Juvenile Cuttlefish Research Articles

Cuttlefish Sepia officinalis Preferentially Respond to Bottom Rather than Side Stimuli When Not Allowed Adjacent to Tank Walls.

Cuttlefish are cephalopods capable of rapid camouflage responses to visual stimuli. However, it is not always clear to what these animals are responding. Previous studies have found cuttlefish to be more responsive to lateral stimuli rather than substrate. However, in previous works, the cuttlefish were allowed to settle next to the lateral stimuli. In this study, we examine whether juvenile cuttlefish (Sepia officinalis) respond more strongly to visual stimuli seen on the sides versus the bottom of an experimental aquarium, specifically when the animals are not allowed to be adjacent to the tank walls. We used the Sub Sea Holodeck, a novel aquarium that employs plasma display screens to create a variety of artificial visual environments without disturbing the animals. Once the cuttlefish were acclimated, we compared the variability of camouflage patterns that were elicited from displaying various stimuli on the bottom versus the sides of the Holodeck. To characterize the camouflage patterns, we classified them in terms of uniform, disruptive, and mottled patterning. The elicited camouflage patterns from different bottom stimuli were more variable than those elicited by different side stimuli, suggesting that S. officinalis responds more strongly to the patterns displayed on the bottom than the sides of the tank. We argue that the cuttlefish pay more attention to the bottom of the Holodeck because it is closer and thus more relevant for camouflage.

Pre-hatching fluoxetine-induced neurochemical, neurodevelopmental, and immunological changes in newly hatched cuttlefish.

Embryonic and early postembryonic development of the cuttlefish Sepia officinalis (a cephalopod mollusk) occurs in coastal waters, an environment subject to considerable pressure from xenobiotic pollutants such as pharmaceutical residues. Given the role of serotonin in brain development and its interaction with neurodevelopmental functions, this study focused on fluoxetine (FLX), a selective serotonin reuptake inhibitor (SSRI, antidepressant). The goal was to determine the effects of subchronic waterborne FLX exposure (1 and 10 μg L(-1)) during the last 15 days of embryonic development on neurochemical, neurodevelopmental, behavioral, and immunological endpoints at hatching. Our results showed for the first time that organic contaminants, such as FLX, could pass through the eggshell during embryonic development, leading to a substantial accumulation of this molecule in hatchlings. We also found that FLX embryonic exposure (1 and 10 μg L(-1)) (1) modulated dopaminergic but not serotonergic neurotransmission, (2) decreased cell proliferation in key brain structures for cognitive and visual processing, (3) did not induce a conspicuous change in camouflage quality, and (4) decreased lysozyme activity. In the long term, these alterations observed during a critical period of development may impair complex behaviors of the juvenile cuttlefish and thus lead to a decrease in their survival. Finally, we suggest a different mode of action by FLX between vertebrate and non-vertebrate species and raise questions regarding the vulnerability of early life stages of cuttlefish to the pharmaceutical contamination found in coastal waters.

Physiological perturbations in juvenile cuttlefish Sepia officinalis induced by subchronic exposure to dissolved zinc

Although cephalopod early life stage development often occurs in coastal areas where contamination is real and continuous, the physiological perturbations induced by contaminants have been rarely investigated. This study focused on the Zn as it is one of the trace metals the most concentrated in coastal waters, worldwide. As Zn-tolerance limits were unknown in juvenile Sepia officinalis, the aim of this study was to estimate the threshold inducing mortality during the 2-first weeks post-hatching, and to determine its sensitivity using digestive and immune enzymatic assays, as well as growth and behavior follow-up during the first 5weeks post-hatching. Our study highlighted a Zn-mortality threshold lying between 185 and 230μgl−1, and growth reductions occurring after 5-week at 108μgl−1 and above, associated with enzymatic perturbations. These results underline a relatively important sensitivity of juvenile cuttlefish to Zn, pointed out by a wide diversity of biomarkers.

