Cuttlefish Eggs Research Articles

Co-infection of Liburna oophaga sp. nov. and Ikanecator primus on cuttlefish (Sepia pharaonis) eggs and the effectiveness of peracetic acid as a treatment

The cuttlefish Sepia pharaonis species complex is emerging as a promising set of organisms for research in neuroscience, the behavioral sciences, and commercial aquaculture. At the same time, information about pathogens and diseases that could affect cuttlefish cultivation in intensive aquaculture settings remains limited. Our study has identified two species of parasite, the protozoan Liburna oophaga sp. nov. and the metazoan Ikanecator primus, that co-infect cuttlefish eggs, increasing mortality and reducing hatching rates. L. oophaga sp. nov. is reported here for the first time to enhance mortality during the incubation period by inducing deformity in cuttlefish eggs. We investigated the application of peracetic acid to parasite elimination during cuttlefish egg incubation. When cuttlefish eggs were treated with a peracetic acid containing product (PAA-product); 35 mg/L PAA + 15 mg/L H2O2, L. oophaga on the surfaces of the eggs were eliminated within 10 min. PAA-product; 70 mg/L PAA + 30 mg/L H2O2 was required to achieve the same effect for I. primus. Immersion treatment with PAA-product at 70 mg/L PAA + 30 mg/L H2O2 reduced parasitic load and improved survival of cuttlefish embryos and hatchling size, demonstrating that PAA product can inhibit and control parasitic co-infections in cephalopod culture.

Spawning substrates of cuttlefish: Type, function, and application

The fertilized eggs of cuttlefish are sticky eggs. Cuttlefish parents prefer to lay eggs on the attached substrates, which help increase the number of eggs and the hatching rate of fertilized eggs. If egg-attached substrates are sufficient, cuttlefish spawning will be reduced or even delayed. With the advances in the construction of marine nature reserves and research on artificial enrichment techniques, domestic and international experts have conducted research on different types and configurations of attachment substrates around cuttlefish resource enhancement. Based on the source of the substrates, we classified cuttlefish spawning substrates into two types, natural and artificial. By summarizing the differences, advantages, and disadvantages of the common economic cuttlefish spawning substrates in offshore areas worldwide, we sort out the functions of two different types of attachment bases, and discussed the practical applications of natural and artificial egg-attached substrates in spawning ground restoration and artificial enrichment. We proposed several thoughts on the future research directions of cuttlefish spawning attachment substrates, aiming to provide reasonable suggestions for cuttlefish habitat restoration, cuttlefish breeding and sustainable development of fishery resources.

First Evidence of Microplastics in the Yolk and Embryos of Common Cuttlefish (Sepia officinalis) from the Central Adriatic Sea: Evaluation of Embryo and Hatchling Structural Integrity and Development.

Once they reach the aquatic environment, microplastics (MPs) are accidentally ingested by aquatic biota, thus entering the food chain with possible negative effects. The present study investigated, for the first time, MP presence in cuttlefish (Sepia officinalis) eggs and their association with embryonic development. Cuttlefish eggs were sampled from four different sites along the Marche region (Senigallia, Ancona, Numana, and San Benedetto del Tronto). Embryo and hatchling biometric parameters were evaluated and the internal structural integrity was examined through histological analysis. MPs were detected and characterized in embryos and yolk samples. MPs were identified in all sites (size < 5 µm), however, their presence has not been associated with an impairment of either embryo or hatchling internal structures. Noteworthy, the highest number of MPs (in both yolk and embryo samples) were found in Numana (37% of the total amount), where the lowest hatchling size was observed. On the other hand, the highest embryo mantle length was associated with the lowest number of MPs detected (9%) in Ancona. Overall, only MP fragments and sphere types (74 and 26%, respectively) were observed, and the most frequent polymers were Polyvinyl chloride (52%), Polypropylene, and Cellulose acetate (15% both). Further studies are needed to assess the possible MP effects on the yolk quality and assimilation.

