Echoentomography for Assessing Braconid Parasitization on Soft-Bodied Tephritid Hosts

SIMPLE SUMMARY: Host parasitization by an endoparasitoid insect can be evaluated relying on three main methods, i.e., dissection under a stereomicroscope, polymerase chain reaction (PCR), or waiting for adult emergence. These approaches show limitations related to the time required for the detection of parasitization and/or the destruction of the sample. In this research, an innovative approach using ultra-high frequency ultrasound (UHFUS) technology was employed to evaluate braconid parasitization of Ceratitis capitata larvae. The UHFUS approach was compared with classic stereomicroscopic dissection, showing that both methods provide comparable diagnostic reliability. Our results support the application of echoentomography as a useful tool for fine, fast, and non-invasive evaluation of the ability of parasitoids to parasitize soft-bodied hosts. ABSTRACT: Entomological approaches currently available for assessing host parasitization require dissection, polymerase chain reaction (PCR), or waiting for adult emergence. The first two methods are relatively fast but destructive, whereas the third one allows the emergence of the parasitoid but it is time consuming. In this framework, new diagnostic imaging tools may contribute to solve the lack of an accurate, rapid, and non-invasive approach to evaluate the parasitization of soft-bodied insects by their endoparasitoids. In this study, ultra-high frequency ultrasound (UHFUS) technology, which is currently used in medical and preclinical fields, was adopted to assess the parasitization of the invasive polyphagous Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), testing 2nd and 3rd instar larvae. Parasitization assays were carried out with the solitary koinobiont endophagous parasitoid Psyttalia concolor (Hymenoptera: Braconidae: Opiinae). The efficacy of UHFUS-based echoentomography was compared with the classical method of dissecting the larval host under a stereomicroscope. Our results showed that the UHFUS diagnostic capability was statistically comparable with that of dissection, both on C. capitata 2nd and 3rd larvae. Overall, UHFUS-based echoentomography may be further considered as a fast, non-invasive, and effective approach to evaluate the parasitoid’s ability to successfully oviposit in soft-bodied hosts.