The characteristics and functional properties of gelatin extracted from squid skin (Loligo vulgaris), using commercial pepsin at a level of 15 Units/g skin, were investigated. The gelatin extraction ...yield was 6.82 g/100 g wet basis, showing high protein content and low fat and ash contents. SDS-PAGE of squid skin gelatin showed high band intensity for the major protein components, especially, α- and β-components. The amino acid profile of squid skin gelatin showed a high percentage of imino acids, essential amino acids and hydrophobic amino acids. Fourier transformed infrared spectroscopy (FT-IR) spectra showed helical structure. Squid skin gelatin was able to form a completely thermo-reversible gel. Gelatin possessed interesting functional properties, which were governed by gelatin concentration.
•This is the first report of the extraction of gelatin from Loligo vulgaris skin.•The amino acid profile of squid skin gelatine showed a high percentage of imino acids.•Gelatin has a good quality with desirable interfacial properties.
Abstract
The inshore commercial squids, Loligo vulgaris and L. forbesii, co-occur in the ecoregions of Celtic Seas and Greater North Sea but the spatio-temporal structure of their spawning ranges is ...poorly understood. To help solve the problem, data sets collected during the last 30 years by British, German, French, and Irish scientists, as well as observations from multinational Citizen Science, were combined. Spawning grounds of L. forbesii were found to form an external semi-circle around the spawning grounds of L. vulgaris, with the latter being centred on the English Channel and southernmost North Sea. The nursery grounds of both species appear to coincide with the respective spawning grounds, though L. forbesii makes much wider use of the North Sea. Seasonally, the position of the spawning grounds of both species is driven by the local temperature regime, although this is possibly subject to interannual variability. Spawning of both species begins around November and gradually progresses eastward following favourable currents and increasing water temperatures. Spawning in both species is mostly over by July, though some egg masses persist until August–November. Nursery grounds follow the same seasonal shift from west to east, at least in L. forbesii.
The inclusion of cephalopods in the legislation related to the use of animals for experimental purposes has been based on the precautionary principle that these animals have the capacity to ...experience pain, suffering, distress, and lasting harm. Recent studies have expanded this view and supported it. Handling cephalopod mollusks in research is challenging and whenever more invasive procedures are required, sedation and/or anesthesia becomes necessary. Therefore, finding adequate, safe, and effective anesthetics appears mandatory. Several substances have been considered in sedating cephalopods, in some instances applying those utilized for fish. However, species-specific variability requires more detailed studies. Despite long-lasting experience being linked to classic studies on squid giant axons, evidence of action on putative anesthetic substances is scarce for
Loligo vulgaris
and particularly for their embryos. The aim of the current study was to evaluate effects elicited by immersion of squid embryos in anesthetic solutions and examine whether these forms display a similar reaction to anesthetics as adults do. Different concentrations of ethanol (EtOH; 2, 2.5, and 3%) and magnesium chloride (MgCl
2
; 1, 1.5, and 1.8%) were tested by adopting a set of indicators aimed at exploring the physiological responses of squid embryos. Forty-two embryos of the common squid
Loligo vulgaris
(stages 27–28) were assigned to three conditions (EtOH, MgCl
2,
and controls) and video recorded for 15 min (5 min before, 5 min during, and 5 min after immersion in the anesthetic solutions). In each group, the heart rate, respiratory rate, buoyancy, chromatophore activity, and tentacles/arms responses were assessed to evaluate the embryos' vitality and responsiveness to stimulation. Both substances provoked a decrease in heart and respiratory rates and inhibited buoyancy, chromatophores, and tentacles/arms responses; no adverse effects were observed. EtOH had a faster onset of action and faster recovery than MgCl
2
, being potentially more adequate as an anesthetic for shorter procedures. Even though MgCl
2
caused a longer muscle relaxation, the reversibility was not confirmed for the 1.8% concentration; however, lower concentrations triggered similar results as the ones obtained with the highest EtOH concentrations. We have shown that the late developmental stages of
Loligo vulgaris
embryos could represent a good model to evaluate anesthetics for cephalopods since they can display similar reactions to anesthetics as adults animals do.
Squid (Loligo forbesii and Loligo vulgaris) mantles were cooked by sous vide cooking using different temperatures (46°C, 55°C, 77°C) and times (30 s, 2 min, 15 min, 1 h, 5 h, 24 h), including samples ...of raw tissue. Macroscopic textural properties were characterized by texture analysis (TA) conducted with Meullenet‐Owens razor shear blade and compared to analysis results from differential scanning calorimetry. The collagen content of raw tissues of squid was quantified as amount of total hydroxyproline using ultra‐high‐performance liquid chromatography. Structural changes were monitored by Raman spectroscopy and small‐angle X‐ray scattering and visualized by second harmonic generation microscopy. Collagen in the squid tissue was found to be highest in arms (4.3% of total protein), then fins (3.0%), and lowest in the mantle (1.5%), the content of the mantle being very low compared to that of other species of squid. Collagen was found to be the major protein responsible for cooking loss, whereas both collagen and actin were found to be key to mechanical textural changes. A significant decreased amount of cooking loss was obtained using a lower cooking temperature of 55°C compared to 77°C, without yielding significant textural changes in most TA parameters, except for TA hardness which was significantly less reduced. An optimized sous vide cooking time and temperature around 55–77°C and 0.5–5 h deserves further investigation, preferably coupled to sensory consumer evaluation.
Practical Application
The study provides knowledge about structural changes during sous vide cooking of squid mantle. The results may be translated into gastronomic use, promoting the use of an underutilized resource of delicious and nutritious protein (Loligo vulgaris and Loligo forbesii).
Electronic tagging methods are used in many studies for aquatic life. By using this method which is also called telemetry it is possible to obtain animal-borne data. However, for the success of the ...study, it is very important to know the response of the animal to the attachment process steps and the attached device. This is particularly hard when used with cephalopods as they will tend to grab on to the device, pull at it and rip it off. This is why there is limited telemetry study on cephalopods. In this study, we have tried to observe the reactions of octopuses (Octopus vulgaris,-Cuvier, 1797) and squids (Loligo vulgaris,-Lamarck, 1798) to a data storage tag which is a kind of telemetry device. The purpose of this work is to determine the duration of the device being attached to the individual, changes in its behavior, reason for detaching the device, injury and possibility of the death of individuals. At the end of the study, and the residence time of the tag varied between 1-7 days and it was determind that the octopuses created wounds on their bodies in order to remove the tag. Squids can carry the tag for 1 week. For both species, no deaths were detected due to tagging, carrying. Also, after remove the tag, individuals survived.
Cephalopods are set apart from other mollusks by their advanced behavioral abilities and the complexity of their nervous systems. Because of the great evolutionary distance that separates vertebrates ...from cephalopods, it is evident that higher cognitive features have evolved separately in these clades despite the similarities that they share. Alongside their complex behavioral abilities, cephalopods have evolved specialized cells and tissues, such as the chromatophores for camouflage or suckers to grasp prey. Despite significant progress in genome and transcriptome sequencing, the molecular identities of cell types in cephalopods remain largely unknown. We here combine single-cell transcriptomics with in situ gene expression analysis to uncover cell type diversity in the European squid
. We describe cell types that are conserved with other phyla such as neurons, muscles, or connective tissues but also cephalopod-specific cells, such as chromatophores or sucker cells. Moreover, we investigate major components of the squid nervous system including progenitor and developing cells, differentiated cells of the brain and optic lobes, as well as sensory systems of the head. Our study provides a molecular assessment for conserved and novel cell types in cephalopods and a framework for mapping the nervous system of
.
This paper focuses on the study of the squid Loligo vulgaris (Lamarck, 1798) reproduction, in the Atlantic southern waters of Morocco (Saharan bank) using data obtained from bottom trawls surveys ...performed by the Research vessel during the period 2000–2014 (springs and autumns seasons). Results shows a marked seasonal periodicity and an irregularity of the spawning periods.
L.vulgaris hatched throughout the year with two distinct peaks, in spring which is the main breeding period, and in autumn.
The sizes at first sexual maturity (L50%) of population squid defines the size at which half of the population (50 %) is mature for each sexes. During spring season squid individuals are characterized by smaller sizes at sexual maturity (males: 15,4 cm; female: 19,16 cm) than those recorded during the autumn season (males: 24,5 cm; female: 21,12 cm). Likewise, squid males are characterized by a more advanced maturity than the one of females, especially during the spring season, this can be explained by environmental factors mostly temperatures, which affect maturity.
In the autumn season, the sex ratio is in favour of females in the smaller sizes below 5 cm. At the intervals of 6 to 19 cm and over 30 cm of mantle length, the sex ratio becomes exclusively in favour of males. Unlike the spring season the sex ratio for small sizes and sizes greater than 29 cm from the mantle is in favour of males.
The length-weight relationship was calculated from biological data collected in surveys. There is a significant correlation between these two variables. The relative weight-length constant b is lower in males than in females.