Effects of embryonic exposure to predators on the postnatal defensive behaviors of cuttlefish

Cuttlefish lack parental care and juveniles face a high predatory risk immediately after hatching. Previous studies have shown that the sensory systems of cuttlefish are functional before hatching, and embryos can recognize predatory visual and chemical cues innately. However, it is not known whether the embryonic experience of predatory cues impacts their postnatal defensive behaviors. Cuttlefish eggs (Sepia pharaonis with transparent capsule and Sepia officinalis with black capsule) were separated into seven groups: one control group and six cue-exposure groups. Embryos in the cue-exposure groups were exposed to either one of three types of predatory cues (visual, chemical, and both) or one of three similar types of non-predatory cues. Primary and secondary defensive behaviors of the cuttlefish hatchlings were examined at one week of age. The results showed that an early exposure to predatory cues in both species altered cuttlefish's hatching time and their postnatal primary defensive behaviors. However, embryonic sensory experience had different impacts on defensive behaviors in two species of cuttlefish. Specifically, visual information appeared to be more salient than olfactory information for S. pharaonis embryos, while both visual and olfactory cues seemed to influence S. officinalis embryos equally. These findings demonstrate that the embryonic sensory experiences of cuttlefish from these two species differentially affect the development of defensive behaviors among hatchlings.

Invertebrate predation on egg masses of the European cuttlefish, Sepia officinalis: An experimental approach

The eggs of the European cuttlefish, Sepia officinalis, develop attached to the seafloor in shallow water habitats and possess a relatively thick black capsule that protects them from the surrounding environment. Since embryological development may take several months, eggs are vulnerable to a variety of threats present in shallow waters, including predation. This study investigates predation of S. officinalis eggs by benthic invertebrates. Twenty-eight invertebrate species from 6 different phyla and with diverse feeding habits were tested as potential predators under laboratory conditions. We also investigated how the feeding traits of these species are related to the mechanical ability to break the egg capsule and prey upon cuttlefish embryos. Species that fed on cuttlefish eggs were the sea snail Bolinus brandaris, the crab Cancer pagurus, the hermit crab Dardanus arrosor, the lobster Homarus gammarus, the invasive blue crab Callinectes sapidus, the shrimp Squilla mantis, the sea urchins Echinus melo, Cidaris sp. and Paracentrotus lividus and the starfish Astropecten aranciacus. It is of note that C. sapidus is a potential predatory crab, which raises the concern that this invasive species may constitute a novel threat for cuttlefish eggs as more populations become established in NE Atlantic waters. Of the biological traits examined, prey capture tools in the tested species best explained the experimental feeding results, suggesting that predation of S. officinalis eggs was determined generally by a mechanical factor and highlighting the importance of the protective egg capsule against predators. However, chemosensory factors are likely to be implicated as well. Thus, this work contributes to the understanding of the ecology of early life stages of cuttlefish and the factors that can affect offspring survival and subsequently impact the recruitment of this species.

Digestive enzyme ratios are good indicators of hatchling yolk reserve and digestive gland maturation in early life stages of cuttlefish Sepia officinalis L.: application of these new tools in ecology and aquaculture.

In Sepia officinalis (Linnaeus, 1758), the digestive gland matures during the first month post-hatching, while a shift from intracellular acid to extracellular alkaline digestion occurs. The purpose of this study was to investigate the possibility of using enzymatic ratios for the description of digestive system maturation in early life stages of S. officinalis. Second, it is intended to apply these new tools as eco-physiological indicators for understanding the impact of cuttlefish eggs' life history from different spawning sites of the English Channel on digestive performance of juveniles. An experimental rearing was performed over 35days after hatching (DAH) on juveniles from wild collected eggs in 2010 and 2011. Four digestive enzyme activities and their ratios [i.e., trypsin, cathepsin, acid (ACP), and alkaline (ALP) phosphatase, ALP/ACP, and trypsin/cathepsin] were studied along with histological features (e.g., internal yolk surface and digestive gland development). The two enzyme ratios were good indicators of digestive system maturation allowing the study of the digestive gland's development. They were highly correlated to juveniles' weight increase and histological features of the gland in early DAH. These ratios described more accurately the shift occurring between the intracellular acid and the extracellular alkaline modes of digestion in S. officinalis and were more specific than separated enzyme activities. Their application as eco-physiological tools revealed that enzyme ratios reflected yolk content and digestive gland development in new hatching juveniles. Finally, ALP/ACP ratio was shown to be a powerful tool to describe growth performance of S. officinalis which is useful for aquaculture optimization.

