Learning in the Box Jellyfish Tripedalia cystophora

Dansk Naturhistorisk forening
Learning in the Box Jellyfish Tripedalia cystophora

by Sofie Dam Nielsen, PhD, Marine Biology Section, Biological Department, Copenhagen University

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Within Cnidaria, the cubozoans constitutes a special group in that they in their medusa stage, the cubomedusae, have advanced image forming eyes and display a range of visually guided behaviours. Further, cubomedusae also have an elaborate central nervous system, which allows for the visual processing needed to support the behavioural repertoire. In their obstacle avoidance behaviour, the medusae visually detect large stationary objects in the immediate vicinity and turn away before collision. For the Caribbean species, Tripedalia cystophora, obstacle avoidance is intimately connected with their feeding behaviour since they hunt copepods between the mangrove prop roots. The medusa is able to optimize feeding without collision by estimating the distance to nearby roots using their visual contrast to the surrounding water. Interestingly, this unique way to measure distance depends on the optical quality of the water, which varies greatly over short periods of time e.g. due to wave actions and rainfall. In the present study we wanted to test the hypothesis that T. cystophora is able to learn and remember changes in the relationship between contrast and distance. Through a series of behavioural experiments where contrast and distance can be controlled separately, we are able to show that they do change their behaviour over time. Further, they can only learn a given contrast:distance relationship when they are allowed the combined information from visual and mechanical stimuli. Our results also show that even one of the most advanced features of nervous systems, the ability to learn and remember, is a fundamental property of nervous systems present already in cnidarians, the earliest branch in the animal kingdom

Figure 1. (A) The box jellyfish, Tripedalia cystophora. Square indicates 1 of the 4 rhopalia. (B) A rhopalium showing the six eyes of four types. The upper (ULE) and lower (LLE) lens eyes resem- ble camera type eyes. PE, pit eye; SE, slit eye.

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When: Thursday 8/2-18 at 19.30

Where: Universitetsparken 15, Bygning 1, Auditorium A, 2100 København Ø
Everybody is welcome
Parking tickets will be handed out