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Octopus vulgaris is a species of great interest in research areas such as neurobiology, ethology, and ecology but also a candidate species for aquaculture as a food resource and for alleviating the fishing pressure on its wild populations. This study aimed to characterize the predatory behavior of O. vulgaris paralarvae and to quantify their digestive activity. Those processes were affordable using the video-recording analysis of 3 days post-hatching (dph), mantle-transparent paralarvae feeding on 18 types of live zooplanktonic prey. We show for the first time in a live cephalopod that octopus paralarvae attack, immobilize, drill, and ingest live cladocerans and copepods with 100% efficiency, which decreases dramatically to 60% on decapod prey (Pisidia longicornis). The majority (85%) of successful attacks targeted the prey cephalothorax while unsuccessful attacks either targeted the dorsal cephalothorax or involved prey defensive strategies (e.g., juvenile crab megalopae) or prey protected by thick carapaces (e.g., gammaridae amphipods). After immobilization, the beak, the buccal mass and the radula were involved in exoskeleton penetration and content ingestion. Ingestion time of prey content was rapid for copepods and cladocerans (73.13 ± 23.34 s) but much slower for decapod zoeae and euphausiids (152.49 ± 29.40 s). Total contact time with prey was always <5min. Contrary to the conventional view of crop filling dynamics observed in adult O. vulgaris, food accumulated first in the stomach of paralarvae and the crop filled after the stomach volume plateaued. Peristaltic crop contractions (-18/min) moved food into the stomach (contractions -30/min) from where it passed to the caecum. Pigmented food particles were seen to enter the digestive gland, 312 ± 32 s after the crop reached its maximum volume. Digestive tract contents passed into the terminal intestine by peristalsis (contraction frequency -50/min) and defaecation was accompanied by an increased frequency of mantle contractions. Current results provide novel insights into both, O. vulgaris paralarvae-live prey capture strategies and the physiological mechanisms following ingestion, providing key information required to develop an effective rearing protocol for O. vulgaris paralarvae. [ABSTRACT FROM AUTHOR]

This study analyzes the effect of low salinity on survival and daily food ingestion of octopus subjected to three different water salinities (20, 25, and 30 psu) for 3 days. During the 3-day experiment, octopuses at 20 psu immediately stopped eating, and all died during the first day; at 25 and 30 psu, the octopuses gradually reduced their feed intake and stopped eating after 2 days, but all survived, and when normal salinity conditions were reestablished (34–35 psu), they ingested 30–40 (~27.5% of the initial food intake) and 70–90 g of food/day (~63% of the initial food intake) respectively over the 5-day recovery period. Water salinity of 30 psu could be considered as the recommended lower limit below which actions, such as transferring the commercial floating cages to another location or submerging them, should be taken in order to prevent the negative effects of low salinities on farmed octopuses. [ABSTRACT FROM PUBLISHER]