The chemical defenses of millipedes (diplopoda): Biochemistry, physiology and ecology

Abstract

a b s t r a c tMillipedes are some of the earliest examples of terrestrial animals, and fossils from the early Carboniferous Period indicate they were also some of the earliest prey. These fossils record ozopores, the openings of chemical defense glands, occurring along the length of the body. The secretions of these glands may consist of topical irritants, repellents, antifeedants, or, in the case of the large and widespread Order Polydesmida, hydrogen cyanide (HCN) gas that can be fatal to other arthropods or even small vertebrates in a confined environment. Müllerian mimicry rings may develop in which unrelated species of millipedes that co-occur closely resemble one another, while participating in a completely differently patterned ring in another part of their geographic range. Chemistry is not the only defense of millipedes. Polyxenids carry tufts of entangling setae, many species rely on crypsis and the ability to roll into a smooth, resistant sphere or coil, and still others have spikey projections that may deter soft-mouthed predators. Nevertheless, chemical defense has been of significance in helminthomorph millipedes at least since the Lower Carboniferous. The distribution of classes of chemical defense compounds follows major phylogenetic groupings. Evidence suggests that the defensive glands of Glomerida arose independently of those of the Helminthomorpha.

A revision of dragon millipedes I: genus Desmoxytes Chamberlin, 1923, with the description of eight new species (Diplopoda, Polydesmida, Paradoxosomatidae)

“…The bright colour probably is a warning signal (Svadova et al 2009, Shear 2015, Marek and Moore 2015). Many mating couples were found during our field surveys, and we collected some representative couples and reared a few specimens of D. euros sp.…”

Massive increase in visual range preceded the origin of terrestrial vertebrates

“…Interestingly, one group of these invertebrates, the millipedes, developed chemical defense systems in the lower Devonian (44). In millipedes that exist today, these systems deter vertebrate predators (45). Hunting in a crocodile-like manner resolves a certain logical tension between the specializations for fully aquatic life seen in the elpistostegalians and adaptations that seem better suited for brief forays onto land: larger eyes and limbs (9, 10) significantly supplemented by tail movement (46).…”

Four new species of the millipede genus Eutrichodesmus Silvestri, 1910 from Laos, including two with reduced ozopores (Diplopoda, Polydesmida, Haplodesmidae)

“…n., both from caves, and unsurprisingly less pigmented, that show strongly or completely reduced ozopores. The function of the defensive glands and their ozopores is known to lie in the production of defence fluids, as a protection against predators (Shear 2015). From the recent paper concerning the adaptation in the cave millipedes to the cave environment (Liu et al 2017) it remains unclear whether or not the suppression may be related to cavernicoly.…”