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J Kathirithamby

Publications and source records attributed to J Kathirithamby.

9 recordsLinked to original sources
PubMed2006

The rapid divergence of the ecdysone receptor is a synapomorphy for Mecopterida that clarifies the Strepsiptera problem.

In arthropods, the regulation by ecdysteroids is mediated by the heterodimer between the ecdysone receptor (ECR; NR1H1) and ultraspiracle (USP/RXR; NR2B4) nuclear receptors. Both ECR and USP/RXR ligand-binding domains experienced a strong acceleration of evolutionary rate in Diptera and Lepidoptera, which belong to the superorder Mecopterida. We performed a phylogenetic analysis of 28 ECR and 30 USP/RXR protein sequences from 36 arthropod species, including representatives from Trichoptera, Mecoptera and Siphonaptera. Our data show that the acceleration of ECR and USP/RXR was a unique event in the ancestor of Mecopterida. Our analysis shows further that Strepsiptera ECR and USP/RXR sequences are unambiguously placed outside of the Mecopterida clade. Protein alignments reveal that eight of 11 synapomorphies support an affinity between Strepsiptera and Coleoptera sequences. The affiliation of Strepsiptera to Diptera should therefore be rejected.

Animals↗
PubMed2005

Assessing the odd secondary structural properties of nuclear small subunit ribosomal RNA sequences (18S) of the twisted-wing parasites (Insecta: Strepsiptera).

We report the entire sequence (2864 nts) and secondary structure of the nuclear small subunit ribosomal RNA (SSU rRNA) gene (18S) from the twisted-wing parasite Caenocholax fenyesi texensis Kathirithamby & Johnston (Strepsiptera: Myrmecolacidae). The majority of the base pairings in this structural model map on to the SSU rRNA secondary and tertiary helices that were previously predicted with comparative analysis. These regions of the core rRNA were unambiguously aligned across all Arthropoda. In contrast, many of the variable regions, as previously characterized in other insect taxa, had very large insertions in C. f. texensis. The helical base pairs in these regions were predicted with a comparative analysis of a multiple sequence alignment (that contains C. f. texensis and 174 published arthropod 18S rRNA sequences, including eleven strepsipterans) and thermodynamic-based algorithms. Analysis of our structural alignment revealed four unusual insertions in the core rRNA structure that are unique to animal 18S rRNA and in general agreement with previously proposed insertion sites for strepsipterans. One curious result is the presence of a large insertion within a hairpin loop of a highly conserved pseudoknot helix in variable region 4. Despite the extraordinary variability in sequence length and composition, this insertion contains the conserved sequences 5'-AUUGGCUUAAA-3' and 5'-GAC-3' that immediately flank a putative helix at the 5'- and 3'-ends, respectively. The longer sequence has the potential to form a nine base pair helix with a sequence in the variable region 2, consistent with a recent study proposing this tertiary interaction. Our analysis of a larger set of arthropod 18S rRNA sequences has revealed possible errors in some of the previously published strepsipteran 18S rRNA sequences. Thus we find no support for the previously recovered heterogeneity in the 18S molecules of strepsipterans. Our findings lend insight to the evolution of RNA structure and function and the impact large insertions pose on genome size. We also provide a novel alignment template that will improve the phylogenetic placement of the Strepsiptera among other insect taxa.

Animals↗
PubMed2004

Fine structure of the Nassonow's gland in the neotenic endoparasitic of female Xenos vesparum (Rossi) (Strepsiptera, Insecta).

Nassonow's gland consists of a number of cells with ducts that open on to the ventral surface of the brood canal in the cephalothoracic region of a neotenic female strepsipteran. The structural organization of the gland is reminiscent of the class 3 of the epidermal gland cells as defined by Noirot and Quennedey [Ann. Rev. Entomol. 19 (1974) 61], which consists of secretory and duct forming cells. The ultrastructure of the Nassonow's gland is described in female Xenos vesparum (Rossi) parasitic in the social wasp Polistes dominulus Christ. The large secretory cells are clustered in groups of three to four, rich in smooth endoplasmic reticulum and produce a secretion made up of lipids. In young females, just before mating, the ultrastructure of the cells and their inclusions indicate that they are active. In old-mated females the Nassonow's gland degenerates. Microvilli line an extracellular cavity and there are pores present in the irregularly thick cuticle of the efferent duct. The small duct forming cells, intermingle with epidermal cells, overlap secretory cells and produce a long efferent duct, the cuticle of which becomes thick close to its opening in the brood canal. Nassonow's gland could be the source of a sex pheromone, which might be capable of attracting the free-living male to a permanently endoparasitic female.

Animals↗
PubMed2004

Tiny genomes and endoreduplication in Strepsiptera.

