Hatching in Coromandel Marsh Dart Damselfly Ceriagrion coromandelianum (Fabricius) (Zygoptera: Coenagrionidae): process and influence of the oviposition substrate

Abstract

Coromandel Marsh Dart Damselfly Ceriagrion coromandelianum (Fabricius) breeds in stagnant pools, small garden tanks and ornamental cement ponds containing submerged and/or floating vegetation. Eggs were collected to observe two aspects of larval development: (1) The hatching rate of eggs deposited in different vegetation (Nymphaea nouchali, Lemna paucicostata, Hydrilla verticillata).  Although C. coromandelianum prefers to oviposit in the broad leaves of N. nouchali, the highest rate of hatching was found in H. verticillata (95.8%) followed by N. nouchali (87.6%) and L. paucicostata (81.3%).  Hatching commenced on Day 5 and was completed by Day 9.  Maximum hatching (56%) was recorded on the sixth day of oviposition followed by the seventh day (20%) in all three substrates. (2) To document the process of hatching as follows: Around three minutes prior to hatching, the embryo exhibits cyclic pumping and pushing movements of the head (caused by the peristaltic movement of the mid- and hind- gut) of low intensity followed by high intensity and long pumping movements interspaced with smaller pulsating movements.  Swelling of the head forces the apical chorion to split along the micropylar chute and like a lid, the apical tip topples over as a conical cap. This allows the prolarva to exit the egg. As it does so, it twists and the thorax swells breaking the prolarval sheath and releasing the first instar larva.