Trace metal concentrations in post-hatching cuttlefish Sepia officinalis and consequences of dissolved zinc exposure

In this study, we investigated the changes of 13 trace metal and metalloid concentrations (i.e. Ag, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, V, Zn) and their subcellular fractionation in juvenile cuttlefish Sepia officinalis reared in controlled conditions between hatching and 2 months post-hatching. In parallel, metallothionein concentrations were determined. Our results highlighted contrasting changes of studied metals. Indeed, As and Fe concentrations measured in hatchlings suggested a maternal transfer of these elements in cuttlefish. The non-essential elements Ag and Cd presented the highest accumulation during our study, correlated with the digestive gland maturation. During the 6 first weeks of study, soluble fractions of most of essential trace metals (i.e. Co, Cr, Cu, Fe, Se, Zn) slowly increased consistently with the progressive needs of cuttlefish metabolism during this period.In order to determine for the first time in a cephalopod how metal concentrations and their subcellular distributions are impacted when the animals are trace metal-exposed, we studied previously described parameters in juveniles exposed to dissolved Zn at environmental (i.e. 50μgl−1) and sublethal (i.e. 200μgl−1) levels. Moreover, oxidative stress (i.e. glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase activities, and lipid peroxidation (LPO)) was assessed in digestive gland and gills after 1 and 2 months exposures. Our results highlighted no or low ability of this stage of life to regulate dissolved Zn accumulation during the studied period, consistently with high sensitivity of this organism. Notably, Zn exposures caused a concentration-dependent Mn depletion in juvenile cuttlefish, and an increase of soluble fraction of Ag, Cd, Cu without accumulation modifications, suggesting substitution of these elements (i.e. Mn, Ag, Cd, Cu) by Zn. In parallel, metallothionein concentrations decreased in individuals most exposed to Zn. Finally, no perturbations in oxidative stress management were detected in gills, whereas modifications of GST, SOD and catalase activity levels were recorded in digestive gland, resulting in an increase of LPO content after a 6-week exposure to low Zn concentration. Altogether, these perturbations are consistent with previously described high sensitivity of juvenile cuttlefish towards Zn. Our results underlined the need to study deeply contamination impact on this animal at this stage of life.

The respiration, excretion and biochemical response of the juvenile common Chinese cuttlefish, Sepiella maindroni at different temperatures

The present study was designed to measure the oxygen consumption, ammonia excretion, stress resistance, energy utilization, and osmoregulatory ability of cuttlefish Sepiella maindroni, an important cultured species of China, at different temperatures. Juvenile cuttlefish were exposed to temperatures of 16, 20, 24, 28, and 32°C for 10days, respectively. Oxygen consumption (R) rates increased significantly from 16 to 28°C and then, slightly decreased at 32°C (P<0.05). Ammonia excretion (U) rates increased with increasing temperature. The highest R Q10 and U Q10 values occurred within 16 and 20°C, and the intermediate R Q10 and U Q10 values were found within 24 and 28°C. The calculated R Q10 dropped to minimum values within 28 and 32°C which suggested that treated groups with temperature of 32°C were under a stressful situation. The suffocation point (SP) and SP/SD (suffocation duration) increased significantly with increasing temperature, and peaked at 28°C, then dropped to the minimum level at 32°C. The SD decreased significantly with increasing temperature. The hemolymph total protein concentration decreased significantly from 16 to 24°C and then increased significantly, reaching a maximum at 32°C. Hepatic superoxide dismutase (SOD) activity was significantly low at 32°C than that of at other temperatures. The lowest and highest branchial Na+, K+-ATPase activity, and Na+ and Cl− contents occurred at 24 and 28°C, respectively. The present results indicate that temperature can modify certain physiological parameters and by enhancing oxygen utilization, optimal temperatures significantly contribute to higher growth rates. It is suggested that the protein increase in the hemoglobin below and above 24°C, will lead to an increase of energy expenditure from protein as an adjustment to temperature changes. Moreover, extremely high temperatures may result in adverse effects on juvenile S. maindroni that are related to ammonia-N and oxidative stress.

