of how they are transmitted. We examined 497 fishes from 22 families, 47 genera, and 78 species captured at Lizard Island, Australia, between May 1997 and April 2003 for hematozoa and ectoparasites. We also investigated whether gnathiid isopods might serve as potential vectors of fish hemogregarines. Fifty-eight of 124 fishes caught in March 2002 had larval gnathiid isopods, up to 80 per host fish, and these were identified experimentally to be of 2 types, Gnathia sp. A and Gnathia sp. B. Caligid copepods were also recorded but no leeches. Hematozoa, found in 68 teleosts, were broadly hemogregarines of 4 types and an infection resembling Haemohormidium. Mixed infections (hemogregarine with Haemohormidium) were also observed, but no trypanosomes were detected in blood films. The hemogregarines were identified as Haemogregarina balistapi n. sp., Haemogregarina tetraodontis, possibly Haemogregarina bigemina, and an intraleukocytic hemogregarine of uncertain status. Laboratory-reared Gnathia sp. A larvae, fed experimentally on bruslitail tangs, the latter heavily infected with the H. bigemina-like hemogregarine, contained hemogregarine gamonts and possibly young oocysts up to 3 days postfeeding, but no firm evidence that gnathiids transmit hemogregarines at Lizard Island was obtained.