Direct and indirect pathways of fitness-impact in a protozoan-infected kissing bug

Abstract.  Parasites can reduce host fitness through short-term mortality, complete or partial castration, or slight reductions in host fecundity. Hosts may reduce reproductive effort as an adaptive strategy to tolerate parasitism. However, host fitness reduction may be unrelated to host adaptation but represent a pathological side-effect of infection. The present study evaluates experimentally the direct and indirect impact of the protozoan parasite Trypanosoma cruzi on the investment of female kissing bugs in reproductive tissue. The presence of the parasite decreases gonad weight but this effect disappears when body size is included as covariate. To examine in more detail the set of causal relationships involved, a structural equation modelling analysis is performed using body size, moulting time and nutrition as predictor variables on gonad weight in the presence and absence of the protozoan. The results obtained indicate that, irrespective of the pathway and status of infection, female kissing bugs showing a slow development tend to have lighter gonads. On the other hand, the importance of blood ingestion for gonad weight is dependent on body size and contingent on the status of infection. Uninfected individuals tend to invest more in reproductive tissue when ingesting more blood during their ontogeny, and the opposite situation is observed for infected insects. These results indicate that gonad weight reduction in T. cruzi -infected Mepraia spinolai (Porter, 1934) is a consequence of nutrition curtailment and body size reduction rather than an adaptive strategy to cope with infection.     

A new species of Triatominae from Tamil Nadu, India

Abstract A new species of the genus Linshcosteus Distant, 1904 (Hemiptera: Reduviidae: Triatominae) is described from specimens collected near Kalakkadu, Tamil Nadu state, southern India. Specimens were found in deep crevices between rocks, in a region of semi‐arid scrub jungle. The distinctiveness of the new species was demonstrated by a morphometric analysis including the five previously described species of Linshcosteus, all from India. Nine measurements of the head were used in an isometric size‐free principal component analysis. In terms of discrete morphology the new species, Linshcosteus karupus sp.n. Galvão, Patterson, Rocha & Jurberg differs from the most similar one, L. kali Lent & Wygodzinsky, 1979 , by its very prominent anterolateral projections of the pronotum, by the length to width ratio of the pronotum, by the pilosity of the head and several other characters, including phallic structures. A revised key is presented for the six species of the genus.     

The architecture of the anterior appendage in the egg of the assassin bug, Zelus longipes (Hemiptera: Reduviidae)

The eggshell of Zelus longipes, a Hemiptera species of the family Reduviidae (assassin bugs), has been studied using Scanning Electron Microscopy (SEM). The emphasis was on the architecture of an anterior appendage connected to the main eggshell of both ovarian and deposited eggs. The analysis of eggs fractured at various angles and levels reveals a relatively complex organization of this appendage. There is a cylindrical outer layer, the veil, of roughly the same diameter as, and continuous with, the main eggshell. At its anterior pole, the veil folds inwards and forms an hourglass-shaped tube that is attached through slender extensions to a curved plate oriented at right angles to the long axis of the egg and spanning the internal diameter of the veil. The plate is solid at the center, shows honeycomb-shaped perforations in its mid-section and contains a very delicate meshwork along its circumference. Underneath the plate lies a hollow cylinder oriented at right angles to the long axis of the egg and attached to the anterior plate of the egg, the operculum. The outer openings of aeropyles lie at the inner face of the veil and at its base. While the outer surface of the entire eggshell appears smooth, the inner face of the anterior appendage is highly and diversely sculptured. The eggs are deposited in batches of at least 15 and completely surrounded by viscous secretion. This substance does not encroach on the anterior appendage. The major function of this appendage may lie in the protection of the aeropyles and particularly in preventing their being clogged by the viscous material.     

Aggression and risk assessment during predatory interactions between first-instarSinea diadema (Fabricius) (Hemiptera: Reduviidae)

The behaviors exhibited by first-instarSinea diadema (F.) (Hemiptera: Reduviidae) during intraspecific interactions are described. Five distinct behaviors were characterized: posturing, striking, stalking, stridulating, and beaking. Distinct bouts of grappling were also noted. Interactions between unfed 2-day-old nymphs, unfed 3-day-old nymphs, and unfed 5-day-old nymphs were recorded and analyzed. The behavior of the nymphs changed with the duration of food deprivation. As the period of food deprivation increased from 2 to 5 days, the frequency of posturing decreased as the frequency of beaking increased. During noncannibalistic interactions, posturing or striking by one nymph was most frequently followed by posturing by the other nymph. In contrast, during cannibalistic interactions, posturing or striking was usually followed by beaking. The incidence of grappling increased with the duration of food deprivation. Moreover, grappling always preceded cannibalism. Although first instars were capable of capturing and killing conspecifics of the same age, cannibalism occurred only after 4 days of food deprivation. These results suggest that a decision-making process is involved. During interactions the nymphs can assess the vulnerability of the opponent. Whereas recently emerged nymphs usually forego the risk of attacking conspecifics, the attacks made by nymphs deprived of food are more persistent despite the danger of predation by their opponent.     

Encounters between adult spined assassin bugs,Sinea diadema (F.) (Hemiptera: Reduviidae): The occurrence and consequences of stridulation

The sequence of events leading to the resolution of agonistic interactions between adult femaleSinea diadema (F.) (Hemiptera: Reduviidae) is described. Contact between these predatory bugs resulted in a series of defensive and offensive actions, including stereotypical posturing and striking movements of the forelegs. Although these encounters usually escalated in intensity and frequency of contact, they rarely resulted in injury or cannibalism. Instead, one individual retreated from the perch. The original resident on the perch retreated in 70% of the encounters. Stridulation was observed during 33% of the encounters. Stridulating individuals retreated more often than their nonstridulating opponents, indicating that stridulation may be a startle mechanism employed by temporarily disadvantaged individuals to escape from encounters. These encounters were conflicts in which the participants are both potential predators and possible prey. The combinations of posturing, striking, and stridulation that occurred during encounters may have provided each bug with information concerning the identity and relative fitness of its opponent. If an individual is fit, it may be advantageous for it to probe the defensive capabilities of its opponent, since its own risk is low, and a less fit opponent could be killed and eaten.     

A new record of amphisexual care in an insect with exclusive paternal care: Rhynocoris tristis (Heteroptera: Reduviidae)

We describe the first record of amphisexual care in an insect with uniparental male care. Male Rhynocoris tristis are noted for aggressively guarding multiple egg masses. When a male is unable or unwilling to guard eggs, a female that has previously contributed eggs returns to the egg mass and defends it until the eggs hatch. We compared the frequency and intensity of parental aggression in both sexes and found no difference in either form of guarding behavior. Evidence of amphisexual care in R. tristis provides an opportunity to quantify the cost of care in both sexes within a single species.An erratum to this article can be found at     

伊朗猎蝽科四新记录种(半翅目:猎蝽科)

记述伊朗猎蝽科Reduviidae真猎蝽亚科Harpactorinae昆虫4新记录种:争土猎蝽Coronus contrarius Reuter,1881、环瑞猎蝽Rhynocons annulatus(Linnaeus,1758)、红胸瑞猎蛴Rhynocoris rubrogularis (Horvfith,1880)及沙地枯猎蝽Vachiria deserta(Becker,1867).