The Sepiidae are a unique species that are not necessarily adapted to only a single environmental condition or biome. They actually inhabit a variety of different temperate environments that give their species diversity in terms of physical and behavioral characteristics. Sepiidae have been observed to inhabit mainly shallow reefs but have also been reported to occupy channels and deep seas up to nearly 200 meters. The Sepiidae are also distributed across the globe as they inhabit a variety of different conditions such as tropical seas to arctic oceans. These varying conditions also give rise to nearly 120 species that allow these organisms to occupy the environments that they do. While the species is not currently endangered, they do have the threat imposed by humans due to pollution and fishing. In particular, Sepiidae found in English Channel inshore waters are commonly fished by european citizens giving rise to the tagging of these fish as well to monitor the movement and behaviour patterns of this species. The results from a study that monitored movement patterns of the Sepiidae observed the following: “even within the inshore spawning grounds cuttlefish may be relatively mobile, over a relatively long spawning phase (up to 6 weeks), with a high degree of plasticity in reproductive behaviour and general movement patterns”.
Most sepiids can withstand a wide range of climate conditions. Most species are found in shallow water where there is more solar energy with a higher productivity rate, but the species is also capable of surviving in deeper, dark waters as deep as 2,000 feet. Additionally, the species prefers to inhabit the warm, tropical low latitude waters around the equator, but are diverse enough to survive in the productively lower habitats of deep waters. The Sepiidae typically spend their winter months in the deep waters, and migrate to shallow waters of coasts to breed in the spring in summer seasons. The species is likely to benefit from the seasonal water currents found in many of the Earth’s largest oceans. The species can ride the Benguela, Peru, and California currents to bring them towards the warmer tropical waters for mating season, and can ride the North Pacific current as well as the North and South Equatorial currents back to colder, deep waters after they have mated.
This unusual biogeographic pattern of the Sepiids covers much of the world but excludes the Americas. The great distances between environments in these locations lead to the divergent evolution between species. This explains the great number of species mentioned above and the vastly diverse adaptations suited for the many different environments. Species that spread from colder waters to warmer coastal areas lost the ability to cross the cold water regions due to their temperature and depth and became unable to mate with the other species of Sepiids.
However, there are a few species of shallow water Sepiids that have the habit of following seasonal migrations. During the spring and summer they remain in inshore waters, but during the fall and winter months they move to depths of 100m to 200m. For these species, most of their time is spent burrowing in the sand during the day and prowling the sea floor at night for food. