Semiaquatic Heteroptera locomotion: coral treaders (Hermatobates weddi, Hermatobatidae), sea skaters (Halovelia septentrionalis, Veliidae), and water striders (Metrocoris histrio, Gerridae). Usual and unusual gaits

Abstract

Using high-speed video recordings, we carried out an analysis of the locomotion gaits of the following aquatic Heteroptera: coral treaders Hermatobates weddi (Hermatobatidae), sea striders Halovelia septentrionalis (Veliidae), and water striders Metrocoris histrio (Gerridae), in the Island of Amami Oshima, Kagoshima Prefecture, Japan. Most insects use an alternating double tripod gait for walking, whereas species of Gerridae and some Veliidae use a synchronous rowing gait. We found that H. weddi used a peculiar locomotion gait, a modification of the double tripod gait. In this special gait, two alternating dipods (mid and hind legs) are used, while the forelegs remained inactive. Contralateral mid and hind stroked simultaneously. The mid leg recovered immediately after the stroke; however, the hind leg was delayed and remained extended after the stroke. Next, the following bipod stroked, and when that mid leg finished the stroke, both ipsilateral mid and hind (the one which did not recover after the stroke) legs recovered together. Turning is also unique in H. weddi because the body axis rotation and the course turning (deflection) were clearly separated in two phases. We compared the kinematics of H. weddi pattern with the synchronous rowing pattern found in H. septentrionalis and M. histrio and discussed some biomechanical consequences. We also analyzed phylogenetic implications of this gait, and we posit that the modified double dipod gait is a uniquely derived character of the family Hermatobatidae. The synchronous rowing gait would be an autapomorphy for the clade Gerridae ? Veliidae. The modified thorax, with the meso and metacoxae horizontally directed, would be a synapomorphy for the superfamily Gerroidea (Hermatobatidae, Gerridae, and Veliidae).

A comparison of the external morphology and functions of labial tip sensilla in semiaquatic bugs (Hemiptera: Heteroptera: Gerromorpha)

“…even though the characteristics of labial tip sensilla and multi-peg structures and the surface of the labial tip were recognizable at the (sub-)family level in the present study, these characters do not provide support for the superfamilies identified by Andersen (1982), Muraji & Tachikawa (2000), Andersen & Weir (2004), Damgaard et al (2005), and Perez-Goodwyn et al (2009) or for the alternative cladogenetic solutions proposed by Damgaard (2008) (Fig. 75), who left unanswered several major questions regarding the future systematics of Gerromorpha.…”

“…Apparently, characteristics of those labial tip sensilla (tall basiconic sensilla) viewed as a synapomorphy in the present study provide support for the monophyly of Veliidae and Gerridae. This provides support for solutions proposed by Andersen (1982), Andersen & Weir (2004) and Perez-Goodwyn et al (2009).…”

“…Moreover, he also points out that Veliidae are a non-monophyletic group and proposes that the subfamilies Ocelloveliinae, Veliinae, Rhagoveliinae, Perittopinae, and Microveliinae + Haloveliinae be raised to family rank. Recently, Perez-Goodwyn et al (2009) have shown, that the gait (double tripod) in Hermatobatidae is intermediate between that of Mesoveliidae, Hebridae, Macroveliidae, and Hydrometridae, in which the gait (double tripod) is a plesiomorphic character, and the clade Gerridae + Veliidae with a gait that is autapomorphic (synchronous rowing). These authors have also identified a new synapomorphic character (horizontally directed meso-and metacoxa) in the superfamily Gerroidea (Hermatobatidae, Gerridae and Veliidae).…”

“…In turn, the lack of elongated placoid sensilla in hydrometrids and hermatobatids places them closer to Macroveliidae, Veliidae and Gerridae (synapomorphy of these five families). Similarly, based on the mode of locomotion Perez-Goodwyn et al (2009) indicate that the gait of hermatobatids is intermediate between that of Mesoveliidae, Hebridae, Macroveliidae, and Hydrometridae (plesiomorphic character of the gait) and the clade Gerridae + Veliidae, in which it is autapomorphic.…”

Physics of sliding on water predicts morphological and behavioral allometry in water striders

“…This also indicates that very small water striders (smaller than the body size modeled here, i.e., <10 mg) could theoretically perform symmetrical mode of locomotion with the "short-foreleg geometry". However, as those theoretically feasible combinations differ in resistance, and the resulting deceleration, and as water striders seem to pay attention to the resistance (as indicated by our observations on A. paludum), we hypothesize that natural selection or adaptive behavioral plasticity towards decreasing resistance may in certain conditions cause evolutionary or behavioral shifts from the ancestral 25,43,44 symmetric striding of water striders with "balanced geometry" towards either the asymmetric locomotion mode or "long-foreleg geometry". Asymmetric locomotion mode substantially decreases resistance and deceleration and increases sliding distance but involves weaker thrust from only one midleg aided by contralateral hindleg (in the habitats where the relatively strong thrust is less important).…”