Using flow cytometry, the genome sizes of two species of Strepsiptera were studied: that of male Caenocholax fenyesi texensis Kathirithamby & Johnston (Myrmecolacidae) at 108 Mb, which is the smallest insect genome documented to date; and those of male and female Xenos vesparum Rossi (Stylopidae), which are 1C = 130 and 133 Mb, respectively. The genome sizes of the following were analysed for comparative purposes: (a) the Hessian fly, Mayetiola destructor (Say), which was previously reported to be the smallest among insects: the male measured at 1C = 121 Mb and the female at 1C = 158 Mb; and (b) the female parasitic, haplodiploid, microhymenopteran wasp, Trichogramma brassicae Bezdenko, which measured at 1C = 246 Mb. The hosts of the strepsipterans were also measured: male Solenopsis invicta Buren, the red imported fire ant (host of male C. f. texensis), which is 1C = 753.3 Mb, and female Polistes dominulus Christ, the paper wasp (host of X. vesparum), is 1C = 301.4 Mb. Endoreduplication (4C) of the genome of the thorax of the male strepsipteran, and higher levels of endoduplication (4, 8, 16C) in the body of the larger female was observed. In contrast, little or no endoreduplication was observed, either in the Hessian fly, or in the parasitic wasp.

Animals↗
PubMed2003

New findings on sperm ultrastructure of Xenos vesparum (Rossi) (Strepsiptera, Insecta).

The systematic position of insect order Strepsiptera is still under debate. It was, therefore, thought of interest to examine the ultrastructure of a strepsipteran in a search for synapomorphies shared with Coleoptera, Diptera, or any other insect order. The fine structure of spermatozoa and the spermatid from Xenos vesparum (Rossi) was re-examined using scanning and transmission electron microscopy and a fixation technique that permits the visualization of the macromolecular organization of the organelles. The spermatozoon was shown to possess several traits that are characteristics of insects in general, such as a 9 + 9 + 2 axoneme, two mitochondrial derivatives containing a crystalline material and two 'zipper lines' present along the sperm tail. Seventeen protofilaments occurred along most of the accessory tubules, which reduced to 16 posteriorly. An acrosome is absent. The neck region contains a prominent centriolar adjunct, which gives rise to two accessory bodies which adhere to the mitochondrial derivatives, and to slender strands of the so-called intertubular material found between the accessory tubules. Of interest is the finding that the glycocalyx consists of prominent filamentous strands, similar to those found in siphonapterans, mecopterans and basal dipterans.

Animals↗
PubMed2001

Stand tall and they still get you in your Achilles foot-pad.

The free-living first-instar larvae of Strepsiptera (Insecta) are the infective stage of the parasitoid. They normally enter the host via the abdominal cuticle, and there have also been reports of entry via the egg of the host. The first-instar larvae of Stichotrema dallatorreanum Hofeneder in Papua New Guinea were found to enter the host orthopteran via the tarsi. This is, to my knowledge, the first report of entry of first-instar larvae of Strepsiptera via the attachment pads (euplantulae) of the host.

Animals↗
PubMed1999

Intron insertion as a phylogenetic character: the engrailed homeobox of Strepsiptera does not indicate affinity with Diptera.

The phylogenetic relationships of the order Strepsiptera are unclear. Affiliation to Coleoptera has been proposed, however this implies that dipteran halteres and strep-sipteran haltere-like organs evolved convergently. An alternative is a sister group relationship with Diptera. In this case, halteres could be homologous but a radical homeotic mutation may have switched their position to the Strepsipteran mesothorax. Ribosomal DNA sequence analysis has been used to support Dipteran affiliation, although this is controversial. Here we investigate the potential of an intron insertion site as a phylogenetic character. We find that the en homeobox gene of the strepsipteran Stichotrema dallatorreanum lacks a derived intron insertion shared by representatives of Diptera and Lepidoptera. We argue against a close affiliation between Strepsiptera and Diptera.

Amino Acid Sequence↗
PubMed1984

Atypical 'fibrillar' flight muscle in strepsiptera.

The fine structure of the principal and ancillary metathoracic flight muscle fibres in the adult male of a strepsipteran, Elenchus tenuicornis, is described. Power-producing dorsal longitudinal and dorso-ventral flight muscles show features consistent with myoneural asynchrony: myofibrils are large and discrete and are separated by large closely packed mitochondria; the sarcoplasmic reticulum is very reduced but engages with T-system membranes in dyads at the mid-sarcomere H-band level. With respect to other asynchronous insect flight muscles, the fibres of Elenchus are anomalous (i) in the small fibre diameter, (ii) in the variable contour of the myofibrils and (iii) in the absence of tracheolar invagination. The functional significance of these structural features is discussed. Ancillary metathoracic muscles are structurally comparable with other synchronous fibres in possessing an extensive SR compartment. Structural evidence for asynchrony in the flight mechanism of Strepsiptera is considered in the context of the evolution of this mechanism throughout the insect Orders.

Actins↗