Biology subjects

Raychoudhury, R.

Publications and source records attributed to Raychoudhury, R..

9 recordsLinked to original sources

bioRxiv2025

Morphological variations in external genitalia do not explain the interspecific reproductive isolation in Nasonia species complex (Hymenoptera: Pteromalidae)

External genitalia play a crucial role in the successful copulation of conspecific partners in insects. Due to their structural specificity, external genitalia have often been used for distinguishing closely related species in different insects. However, in the young Pteromalid species complex Nasonia, these structures have not received much attention. Nasonia is a genus of parasitoid wasps, that lays eggs and completes its life cycle in dipteran pupae. All behavioral studies (including this study) conducted on this genus indicate that varied prezygotic isolation operates among these recently diverged ([~]1 million years) species. Whether such prezygotic isolation is caused by the incompatibility in their reproductive organs is not known. Here, we studied the internal male reproductive system of the four species and show that all four species have a similar organisation and thus ruling it out as a potential barrier. Furthermore, to investigate the role of male external genitalia as a prezygotic barrier, we also examined the ultrastructural details, including aedeagal length, aedeagal aperture length, and digital spines. We show that all these parameters and sperm length show variations across the four species. However, these variations do not correlate with the female acceptance of the heterospecific males. Therefore, we conclude that there must be other olfactory or behavioral isolating mechanisms and spatial or temporal factors that maintain the reproductive isolation of these four species.

zoology↗

bioRxiv2025

Nasonia vitripennis males exhibit greater effort and competency in detecting hosts with conspecific females than other Nasonia males.

Nasonia is a species complex of four parasitoid wasps. N. vitripennis is cosmopolitan, while the other three species are micro-sympatric with it. This distribution can select for distinct species-specific mate recognition capabilities. However, whether Nasonia males can identify hosts with conspecific females against hosts with heterospecific females is not known. Therefore, we tested this hypothesis in a cafeteria-based choice assay and show that N. vitripennis males can distinguish hosts with conspecific wasps against those parasitised by N. giraulti and N. oneida, exhibiting longer search time and distance traversed with faster search speed. We also found that N. longicornis males can distinguish hosts with conspecific wasps, but only against the hosts parasitised by N. oneida. We further investigated the pairwise differences in the cuticular hydrocarbon (CHC) profiles of the parasitised hosts and adult female wasps. The results reveal that the males show this ability only when the compounds responsible for differences in adult female CHC profiles were also the key differentiators of the host CHC profiles. The comparative mate searching behaviour of males of all reported species within a genus has rarely been studied. Therefore, this study makes a significant contribution to our understanding of interspecific variation of conspecific-mate searching behaviour.

zoology↗

bioRxiv2024

Parasite-induced replacement of host microbiota- Impact of Xenos gadagkari parasitization on the microbiota of Polistes wattii

AbstractO_ST_ABSBackgroundC_ST_ABSThe study of microbiota of social insects under different ecological conditions can provide important insights into the role of microbes in their biology and behaviour. Polistes is one of the most widely distributed and extensively studied genera of social wasps, yet the microbiota of any species of Polistes or any primitively eusocial wasp is still unknown. Polistes wattii is an abundantly distributed Asian wasp which hibernates in winter and exhibits a unique biannual nest founding strategy. It is often parasitized by the strepsipteran endoparasite Xenos gadagkari, which changes the morpho-physiology and behaviour of their hosts. In this study we employ 16S rRNA amplicon sequencing, using the Oxford Nanopore platform, to study the microbial community associated with P. wattii and compared the microbiota of the unparasitized male and female P. wattii with their parasitized counterparts. ResultsThe microbiota of females from preemergence solitary foundress nests differs from the females from the late colony phase of multiple foundress nests. The males and females also differ in their microbiota. To estimate the effect of strepsipteran parasitism on the microbiota of P. wattii, we compared the unparasitized wasps with that of the female and male X. gadagkari parasitoids and parasitized wasps. We show that the microbiota of the parasitoids and the parasitized wasps are dominated by Wolbachia and Providencia. {beta}-diversity differences indicated that the parasitoid replaces and homogenizes the microbiota of P. wattii. Although the normal microbiota of P. wattii resembles that of highly eusocial vespid wasps, we show X. gadagkari parasitization replaces the microbiota of P. wattii and it becomes more like the microbiota of strepsipterans. Therefore, it appears that X. gadagkari and other such strepsipteran parasitoids may have a bigger impact on the biology of their hosts, than previously thought. ConclusionThis is the first study of microbiota of any primitively eusocial Polistine wasp and any strepsipteran parasitoid associated with a hymenopteran species. Although strepsipteran parasitoids are commonly found in hymenopteran insects, the change on the microbiota of the host due to the parasitism was not known before. This study shows the drastic impact of the parasitoid on the microbiota of the host.

