Differences in competitive ability for the occupancy of shelters in triatomines

Abstract

Triatomines (Hemiptera: Reduviidae: Triatominae) are nocturnal blood-sucking insects. During daylight hours they remain in an akinetic state inside their shelters, whereas at dusk they become active and move outside. When they are outside their shelters during the photophase, triatomines are vulnerable to diurnal predators and the period just before dawn is critical to their survival. This work analyses the existence of competitive interactions involved in the occupancy of shelters by triatomines. Behavioural assays were performed in which nymphs of different stages, nutritional status or species were released in an experimental arena containing a space-limited artificial shelter. The proportions of individuals occupying the shelter during the photophase were quantified to estimate the competitive abilities of each stage and species. Intraspecific comparisons showed higher levels of shelter occupancy for fourth over fifth instars and fed over unfed nymphs of Triatoma infestans. Interspecific comparisons showed higher rates of shelter occupancy for Triatoma sordida in comparison with T. infestans, and for T. infestans over Rhodnius prolixus. Arrival order was also relevant to determining shelter occupancy levels: early arrival was advantageous in comparison with later arrival. The study of intra- and interspecific competitive interactions for shelter occupancy provides relevant information about colonization and recolonization processes in the natural environments of triatomines.

Shelter selection in the kissing bugs Triatoma infestans and Rhodnius prolixus: Intra‐ and inter‐specific interactions and quality evaluation

“…In the first part of this work, a mixed group of fed and unfed nymphs showed an even coexistence inside all the shelters available, although previous works show that the physiological feeding status of a triatomine insect directly affects its mobility, locomotor activity, competing capacities for shelters, and host-seeking behaviour (Lazzari, 1992;Takano-Lee & Edman, 2001;Zacharias et al, 2017). Therefore, it is expected to see shelters in nature occupied by conspecifics with different degrees of feeding in T. infestans and R. prolixus.…”

“…However, nutritional status has also a clear effect on this rhythmicity, since fasted T. infestans showed an increased frequency of entry and exit from their shelters . Similarly, Zacharias et al (2017) demonstrated that occupancy levels of shelters are higher in fed than in fasted nymphs of the same species. In R. prolixus, Takano-Lee and Edman (2001) described that fasted nymphs sought more shelter than recently fed ones.…”

“…On its base, a rectangular piece of filter paper (3 cm  2 cm) acted as an attractive substrate for insects. This type of shelter has proven to be adequate to house different triatomine species in previous experiments carried out in our laboratory (Zacharias et al, 2017). Ten replicates of each series were performed.…”

“…In R. prolixus , Takano‐Lee and Edman (2001) described that fasted nymphs sought more shelter than recently fed ones. As well, different nymphal instars of different species of triatomines present different levels of occupancy of artificial shelters under controlled conditions in laboratory experiments (Zacharias et al, 2017). These authors reported that fourth‐instar nymphs were more frequently found inside shelters than fifth‐instar ones, and that T. infestans was more motivated to enter shelters as compared to T. sordida and R. prolixus .…”

Enhancing fitness in offspring of crosses between two triatomine species

“…Specimens of the four studied cohorts required a low number of blood meals to molt, which suggests a higher fitness. This would be an advantage because a triatomine may be at risk each time it leaves the harborage to locate a host (Zacharias et al ). The accumulative mortality of M. bassolsae was noticeably higher in moltings from the 1 st to the 2 nd instar, from the 5 th instar to the adult stage, and in the total percentage, in comparison to the other three studied cohorts.…”