From Trap to Nursery. Mitigating the Impact of an Artisanal Fishery on Cuttlefish Offspring

BackgroundOverexploitation and the impact of several types of human activities have caused declines of marine resources. The direct and active involvement of fishermen in the management of marine resources is effective not only for resource conservation, but also for changing fishermen’s attitudes. In this study, we proposed and tested the efficacy and suitability of a measure for mitigating the impact of a trap fishery on cuttlefish eggs in the North Adriatic Sea. This measure directly involves fishermen in promoting the conservation of the early, and more vulnerable, stages of the cuttlefish life cycle.Methodology/Principal findingsThrough surveys on fishing boats and interviews with fishermen, we found that traps placed in coastal areas during the cuttlefish breeding season have a high impact on cuttlefish eggs, with over 3 million eggs likely being destroyed by 3750 traps of 15 fishermen in less than 3 miles of coast. The use of removable ropes attached inside traps as an additional substrate for egg deposition allowed the recovery of 23.7% of the eggs deposited on the traps on average, without affecting the catch rate of adults. Experiments examining hatching success in the field highlighted the need for a careful choice of hatching sites to maximise the efficacy of the mitigation measure.Conclusions/SignificanceThe proposed mitigation measure reduced the impact of fishing on cuttlefish eggs, with no significant effect on the commercial catch. Fishermen showed a positive attitude towards the application of this measure, which is inexpensive and easy to employ. The direct involvement of fishermen in the management of this resource and the maintenance of traditional fishing methods are a novel aspect of the proposed measure and represent the basis for its success.

A new haemocyanin in cuttlefish (Sepia officinalis) eggs: sequence analysis and relevance during ontogeny

BackgroundHaemocyanin is the respiratory protein of most of the Mollusca. In cephalopods and gastropods at least two distinct isoforms are differentially expressed. However, their physiological purpose is unknown. For the common cuttlefish Sepia officinalis, three isoforms are known so far, whereas for only two of them the complete mRNA sequences are available. In this study, we sequenced the complete mRNA of the third haemocyanin isoform and measured the relative expression of all three isoforms during embryogenesis to reveal a potential ontogenetic relevance.ResultsThe cDNA of isoform 3 clearly correlates to the known Sepia officinalis haemocyanin subunits consisting of eight functional units and an internal duplicated functional unit d. Our molecular phylogenetic analyses reveal the third isoform representing a potentially ancestral haemocyanin isoform, and the analyses of the expression of haemocyanin type 3 reveal that haemocyanin type 3 only can be observed within eggs and during early development. Isoforms 1 and 2 are absent at these stages. After hatching, isoform 3 is downregulated, and isoform 1 and 2 are upregulated.ConclusionsOur study clearly shows an embryonic relevance of the third isoform, which will be further discussed in the light of the changes in the physiological function of haemocyanin during ontogeny. Taken together with the fact that it could also be the isoform closest related to the common ancestor of cuttlefish haemocyanin, the phylogeny of cuttlefish haemocyanin may be recapitulated during its ontogeny.

Using the giant Australian cuttlefish (Sepia apama) mass breeding aggregation to explore the life cycle of dicyemid parasites

Dicyemid mesozoan parasites, microscopic organisms found with high intensities in the renal appendages of benthic cephalopods, have a complex, partially unknown life cycle. It is uncertain at which host life cycle stage (i.e. eggs, juvenile, adult) new infection by the dispersive infusoriform embryo occurs. As adult cephalopods have a short lifespan and die shortly after reproducing only once, and juveniles are fast-moving, we hypothesize that the eggs are the life cycle stage where new infection occurs. Eggs are abundant and sessile, allowing a huge number of new individuals to be infected with low energy costs, and they also provide dicyemids with the maximum amount of time for survival compared with infection of juvenile and adult stages. In our study we collected giant Australian cuttlefish (Sepia apama) eggs at different stages of development and filtered seawater samples from the S. apama mass breeding aggregation area in South Australia, Australia, and tested these samples for the presence of dicyemid DNA. We did not recover dicyemid parasite cytochrome c oxidase subunit I (COI) nucleotide sequences from any of the samples, suggesting eggs are not the stage where new infection occurs. To resolve this unknown in the dicyemid life cycle, we believe experimental infection is needed.

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.