microbiology↗

bioRxiv2024

Microbiota drives the sexually dimorphic infection outcomes in mealworm beetles

Sexually dimorphic responses to pathogenic infections in animals may stem from sex-specific differences in their life history and immune investment. Recent evidence highlights that such sex-specific variations in immune responses can also be critically regulated by microbiota. However, direct experiments to test how microbiota jointly impacts sex-specific immunity and vulnerability to pathogens are still limited. To this end, we used Tenebrio molitor beetles to first establish that sexes appear to differ in their microbiota composition and infection responses. Females were more vulnerable to bacterial infections and carried a higher bacterial load than males. When we depleted the microbiome, only females improved their post-infection survival, leading to a loss of sex-specific infection outcomes. Males, on the other hand, remained unaffected. Microbiota reconstitution (via feeding on faecal matter) of microbiota-depleted females increased their susceptibility to infection again, restoring the sexual dimorphism. We thus found a causal association between microbiome and infection responses. We also found reduced expression of an antimicrobial peptide tenecin 1 in females, which could be associated with their higher infection susceptibility, but such immune gene-vs-phenotypic associations were not consistent across microbiota manipulations. Immune strategies that are required to mediate the causal links between microbiome and infection response might thus vary with microbiota manipulations, warranting future investigations.

evolutionary biology↗

bioRxiv2024

Morphology, biology and phylogeny of Xenos gadagkari sp.nov. (Strepsiptera: Xenidae): an endoparasite of Polistes wattii (Hymenoptera: Vespidae).

We report the morphology, biology and phylogeny of a new strepsipteran endoparasitic species: Xenos gadagkari, from the primitively eusocial wasp Polistes wattii from Punjab, India. We report a high abundance of the endoparasite in P. wattii population of our study area and provide the morphological description of adult males, male puparium and neotenic females. This species is sufficiently different from other Xenos sp reported from various social wasps and therefore, constitutes a new species, X. gadagkari Sen and Nain, sp. nov. Although there are a few reports of Strepsipteran parasites from India, this is the first confirmational report with a thorough description of a Xenos species from the Indian population of P. wattii and underscores the need for further investigation of the diversity and distribution of this group in India. Our findings contribute to the growing body of knowledge on Xenos and provide a foundation for future behavioural, microbial and molecular studies on this enigmatic group of insects.

zoology↗

bioRxiv2023

Partnership with both fungi and bacteria can protect Odontotermes obesus fungus gardens against fungal invaders.

Fungus-growing termites, like Odontotermes obesus, cultivate Termitomyces as their sole food source on fungus combs which are continuously maintained with foraged plant materials. This necessary augmentation also increases the threat of introducing pathogenic fungi capable of displacing Termitomyces. The magnitude of this threat and how termites prevent pathogens remain largely unknown. This study identifies this pathogenic load by establishing the pan-mycobiota of O. obesus from the fungus comb and termite castes. Furthermore, to maximize the identification of such pathogenic fungi, the mycobiota of the decaying stages of the unattended fungus comb were also assessed. The simultaneous assessment of the microbiota and the mycobiota of these stages identified possible interactions between the fungal and bacterial members of this community. Based on these, we propose a possible interaction among the crop fungus Termitomyces, the weedy fungus Pseudoxylaria and some bacterial mutualists. These possibilities were then tested with in vitro interaction assays which suggest that Termitomyces, Pseudoxylaria and bacterial mutualists all possess anti-fungal capabilities. We propose a multifactorial interaction model of these microbes, under the care of the termites, to explain how their interactions can maintain a predominantly Termitomyces monoculture.

