Structure and function of the eversible organs of several genera of larval firefly (Coleoptera: Lampyridae)

Abstract

Larval defensive behaviour and eversible organ morphology were compared in the firefly species Luciola cruciata Motschulsky 1854, L. lateralis Motschulsky 1860, L. leii Fu et Ballantyne 2006, Lampyris noctiluca Linnaeus 1767, Pyrocoelia analis Fabricius 1801, P. pectoralisOliver 1883, P. sp. and two Diaphanes species. In all cases the eversible organs are located on the pleural cuticle, dorsal to the spiracle, but there is considerable variation between species in their number, size and shape. In La. noctiluca they are confined to the abdomen, whereas in the other species they also occur on the meta-and mesothorax. In La. noctiluca and the Pyrocoelia species the organs are columnar in shape, contrasting with the forked organs of the Luciola and Diaphanes species. The eversible organs of the Luciola species, which are all aquatic, are remarkably larger (relative to body length) than those of the other, terrestrial species. On organ eversion the Luciola species emit an odour resembling pine oil, the Diaphanes species smell weakly of mint and L. noctiluca and the Pyrocoelia species produce no discernible scent, though ants are nonetheless repelled by contact with everted L. noctiluca organs. The organs of all the species studied support protuberances on their external surface, though these too vary in shape, size and ornamentation between species. In all species except L. noctiluca each protuberance is connected to a well-developed globular body via a long, thick stalk. Circular foveae are located in the centres of these globular bodies. The globular bodies consist of secretory cells characterized by the presence of numerous mitochondria and an extensive system of cisternae and tubular endoplasmic reticulum. Behavioural tests revealed that small larvae run away instead of becoming immobile and glowing, whereas large larvae start to glow when disturbed. The study shows that the eversible larval organs form an important part of a defensive arsenal in the Lampyridae.

A comprehensive review and call for studies on firefly larvae

“…1A ). When disturbed, those glands are everted and release a strong smell as well as a repellent substance ( Fu et al, 2007 ; Fu et al, 2009 ), but sometimes only specific threats will trigger the eversion of these glands ( e.g. , ants— Tyler, 2001a ; Tyler, 2001b ; Tyler & Trice, 2001 ).…”

“…, Darwin, 1859 ; Fu et al, 2007 ). Otherwise, larvae typically glow when disturbed, as a warning to potential predators, or evert repugnatorial glands if they can ( Fu et al, 2009 ).…”

“…1A). When disturbed, those glands are everted and release a strong smell as well as a repellent substance (Fu et al, 2007;Fu et al, 2009), but sometimes only specific threats will trigger the eversion of these glands (e.g., ants -Tyler, 2001a;Tyler, 2001b;Tyler & Trice, 2001). Pleural defensive glands have been discovered fairly recently, studied in just a handful of species, and their biological meaning for firefly ecology and evolution is yet to be understood.…”

“…1A, e.g Aquatica Fu, Ballantyne & Lambkin, 2010, and some Luciola Laporte, 1833) (e.g., Jeng, Lai & Yang, 2003;Fu, Ballantyne & Lambkin, 2012b;Ballantyne & Lambkin, 2013). Aquatic backswimmers (e.g., Sclerotia substriata (Gorham, 1880) and S. aquatilis (Thancharoen et al, 2007)) lack gills like the semiaquatic larvae, which have distinctly harder exoskeletons, and use their pygopodia to adhere to floating objects (Fu, Wang & Lei, 2005;Fu et al, 2005a;Fu et al, 2005b;Fu et al, 2007;Fu et al, 2009;Fu, Ballantyne & Lambkin, 2012b;Sato, 2019). Interesting ontogenetic shape changes have been reported for the lucioline genus Sclerotia Ballantyne, 2016, where apneustic early larvae become metapneustic in later instars (Fu, Ballantyne & Lambkin, 2012b).…”

Estimation of dispersal ability responding to environmental conditions: larval dispersal of the flightless firefly, Luciola parvula (Coleoptera: Lampyridae)

“…Many lampyrid taxa are known to be distasteful or toxic to a variety of generalist predators (arthropods, birds, amphibians, reptiles, and fish; see Lewis and Cratsley (2008)). Larvae of Luciola cruciata, L. lateralis, L. leii, and several other firefly species have recently been discovered to possess specialized defensive organs against aquatic and terrestrial predators (Fu et al 2007(Fu et al , 2009.…”