Subimaginal wing morphology and instant flight capabilities after last instar moulting in mayflies

DOMÍNGUEZ, EDUARDO; STANICZEK, ARNOLD H.

Turin

Congreso; 2024 JOint meeting of the XVII International Conference on Ephemeroptera and XXI International Sympoisum on Plecoptera; 2024

Universita di Torino and Universidad de Granada

Insect wings do not only consist of cuticle, butare also equipped with epidermal cells, tracheae, and neurons that requireoxygen and other substances to maintain their functionality. These requirementsare fulfilled by the hemolymph that circulates in the veins. In all pterygotes,including mayflies, the wing hemolymph decreases in the adult. Epidermal cells obliterate,so dorsal and ventral layers of the cuticle become attached to each other,except for the areas where the wing veins are located. In freshly emergedimagines, hemolymph is pumped into the veins immediately after moulting toexpand the wings. After wing expansion, the hemolymph is removed, resulting ina functional imaginal wing being even lighter than the initially folded wingpad. However, in the subimaginal wings of mayflies, the epidermal cells remainhypertrophied and a high amount of hemolymph still remains in a functional wingat the moment of its emergence from the last nymphal instar. In other insects, theobliteration of epidermal cells is necessary for a functional wing. This is notthe case for mayfly subimagines, which not only are able to flight but also todo that immediately after emerging from the last nymphal instar, an importanttrait to escape from the many predators at this very vulnerable moment of thelife cycle. This is very striking, as other winged insects need a considerableamount of time (as in teneral adults of Odonata and Plecoptera) for the wingsto harden before being able to take to the air. Here, we delve into some of thecharacteristics of the mayfly subimaginal wing, and how they may allow their unusualcapability of flying immediately after emergence. Also discussed are the modeof wing folding inside the nymphal wing pads, their different ways ofunfolding, and the role of bullae therein.