The insect spermatheca: an overview.

The mating biology of termites: A comparative review

While hybridization of an invasive species with a native species is a common occurrence, hybridization between two invasive species is rare. Formosan subterranean termites (Coptotermes formosanus) and Asian subterranean termites (C. gestroi) are both ecologically successful and are the two most economically important termite pests in the world. Both species have spread throughout many areas of the world due to human activity; however, their distributions overlap in only three narrow areas because of distinct ecological requirements. In south Florida, where C. formosanus and C. gestroi are both invasive, the dispersal flight seasons of both species overlapped for the first time on record in 2013 and 2014. Pairings of heterospecific individuals were readily observed in the field and C. gestroi males preferentially engaged in mating behavior with C. formosanus females rather than females from their own species. In the laboratory, heterospecific and conspecific pairings had an equal colony establishment rate, but heterospecific incipient colonies had twice the growth rate of conspecific incipient colonies, suggesting a potential case of hybrid vigor. As all pre-zygotic barriers were lifted between the two species in the field, the apparent absence of post-zygotic barriers in the laboratory raises the possibility for introgressive hybridization in south Florida. While laboratory observations remain to be confirmed in the field, and the alate hybrid fertility is currently unknown, our results raise a tangible concern about the hybridization of two major destructive pest species. Such hybridization would likely be associated with a new economic impact.

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Hybridization of two major termite invaders as a consequence of human activity.

Despite the ubiquitous nature of sperm storage in invertebrates, relatively little is known about its costs, or the impact that immune activation can have on a female's ability to maintain viable sperm stores. We explored the effects of an immune challenge on sperm storage under food-limited and ad libitum conditions in the field cricket, Teleogryllus oceanicus, by injecting mated adult females with either a LD5 dose of live bacteria or a nonpathogenic immune elicitor [lipopolysaccharide (LPS)] and then scoring the viability of their stored sperm. Females that were infected with bacteria showed a reduction in the viability of stored sperm 48 h after infection; interestingly, this pattern was not evident when females were injected with LPS. Reduction in sperm viability post-infection may reflect a reproductive trade-off between immune function and sperm store maintenance, as only females injected with bacteria showed an elevated antibacterial immune (lytic) response. Alternatively, bacteria may act directly on sperm quality. Dietary manipulations showed that lytic activity in females is condition dependent, irrespective of their immune challenge treatment. Diet affected the ability of females to maintain the viability of stored sperm, suggesting that sperm storage is condition dependent. That bacterial infection associated with a reduction in stored sperm quality has potentially important implications for the outcomes of sperm competition in T. oceanicus and in other species in which females store sperm between matings.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/jeb.12278

Females suffer a reduction in the viability of stored sperm following an immune challenge

Transcriptome profiling of female alates and egg-laying queens of the Formosan subterranean termite.

Primary reproductives of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), complete their first reproductive cycle in ≈60 d after nest formation. During this period, the pairs mate several times. The spherical, aflagellate sperm, after transfer by the male, are stored in the female’s spermatheca. Sperm numbers in the spermatheca increase significantly between day 20 and 40, and thereafter they show a steep decline, indicating that the pairs may not be mating after day 40. The spermatheca is bean shaped with an extremely narrow duct. The thick wall of the spermatheca consists mainly of type 3 cells made up of secretory and duct cells. Cuticle-lined ducts are interspersed throughout these cells. Finger-like extensions of the cuticle-lined interior wall project into the spermathecal lumen. The secretory cells presumably provide nutrition for the sperm during their long storage. Eleven anaerobic and six aerobic species of bacteria were cultured and identif...

https://bioone.org/journals/annals-of-the-entomological-society-of-america/volume-100/issue-3/0013-8746(2007)100[418:SOSSDA]2.0.CO;2/Structure-of-Spermatheca-Sperm-Dynamics-and-Associated-Bacteria-in-Formosan/10.1603/0013-8746(2007)100[418:SOSSDA]2.0.CO;2.pdf

Asiiok Raina

Papers

Structure of Spermatheca, Sperm Dynamics, and Associated Bacteria in Formosan Subterranean Termite (Isoptera: Rhinotermitidae)