The ostracod springtail — camera recordings of a previously undescribed high-speed escape jump in the genus Tanycypris (Ostracoda, Cypridoidea)

Abstract

During an ostracod sampling campaign in the city of Munich (Germany) samples were taken from containers in a greenhouse of the Munich Botanical Garden. Beside the ubiquitous speciesCypridopsis vidua(O. F. Müller, 1776), the samples contained four alien species, i.e.,Chlamydotheca arcuata(Sars, 1901),Strandesia bicuspis(Claus, 1892),Tanycypris centaChang, Lee & Smith, 2012, andTanycypris alfonsiNagler, Geist & Matzke-Karasz, 2014. While sorting the livingTanycyprisspecimens, a yet undescribed usage of the caudal rami was observed. Freshwater ostracods usually move on or in the sediment by using their first and second antennae, walking legs and — if not reduced — their caudal rami. During (non-swimming) locomotion of most freshwater ostracods with well-developed caudal rami, they help pushing the body forward by being used as a lever. This movement can be fast, but has never been reported to include sudden jumps. In contrast, both investigatedTanycyprisspecies show an extraordinarily fast movement, especially when disturbed. Recordings with a high-speed camera were made, shooting horizontally into a 1.5-mm-thick micro-aquarium. The fast movement could be identified as a powerful jump, much resembling the movement of a catapult, propelled by a very rapid repulsion of the caudal rami from the ground. Although sized only around 1 mm, the observed specimens reached top speeds of up to 0.75 ms−1. Anatomically, this speed is obtained by the exceptional length of the caudal rami inTanycypris, combined with a well-developed musculature, which stretches from a broadened posterior end of soft body along the so-called ‘caudal rami attachment’. The jump itself resembles that of springtails or fleas, where the jump is powered by the energy previously stored in an elastic proteinaceous material; however, inTanycyprisno such mechanism could be detected and thus the energy for the catapult-like jump must be considered muscular, possibly aided by tendon-like structures and/or a mechanism involving a muscular pre-tension by a click-joint as recorded for Squillids.