A method for long-term electronic tagging and tracking of juvenile and adult European common cuttlefish Sepia officinalis

The physiology and behaviour of captive cuttlefish have been well studied over recent decades and yet very few parallel studies have investigated the movements and behaviour of free-ranging animals. One reason for this gap is that methods for longer term tracking are not well developed for the majority of species, especially those of smaller size. In this study we describe a methodology for the long-term attachment of electronic tags to free-ranging cuttlefish of a broad size range. Five common cuttlefish Sepia officinalis (122–240mm mantle length) were fitted with temperature and depth-logging archival tags attached to the internal cuttlebone of the living animal (tag weight was <1.8% of body weight). Tagged animals recovered rapidly from sedative and surgical procedures and resumed feeding within 24h of tag attachment. Laboratory-kept cuttlefish maintained in a 2-m deep aquarium exhibited diel vertical movements, spending daylight hours close to the bottom and ascending into the water column at night, a behaviour which is consistent with normal diel vertical migration seen in other marine organisms such as zooplankton and fish. That regular feeding and expected patterns of depth use were observed indicates that tag attachment did not impede normal behaviours. Furthermore, tags remained attached to laboratory cuttlefish for up to 5months, from first tagging through to natural mortality, and with the tag remaining attached to the cuttlebone post mortem. We also found that cuttlebones with attached tags remained buoyant at the water's surface post mortem, offering the unique opportunity to recover archival tags from cuttlebones washed ashore. The capacity for long-term attachment to juvenile cuttlefish and recovery following natural mortality identifies the potential of this method for recording near ‘lifetime’ behaviour and movements of cuttlefish in their natural environment.

Maturation of polarization and luminance contrast sensitivities in cuttlefish (Sepia officinalis)

Polarization sensitivity is a characteristic of the visual system of cephalopods. It has been well documented in adult cuttlefish, which use polarization sensitivity in a large range of tasks such as communication, orientation and predation. Because cuttlefish do not benefit from parental care, their visual system (including the ability to detect motion) must be efficient from hatching to enable them to detect prey or predators. We studied the maturation and functionality of polarization sensitivity in newly hatched cuttlefish. In a first experiment, we examined the response of juvenile cuttlefish from hatching to the age of 1 month towards a moving, vertically oriented grating (contrasting and polarized stripes) using an optomotor response apparatus. Cuttlefish showed differences in maturation of polarization versus luminance contrast motion detection. In a second experiment, we examined the involvement of polarization information in prey preference and detection in cuttlefish of the same age. Cuttlefish preferentially chose not to attack transparent prey whose polarization contrast had been removed with a depolarizing filter. Performances of prey detection based on luminance contrast improved with age. Polarization contrast can help cuttlefish detect transparent prey. Our results suggest that polarization is not a simple modulation of luminance information, but rather that it is processed as a distinct channel of visual information. Both luminance and polarization sensitivity are functional, though not fully matured, in newly hatched cuttlefish and seem to help in prey detection.

Effects of early visual experience on the background preference in juvenile cuttlefish Sepia pharaonis

Although cuttlefish are capable of showing diverse camouflage body patterns against a variety of background substrates, whether they show background preference when given a choice of substrates is not well known. In this study, we characterized the background choice of post-embryonic cuttlefish (Sepia pharaonis) and examined the effects of rearing visual environments on their background preferences. Different rearing backgrounds (enriched, uniformly grey and checkerboard) were used to raise cuttlefish from eggs or hatchlings, and four sets of two-background-choice experiments (differences in contrast, shape, size and side) were conducted at day 1 and weeks 4, 8 and 12 post-hatch. Cuttlefish reared in the enriched environment preferred high-contrast backgrounds at all post-embryonic stages. In comparison, those reared in the impoverished environments (uniformly grey and checkerboard) had either reversed or delayed high-contrast background preference. In addition, cuttlefish raised on the uniformly grey background, exposed to a checkerboard briefly (0.5 or 3 h) at week 4 and tested at week 8 showed increased high-contrast background preference. Interestingly, cuttlefish in the enriched group preferred an object size similar to their body size at day 1 and week 4, but changed this preference to smaller objects at week 12. These results suggest that high-contrast backgrounds may be more adaptive for juvenile cuttlefish, and visually enriched environments are important for the development of these background preference behaviours.

