ALBERT

Description: A detailed analysis of lower rostral beak length (LRL) to body size and wet body mass measurements was carried out for the squids Loligo forbesi, Todarodes sagittatus and Todaropsis eblanae. Specimens were sampled in the northern North Sea during two research cruises of FRV WALTHER HERWIG III in January/February of 1998 and 1999. Altogether 241 specimens of Loligo forbesi (ML = 45–376 mm), 108 specimens of Todarodes sagittatus (ML = 173–325 mm) and 97 specimens of Todaropsis eblanae (ML = 30–127 mm) were investigated to correlate lower rostral beak length with both mantle length and wet body mass. Linear relationships between LRL and mantle length and powerfunctional relationships between LRL and wet body mass were calculated for all three species. By calculating these correlations separately for males and females, no obvious sex-specific relationships were found. The presented data will upgrade the information on beak/mantle length/body mass relationships of major cephalopod species of the North Sea. They provide essential information for future use in estimates of cephalopod prey biomass in North East Atlantic top predators such as whales, seals, seabirds and fishes.

Description: From April to June of 1987 R/V Meteor collected zooplankton and micronekton samples in the northeastern part of the Arabian Sea. One hundred and fifty-seven cephalopod specimens were captured by oblique IKMT hauls through water depths from 1,000 to 0 m and identified to the lowest possible taxon. Thirteen species of nine families were recorded. The majority of the specimens were early life stages of pelagic oceanic species. The cranchiid squid Liocranchia reinhardti was the dominant form (108 specimens) followed by the enoploteuthid squids Abraliopsis lineata (22) and Abralia marisarabica (9). Size-frequency compositions and maps of the geographical distribution are compiled for the most abundant species. The data reveal a tropical cephalopod fauna and will improve the poor knowledge on the distribution patterns of pelagic cephalopods in the Indian Ocean.

Description: Cephalopods (n = 515) were identified from a series of plankton and fine meshed mid-water trawls, taken between 1977 and 1999, around the British Isles. The collections were not directed at cephalopods, but provide valuable information on the distribution of planktonic species and on the paralarvae of the benthic species. The most abundant species in neritic areas were the octopod Eledone cirrhosa and the sepiolids, Sepietta oweniana and Sepiola atlantica. Eledone cirrhosa were common in samples to the north and west of Scotland, particularly in early summer. The mantle lengths of E. cirrhosa were 4–8 mm, indicating a brief planktonic existence or, perhaps, net avoidance by larger specimens. In the shelf-break collections from the west of Scotland and Ireland the squids Brachioteuthis spp., Gonatus sp., Teuthowenia megalops and rynchoteuthions of the Ommastrephidae were abundant. Two types of rhynchoteuthion were found and were probably Todarodes sagittatus, Illex coindetii or Todaropsis eblanae. Despite the abundance of Loligo forbesi around the British Isles, it was rarely taken in plankton collections, probably indicating that it does not have a planktonic paralarva.

Description: Incirrate octopods (those without fins) are among the larger megafauna inhabiting the benthic environments of all oceans, commonly in water depths down to about 3,000 m. They are known to protect and brood their eggs until the juveniles hatch, but to date there is little published information on octopod deep-sea life cycles and distribution. For this study, three manganese-crust and nodule-abundant regions of the deep Pacific were examined by remote operated-vehicle and towed camera surveys carried out between 2011 and 2016. Here, we report that the depth range of incirrate octopods can now be extended to at least 4,290 m. Octopods (twenty-nine individuals from two distinct species) were observed on the deep Ka'ena and Necker Ridges of the Hawaiian Archipelago, and in a nodule-abundant region of the Peru Basin. Two octopods were observed to be brooding clutches of eggs that were laid on stalks of dead sponges attached to nodules at depths exceeding 4,000 m. This is the first time such a specific mineral-biota association has been observed for incirrate octopods. Both broods consisted of approximately 30 large (2.0-2.7 cm) eggs. Given the low annual water temperature of 1.5°C, it is likely that egg development, and hence brooding, takes years [Robison et al. (2014), doi:10.1371/journal.pone.0103437]. Stalked-sponge fauna in the Peru Basin require the presence of manganese nodules as a substrate, and near total collapse of such sponge populations was observed following the experimental removal of nodules within the DISCOL (DISturbance and COLonisation) area of the Peru Basin [Bluhm (2001), doi:10.1016/S0967-0645(01)00070-4]. Stalked fauna are also abundant on the hard substrates of the Hawaiian archipelago. The brooding behavior of the octopods we observed suggests that, like the sponges, they may also be susceptible to habitat loss following the removal of nodule fields and crusts by commercial exploitation.