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Lateralization appears as a left–right asymmetry of morphology and behaviour in many animal species including both vertebrates and invertebrates and provides functional advantages for survival. Lateralization is expressed at individual and population levels (most individuals in a group are lateralized in the same direction) and switches during ontogeny. Lateralization has been observed in coleoid cephalopods (squid, cuttlefish and octopus) which possess sophisticated lens eyes and a large brain, the largest among invertebrates. In this study, we investigated ontogenetic changes in the lateralization of oval squid, Sepioteuthis lessoniana, by observing their behaviour and the brain region, that is, the optic lobes, that process visual information. Behavioural lateralization was tested by observing which eye solitary and group individuals used to detect prey, predators and conspecifics. Optic lobe lateralization was examined by estimating the left and right optic lobe volumes using microcomputed tomography. We found that eye use and optic lobe lateralization in oval squid changed with the development of schooling behaviour. The right eye was used at a population level for detecting specific targets during the preschooling period, while no trend was detected in both the solitary and group conditions during the schooling period. In the period before school formation, the right eye was used for detecting conspecifics in the solitary condition, while in the group condition, the right eye was used for detecting predators and conspecifics. The strength of eye use, regardless of the direction, appeared at the population level in both the solitary and the group conditions during all life stages. The volume of the right optic lobe gradually became larger than the left lobe during the schooling period, although this was not correlated with behavioural lateralization. The potential role of lateralization in oval squid is discussed.

Cephalopods have acquired numerous novelties and expanded their habitats to various marine environments as highly agile predators. Among cephalopod novelties, multiple arms are used for complex behaviors, including prey capture. Suckers on arms are innovative features for realizing these arm functions. In addition, tentacles in Decapodiformes (squids and cuttlefishes) are arms specialized in prey capture and tentacular suckers show unique morphologies. However, little is known about the developmental process of sucker formation that should differ between tentacles and other arms. In this study, therefore, sucker formation processes on second arms and tentacles were observed and compared in a bigfin reef squid, Sepioteuthis lessoniana, to reveal the developmental processes forming the unique sucker morphologies, especially in tentacles. Morphological and histological observations of suckers during embryogenesis showed that, in second arms, the sucker-producing area appeared at the most distal part. At the most proximal side of the sucker-producing area, new sucker buds were isolated by invagination of the epithelial tissue. At the proximal arm parts, suckers with functional structures were observed. In tentacles, although the basic sucker formation pattern was similar to that in second arms, sucker formation started at earlier embryonic stages and the number of suckers was drastically increased compared to that in second arms. In addition, although 4 sucker rows were observed at the tentacular club, i.e., the thickest part of a tentacle, our observations suggested that 2 sets of 2 sucker rows are compressed to form the 4 rows. Therefore, the sucker-formation processes are temporally and spatially different between arms and tentacles. In addition, S. lessoniana shows conserved and unique patterns of sucker formation in comparison with previously described species, suggesting that sucker formation patterns were diversified among Decapodiformes lineages. This article is protected by copyright. All rights reserved.

Sepioteuthis lessoniana is a crucial squid species in fisheries and plays a critical role in marine ecosystems. At least two taxa of the squid species have been identified in the waters around Japan; however, the basic biological information of these taxa is limited. In this study, the taxa composition of Sepioteuthis was examined using molecular evidence, and the life-history traits and statolith shape of these taxa were analyzed to elucidate the potential population structure. A total of 142 squid samples were collected from six locations around Nagasaki (southwestern Japan) where high taxonomic diversity has been found previously. Three taxa (Sepioteuthis sp. 1, sp. 2, and sp. 2A) were identified based on the mitochondrial cytochrome oxidase c subunit I (COI) gene, among which Sepioteuthis sp. 2A was defined for the first time. Sepioteuthis sp. 2 was predominant in the region (average occurrence rate 84%), whereas Sepioteuthis sp. 1 was rare, with only two individuals found near Goto Islands. The mantle length composition, mantle length–body weight relationship, age structure, and average growth rates were similar between Sepioteuthis sp. 2 and sp. 2A. However, Sepioteuthis sp. 2 mainly hatched during summer (June–July), whereas Sepioteuthis sp. 2A hatched during winter (December–February). The statolith shapes of the squids were similar between the taxa, although slight differences were noted in the wing regions. The three taxa largely overlapped in a principal component analysis bi-plot based on variations extracted from five life-history traits. These results suggest that at least three taxa of Sepioteuthis inhabited the region, although few differences were found between them in life-history traits or statolith shapes that might be substantially influenced by regional oceanographic conditions. This study provides essential information on the population structure and connectivity of the squid, which is crucial in the context of conservation and management measures for fisheries.

The measured gross alpha and gross beta activities in the edible muscle tissues of eleven selected marine species along the coast of North Vietnam varied from 10.2 ± 1.5 to 73.2 ± 8.1 Bq/kg (wwt) and from 10.6 ± 0.4 to 68.8 ± 2.8 Bq/kg (wwt), respectively. The lowest gross alpha activity was recorded for bigfin reef squid (Sepioteuthis lessoniana) as a result of its carnivorous diet, and the highest alpha activity was noted for blood cockle (Anadara granosa) as a result of its omnivorous diet. However, the gross beta activities in both carnivorous and omnivorous species were similar. The highest and lowest gross beta activities were observed for narrow-barred Spanish mackerel (Scomberomorus commerson) and for bigfin reef squid and squid (Teuthida), respectively. All three aforementioned species have carnivorous diets. The calculated annual committed effective dose resulting from the consumption of 25 kg of muscle tissue per year varied from 192 to 1375 μS with an average of 689 μS.