Food imprinting and visual generalization in embryos and newly hatched cuttlefish, Sepia officinalis

Juvenile cuttlefish spontaneously prefer shrimp to crabs. This preference can be changed by early visual learning during embryonic and postembryonic life and has been related to a form of food imprinting. Nevertheless, it is unknown whether generalization occurs in conjunction with this early learning process. We found that inexperienced hatchling cuttlefish preferred ‘black’ to ‘white crab’ for their first meal, the black ink envelope of cuttlefish eggs did not prevent embryos discriminating between black and white crabs and embryonic or postembryonic visual familiarization to ‘white crabs’ induced a subsequent visual preference for ‘white crabs’ over ‘black crabs’ in the hatchling's first meal. Finally, juvenile cuttlefish previously pre- or postnatally exposed to ‘white crabs’ preferred ‘black crabs’ to shrimp, indicating for the first time that prey generalization occurs as early as the embryonic stages in cuttlefish. Such cognitive abilities could confer important adaptive advantages in processing information about prey likely to be available in the egg-laying environment at hatching and in the course of juvenile dispersal.

Visual lateralization is task and age dependent in cuttlefish, Sepia officinalis

The behavioural lateralization observed in several invertebrate species appears to parallel the phenomenon seen in vertebrates. However, it is not yet clear whether lateralization in invertebrates varies within an individual across development as it does in vertebrates. We examined when during postembryonic development juvenile cuttlefish begin to show side-turning preferences in a T-shaped apparatus. We also determined whether or not the direction of turning was stimulus dependent by providing, or not providing, shelters in the two choice arms of the apparatus. We found that as the animals aged from 3 to 45 days posthatch they progressively developed a left-turning bias but only when shelters were provided in the apparatus. We suggest that left-turning biases in cuttlefish result from an eye use preference. Emergence of visual lateralization at the time of dispersal may afford juveniles greater behavioural efficiency by enabling them to look out for escape routes while hunting. The left visual field may be associated with rapid responses as in many species of vertebrates. Determining the role of the right visual field of cuttlefish when looking for prey may provide evidence for homology between lateralization in invertebrates and vertebrates.

Effects of increased tank bottom areas on cuttlefish (Sepia officinalis, L.) reproduction performance

The objective of this research was to determine the effects of using tanks with different bottom areas/volumes on the growth and reproduction of the European cuttlefish, Sepia officinalis. One hundred and eighty-four juvenile cuttlefish (46.1 ± 20.9 g) were used to test replicates of 9000 L (6.67 m 2 ), 750 L (1.54 m 2 ) and 250 L (0.79 m 2 – control). Growth and reproduction data were registered. In addition, egg proximate composition differences were assessed by collecting egg samples from each tank. Regarding growth, no statistical differences between tank types were found (P > 0.05), but total absolute mortality was lower in 9000 L tanks. As for reproduction, differences were found (P < 0.05) between individual tanks for mean egg (MEW), male (MW♂) and hatchling (MHW) weights; and egg batch number. One of the 9000 L tanks displayed the highest overall and individual fecundity (16 593 and 1383 eggs respectively) and egg viability (~72%) ever obtained in our facilities. Differences (P < 0.05) regarding egg proximate composition of different tanks were noted. Significant (P < 0.05) correlations were established between the duration of reproduction stage and batch, MEW and MW♀, egg viability and MHW, and MHW and egg ash content. The present results might be related to sex ratios, differences in weight between ♀ and ♂, and/or derived from breeders condition.

The effects of tank colours on the growth and survival of cuttlefish (Sepia officinalis, Linnaeus 1758) hatchlings and juveniles

The effects of different tank colours (white, yellow sandy and black) on the growth, mortality and biomass production were studied for hatchling and early juvenile cuttlefish. For hatchlings, the use of different colour tanks did not promote differences in growth due to the higher variability (standard deviation) found in the white- and sand-coloured tanks. Black tanks promoted the lowest and highest values for total mortality and biomass respectively. For juveniles, the use of different tank colours promoted different growth (P<0.05), but not mortality. Black tanks promoted the best results in terms of growth and biomass. The results obtained in the present study advise the use of black (or dark colour) tanks in the hatchling and early juvenile stages to reduce the standard deviations associated with growth, mortality and biomass production. This will contribute to minimize problems associated with slow and fast growers and competition.

