ITAG: an eco-sensor for fine-scale behavioral measurements of soft-bodied marine invertebrates

Jorge Fontes,Kakani Katija,Pedro Afonso,K. Alex Shorter,Thomas Hurst,T. Aran Mooney

doi:10.1186/s40317-015-0076-1

Abstract

Soft-bodied marine invertebrates comprise a keystone component of ocean ecosystems; however, we know little of their behaviors and physiological responses within their natural habitat. Quantifying ocean conditions and measuring organismal responses to the physical environment is vital to understanding the species or ecosystem-level influences of a changing ocean. Here we describe a novel, soft-bodied invertebrate eco-sensor tag (the ITAG), its trial attachments to squid and jellyfish, and the fine-scale behavioral measurements recorded on captive animals. Tags were deployed on five jellyfish (Aurelia aurita) and eight squid (Loligo forbesi) in laboratory conditions for up to 24 h. Using concurrent video and tag data, movement signatures for specific behaviors were identified. These behaviors included straight swimming (for jellyfish), and finning, jetting, direction reversal and turning (for squid). Overall activity levels were quantified using the root-mean-squared magnitude of acceleration, and finning was found to be the dominant squid swimming gait during captive squid experiments. External light sensors on the ITAG were used to compare squid swimming activity relative to ambient light across a ca. 20-h trial. The deployments revealed that while swimming was continuous for captive squid, energetically costly swimming behaviors (i.e., jetting and rapid direction reversals) occurred infrequently. These data reflect the usefulness of the ITAG to study trade-offs between behavior and energy expenditure in captive and wild animals. These data demonstrate that eco-sensors with sufficiently high sampling rates can be applied to quantify behavior of soft-bodied taxa and changes in behavior due to interactions with the surrounding environment. The methods and tool described here open the door for substantial lab and field-based measurements of fine-scale behavior, physiology, and concurrent environmental parameters that will inform fisheries management, and elucidate the ecology of these important keystone taxa.

Highlights

Soft-bodied marine invertebrates comprise a keystone component of ocean ecosystems; we know little of their behaviors and physiological responses within their natural habitat
There is increasing evidence that changing environmental conditions may have a variety of influences on squid and jellyfish behavior, physiology and ecology
The invertebrate tag (ITAG) consists of two components (Fig. 1): (a) a buoyant waterproof eco-sensor package that records behavioral and environmental data, and (b) a base that serves as the point of attachment to the animal

Summary

Introduction

Soft-bodied marine invertebrates comprise a keystone component of ocean ecosystems; we know little of their behaviors and physiological responses within their natural habitat. Soft-bodied invertebrates such as squid and jellyfish play critical roles in many ocean ecosystems. There is increasing evidence that changing environmental conditions may have a variety of influences on squid and jellyfish behavior, physiology and ecology. Some medusae may undergo reverse development when environmental conditions are reproductively unfavorable, enabling “temporal persistence” and longer foraging periods [21]. Understanding these changes is vital to properly manage soft-bodied invertebrates fisheries (i.e., ecosystemically), as well as other fisheries and systems where these species play a key ecological role [22, 23]

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Conclusion