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Renate Matzke-Karasz, Christina Nagler and Simon Hofmann

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 species Cypridopsis vidua (O. F. Müller, 1776), the samples contained four alien species, i.e., Chlamydotheca arcuata (Sars, 1901), Strandesia bicuspis (Claus, 1892), Tanycypris centa Chang, Lee & Smith, 2012, and Tanycypris alfonsi Nagler, Geist & Matzke-Karasz, 2014. While sorting the living Tanycypris specimens, 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 book-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 investigated Tanycypris species 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 in Tanycypris, combined with a well-developed musculature, which stretches from a broadened posterior end of soft book-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, in Tanycypris no 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.

Restricted Access

Renate Matzke-Karasz, Christina Nagler and Simon Hofmann

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 species Cypridopsis vidua (O. F. Müller, 1776), the samples contained four alien species, i.e., Chlamydotheca arcuata (Sars, 1901), Strandesia bicuspis (Claus, 1892), Tanycypris centa Chang, Lee & Smith, 2012, and Tanycypris alfonsi Nagler, Geist & Matzke-Karasz, 2014. While sorting the living Tanycypris specimens, 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 investigated Tanycypris species 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 in Tanycypris, 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, in Tanycypris no 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.