ecology↗

bioRxiv2021

Bacterial supergroup specific "Cost" of Wolbachia infections in Nasonia vitripennis

The maternally-inherited endosymbiont, Wolbachia, is known to alter the reproductive biology of its arthropod hosts for its benefit and can induce both positive and negative fitness effects in many hosts. Here we describe the effects of the maintenance of two distinct Wolbachia infections, one each from supergroups A and B, on the parasitoid host Nasonia vitripennis. We compare the effect of Wolbachia infections on various traits between the uninfected, single A infected, single B infected, and the double infected strains with their cured versions. Contrary to the previous reports, our results suggest that there is a significant cost associated with the maintenance of Wolbachia infections where traits like family size, fecundity, longevity, and rates of male copulation are compromised in Wolbachia infected strains. The double infected and supergroup B infection strains show higher Wolbachia titer than supergroup A. The double infected Wolbachia strain has the most detrimental impact on the host as compared to single infections. Moreover, there is a supergroup-specific negative impact on these wasps as the supergroup B infections elicit the most pronounced negative effects. These findings raise important questions on the mechanism of survival and maintenance of these reproductive parasites in arthropod hosts.

evolutionary biology↗

bioRxiv2021

The males of the parasitoid wasp, Nasonia vitripennis, can identify which fly hosts contain females.

The reproductive success of a male is limited by the number of females it can mate with. Thus, males deploy elaborate mate-finding strategies to maximize access to females. In the haplodiploid wasp genus, Nasonia, which are parasitoids of cyclorrhaphous flies, mate-finding is restricted to the natal patch, where males compete for access to females. This study investigates whether there are any additional mate finding strategies of males, especially, whether they can identify the presence of adult females which are still inside the fly host. Results reveal that only one out of the four species, N. vitripennis, can distinguish which hosts specifically have adult female wasps indicating a species-specific unique mate-finding capability. Behavioral assays revealed that the cues used by N. vitripennis males are olfactory in nature and not auditory or visual. GC-MS analyses show that these olfactory cues are female-specific cuticular hydrocarbons (CHCs), possibly emanating from within the fly puparium. Further assays indicated that N. vitripennis males can also detect differences in the concentrations of compounds to identify female-specific cues from male-specific ones. This study, therefore, uncovers a previously unknown mate-finding strategy in one of the most widely studied parasitoid wasp.

ecology↗

bioRxiv2021

Pseudomonas can prevent the parasitic fungus, while keeping the crop fungus unaffected, in the gardens of Odontotermes obesus.

Insects that farm monocultures of fungi are canonical examples of nutritional symbiosis as well as independent evolution of agriculture in non-human animals. But just like in human agriculture, these fungal crops face constant threat of invasion by weeds which, if unchecked, takes over the crop fungus. In fungus-growing termites, the crop fungus (Termitomyces) faces such challenges from the parasitic fungus Pseudoxylaria. The mechanism by which Pseudoxylaria is suppressed is not known. However, evidence suggests that some bacterial secondary symbionts can serve as defensive mutualists by preventing the growth of Pseudoxylaria. However, such secondary symbionts must possess the dual, yet contrasting, capabilities of suppressing the weedy fungus while keeping the growth of the crop fungus unaffected. This study describes the isolation, identification and culture-dependent estimation of the roles of several such putative defensive mutualists from the colonies of the wide-spread fungus-growing termite from India, Odontotermes obesus. From the 38 bacterial cultures tested, a strain of Pseudomonas showed significantly greater suppression of the weedy fungus than the crop fungus. Moreover, a 16S rRNA pan-microbiome survey, using the Nanopore platform, revealed Pseudomonas to be a part of the core microbiota of Odontotermes obesus. A meta-analysis of microbiota composition across different species of Odontotermes also confirms the wide-spread prevalence of Pseudomonas within this termite. These evidence indicate that Pseudomonas could be playing the role of defensive mutualist within Odontotermes.

evolutionary biology↗