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Having been successfully bred in semi-intensive and intensive aquaculture systems, oval squids of the Sepioteuthis lessoniana species complex are emerging as promising candidates for research and industry. Nevertheless, information about pathogens and diseases that may affect squid aquaculture remains sparse. In this study, we identify new parasitic copepod species that causes squid mortality and decreases squid hatching rates, and we also offer a solution to eliminate the pathogen during incubation of squid eggs. The newly discovered copepod Ikanecator primus gen. et sp. nov. was identified on oval squid eggs for the first time using both morphological and molecular diagnostic markers. In the genomes of the copepod and associated microbiome, we identified multiple genes for enzymes involved in cephalopod eggshell degradation in genomes of the copepod and associated microbiome. Furthermore, we conducted experiments to assess efficacy of peracetic acid in inhibiting the I. primus gen. et sp. nov. both in vitro and in vivo using immersion treatment. We established that a 2-min exposure to a concentration of 250 μl/L of peracetic acid containing product (PAA-product; 35 mg/L PAA and 15 mg/L H2O2) inhibited the development of nauplii in vitro. All parasites exposed to a concentration of 500 μl/L of PAA-product (70 mg/L PAA and 30 mg/L H2O2) were eliminated within two minutes. On top of this, the immersion treatment with 500 μl/L of PAA-product (70 mg/L PAA and 30 mg/L H2O2) improved survival of squid embryos and increased size of squid hatchlings compared with control and the immersion treatment with 125 μl/L of PAA-product (17.5 mg/L PAA and 7.5 mg/L H2O2) and the immersion treatment with 250 μl/L of PAA-product (35 mg/L PAA and 15 mg/L H2O2). These findings suggest that PAA holds a great potential as inhibitor and controller of parasitic copepod infections and for overall health management in cephalopod culture. [ABSTRACT FROM AUTHOR]

The relative contribution of Sepioteuthis sp. 1 and Sepioteuthis sp. 2 to oval squid fishery stocks in western Japan was examined using microsatellite DNA and partial sequences of mitochondrial cytochrome oxidase subunit I. A total of 1718 Sepioteuthis spp. individuals from 19 populations were identified to determine the proportion of each species in fishery stocks. Samples from Tanegashima and Yakushima Islands in southwestern Japan were also examined to determine depth distributions. DNA was used to refer 233 (17.3 %) individuals to Sepioteuthis sp. 1 and 1421 (82.7 %) individuals to Sepioteuthis sp. 2. Sepioteuthis sp. 1 was found on the Pacific side of mainland Japan, but was predominant in Tanegashima (77.1 %) and Yakushima Islands (100 %), suggesting its distribution was limited by the warmer waters of the Kuroshio Current. In contrast, Sepioteuthis sp. 2 was most commonly found around mainland Japan. Whereas Sepioteuthis sp.1 was caught in 10 to 53 m depth, Sepioteuthis sp. 2 was caught in 2 to 30 m depth. Differences in the spatial and bathymetric distributions of these two species might reflect differences in temperature preference, spawning depth, and migration patterns. Our results would be useful for managing the fishery stocks and spawning grounds of both species. [ABSTRACT FROM AUTHOR]

The big-fin reef squid, Sepioteuthis cf. lessoniana (Lesson 1930), is an important commodity species within artisanal and near-shore fisheries in the Indian and Indo-Pacific regions. While there has been some genetic and physical evidence that supports the existence of a species complex within S. cf. lessoniana, these studies have been extremely limited in scope geographically. To clarify the extent of cryptic diversity within S. cf. lessoniana, this study examines phylogenetic relationships using mitochondrial genes (cytochrome oxidase c, 16s ribosomal RNA) and nuclear genes (rhodopsin, octopine dehydrogenase) from nearly 400 individuals sampled from throughout the Indian, Indo-Pacific, and Pacific Ocean portions of the range of this species. Phylogenetic analyses using maximum likelihood methods and Bayesian inference identified three distinct lineages with no clear geographic delineations or morphological discriminations. Phylogeographic structure analysis showed high levels of genetic connectivity in the most widespread lineage, lineage C and low levels of connectivity in lineage B. This study provides significant phylogenetic evidence for cryptic lineages within this complex and confirms that cryptic lineages of S. cf. lessoniana occur in sympatry at both small and large spatial scales. Furthermore, it suggests that two closely related co-occurring cryptic lineages have pronounced differences in population structure, implying that underlying differences in ecology and/or life history may facilitate co-occurrence. Further studies are needed to assess the range and extent of cryptic speciation throughout the distribution of this complex. This information is extremely useful as a starting point for future studies exploring the evolution of diversity within Sepioteuthis and can be used to guide fisheries management efforts. [ABSTRACT FROM AUTHOR]