Edge detection and texture classification by cuttlefish

Cephalopod mollusks including octopus and cuttlefish are adept at adaptive camouflage, varying their appearance to suit the surroundings. This behavior allows unique access into the vision of a non-human species because one can ask how these animals use spatial information to control their coloration pattern. There is particular interest in factors that affect the relative levels of expression of the Mottle and the Disruptive body patterns. Broadly speaking, the Mottle is displayed on continuous patterned surfaces whereas the Disruptive is used on discrete objects such as pebbles. Recent evidence from common cuttlefish, Sepia officinalis, suggests that multiple cues are relevant, including spatial scale, contrast, and depth. We analyze the body pattern responses of juvenile cuttlefish to a range of checkerboard stimuli. Our results suggest that the choice of camouflage pattern is consistent with a simple model of how cuttlefish classify visual textures, according to whether they are Uniform or patterned, and whether the pattern includes visual edges. In particular, cuttlefish appear to detect edges by sensing the relative spatial phases of two spatial frequency components (e.g., fundamental and the third harmonic Fourier component in a square wave). We discuss the relevance of these findings to vision and camouflage in aquatic environments.

Ontogeny of Oxytocin-Like Immunoreactivity in the Cuttlefish, Sepia officinalis, Central Nervous System

In vertebrate species, the neuropeptide oxytocin (OT) has been implicated in neural and behavioral development. Although several OT-like peptides have been characterized in invertebrate species, the ontogenesis of the OT-like system has not yet been described in these species. Thus, the aim of the present study was to perform an immunohistochemical investigation of the spatiotemporal distribution of OT-like elements in the central nervous system (CNS) of a decapod cephalopod mollusc, the cuttlefish, Sepia officinalis, during the first 3 months of postembryonic development. On the day of birth, OT-like immunoreactivity was detected throughout the whole CNS. Some nervous structures (e.g. the magnocellular lobes) exhibited a stained pattern in newborns similar to that reported in our previous study in adult cuttlefish whereas other lobes (e.g. the vertical lobe complex) showed maturation during the first weeks of life. Finally, at the age of 60 days, the general pattern of staining in the CNS was comparable to the adult distribution. The putative roles of the OT-like system with regard to the development of some behaviors in juvenile cuttlefish are discussed. The present study provides a neurochemical basis for the investigation of postnatal development of complex behaviors in cephalopods and suggests, for the first time in an invertebrate species, important organizational effects for the OT-like system in the course of the first weeks of life.

Effect of body mass, temperature and food deprivation on oxygen consumption rate of common cuttlefish Sepia officinalis

Predictions of short and long term changes in Sepia officinalis metabolism are useful, since this species is both economically important for aquaculture and also is an ideal experimental laboratory organism. In this study standard and routine oxygen consumption rates of newly hatched and juvenile laboratory raised cuttlefish S. officinalis ranging between 0.04 and 18.48 g dry body mass (Dm), were measured over a range of temperatures (10, 15, 20 and 25°C). The mass exponent (b) ranged between 0.706 and 0.992 for standard oxygen consumption and between 0.694 and 0.990 for routine oxygen consumption. Oxygen consumption scaled allometrically (b = 0.7) with body mass for cuttlefish 2 g, MO2 = 0.076Dm0.9831.091T for standard oxygen consumption; cuttlefish 2 g, MO2 = 0.225Dm0.9621.081T for routine oxygen consumption. Using these equations it was estimated that a cuttlefish of 1 g Dm held at 20°C, eating 5% Dm day−1 and undergoing standard and routine metabolism consumes 21.3 and 35.4%, respectively of its total daily energy intake. Juvenile cuttlefish (3.32–5.08 g Dm) held at 15°C and deprived of food for 27 days maintained a stable standard oxygen consumption rate for the first 6 days following starvation. By the 18th day without food, oxygen consumption rate had declined by 53% and further declined to 65% below the standard oxygen consumption rate on the 27th day. Upon resumption of feeding, the respiration rate returned immediately to the initial level prior to food deprivation. The present study defines the basic energy requirements and general physiological state of young cuttlefish at temperatures of 10–25°C with and without food.