The cephalopods are known to be commercially and ecologically important around the world. This group constitutes four major groups, Cuttlefishes, Squids, Octopuses, and Nautilii. The first three groups are present in the Egyptian Mediterranean and Red Seas and constitute a main component in the fisheries industry in Egypt. In order to understand the biology and ecology of any species, its identification should be conducted properly to maximize the accuracy of any study. The present monograph is prepared to demonstrate an identification key for the squid species of order Teuthoidea in the Egyptian waters. This is the second publication demonstrating a first-in-kind identification key for the three major cephalopod groups. The first monograph was about the cuttlefishes. Six Egyptian squid species were recorded; Loligo vulgaris, Loligo forbesi, Loligo duvauceli, Alloteuthis media, Illex coindetii, and Sepioteuthis lessoniana. Four of them; Loligo vulgaris, Loligo forbesi, Alloteuthis medi and Illex coindetii were recorded in the Mediterranean waters, while the other 2 species, Loligo duvauceli and Sepioteuthis lessoniana were recorded in Suez Gulf, Red Sea. Two squid species; Loligo forbesi and Sepioteuthis lessoniana were recorded in both the Mediterranean and Red Seas. Specimens of each species were collected for the purpose of identification using external morphological features. Body structures were separated and drawn by using a zoom stereoscopic microscope provided with a Camera Lucida drawing tube. The body structures were also photographed by a Canon Digital Camera.

Squid Sepioteuthis lessoniana is a sought-after fisheries commodity, leading to a high exploitation rate. This affects the sustainability of Squid (S. lessoniana) resources in wild, especially Spermonde Island. The aim of this study was to determine the population dynamics and the exploitation rate of Squid (S. lessoniana) in the Spermonde Islands of South Sulawesi. The results of the study are expected to provide information on the level of utilization of Squid and as a basis for sustainable management of squid in Spermonde Islands. The present study was conducted from March to July 2019 in Spermonde Islands, South Sulawesi. A survey was performed by direct measurement of the fish captured by local fishermen and merchants. Data collected on length and weight of squid were carried out for 3 or 4 times a week. The results showed length of squid ranged from 06 to 28 cm, the relationship between the length of the weight was negative allometric, the age group consisted of 4, the growth rate (K) of 0.37 per year, the maximum length (L max) of 31.5 cm, the total mortality rate (Z) of 2.85 per year, the natural mortality rate (M) of 0.95 per year, the capture mortality rate (F) of 1.90 per year and the exploitation rate is classified into over-exploitation.

Diversification of marine culture has an effective value for the sustainability of the livelihoods of small fishermen. In addition it can play a role in preventing the threat of utilization that is not environmentally friendly. Cuttlefish is one of the types of marine biota commodity that has high economic value and has the potential to be developed as a fishery diversification community. The purpose of this study was to determine the indicators of the potential of cuttlefish cultivation as a diversification strategy for small fishermen's cultivation and seagrass conservation in the study location. The research method used is the method of direct observation and interviews. Data analysis uses descriptive statistical analysis. The results showed that the average cuttlefish seedlings were 1293.5 individuals / month and the average cuttlefish caught by fishermen landed at TPI Tanjung Luar was 1229 individuals / month consisting of three species namely Sepia latimanus, Sepia pharaonis and Sepioteuthis lessoniana. In addition, marine cultivation has developed into the choice of livelihood for small fishermen, although it is still complementary. Furthermore, the group of farmers plays an active role in preventing local threats from uses that are not environmentally friendly. The conclusion is the diversification of cultivation with cuttlefish community is of strategic value to overcome the problem of the sustainability of small fishing livelihoods and local scale seagrass conservation in the study location. Therefore, diversification of cuttlefish culture can be considered, especially at the scale of small fishermen as a policy of developing seafood products to achieve food security, both at local, regional and national scale.

The oval squid Sepioteuthis lessoniana is polyandrous, and a female mates with several males during a spawning season. This has resulted in two alternative male mating tactics in this species. The larger consort males usually use the male-parallel (MP) mating posture to put spermatophores at the opening of the oviduct; the smaller sneaker males predominantly use the male-upturned (MU) mating posture to place spermatophores around the female’s buccal membrane. Since squid eggs are released from the oviduct, MP mating is expected to have a higher fertilization rate than MU mating. Given the fact that these two male mating tactics are largely dependent on the body size of the male relative to the female, it is unclear how the smaller males are able to reproductively compete with the larger males. On analyzing spermatophore and sperm morphology from populations of adult male squids, spermatophore size was found to be positively correlated with mantle length of these squids, but sperm length was negatively correlated with squid mantle length. More importantly, no distinct size dimorphism exists in relation to either spermatophore morphology or sperm morphology. The overlap in size distributions of the spermatophores and sperms of the male squid thus implies that medium-sized males may have flexible reproductive strategies, switching between MP and MU mating tactics depending on the context of the mating event and/or female choice. This presumed behavioral plasticity might increase the reproductive success of these males and maintain the dynamic stability of two alternative mating types in this polyandrous species.

The accessory nidamental gland (ANG) is part of the reproduction organ in the majority of female cephalopods, including the bigfin reef squid Sepioteuthis lessoniana, an economically important fishery product. Microbes in Alphaproteobacteria, Gammaproteobacteria, and Verrucomicrobia have been suggested to play a role in the maturation of the S. lessoniana ANG and are responsible for its color. However, the bacterial composition and dynamics of the different maturation stages of the ANG remain unclear. In the present study, we surveyed ANG-associated bacterial dynamics in wild-caught S. lessoniana at various developmental stages in different populations over 3 years. The results obtained showed that the ANG bacterial community shifted gradually and decreased in diversity throughout maturation. Verrucomicrobia occupied the ANG during the early stages in large numbers, and was replaced by Bacteroidia, Alphaproteobacteria, and Gammaproteobacteria in the later stages. Flavobacteriales and Alphaproteobacteria both appeared to contribute to pigmentation, while Bacteroidia, Alphaproteobacteria, and Gammaproteobacteria may be involved in enriching the heme biosynthesis pathway in the ANG with the maturation of S. lessoniana. The present results provide an open question of whether S. lessoniana actively selects the bacterial community in the ANG to adjust to its surrounding environment.