Abstract: Many animals release secretions in defense against predators. Some marine molluscs, including cephalopods (squid, octopus, cuttlefish) and gastropods (sea hares), release a colored ink secretion. Observational evidence supports the idea that inking is a defensive behavior that protects cephalopods from predators by forming a visual smokescreen or visual mimic (pseudomorph). Another possible function of cephalopod ink is to act against the chemical senses of predators either as a deterrent or distracting food mimic (phagomimic). Experimental tests of both hypotheses are lacking for cephalopods. In our study, we tested the hypothesis that squid use ink as a defense against attacks by predatory fish by performing three sets of experiments to examine the behavior of juvenile French grunts, Haemulon flavolineatum, toward ink from Caribbean reef squid, Sepioteuthis sepioidea. In the first set of experiments, a pseudomorph assay, in which ink was presented between a fish and a piece of food, assessed effects of ink on the approach and capture phase of a predator''s attack. This showed that a pseudomorph of squid ink hindered the attack by significantly delaying food capture as well as evoking significantly more avoidance of or biting at the pseudomorph compared to a control pseudomorph of carboxymethylcellulose. A pseudomorph of carboxymethylcellulose plus food color to simulate the color of squid ink had a similar effect to the squid ink pseudomorph. In a second set of experiments, a disc assay, in which ink was added to meat-flavored paper discs, examined ink''s effect on the consumption of food, simulating ink''s protective effect if a squid and its ink are taken into a predator''s mouth. This showed that squid ink added to meat-flavored discs significantly changed handling of the discs and increased, though non-significantly, their rejection. The same food color as used in the pseudomorph assay, when added to meat-flavored discs, significantly affected handling and rejection of the discs, showing that the food color itself, intended as a control, is unpalatable. In the third set of experiments, the disc assay was used to show that ink did not increase the acceptance of unflavored (i.e. without meat) discs, a result suggesting that ink is not a phagomimic. Our study presents the first experimental results supporting the hypothesis that inking protects squid against predatory fish, and that it acts during both the capture and consummatory phases of attacks: during the capture phase through visual and/or chemical effects against predators, and during the consummatory phase through unpalatable chemicals. [Copyright &y& Elsevier]

Abstract: Animals often respond to attacks from predators with behaviors directed at the predator that increase the probability of escape. Some animals also respond to attacks with behaviors that release signals or cues that are detected by conspecifics and enhance escape. Cephalopods, with their complex nervous systems, produce many behaviors, one of which is ejecting ink when attacked by predators. Ink is thought to enhance the ability of the inking cephalopod to escape from the predator, which is a reasonable idea but is lacking experimental support and description of mechanisms. Inking might also serve as an alarm cue, evoking alarm responses in conspecifics. The aim of our study was to determine if ink of the Caribbean reef squid, Sepioteuthis sepioidea, is a conspecific alarm cue. We studied freely behaving animals in the laboratory to determine if they produced alarm or escape behavior in response to ink. We observed that squid responded to conspecific ink introduced into their aquarium with deimatic behaviors containing chromatophore elements (‘eye spots’, ‘all brown’, and ‘flashing’), cryptic behaviors with chromatophore elements (‘clear’, ‘plaid’, ‘dark arms’), cryptic behaviors with postural responses (‘sargassum’, ‘bad hair’), and protean behavior (‘fin movement’, ‘inking’, ‘jetting’). Squid also responded to ink introduced into an adjacent aquarium within view, thus demonstrating that vision can contribute to the alarm response. Melanin-free ink did not evoke a significant alarm response. This is the first experimental demonstration that squid respond to ink of conspecifics as a visual alarm cue. Ink may also provide a chemical alarm cue for S. sepioidea, though further behavioral studies are needed to explore this. [Copyright &y& Elsevier]

Abstract: This paper describes a new method developed to directly measure size and temperature specific growth rates of individual wild squid. Our tag and recapture method is complimentary to previously employed statolith aging methods but provides finer scale detail. The Caribbean reef squid, Sepioteuthis sepioidea, is an ideal model organism for field work on squid life-history as they live in shallow coastal areas and are accessible. These squid were tagged and monitored for tag retention and growth rates over a period of 56 days in the laboratory and 27 days in the field. A total of 103 squid were tagged, 10 in the laboratory and 93 in the field. Visible Implant Elastomer (VIE) tags and Visible Implant Alphanumeric (VI Alpha) tags were used during this experiment. None of the VI Alpha tags were retained in laboratory animals, but VIE tags remained visible for the duration of the laboratory study and were used in all field studies. The 10 recaptured squid weighed from 19.1 to 122.9g with an average and standard deviation recapture weight of 56.9±35.5g, compared to their original weights of 48.0±30.5g. In the field, these squid had instantaneous growth rates of 1.19–3.10 with an average growth rate of 1.93±0.71 at temperatures ranging from 19.5 to 23.7°C. [Copyright &y& Elsevier]