Radioisotopes Demonstrate the Contrasting Bioaccumulation Capacities of Heavy Metals in Embryonic Stages of Cephalopod Species

Cephalopods play a key role in many marine trophic food webs and also constitute alternative fishery resources in the context of the ongoing decline in finfish stocks. Most coastal cephalopod species of commercial importance migrate into shallow waters during the breeding season to lay their eggs, and are consequently subjected to coastal contamination. Eggs of common cuttlefish Sepia officinalis, European squid Loligo vulgaris, common octopus Octopus vulgaris and the sepiolid Rossia macrosoma were exposed during embryonic development to dissolved 110mAg, 109Cd, 60Co, 54Mn and 65Zn in order to determine their metal accumulation efficiencies and distribution among different egg compartments. Cuttlefish eggs, in which hard shells enclose the embryos, showed the lowest concentration factor (CF) values despite a longer duration of exposure. In contrast, octopus eggs, which are only protected by the chorionic membrane, accumulated the most metal. Uptake appears to be linked to the selective retention properties of the egg envelopes with respect to each element. The study also demonstrated that the octopus embryo accumulated 110mAg directly from the dissolved phase and also indirectly through assimilation of the contaminated yolk. These results raise questions regarding the potential contrasting vulnerability of early life stages of cephalopods to the metallic contamination of coastal waters.

Early exposure to odors changes later visual prey preferences in cuttlefish

Developmental studies have shown that environmental stimulation received by a developing sensory system can alter the developmental outcome of both that sensory system and other aspects of the nervous system. We investigated the ecologically relevant question of whether prior exposure to prey early in development within one sensory modality could influence later prey choice within a different sensory modality. Cuttlefish are visual predators; they can detect prey odors but attacks on prey cannot be elicited without visual stimulation. Cuttlefish eggs were exposed to the odor of shrimp (preferred prey), crabs (non-preferred prey), mollusks (non-prey), or a seawater control (no prey). Seven days after hatching, prey preferences were tested with a visual choice test between crabs and shrimp. Hatchlings exposed to crabs odors and the seawater control were significantly more likely to attack shrimp. Hatchlings exposed to mollusk odors showed no visual prey preference, while those exposed to shrimp preferentially attacked crabs. These results demonstrate a complex relationship between an early sensory exposure and later prey preference

Characteristics of the tertiary egg membrane of cuttlefish Sepiella maindroni de Rochebrune

We separated tertiary egg membrane (TGM) from 2- and 25-day-old eggs of cuttlefish Sepiella maindroni de Rochebrune, and revealed its ultrastructure, physical (solubility, barrier property) and biochemical (histology, histochemistry, nutritional components, bacteriostasis) characteristics. The results show that TGM could not be dissolved with natural seawater, alcohol, ether or hydrochloric acid (HCl), but it could be dissolved with 2-chloroethanol, diethylamine, and sodium hydroxide (NaOH). The black TGM was more effective in blocking off mud particulates, microorganisms (Chlorella vulgaris, Vibrio alginolyticus) and lighter than the white TGM. The elasticity of black and white TGMs was 1.8 N and 1.5 N, respectively. There were some ink particulates and rod-shaped bacteria in the black TGM. The nutritional components were different between black and white TGMs: Lipid content was lower and protein content was higher in the black TGM. TGM could also inhibit the growth of Vibrio alginolyticus.

Sexually Mature Cuttlefish are Attracted to the Eggs of Conspecifics

Cuttlefish typically are solitary, but form aggregations to spawn. We tested the hypothesis that bioactive factors in the eggs of conspecifics may facilitate the formation of spawning groups of Sepia officinalis. Cuttlefish detected odors from cuttlefish eggs, resulting in an increased ventilation rate. Extracts from female ovaries induced the largest increase in ventilation rate, suggesting that this organ could be a potential source of the bioactive chemicals. In y-maze assays, sexually mature, but not subadult, cuttlefish, were attracted to odors of cuttlefish eggs. These data suggest that Sepia eggs could be a source of reproductive pheromones.