Bigfin reef squid (Sepioteuthis lessoniana) is a candidate squid species that has potential to be utilized in aquaculture on a commercial scale. Although this species has been successfully cultured over multiple generations, appropriate feeding strategies are still limited due to a lack of understanding of its digestive physiology. The present study focused on digestive enzymes and chyme characteristics in terms of time response profiles following feeding. Squids (1.78 ± 0.05 g body weight) were serially collected at different post-prandial times (0, 0.5, 1, 2, 4, 6, 8, 12, 18 and 24 h) and the specimens were used in the analysis of digestive enzymes (n = 10) and chyme characteristics (n = 5). Food provided to the animals substantially transited to the gastrointestinal tract and peaked at 1 h after feeding, and then dramatically decreased with post-prandial time (P

Sepioteuthis lessoniana is a widely distributed neritic squid in the Indo-Pacific Ocean. It is an important species in fisheries, but species management is difficult because of inadequate information regarding its life history. The daily growth and δ18O values from the core to the edge of statoliths of S. lessoniana collected in northern Taiwan were analyzed to predict the experienced temperature history along with ontogenetic stages. The probability of occurrence in a given area at each life stage in three seasonal groups was determined using salinity values, deduced and measured temperatures, and the known ecology of S. lessoniana. The results showed that ontogenetic variation in the statolith δ18O values in S. lessoniana reflected the seasonal temperature fluctuation observed in Taiwanese waters, which indicated the reliability of the prediction method. Complex and diverse distribution and movement patterns were observed in the three seasonal groups. The results also indicated the importance of the waters near the coast of northeastern Taiwan as a spawning ground. Based on a model prediction, the distribution of S. lessoniana is likely associated with water temperature and current. A potential migration route from the Penghu Islands to northeastern Taiwan suggests a high level of population connectivity in S. lessoniana in Taiwan. This study provides information on the spatial and vertical distribution of S. lessoniana at various ontogenetic stages, which is essential for resource management and conservation of this commercial species.

MORPHOLOGY, CLASIFICATION, AND DISTRIBUTION OF SQUID FAMILY LOLINGINIDAE. Squids are one of Indonesian export commodities that is produced in frozen, salted, dried or canned, however the information about biology, ecology, habitat and distribution of squid are little known. Squid have ten tentacles equipped with suction, and generates ink to defend against their enemies. Squids are demersal or semi-pelagic animal that lives in the waters column up to a depth of 400 m with diurnal movements. Squids reproduce sexually and by deocious. Squids with family Lolinginidae (genus Lolious) are distributed across the Indonesian waters with temperatures of 8 to 32 C and salinity of 8.5 to 30 ppm. Familly Lolinginidae is grouped into several genera included Afrololigo, Allotheuthis, Dorytheuthis, Heterololigo, Loliolus, Lollinguncula, Pickfordiateuthis, Sepioteuthis, dan Urotheuthis

There is increasing evidence that projected near‐future carbon dioxide (CO2) levels can alter predator avoidance behaviour in marine invertebrates, yet little is known about the possible effects on predatory behaviours. Here we tested the effects of elevated CO2 on the predatory behaviours of two ecologically distinct cephalopod species, the pygmy squid, Idiosepius pygmaeus, and the bigfin reef squid, Sepioteuthis lessoniana. Both species exhibited an increased latency to attack and altered body pattern choice during the attack sequence at elevated CO2. I. pygmaeus also exhibited a 20% decrease in predation rate, an increased striking distance, and reduced preference for attacking the posterior end of prey at elevated CO2. Elevated CO2 increased activity levels of S. lessoniana comparable to those previously shown in I. pygmaeus, which could adversely affect their energy budget and increase their potential to be preyed upon. The effects of elevated CO2 on predatory behaviours, predation strategies and activity levels of cephalopods reported here could have far‐reaching consequences in marine ecosystems due to the ecological importance of cephalopods in the marine food web.

Bigfin reef squid (Sepioteuthis lessoniana) is an economically important exported aquatic animal in Thailand, but little is known about its husbandry, which needs to be clarified. In this study, the ontogenic development of the main digestive enzymes (pepsin, trypsin, chymotrypsin, lipase and amylase) was investigated within 30 days after hatching (DAH). Fertilized eggs of the wild cuttlefish were hatched and then distributed into four replicate aquaria assigned to varying collection times (0, 5, 10, 15, 20, 25 and 30 DAH). The development of pepsin suggests acidic digestion functionality at 5 DAH, and its specific activity was maintained over the studied period. Specific activities of the serine proteases, trypsin and chymotrypsin, fluctuated significantly with similar pattern, and appear to be the key enzymes contributing ontogenic changes in protein catabolism. The specific activity of lipase was relatively high at 0 DAH, dramatically increased by 5 DAH, and then appeared constant until the end of observations, suggesting important role in utilizing the lipid from yolk at hatching, as well as probably in sparing protein utilization. Dramatic increase in amylase specific activity occurred by 10 DAH after which the activity was constant until 30 DAH, suggesting the utilization of carbohydrate as energy evolves comparatively late. Findings from the current study could be used to manage nutritional protocols according to the digestive enzyme patterns, as well as to develop artificial diets for rearing S. lessoniana.

