First instar larvae of endemic Australian Miltogramminae (Diptera: Sarcophagidae)

Krzysztof Szpila,Nikolas P Johnston,James F Wallman,Kinga Walczak,Thomas Pape

doi:10.1038/s41598-020-80139-x

Abstract

The first instar larva of a species of the Australian endemic genus Aenigmetopia Malloch is described for the first time, along with the first instar larvae of three other Australian species representing the genera Amobia Robineau-Desvoidy and Protomiltogramma Townsend. Larval morphology was analysed using a combination of light microscopy, confocal laser scanning microscopy and scanning electron microscopy. The following morphological structures are documented: pseudocephalon, antennal complex, maxillary palpus, facial mask, modifications of thoracic and abdominal segments, anal region, spiracular field, posterior spiracles and details of the cephaloskeleton. Substantial morphological differences are observed between the three genera, most notably in the labrum and mouthhooks of the cephaloskeleton, sensory organs of the pseudocephalon, spinulation, sculpture of the integument and form of the spiracular field. The first instar larval morphology of Aenigmetopia amissa Johnston, Wallman, Szpila & Pape corroborates the close phylogenetic affinity of Aenigmetopia Malloch with Metopia Meigen, inferred from recent molecular analysis. The larval morphology of Amobia auriceps (Baranov), Protomiltogramma cincta Townsend and Protomiltogramma plebeia Malloch is mostly congruent with the morphology of Palaearctic representatives of both genera.

Highlights

The first larval instar of Miltogramminae show diverse and peculiar morphologies, which most likely reflect adaptations to locating suitable food sources by digging through sand, often combined with different types of kleptoparasitism1
The habitus of the first instar of Ae. amissa, Am. auriceps, P. cincta and P. plebeia follows the general pattern for the Calyptratae, with the body being divided into a bilobed pseudocephalon equipped with antennal and maxillary sensory organs, three thoracic segments (t1–t3), seven abdominal segments (a1–a7), and an anal division carrying the posterior spiracles (Fig. 5A,B,E,F)
The first molecular-based reconstruction of the phylogeny of the Miltogramminae enabled a formal testing of the hypotheses for the evolution of the larval morphology and feeding strategies of this taxon1

Summary

Introduction

The first larval instar of Miltogramminae show diverse and peculiar morphologies, which most likely reflect adaptations to locating suitable food sources by digging through sand, often combined with different types of kleptoparasitism. The Australian fauna constitutes only a small part of the global miltogrammine d iversity, with a noteworthy high proportion for Protomiltogramma (32.4% of global diversity), modest for Amobia (21.4%), and very low for the other genera: Macronychia (3.8%), Metopia (4.9%), Miltogramma (3.4%) and Senotainia (1.5%)6–14,. The present study fills an important gap in the morphospace of a large taxon of Diptera by providing the first morphological documentation of the preimaginal stages of four Australian miltogrammine species: [1] endemic Aenigmetopia amissa Johnston, Wallman, Szpila & Pape, Protomiltogramma cincta Townsend, Protomiltogramma plebeia Malloch; and [2] Amobia auriceps (Baranov), widely distributed in the Oriental and Australasian-Oceanian regions. Special focus is on the systematic position of Aenigmetopia, the only endemic genus of Australian miltogrammines

Methods

Results

Conclusion