•The paper provides a pioneer tool to differentiate visually between egg masses of two sympatric commercial squids, L. vulgaris and L. forbesii.•Celtic Sea and western English Channel are spawning ...grounds of L. vulgaris in late winter – spring. No reproduction of L. forbesii was found there during this season.•L. forbesii forages in Celtic Sea and English Channel but reproduces in deeper water further west, mostly west of Ireland.
European squid, Loligo vulgaris and veined squid, Loligo forbesii have nearly coinciding distributions in the northeast Atlantic, a similar reproductive seasonality, and largely overlapping depth ranges of spawning grounds. There are no unambiguous criteria to distinguish between egg masses of both species. This pioneering study was focused on the Celtic Sea and western part of the English Channel and combined both research survey data and observations by recreational divers (“citizen science”). Loligo vulgaris was found to reproduce there in late winter – spring; distribution of egg masses coincided with a bottom temperature range of 8.5−10 °C and bottom salinities of 35–35.5 psu. No L.forbesii egg masses were found across the study area though they are known from literature to occur in deeper areas further west. Based on original material and data from the literature, we provide a guideline to distinguish between egg masses of both squids based on egg size and embryonic stage as a tool to map species-specific spawning grounds, towards improved understanding of population structure, migrations and development of fisheries management measures.
•To include angler heterogeneity improves the accuracy of the harvest estimations.•Recreational squid harvest constitutes 34% of commercial landings.•Recreational harvest should be considered in ...mixed fisheries management.
Although some stocks are being severely exploited by recreational fishing, estimating the biomass extracted (harvest, H) by recreational fisheries is difficult, especially for marine recreational fisheries. One way to estimate H by recreational fisheries is to combine the fishing effort (E) with catch-per-unit-of-effort (CPUE) data. However, naively ignoring heterogeneity in E and CPUE may result in biased and imprecise estimates of H. We propose a framework to address three relevant heterogeneity levels: the spatial and temporal heterogeneity of recreational E, environmental effects on recreational CPUE, and the variability in angler skills (between-angler heterogeneity). Specifically, we combine (i) space-time model predictions of E (number of boats per km2) on the day scale (i.e., fishing trips), (ii) environmentally driven model predictions of daily catch (number of squid per fishing trip), and (iii) off- and on-site surveys to account for angler heterogeneity. The precision of the H estimates was assessed using bootstrap confidence intervals. This framework was applied to the recreational fishery for the squid Loligo vulgaris at Palma Bay (Mallorca Island, western Mediterranean). The estimated effort was 15,750 angler-fishing trips (95% CI: 13,086 to 18,569), which yielded an annual harvest of 20.6 tons (95% CI: 16.9–24.5). This harvest was estimated to represent 34% of the total commercial landings in Mallorca, which highlights the importance of recreational harvesting and the need to account for recreational fisheries to improve squid stock management. The framework proposed here provides a promising tool for estimating H in other heterogeneous recreational fisheries and may be the first step toward assessing the actual impact of recreational fisheries on squid populations.
Coleoid cephalopods are characterized by internalization of their shell, and are divided into the ten‐armed Decabrachia (squids and cuttlefish) and the eight‐armed Vampyropoda (octopuses and vampire ...squid). They have a rich fossil record predominantly of the limited biomineralized skeletal elements they possess: arm hooks, statoliths, mouthparts (the buccal mass) and internal shell (gladius or pen), although exquisitely preserved soft tissue coleoids are known from several Lagerstätten worldwide. Recent studies have shown that although morphological similarities between extant decabrachian gladii and fossil examples exist, no known examples of fossil decabrachians are currently known. However, molecular clock data and phylogenetic bracketing suggest that they should be present in Lagerstätten that are rich in vampyropod soft tissue fossils (i.e. Hâkel and Hâdjoula Lagerstätten, Cretaceous, Lebanon). We propose that a hitherto unknown taphonomic bias pertaining to the differing methods of buoyancy control within coleoid groups limits preservation potential. Both negatively and neutrally buoyant decabrachians use chemical buoyancy control (ammonia) whereas vampyropods do not. In the event of rapid burial in an environment conducive to exceptional preservation, ammonia dramatically decreases the ability of the decabrachian carcass to generate the required pH for authigenic calcium phosphate replacement, limiting its preservation potential. Moreover, the greater surface area and comparatively fragile dermis further decrease the potential for fossilization. This taphonomic bias may have contributed to the lack of preserved labile soft‐tissues in other cephalopods groups such as the ammonoids.
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