Oval squids are polyandrous, with one female mating with multiple males during the spawning season. There are two alternative male mating tactics used by Sepioteuthis lessoniana. Larger males place spermatophores at the opening of the oviduct using a male-parallel mating posture, whereas smaller males attach spermatophores around the female buccal membrane using a male-upturned mating posture. If the route of egg transportation is taken into consideration, male-parallel mating would be expected to result in higher fertilization success than male-upturned mating. Although these male mating tactics are largely dependent on the body size of the male relative to that of the female, it is unclear how female choice affects the male's mating tactics and his mating success. Squids are highly visual animals, and they communicate through dynamic body patterning. In the present study, we observed that smaller male squids in captivity would attempt to mate with a larger female using the male-parallel tactic repeatedly, but they failed to be successful most of the time because of a rejection signal by the female. In contrast, when the males switched to the male-upturned tactic, the mating success rate was increased significantly, with much less female rejection signal. This finding suggests that female squids signal their mating receptivity visually and that male squids alter their mating tactics accordingly. This is the evidence to support the hypothesis that the switch in male mating tactics depends on female choice in oval squids and that this is transmitted via visual communication.

The bigfin reef squid Sepioteuthis lessoniana is a neritic species widely distributed in coastal waters of the Indo-Pacific region and is of interest to fisheries for its high commercial value. Squid samples were collected from Keelung (KL) and Penghu (PH), around northern Taiwan from October 2012 to September 2013. A total of 949 squid were examined, and 620 squid were aged using statoliths. The age range of the squid in KL (55–183 days) was similar to that in PH (77–186 days). The squid hatched almost year-round, except in January and December in KL. Two seasonal cohorts were identified: a spring cohort (hatched in March to May) and an autumn cohort (July to October). Concentrations of nine trace elements in statoliths were analysed using solution-based inductively coupled plasma mass spectrometry (ICP-MS). Significant differences in Fe/Ca, Cu/Ca and Sr/Ca were found between the two locations, while significant differences in concentration ratios of Sr/Ca and Ba/Ca were noted between the two seasonal cohorts. Results of a principal component analysis and cluster analysis varied in life-history traits between the two geographic stocks and in elemental concentrations between the two seasonal cohorts. Squid in KL and PH might undertake different migration routes, while seasonal variability in oceanographic conditions was apparent in the two locations.

Indexación: Scopus. According to the vicariant hypothesis proposed by Brakoniecki (1986) the closure of the Sea of Tethys and the opening of the Atlantic Ocean would play an important role in the history of squids of the family Loliginidae, which is reflected in its current neritic distribution. Our study evaluated this hypothesis and alternative ideas to understand the historical biogeography of loliginid squids. This work is based on a phylogenetic hypothesis rebuilt with mitochondrial and nuclear sequences that incorporates the estimation of divergence times and ancestral distribution. Our results sustain that the squids of the family Loliginidae would have originated in the Western Pacific during the Late Paleocene about 59 My, following, during their diversification, at least 20 dispersion and 6 vicariant events. The first vicariant event fragments the ancestral distribution, remaining the ancestor of Sepioteuthis in the south and the subfamily Loligininae in the north. Successive events of dispersion, and some of vicariance (unrelated with the movement of tectonic plates and opening of the Atlantic Ocean), modeled it distribution. Our inference suggest a different origin compared to proposed by Brakoniecki (Tethys Sea), consistent with a center of origin that supports the most diversity of the family, with a predominance of dispersion processes over vicariant events, which explain the present distribution pattern. http://www.lajar.cl/pdf/imar/v45n1/Art%C3%ADculo_45_1_11.pdf

Female and male specimens of Doridicola similis Ho and Kim, 2001 (Copepoda: Poecilostomatoida: Rhynchomolgidae) from the gills of the loliginid squid Sepioteuthis sp. (called shiro-ika) (Cephalopoda: Myopsida: Loliginidae) in coastal Pacific waters of central Japan are described as a new country record. This collection represents the second record of D. similis and expands its distribution range from the Gulf of Thailand (type locality) northeast to the western North Pacific Ocean off central Japan.

Cephalopods in nature undergo highly dynamic skin coloration changes that allow rapid camouflage and intraspecies communication. The optic lobe is thought to play a key role in controlling the expansion of the chromatophores that generate these diverse body patterns. However, the functional organization of the optic lobe and neural control of the various body patterns by the optic lobe are largely unknown. We applied electrical stimulation within the optic lobe to investigate the neural basis of body patterning in the oval squid,Sepioteuthis lessoniana. Most areas in the optic lobe mediated predominately ipsilateral expansion of chromatophores present on the mantle, but not on the head and arms; furthermore, the expanded areas after electrical stimulation were positively correlated with an increase in stimulating voltage and stimulation depth. These results suggest a unilaterally dominant and vertically converged organization of the optic lobe. Furthermore, analyzing 14 of the elicited body pattern components and their corresponding stimulation sites revealed that the same components can be elicited by stimulating different parts of the optic lobe and that various subsets of these components can be coactivated by stimulating the same area. These findings suggest that many body pattern components may have multiple motor units in the optic lobe and that these are organized in a mosaic manner. The multiplicity associated with the nature of the neural controls of these components in the cephalopod brain thus reflects the versatility of the individual components during the generation of diverse body patterns.SIGNIFICANCE STATEMENTNeural control of the dynamic body patterning of cephalopods for camouflage and intraspecies communication is a fascinating research topic. Previous studies have shown that the optic lobe is the motor command center for dynamic body patterning. However, little is known about its neural organization and the mechanisms underlying its control of body pattern generation. By electrically stimulating the optic lobe of the oval squids and observing their body pattern changes, surprisingly, we found that there is no somatotopic organization of motor units. Instead, many of these components have multiple motor units within the optic lobe and are organized in a mosaic manner. The present work reveals a novel neural control of dynamic body patterning for communication in cephalopods.