Acid phosphatase and cathepsin activity in cuttlefish (Sepia officinalis) eggs: the effects of Ag, Cd, and Cu exposure

AbstractLacoue-Labarthe, T., Le Bihan, E., Borg, D., Koueta, N., and Bustamante, P. 2010. Acid phosphatase and cathepsin activity in cuttlefish (Sepia officinalis) eggs: the effects of Ag, Cd, and Cu exposure. – ICES Journal of Marine Science, 67: 1517–1523. Changes in the activity levels of acid phosphatase (AcP) and cathepsin during cuttlefish embryo development are described, as are the effects of exposure to heavy metals. Enzyme activity kinetics appear to be linked to the developmental stage. The activities of both enzymes increased during the final days of development, suggesting de novo production by the maturing embryo in the digestive gland. The effects of selected heavy metals, Ag (0.06, 1.2, 60, 1200 ng l−1), Cd (31, 61, 305, 610 ng l−1), and Cu (0.23, 2.3, 23, 230 µg l−1), were assessed based on AcP and cathepsin activities at the end of embryonic development and on hatchling weight. Enzyme activities were not impacted by Ag but were significantly inhibited by Cd, at all four concentrations for AcP and at 610 ng l−1 for cathepsin. Cu (at 2.3 µg l−1) stimulated AcP activity. No cause–effect relationship was found between the effects of metals on the enzyme activities and hatchling weight, suggesting that heavy metals could affect other physiological functions during embryogenesis.

Contrasting accumulation biokinetics and distribution of 241Am, Co, Cs, Mn and Zn during the whole development time of the eggs of the common cuttlefish, Sepia officinalis

Cuttlefish eggs were exposed to 241Am, Co, Cs, Mn and Zn for different periods of time during the 50-d of the embryonic development at 17 °C. Exposures were carried out using background dissolved concentrations of the metals, using the corresponding γ-emitting radiotracers ( 241Am, 57Co, 134Cs, 54Mn and 65Zn). Eggs were then placed in non-contaminating conditions. Experiments allowed assessing 1) the uptake and depuration kinetics of the selected elements and 2) their distribution among the different egg compartments (i.e. eggshell, vitellus, peri-vitelline fluid and embryo). 241Am, Co and Zn were accumulated continuously by the eggs all along the development time, whereas Mn reached saturation after one month of exposure. Interestingly, the uptake kinetics of Cs tightly followed the weight variation of the eggs, mainly because of water influx/outflux. During the first month of the embryonic life, 241Am, Co, Cs, Mn and Zn remained associated with the eggshell, indicating that the latter acted as an efficient shield against their penetration. Nevertheless, from this time onwards, Co, Cs, Mn and Zn accumulated more or less efficiently in the embryo according to the following order: Cs > Zn > Mn > Co. 241Am was the only element tested that did not cross the eggshell all along the exposure time. The depuration kinetics revealed that the retention capacity of the eggs varied during the embryonic life. The contrasting accumulation biokinetics are discussed in terms of chemical and biological processes occurring during the cuttlefish egg development.

Impacts of seawater desalination on the giant Australian cuttlefish Sepia apama in the upper Spencer Gulf, South Australia

With seawater desalination expanding rapidly, it is important that ecological studies are undertaken to determine the effects of brine discharge on the marine species in the area. The abundance of giant Australian cuttlefish ( Sepia apama, Gray 1849) eggs and environmental data were recorded at nine sites near Point Lowly, Spencer Gulf, South Australia, an area where the largest desalination plant in the Southern hemisphere is proposed. In addition, the effects of different concentrations of desalination brine on the growth, survival and condition of cuttlefish embryos were investigated. The primary egg-laying sites for the cuttlefish were in the vicinity of Stony Point (sites 4 and 3) and the area with the least egg abundance was on the eastern and western areas around Point Lowly (sites 9 and 7) where no eggs were found. The survival of embryos decreased with an increase in salinity, with no embryos surviving to full term in salinities greater than 50‰. Mean weight and mantle length also decreased with increasing salinity. Besides elevated salinity, the brine also had increased concentrations of Ba, Ca, K, Sr and Mg relative to water near Point Lowly. Brine discharge from seawater desalination poses a potential threat to the unique spawning aggregation of the giant Australian cuttlefish, in the upper Spencer Gulf, South Australia.

