Behavioural responses of the yellow emitting annelid Tomopteris helgolandica to photic stimuli

Abstract

In contrast to most mesopelagic bioluminescent organisms specialised in the emission and reception of blue light, the planktonic annelid Tomopteris helgolandica produces yellow light. This unusual feature has long been suggested to serve for intraspecific communication. Yet, this virtually admitted hypothesis has never been tested. In this behavioural study of spectral colour sensitivity, we first present an illustrated repertoire of the postures and action patterns described by captive specimens. Then video tracking and motion analysis are used to quantify the behavioural responses of singled out worms to photic stimuli imitating intraspecific (yellow) or interspecific (blue) bioluminescent signals. We show the ability of T. helgolandica to react and to contrast its responses to bioluminescent-like blue and yellow light signals. In particular, the attractive effect of yellow light and the variation of angular velocity observed according to the pattern of yellow stimuli (flashes versus glows) support the intraspecific communication hypothesis. However, given the behavioural patterns of T. helgolandica, including mechanically induced light emission, the possibility that bioluminescence may be part of escape/defence responses to predation, should remain an open question.

Systematic Distribution of Bioluminescence in Marine Animals: A Species-Level Inventory

“…These photophores are easy to spot using the naked eye, even by a luminescence non-specialist since (i) they are often relatively large with a wellidentifiable structure adapted to their role (e.g., they typically have a pigmented sheath with accessory optical structures such as lenses and/or filters [96]), and (ii) they produce a long lasting-light display (typically 'glows', which last >2 s) even in moribund specimens, which facilitate field and laboratory observations [97]. On the other hand, many of the luminescent taxon-poor groups contain benthic species with virtually invisible photogenic structures (e.g., isolated photocytes or internal secretory organs) involved in short light displays (e.g., typically 'flashes', which last ≤2 s) upon predator stimulation [16,[98][99][100][101][102][103]. This strongly suggests the underrepresentation of luminescent taxa in some taxonomic groups to reflect (at least partly) an experimental bias rather than a difference in functional ecology.…”

Morphological convergence and adaptation in cave and pelagic scale worms (Polynoidae, Annelida)

“…The extent of such behaviours are poorly documented, but are known to also occur in a variety of invertebrates, like appendicularians, chaetognaths and annelids 4 . Tomopterids (Annelida), fast, agile swimmers capable of escape, displays a distinctive curling behaviour when agitated, interpreted as a form of Batesian mimicry given that their primary predator avoidance is their transparency and speed 10 , 48 . Similar to tomopterids , the holopelagic Drieschia (pers.…”

“…However, Drieschia has strongly fluorescent cells in their elytra, which typically indicates bioluminescent capabilities, similar to other polynoids with bioluminescent elytra 49 . Additionally, all members of Tomopteridae emit bioluminescent light 48 , 49 and have also been observed “curling”. It should be noted though that tomopterids eject bioluminescent mucus from the tips of their parapodia, which is unlikely to be used as a form of camouflage, but instead act as a “burglar alarm”.…”

A review of mechanically stimulated bioluminescence of marine plankton and its applications

“…These discarded segments are used to distract predators while the worm escapes (Osborn et al, 2009). It is thought that bioluminescence in pelagic polychaetes is mainly used as a predator deterrent, with the exception of Syllid and Tomopterid worms, which also use bioluminescence for mating and intraspecific signaling (Fischer and Fischer, 1995;Gouveneaux et al, 2018). Francis et al (2016) studied the bioluminescence of two planktonic Flabelligeridae species, Flota flabelligera and Poeobius meseres.…”