Coleoid cephalopods (squid, cuttlefish, and octopus) have a well-developed and complex central nervous system. Its absolute size is the largest among invertebrates, and the brain-to-body mass ratio is larger than that of fish and reptiles and equivalent to that of birds and mammals. Although a number of histological studies have been conducted on the brains of cephalopods, most of them used a light microscope or an electron microscope, which show the microstructure of the brain, but often cannot image the whole brain instantaneously. Of late, micro computed tomography (CT) has gained popularity for imaging animal brains because it allows for noninvasive three-dimensional (3D) reconstruction and preprocessing that are not cumbersome. To perform micro-CT on cephalopod brains, we first tested conditions suitable for preprocessing, paying special attention to staining conditions that would provide high contrast images. Four agents, iodine in 99.5% ethanol, iodine potassium iodide in water (IKI), phosphotungstic acid in 70% ethanol, and nonionic iodinated contrast agent in water, were tested at various concentrations and durations on brain of juvenile oval squid. To evaluate the quality of staining, we calculated the contrast ratio of the two-dimensional (2D) images and compared 3D segmentation of the best and worst 2D images. We concluded that 3% IKI staining for 7 days was the best combination to enhance the images contrast of the oval squid brain, in which each brain lobe was clearly detected and 3D segmentation of the whole brain was possible. The wider applicability of this preprocessing method for micro-CT of the brains of other cephalopods is discussed.

The use of mass-marking techniques of enriched stable isotopes has increased in studies of ecology, movement patterns and the dispersal of marine organisms. However, the efficacy of this technique and its potential effects on hatchling size and statolith chemistry of cephalopods are yet to be investigated. Sepioteuthis lessoniana egg capsules were collected from northern Taiwan and assigned randomly to 137Ba-spiking experimental groups at 0.2, 0.5 and 1ppm and three immersion durations (1, 3 and 7 days). Immersion duration >3 days produced significantly lower 138Ba:137Ba ratios, with 100% marking success, indicating that it is a reliable marking technique. The 137Ba mass marking had a positive effect on size at hatch and was likely to affect statolith trace element incorporation, including Cu, Zn and Pb. These findings highlight that it is necessary to consider the species-specific effects on hatchling size and physiological responses in when using stable isotopes mass-marking techniques.

Cephalopods have the most complicated central nervous system (CNS) of all invertebrates at both anatomical and functional levels as demonstrated by the pioneering neuroanatomical work of Cajal and Young decades or indeed a century ago. An octopus brain with over 200 million neurons is equivalent, numerically at least, to that of a rat. Brain complexity, their rich behavioral repertoire and most famously the eye, highlight cephalopods and vertebrates as an example of convergent evolution. Perhaps due to its size and complexity, our knowledge of the cephalopod brain still relies mostly on old histological approaches and a few attempts at dye-labelled projections. Here using the new technique of diffusion magnetic resonance imagery (dMRI) tempered with highly conservative tract-acceptance thresholds and cross-validated with traditional histology and neural tracers, we reveal 153 previously undescribed lobe interconnections and novel within-lobe morphologies in the brain of the reef squid, Sepioteuthis lessoniana. Almost all established connections are re-confirmed and the beginnings of a new brain-wide neural connection “atlas” is erected. As with vertebrate examples, using the complementary techniques of MRI, traditional histology and dye-based tractography, such a ‘circuit diagram’ for cephalopod neural architecture leads to a better understanding of their complex behaviors. It also supports emerging hypotheses around anatomical and functional convergence with parts of the vertebrate central nervous system, including projections of overall body axes. Notably it provides a firm base upon which to place the currently fashionable but contentious cephalopod cognitive capabilities.

Paralarvae of nine species of cephalopods, including the bobtail squid (Euprymna hyllebergi), sharp-tail pygmy squid (Idiosepius pygmaeus), bigfin reef squid (Sepioteuthis lessoniana), needle cuttlefish (Sepia aculeata), spineless cuttlefish (Sepiella inermis), Pharaoh cuttlefish (Sepia pharaonis), marble octopus (Amphioctopus aegina), lesser blue-ringed octopus (Hapalochaena maculosa), and muddy argonaut (Argonauta hians) were collected from broodstock that had been cultured in the laboratories of the Department of Marine Science, Faculty of Fisheries of Kasetsart University in Bangkok, Thailand. The external morphological characteristics of the paralarva of each species were observed and recorded, such as the number and pattern of chromatophores, weight, length, and length index of the mantle. The compiled information would be a useful reference for the identification of cephalopods, especially at species level.

In vitro fertilization of squid requires the jelly substance found in the female oviducal gland; yet, the active component of this substance that facilitates fertilization remains unknown. Here, we used biochemical methods to separate the jelly substance of Todarodes pacificus (Oegopsida) and Sepioteuthis lessoniana (Myopsida family) into four fractions; specifically, two water soluble fractions (Molecular weight > 10,000 and

Anthropogenic carbon dioxide (CO2) emissions are being absorbed by the oceans, a process known as ocean acidification, and risks adversely affecting a variety of behaviours in a range of marine species, including inhibited learning in some fishes. However, the effects of elevated CO2on learning in advanced invertebrates such as cephalopods are unknown. Any impacts to the learning abilities of cephalopods could have far-reaching consequences for their populations and the communities they inhabit. Cephalopods have some of the most advanced cognitive abilities among invertebrates and are one of the few invertebrate taxa in which conditional discrimination has been demonstrated, though the trait has not been demonstrated in any species of squid. Here, we tested for the first time the capacity for conditional discrimination in a squid species (Sepioteuthis lessoniana). Furthermore, we investigated the effects of projected future CO2levels (1,084 µatm) on conditional discrimination and learning more generally. A three-task experiment within a two-choice arena was used to test learning and conditional discrimination. Learning was measured by improvements in task completion in repeated trials over time and the number of trials required to pass each task. Squid exhibited significant learning capabilities, with an increase in correct choices over successive trials and a decrease in the number of trials needed to complete the successive tasks. Six of the 12 squid tested successfully passed all three tasks indicating a capacity for conditional discrimination in the species. Elevated CO2had no effect on learning or on the capacity for conditional discrimination in squid. This study highlights the remarkable cognitive abilities ofS. lessoniana, demonstrated by their capacity for conditional discrimination, and suggests that ocean acidification will not compromise learning abilities. However, other behavioural traits in the species have been shown to be altered at comparable elevated CO2conditions. It is not clear why some ecologically important behaviours are altered by elevated CO2whereas others are unaffected. Future research should focus on the physiological mechanism responsible for altered behaviours in squid at elevated CO2.

