Reproductive behavior and early immature morphology of Portschinskia magnifica: implications for evolutionary biology in bot flies (Diptera: Oestridae).

Abstract

Portschinskia Semenov is a rare genus of bot flies whose larvae are obligate parasites of pikas and murine rodents, crucial for understanding the evolutionary biology of Oestridae. However, limited information on their adult biology and early immature stages has hindered the progress. Here, we provided the first documentation of adult oviposition, behavior, and morphology of newly hatched first instars of P. magnifica Pleske. Using confocal laser scanning microscopy and scanning electron microscopy, we characterized the ultrastructure of egg and first-instar larva, identifying key traits facilitating attachment. Eggs were deposited individually or in groups, and glued on non-host surfaces with white adhesive substances, without specialized attachment organ. Newly hatched first instars were circled with an anterior spinose band on each body segment except the anal division, awaited hosts in an upright position, and anchored to the egg shell by their anal division, likely supported by curved spines originating from the peritreme of the posterior spiracles. Evolutionary analyses of reproductive behavior across the 4 bot fly subfamilies reveal at least 3 times independent evolution of oviposition on non-host surfaces in Portschinskia or the Hypodermatinae clade as a sister group to Ochotonia, Gasterophilus pecorum (Fabricius) (Gasterophilinae), and Cuterebrinae. In contrast, species in the Oestrinae are larviparous, depositing first instars directly onto hosts. Our findings shed light on oviposition behavior and early immature morphology of the rare genus Portschinskia, offering insights into reproductive strategies and evolutionary adaptations of bot flies.