Summary: Here, we present 10 observations of the European cuttlefish Sepia officinalis (Linnaeus 1758) forming groups of up to 30 individuals along the South Coast of the UK. The majority of the observed cuttlefish appeared to be juveniles or subadults and showed different shoaling orientations, such as linear or spherical-shaped formations. This indicated the grouping behaviour did not derive from coincidental accumulations. No mating or courtship behaviour could be identified in these groups, and as all observations were made in August or September, and therefore outside their mating season (March to June), it is unlikely that reproductive behaviour motivates these aggregations. As S. officinalis is known to migrate to deeper overwintering grounds in autumn, we propose that cuttlefish may temporarily form groups in late summer/early autumn as part of their migration pattern, and that their shoaling behaviour likely offers similar fitness benefits as in other migrating shoaling species.
Summary: Here, we use photo and video footage collected through the Cephalopod Citizen Science Project to describe the hunting, burying, mating and spawning behaviour of the stout bobtail squid Rossia macrosoma (Delle Chiaje, 1830) from Scottish waters. Based on our long-term observations, we were able to determine a spawning period from August to November based on different behavioural traits for this species. Furthermore, we observed R. macrosoma to be able to adhere a sand grain layer (‘sand coat’) to its dorsal mantle. This behavioural feature has only been reported for two genera of the sepiolid subfamily Sepiolinae so far, and therefore represents the first of this kind for the subfamily Rossiinae. Lastly, we identified a local sea urchin species as an active predator of egg batches of R. macrosoma and discussed the cryptic egg laying behaviour of this bobtail squid species in terms of its protective traits to avoid egg predation.
Summary: Bottletail squids (Cephalopoda: Sepiadariidae) spend the daytime buried in the sediment; however, their burying behaviour has not yet been described in detail. In the present study, the burying pattern of a single tropical bottletail squid Sepiadarium kochii Steenstrup 1881 is analysed for different behavioural characteristics. Burying in S. kochii consists of a rapid sequence of strong, alternating forward- and backward directed funnel jets which obscure the individual almost fully with sediment, followed by a single flinging movement of the dorsolateral arm pair to cover the remaining exposed body parts with sand.
Summary: Previous studies on insects, spiders and fish have shown that gaze stabilisation is achromatic (= ‘colour-blind’), meaning that chromatic contrast alone (in the absence of apparent intensity contrasts) does not contribute to gaze stabilisation. Following the assumption that polarization vision is analogous in many ways to colour vision, the present study shows that five different crustacean species do not use the polarization of light alone for gaze stabilisation, despite being able to use this modality for detecting predator-like objects. This work therefore suggests that the gaze stabilisation in many crustaceans cannot be elicited by the polarization of light alone.
Summary: Besides a general description of the behavioural ecology of the spotty bobtail squid Euprymna parva, a first observation of an up to now undescribed inking behaviour of sepiolids is reported in this study. E. parva was observed to eject a stretch of ink (‘ink rope’), approximately 4–5 times the length of the animal, and hold on to it motionless, potentially as a masquerade to resemble a floating seagrass leave. The present study further provides detailed information on daily time and activity budgets as well as the tentacular strike speed during hunting, two up to now barely investigated behavioural aspects of the sepiolid ecology.