The wide disparity in adult body size observed both within and among animal taxa has long attracted widespread interest, with several general rules having been proposed to explain trends in body size evolution. Adult body size disparity among the cephalopod mollusks is remarkable, with adult body sizes ranging from a few centimeters to several meters. Some of the smallest cephalopods are found within Pickfordiateuthis, a group comprising three described species of squid found in the western Atlantic and tropical eastern Pacific. Pickfordiateuthis pulchella, the type species of the genus, was initially proposed to be closely related to the loliginid squids (Loliginidae), with subsequent descriptions of additional species supporting a placement within Loliginidae. Pickfordiateuthis is remarkable in that all species reach sexual maturity at about one-fifth to one-tenth the size seen in most loliginid species. To date, no phylogenetic analyses have included representatives of Pickfordiateuthis. To infer the phylogenetic position of Pickfordiateuthis and explore its implications for body size evolution, we collected specimens of Pickfordiateuthis pulchella from Brazilian waters and sequenced regions of two loci—the mitochondrial large ribosomal subunit (rrnL a.k.a. 16S) gene and the nuclear gene rhodopsin. Maximum likelihood and Bayesian analyses of these sequences support a placement of Pickfordiateuthis pulchella as sister to a clade comprising the Western Hemisphere loliginid genera Doryteuthis and Lolliguncula. Analyses of body size evolution within Loliginidae suggest that a shift to a smaller body size optimum occurred along the lineage leading to P. pulchella, with some evidence of shifts toward larger sizes in the ancestors of Loligo and Sepioteuthis; these inferences seem to be robust to phylogenetic uncertainty and incomplete taxon sampling. The small size and juvenile-like morphological traits seen in adult Pickfordiateuthis (e.g., sepiolid-like fins and biserial sucker arrangement in the tentacles) may be due to paedomorphosis.

Long-term exposure to projected future CO2 levels has no effect on the aerobic performance of two tropical cephalopod species. The resting oxygen uptake rates, maximal oxygen uptake rates, aerobic scope, and recovery time of both bigfin reef squid and two-toned pygmy squid were unaltered by elevated CO2., Squid and many other cephalopods live continuously on the threshold of their environmental oxygen limitations. If the abilities of squid to effectively take up oxygen are negatively affected by projected future carbon dioxide (CO2) levels in ways similar to those demonstrated in some fish and invertebrates, it could affect the success of squid in future oceans. While there is evidence that acute exposure to elevated CO2 has adverse effects on cephalopod respiratory performance, no studies have investigated this in an adult cephalopod after relatively prolonged exposure to elevated CO2 or determined any effects on aerobic scope. Here, we tested the effects of prolonged exposure (≥20% of lifespan) to elevated CO2 levels (~1000 μatm) on the routine and maximal oxygen uptake rates, aerobic scope and recovery time of two tropical cephalopod species, the two-toned pygmy squid, Idiosepius pygmaeus and the bigfin reef squid, Sepioteuthis lessoniana. Neither species exhibited evidence of altered aerobic performance after exposure to elevated CO2 when compared to individuals held at control conditions. The recovery time of I. pygmaeus under both control and elevated CO2 conditions was less than 1 hour, whereas S. lessoniana required approximately 8 hours to recover fully following maximal aerobic performance. This difference in recovery time may be due to the more sedentary behaviours of I. pygmaeus. The ability of these two cephalopod species to cope with prolonged exposure to elevated CO2 without detriment to their aerobic performance suggests some resilience to an increasingly high CO2 world.

The arms and tentacles of squid (Family Loliginidae: Sepioteuthis sepioidea (Blainville), Loligo pealei (LeSueur), Loligo plei (Blainville), Loliguncula brevis (Blainville)) do not possess the hardened skeletal elements or fluid-filled cavities that typically provide skeletal support in other animals. Instead, these appendages are made up almost entirely of muscle. It is suggested here that the musculature serves as both the effector of movement and as the skeletal support system itself. High-speed movie recordings were used to observe prey capture by loliginid squid. Extension of the tentacles (1 pair) during prey capture is probably brought about by contraction of transverse muscle fibers and circular muscle fibers. Contraction of longitudinal muscle fibers causes retraction of the tentacles. Torsion of the tentacles during extension may be the result of contraction of muscle fibers arranged in a helical array. The inextensible but manipulative arms (4 pairs) may utilize a transverse muscle mass to resist the longitudinal compression caused by contraction of the longitudinal muscles which bend the arms. A composite connective tissue/muscle helical fiber array may twist the arms.