Bioaccumulation of inorganic Hg by the juvenile cuttlefish Sepia officinalis exposed to 203Hg radiolabelled seawater and food

er , 98000 Principality of Monaco ABSTRACT: Uptake and depuration kinetics of inorganic mercury (Hg) were investigated in the juvenile common cuttlefish Sepia officinalis following exposures via seawater and food using a sen- sitive radiotracer technique ( 203 Hg). Cuttlefish readily concentrated 203 Hg when exposed via seawa- ter, with whole body concentration factors >260 after only 10 d of exposure. The total Hg accumu- lated from seawater was depurated relatively fast with a radiotracer biological half-life (Tb!) of 17 d. During both exposure and depuration periods, accumulated Hg was mainly (>70%) associated with the muscular parts of the cuttlefish. However, the proportion of the whole-body Hg content associ- ated with the digestive gland increased during exposure and depuration phases, suggesting that the metal was transferred from the muscles towards this organ for detoxification. When fed with radio- labelled food, cuttlefish displayed high assimilation efficiency (>90%) and the metal was found to be mainly located in the digestive gland (60% of the whole Hg content). Nevertheless, high depuration rates resulted in short Tb! (i.e. 4 d), suggesting that this organ has a major role in Hg detoxification and depuration. Whatever the exposure pathway, a low proportion of Hg (<2%) was found in the cut- tlebone. Assessment of the relative contribution of the dietary and dissolved exposure pathways to inorganic Hg bioaccumulation in juvenile cuttlefish revealed that Hg was mainly accumulated from food, which contributed 77 ± 16% of the global metal bioaccumulation.

The use of alternative diets to culture juvenile cuttlefish, Sepia officinalis: effects on growth and lipid composition

The effects of feeding three natural frozen diets, grass shrimp (Palaemonetes sp.), crayfish (Procambarus clarkii) and fish (Sardina pilchardus) and two semi-humid artificial diets (based on fish or shrimp powder) to the cuttlefish, Sepia officinalis, were analysed. Growth rate and feeding rate [FR; % body weight (BW) day−1] and food conversions (FC, %) were determined. Cuttlefish fed shrimp grew larger (3.8% BW day−1) and had the highest FC, followed by those fed crayfish, and sardine. The highest FR was obtained for cuttlefish fed crayfish (10.5% BW day−1). Although both artificial diets were accepted, none produced growth. Digestive gland-to-body weight ratio (DG/BW ratio) was calculated for animals fed each diet. A positive correlation (r = 0.94) between cuttlefish ingestion FR and DG weight was obtained. Mortality occurred mainly during the last week, and some cannibalism occurred among cuttlefish fed artificial diets. Finally, lipid composition of diets, DG and mantle of each group were analysed. Sardine diet was characterized by high levels of triacylglycerol (TG), whereas the main difference between shrimp and crayfish was the higher n-3/n-6 ratio found in shrimp. Changes in the lipid composition of DG were related to diet, but did not correlate with growth data. A strong loss of TG in the DG of artificial diets groups was notable. No differences in mantle lipid composition among the natural diets were found, but artificial diet groups showed higher contents of neutral lipids in their mantle respect to natural diets. According to results obtained, crayfish (P. clarkii) could be used as an alternative prey for rearing S. officinalis compared with shrimp. Artificial diets showed the worst effects in growth and mortality as well as the stronger influence on DG and mantle lipid composition of cuttlefish.

