Occurrence of diapause in neotropical parasitoids attacking Anastrepha fraterculus (Diptera: Tephritidae) in a subtropical rainforest from Argentina

Abstract

Incidence of diapause in neotropical parasitoid species associated with the tephritid fruit fly Anastrepha fraterculus (Wiedemann) infesting three major host plants collected from the southernmost end of Argentinean Yungas rainforest was studied. Three other objectives were the frequency of diapause according to the fruiting season of Prunus persica (L.) Batsch (peach), Psidium guajava L. (guava) and Juglans australis Grisebach (walnut); the length of diapause period for each recovered parasitoid species; and the proportion of diapausing parasitoid individuals that displayed prolonged diapause. Between 2001 and 2003, infested ripe fruits were weekly collected in wild vegetation areas. A portion of the fruit samples was processed at the same collection site. Recovered A. fraterculus puparia were kept under natural environmental conditions inside a wooden frame cage covered with a cloth mesh. The remaining halves of fruit samples were taken to the laboratory and puparia were kept under environmental controlled condition. Unenclosed puparia were kept for 2 years. Diapause period fluctuated between 131 and 426 days and was observed in all recovered parasitoid species (Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), Opius bellus Gahan, Utetes anastrephae (Viereck) and Aganaspis pelleranoi (Brèthes)). All diapausing individuals dissected from host puparia were instar III and were also remarkably different from non-diapausing larvae because of their smaller body size. The 65% of all diapausing individuals was recorded in early autumn and was recovered from A. fraterculus larvae that had developed in guava. Prolonged diapause was recorded in a small fraction of the diapausing populations of D. brasiliensis, D. areolatus and A. pelleranoi. Results suggest that diapause is an adaptive mechanism that allows parasitoids to overcome periods of marked host scarcity given that guava is the last widely available host plant before the winter season begins.

Biological attributes of diapausing and non-diapausing Doryctobracon areolatus (Hymenoptera, Braconidae), a parasitoid of Anastrepha spp. (Diptera, Tephritidae) fruit flies

“…Under our laboratory-controlled conditions and using mass-reared A. ludens as hosts, we found that diapause in D. areolatus has been maintained after 23 generations, suggesting a genetic component. The developmental time of diapausing individuals ranged from 70 to 281 days, which is shorter than those reported for this species when they were collected in the field in Mexico, Brazil and Argentina (Aluja et al 1998;Carvalho 2005;Ovruski et al 2016). These reports included wild individuals coming from different fruit fly species hosts (A. obliqua, A. ludens, A. fraterculus, A. serpentina Another factor affecting diapause duration is the metabolic reserves of individuals (Ishihara and Shimada 1995;Hahn and Denlinger 2007), because only those larvae with enough nutritional resources will survive this period (Ellers and van Alphen 2002).…”

“…Despite we found that diapausing individuals had a lower pupal weight, -which could mean lower fat reserves -and adults emerging from diapause were smaller, there were no difference in adult percent emergence between the two cohorts. Aluja et al (1998) and Ovruski et al (2016) previously noted the smaller larval and pupal weight of diapausing individuals, but no comparisons had been made on adult dimensions. Wings also were longer in non-diapausing wasps and this could be associated with the greater flight ability observed in this cohort.…”

“…This suggests that diapause in D. areolatus has a hard-wired genetic component and may represent an adaptation to host scarcity in the field (Denlinger 1986). Although the frequency of diapause in D. areolatus has been previously associated with the fruit species used by the fruit fly host (Ovruski et al 2016), in this study, we used the same fruit species (P. guajava) and we still found differences between diapausing and non-diapausing individuals respect to maternal age and the proportion of offspring entering into diapause. Some studies proposed that parents might determine whether their offspring enters into diapause (Denlinger 2002;Hahn and Denlinger 2007).…”

“…Since these parasitoids are holometabolous, each species has a different rate of development, which also largely depends on the host (stage, instar, condition). Some species may diapause (Aluja et al 1998;Carvalho 2005;Ovruski et al 2016).…”

“…However, it has also been observed in organisms that live in tropical regions (Denlinger 2002). Several species of tephritid fruit fly parasitoids native to the Neotropics have been reported to diapause: Doryctobracon areolatus (Szépligeti), Doryctobracon brasiliensis (Szépligeti), Utetes anastrephae (Viereck), Opius bellus (Gahan) as well the introduced species Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae), Aganaspis pelleranoi (Brèthes) and Odontosema anastrephae (Borgmeier) (Hymenoptera: Figitidae) (Aluja et al 1998;Carvalho 2005;Ovruski et al 2016). It has been reported that D. areolatus is the species that diapauses with greater frequency and with the longest duration: up to 11 months in fruits of Spondias mombin L. (Anacardiaceae) in Mexico (Aluja et al 1998), and 414 days in fruits of Eugenia uniflora L. (Myrtaceae) in Brazil (Carvalho 2005).…”