Unlike vitellogenin, which is the sole major precursor of yolk protein in all oviparous vertebrates, a variety of major precursor of yolk proteins are found among oviparous invertebrates. Sea urchins have a transferrin-like yolk protein, while all other major precursors of yolk proteins in oviparous invertebrates belong to the superfamily of large lipid transfer proteins (LLTPs). However, a comprehensive understanding of vitellogenesis is absent in cephalopods. To understand control of vitellogenesis by the LLTPs gene, two vitellogenins (VTG1 and VTG2), two apolipophorins (APOLP2A and APOLP2B), and a cytosolic large subunit of microsomal triglyceride transfer protein (MTTP) found in the bigfin reef squid. Only the two VTGs showed high levels of expression in mature females compared to males.We further analyzed the expression profile and localization of both VTGs/VTGs during ovarian development. Our data showed that VTGs/VTGs expressions were correlated to the female reproductive cycle. Ovarian VTG1 and VTG2 were localized in the follicle cells but not in oocytes. In addition, VTG1 and VTG2 were represented in follicle cells and oocytes. Thus, our results showed that both VTGs were synthesized by follicle cells and are then delivered to oocytes. In addition, we demonstrated that VTGs were the major precursor of yolk protein in bigfin reef squid. We also found differential proteolytic cleavage processes of VTG1 and VTG2 during VTGs accumulation in oocytes. Therefore, our data shed light on the molecular mechanism of the yolk accumulation pathway in cephalopods.Summary SentenceTwo distinct vitellogenins, which are synthesized by the follicle cells, are the major precursor of yolk protein of oocytes in bigfin reef squid.

Present study consisted a possible novel natural antimicrobial agent replacing chemicals for preventing the microbial growth and microbial biofilm accumulated on silicone. Since squid ink has long proved to play various primary roles in wide ranges of alternative therapeutic medicine and food applications. This research was designed to report the potential antimicrobial effects of squid ink especially after heat treatment against the microorganisms causing biofilms. Various temperature conditions comprising room temperature (RT), 40, 60, 80, and 100°C were applied to the crude squid ink. Two fresh ink samples isolated from splendid squid (Loligo duvauceli) and soft cuttlefish (Sepioteuthis lessoniana) were determined for their antimicrobial activities after heat treatment on most reported microbes causing biofilms on these plastic substrates. The results showed that after pretreatment at RT-50°C for 15 min, fresh crude ink ofL.duvauceliconsistently presented higher bioactive activity (> 15 mm diameter) thanS.lessoniana(5-10 mm diameter), based on a zone of inhibition of disc diffusion method. From this study, both squid inks could definitely be future applied as active antimicrobial ingredients into silicone.

The level of genetic diversity and population differentiation of oval squid Shiro-ika Sepioteuthis sp. 2 around mainland Japan were examined using highly polymorphic DNA markers. Ten microsatellite loci showed relatively low genetic diversity (average observed heterozygosity H O = 0.68, overall mean number of alleles N A = 10.0) as compared with other squid, which may be explained by a recent history of population expansion. Populations from 12 sites along the coastline of Japan were genetically homogeneous, as measured by F ST values (global F ST: −0.0006; pairwise F ST: from −0.0046 to 0.0083), R ST values (global R ST: 0.0025; pairwise R ST: from −0.0076 to 0.03), a neighbor-joining (NJ) tree based on Cavalli-Sforza and Edwards chord distance, Bayesian clustering or analyses of three geographical groups (Sea of Japan, Seto Inland Sea, and Pacific Ocean; F CT = −0.0005), and should be considered as a single fishery stock. Allele frequencies also showed a high degree of similarity across different years in the samples taken from Hiroshima. Factors influencing this homogeneity include genetic exchange without barriers preventing gene flow, larval dispersal, and active adult migration of Sepioteuthis sp. 2.

The bigfin reef squid Sepioteuthis lessoniana is a neritic squid widely distributed in the Indo-Pacific region and of interest to fisheries for its high commercial value. The age and growth of this squid has been studied along its distribution range, from Japan to Australia; however, the life-history parameters of this squid around Taiwan are unclear. In this study, growth and maturation of S. lessoniana in the waters off northern Taiwan between April 2009 and March 2010 was studied using statolith microstructure analysis. Statoliths of 142 females (88–355 mm mantle length, ML) and 129 males (85–401 mm ML) were read. The oldest female was mature at 216 days (355 mm ML), whereas the oldest male was mature at 209 days (345 mm ML). The squids hatch almost year-round, except in January and February, peaking in May and August–September. The ML-at-age data were best described by Schnute and linear functions for the females and males, respectively. The males attained a higher size-at-age than the females. Maturity ogives by age and ML class indicated that females mature later and at a larger size than males. Growth and maturation parameters of seasonal cohorts showed little difference, although squids hatching in warmer seasons tend to have a faster growth rate and higher size-at-age than those hatching in colder seasons for both sexes. The differences of life-history traits between seasonal cohorts could be inferred by progressive changes in the life-history traits of the squids hatching during transitional months, i.e. months between two peak seasons. These results provide essential life-history traits and improve our understanding of S. lessoniana populations in the waters off northern Taiwan.

The optic lobe is the largest brain area within the central nervous system of cephalopods and it plays important roles in the processing of visual information, the regulation of body patterning, and locomotive behavior. The oval squid Sepioteuthis lessoniana has relatively large optic lobes that are responsible for visual communication via dynamic body patterning. It has been observed that the visual behaviors of oval squids change as the animals mature, yet little is known about how the structure of the optic lobes changes during development. The aim of the present study was to characterize the ontogenetic changes in neural organization of the optic lobes of S. lessoniana from late embryonic stage to adulthood. Magnetic resonance imaging and micro-CT scans were acquired to reconstruct the 3D-structure of the optic lobes and examine the external morphology at different developmental stages. In addition, optic lobe slices with nuclear staining were used to reveal changes in the internal morphology throughout development. As oval squids mature, the proportion of the brain making up the optic lobes increases continuously, and the optic lobes appear to have a prominent dent on the ventrolateral side. Inside the optic lobe, the cortex and the medulla expand steadily from the late embryonic stage to adulthood, but the cell islands in the tangential zone of the optic lobe decrease continuously in parallel. Interestingly, the size of the nuclei of cells within the medulla of the optic lobe increases throughout development. These findings suggest that the optic lobe undergoes continuous external morphological change and internal neural reorganization throughout the oval squid's development. These morphological changes in the optic lobe are likely to be responsible for changes in the visuomotor behavior of oval squids from hatching to adulthood.

