Browsing by Author "Drerup, Christian"
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- Behavioural aspects of the spotty bobtail squid Euprymna parva (Cephalopoda: Sepiolidae)Publication . Drerup, Christian; Sykes, António; Cooke, Gavan M.Bobtail squids (Sepiolidae, Cephalopoda) have recently been growing in popularity in scientific studies due to their symbiotic relationship with light producing bacteria and their corresponding light emitting organs. However, the overall knowledge on the behaviour of sepiolids is based on observations on just a few of the roughly 70 extant species and must still be considered as sparsely. Understanding their behavioural ecology is not only beneficial to further grasp the complex behavioural patterns of cephalopods, it is also vital for establishing a good welfare practice when holding sepiolids in captivity. Hence, the present study characterised several behavioural aspects of the spotty bobtail squid Euprymna parva. Although the burying, hunting and mating behaviour as well as most escape responses of this less investigated sepiolid species greatly resembled those of other observed bobtail squids, differences to sepiolids from other genera or even from the same genus could be identified in the present study. Additionally, the first observation of an up to now undescribed inking behaviour of sepiolids is reported. 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.
- Habitat preference and behavioural ecology of bobtail squids (Sepiolidae)Publication . Drerup, Christian; Sykes, António V.; Ruskin, AngliaBobtail squids (Sepiolidae, Cephalopoda) have recently become popular in scientific studies as model organisms due to their symbiotic relationship with light producing bacteria. However, the overall knowledge on the behaviour of sepiolids is based on observations on just a few of the roughly 70 extant species and must still be considered as sparsely. As understanding their behavioural ecology is vital for establishing a good welfare when holding sepiolids in captivity, the present thesis aimed at improving the knowledge on the ecology of these cephalopods. In a first study, several behavioural aspects of the so far less-investigated bobtail squid species Sepiola parva were analysed, showing that the behavioural ecology of this sepiolid greatly resembled the observations reported for other bobtail squids. Furthermore, this study did not only present the first detailed information for sepiolids about activity and time budgets as well as the positioning towards the prey and the tentacle speed during hunting events; it also provided the first evidence for the ability to adhere a ‘sand coat’ in the genus Sepiola and the use of ‘ink ropes’ for sepiolids in general. In a subsequent study, the burying behaviour of Sepiola sp. was analysed with regards to the effect of different sediment types. It was shown that the mean grain size played a major role in both the duration and the number of body movements (funnel jets/ arm sweeps) in different burying characteristics. While the latency until the start of burying, the duration and number of funnel jets of phase 1 and the total burying duration was the shortest/lowest on medium grained sediment samples and correspondingly extended on finer and coarser sediment samples, the duration of phase 2 and the number of arm sweeps within phase 2 was the longest/highest on coarser sediment and decreased the finer the sediment was.