Lipid characterization of both wild and cultured eggs of cuttlefish (Sepia officinalisL.) throughout the embryonic development

The present work reports a characterization of mean wet weight and moisture, the lipid class and fatty acid (FA) composition from the total lipids (TL), of both culture and wild eggs of the cuttlefish, Sepia officinalis, throughout the embryonic development. Additionally, reproductive data, such as the number of spawnings, number and mean weight of eggs and duration of spawning period of cultured cuttlefish is provided. Both types of eggs were similar in mean wet weight, moisture content, TL content and lipid composition throughout embryonic development. Females from the cultured group spawned 13 times and laid 8654 eggs in 64 days, with a mean weight of 0.607 ± 0.179 g. A sex ratio of 1.57 (11♀ for 7♂) promoted an individual fecundity of 787 eggs/♀ (the biggest until now on our culture facilities), which might be related to increased bottom areas. The TL increased with day/stage of embryonic development (P 0.05). Eggs displayed predominant levels of phosphatidylcholine, phosphatidylethanolamine (PE), cholesterol and triacylglycerol at the end of embryonic development. Polar and neutral lipids of both eggs groups remained consistently proportional (∼50% for each lipid fraction) and a significant increase (P < 0.05) was observed in phosphatidylserine, PE and free FA throughout the embryonic development. In either egg type and day, 16:0, 18:0, 20:5n-3 and 22:6n-3 accounted for approximately 70 g Kg−1 of all FA and saturated and n-3 totals seemed to have the same proportion in the cuttlefish eggs. The present results suggest that lipids are not used as energetic substrate but as structural components in cuttlefish egg.

Differential bioaccumulation behaviour of Ag and Cd during the early development of the cuttlefish Sepia officinalis

Cuttlefish eggs were exposed to background concentrations of dissolved Ag and Cd, using the radiotracers 110mAg and 109Cd. At different time of the embryonic development (50 days), some eggs were placed in non-contaminating conditions. During the experiment, the uptake and depuration kinetics, and distribution of these metals among the egg compartments (i.e. eggshell, vitellus, peri-vitelline fluid and embryo) were assessed. In parallel, experiments were conducted with sub-lethal concentrations of stable Ag and Cd (2 and 1 μg l −1, respectively) to compare the metal behaviour at higher concentrations. From the spawning date up to 1 month of development, both metals were taken up efficiently by the eggs, reaching load/concentration ratio (LCR) of 1059 ± 75 and 239 ± 22 for 110mAg and 109Cd, respectively. From this time onwards, 110mAg activity continued to increase in eggs, whereas 109Cd kinetics displayed a significant decrease. Whatever the developmental stage, Cd was mainly associated with the eggshell all along the exposure experiment. In addition, both stable Cd concentrations and 109Cd LCR remained low in the embryo all along the embryonic development, indicating that the eggshell acted as an efficient shield against the penetration of this metal. In contrast, 110mAg passed through the eggshell from day 30 onwards and was then accumulated in the embryo, which contained more than 40% of the whole egg metal burden at the end of the exposure period. In depuration conditions, it is noteworthy that Ag continued to accumulate in the embryo indicating translocation processes from the eggshell and a high affinity of the metal for the embryo tissues. Overall our results showed that at day 30 of the embryonic development the cuttlefish eggshell becomes permeable to Ag but not to Cd. Exposure to stable metals confirmed the saturation capacities of the eggshell for Cd and the Ag penetration properties.

An alternative mechanism to reduce intracapsular hypoxia in ovicapsules of Fusitriton oregonensis (Gastropoda)

Oxygen supply inside egg masses has been reported as a constraint of embryo development. Many species that enclose their eggs in jelly masses or ovicapsules have strategies to avoid or reduce intracapsular hypoxia. In some amphibian species, a decrease in the wall thickness of the egg capsule over time produces an increase in oxygen conductance of the wall, reducing the problem of intracapsular oxygen limitation. Previous studies of gastropods have reported a decrease in the thickness of the capsules during development. However, there are no studies relating capsule thinning to the oxygen limitation problem in this group. This study links the thinning of egg capsules with oxygen diffusion as a possible mechanism to reduce or avoid hypoxia inside the capsules of the gastropod Fusitriton oregonensis. Capsule thickness, capsule area, oxygen partial pressure inside and outside the capsule, and oxygen consumption of the embryos at early and late developmental stages were measured. The conductance and the diffusion coefficients of the capsule were estimated using these measurements. Results showed that (1) capsule thickness decreased throughout development by about 50%, (2) oxygen consumption of embryos increased from early to late stages, (3) oxygen partial pressure inside the capsule did not change during development, (4) conductance coefficient increased with time, and (5) estimation of diffusion coefficient was lower than amphibian egg jelly, shark capsules, egg fishes, and eggs of giant cuttlefish. The reduction in the thickness of the capsule wall and the associated increase in its conductance during embryonic development may reduce oxygen constraints, especially at late developmental stages.