Cephalopods use a diverse range of body patterns for visual communication. Each pattern is composed of several distinct chromatic components that are under neural control and are expressed dynamically. In the oval squid Sepioteuthis lessoniana, males use distinct body patterns to interact with females and other males at the spawning site. To systematically examine their visual signals during reproductive behavior, an ethogram of 27 body pattern components produced by S. lessoniana was observed in both the wild and captivity; these were then characterized. Five behaviors were commonly seen among these reproductively active squids, namely parallel swimming, male guarding, male-male fighting, male-parallel mating, and male-upturn mating. Each behavior was found to be composed of the expression in a temporal sequence of different chromatic components. By analyzing the dynamic body patterning time series associated with each behavior, it was found that a certain subset of components was expressed simultaneously or sequentially in response to conspecifics. Importantly, the results not only revealed that each behavior is composed of multiple chromatic components, but the findings also showed that each component is often associated with multiple behaviors. To gain insight into the visual communication associated with each behavior in terms of the body patterning's key components, the co-expression frequencies of two or more components at any moment in time were calculated in order to assess uniqueness when distinguishing one behavior from another. This approach identified the minimum set of key components that, when expressed together, represents an unequivocal visual communication signal. While the interpretation of the signal and the associated response of the receiver during visual communication are difficult to determine, the concept of the component assembly is similar to a typical language within which individual words often have multiple meanings, but when they appeared together with other words, the message becomes unequivocal. The present study thus demonstrates that dynamic body pattering, by expressing unique sets of key components acutely, is an efficient way of communicating behavioral information between oval squids.

Cephalopods (cuttlefishes, squids and octopuses) are highly commercially important marine organisms in the Andaman Islands. DNA barcoding is an effective tool used for identification of individuals at the lowest taxon (species) level and is been widely used for the detection of structural ambiguity of several organisms. In the present study, DNA fragments of mitochondrial cytochrome c oxidase 1 (COI) gene comprising 658 base pairs (bp) were amplified by employing forward LCO 1490 and reverse HCO 2198 primers. Amplified sequences were trimmed to length of 583 bp for complete alignment. The average nucleotide frequencies were studied for eight individuals belonging to seven species (Sepia pharaonis, Sepia aculeata, Uroteuthis duvauceli, Sepioteuthis lessoniana, Octopus cyanea, Abdopus aculeatus, Octopodidae sp.) as A = 29.82%, T = 35.35%, G = 15.33% and C = 19.35%, respectively. Genetic studies revealed that the eight individuals of Coleoid cephalopods belonged to three taxonomic groups viz, (Sepioidea, Myopsida and Octopoda) under different families (Sepiidae, Loliginidae, Octopodidae).

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.

β-Chitin and its chitosan from the gladius of Sepioteuthis lessoniana have been isolated, purified, characterised and compared with the commercial chitosan. Ash, moisture, mineral, metal and elemental content were analyzed using standard techniques. The optical activity of chitin was found to be levorotatory. The degree of deacetylation was calculated by potentiometric titration and (1)H NMR. Viscosity average molecular weight of β-chitosan was calculated by viscometry and size average molecular weight by GPC. The structure of β-chitosan was elucidated with FT-IR and NMR. Thermal nature, crystalline structure and morphology of β-chitosan were characterised through DSC, XRD and SEM, respectively. The water and fat binding capacity of β-chitosan presently studied was significantly higher than that of the commercial chitosan. The result of the present study adds that S. lessoniana gladius is also an additional source of β-chitin and chitosan of higher yield, lower molecular weight and higher degree of deacetylation.

The oval squid Sepioteuthis lessoniana is one of the most economically important squid species in Japan; however, its population structure is poorly understood due to the lack of hypervariable markers. Such information is critical for managing sustainable fisheries, as well as for ensuring the existence of wild S. lessoniana stocks. Eleven candidate microsatellite loci were isolated from a small insert genomic DNA library. Polymorphisms in these 11 loci were screened in 24 wild individuals. The number of alleles per locus was found to range from 5 to 19 alleles, and the observed heterozygosity ranged from 0.292 to 0.958. No evidence for linkage disequilibrium was detected among all the loci. The genotypic proportions conformed to Hardy-Weinberg equilibrium, except at one locus. In conclusion, these polymorphic microsatellite loci may be used to develop a genetic framework to manage S. lessoniana in the future.

Coleoid cephalopods (squid, cuttlefish, and octopus) have the largest and most complex brains of all invertebrates and show behavioral abilities similar to those of vertebrates. Among the coleoids, the oval squid Sepioteuthis lessoniana forms well-structured schools that are indicative of sociality. These behaviors are re flected in aspects of the well-developed brain. In this study, we focused on the role of the cephalopod brain in complex behavior. In order to reveal the network of γ-aminobutyric acid (GABA) in coleoids, we examined the immunohistochemical localization of glutamic acid decarboxylase (GAD), which is the synthetic enzyme of GABA, in the brain of young S. lessoniana. We found that GABAergic neurons and their axons were distributed throughout the brain. GABA neurons were abundantly localized in the inferior frontal lobe, which is involved in controlling arm motions, and in the subesophageal masses, which are lower and intermediate centers of action. GABAergic fibers were abundantly localized in the tract that runs from the superior frontal lobe to the vertical lobe. These results sug- gested the involvement of GABA in both cognitive behaviors (such as learning and memory) and in movement.