Effects of food thermal treatment on growth, absorption, and assimilation efficiency of juvenile cuttlefish, Sepia officinalis

The diet of frozen grass shrimp (P. varians) was compared to similar grass shrimp that had suffered either boiling, drying at 60°C, or freeze-drying by lyophilization at −40°C. In experiment 1, cuttlefish fed the frozen shrimp were significantly larger (P 0.05) between cuttlefish fed the frozen or the freeze-dried shrimp, whereas cuttlefish fed the dried shrimp were smaller at the end of the experiment. Growth rates of cuttlefish fed the dried shrimp were lower, compared with those for cuttlefish fed the frozen and freeze-dried shrimp, with no significant differences (P > 0.05) between them. Cuttlefish fed freeze-dried and frozen shrimp showed a higher trypsin activity compared to animals fed boiled and dry (60°C) shrimp. A higher proportion of absorbed energy was channelled into biomass production in animals fed frozen and freeze-dried shrimp (56% and 43%, respectively) than for animals fed oven-dried (60°C) or boiled shrimp. The heat treatment suffered by the shrimp, either dry or wet, negatively affected diet quality, probably due to denaturation, and loss (by boiling) of proteins and amino acids. Additionally, the heating processes may have oxidized the lipids to a large extent, contributing to the loss of the polar lipids (polyunsaturated fatty acids), which are essential for cephalopods as for other organisms. Freeze-drying by lyophilization (negative temperatures) did not affect the nutritional quality of the shrimp.

Effects of prey nutritional quality on the growth and survival of juvenile cuttlefish, Sepia officinalis (Linnaeus, 1758)

This investigation examined the eiect of prey condition on the growth and survival of juvenile cuttle¢sh (Sepia o⁄cinalis). In the ¢rst group, cuttle¢sh were fed with daily captured live Palaeomonetes varians from the wild [daily prey (DP)], the second group was fed 5 days stocked and starved P. varians [starved prey (SP)], while in the third group, cuttle¢sh were fed 8 days stocked P. varians fed with an arti¢cial diet [fed prey (FP)]. Mean instantaneous growth rate (IGR) was 2.8 1% body weight day 1 (bw day 1 ), 3.3 1.1% bw day 1 and 4.9 0.5% bw day 1 for SP, DP and FP respectively. At the end of the experiment, ¢nal weight gain (Wg )w as 121 21.6%, 153.8 17.3% and 295 29.8% for SP, DP and FP respectively. No signi¢cant diierences were found (P40.05) between growth curves for every group tested, or for the food conversions between those same groups (P40.05), but statistical diierences (Po0.05) were found in IGR between DP vs. FP and SP vs. FP. Mortality was 2 and1for SP and DP respectively. Results indicate that prey starvation should not be considered when feeding juvenile cuttle¢sh, as prey can only be stocked if proper arti¢cial diets are provided, to obtain optimal growth.

Effects of live prey availability on growth and survival in the early stages of cuttlefish Sepia officinalis (Linnaeus, 1758) life cycle

This investigation examined the effects of live prey availability on growth and survival of Sepia officinalis. Two independent experiments, comprising two feed rations each, were performed, using adequate prey size. In the first experiment, cuttlefish hatchlings were fed live mysids, Paramysis nouvelli [(feed ratio I (fr I)], at 15% body weight per day (bw day−1) (fr I15) and 30% bw day−1 (fr I30). In the second experiment, juvenile cuttlefish were fed live Atlantic ditch shrimp, Paleomonetes varians (fr II), under the same experimental design. In both experiments, the final mean weight, feeding rate and instantaneous growth rate were higher when animals were fed feed ratio fr II15 and fr II30 (30% bw day−1). The results indicate that prey availability influenced weight gain, irrespective of the prey used, during the first 2 months of cuttlefish life cycle. This effect seems to be more noticeable when a certain limit of prey is achieved. For cuttlefish fed fr II, the optimal prey density is thought to be under 2.5 g prey L−1 (i.e. 14 shrimp L−1). Results indicate that cuttlefish can withstand prey densities up to 120 mysids L−1 for cuttlefish up to 3 weeks old and 19 shrimps L−1 for cuttlefish up to 6 weeks old.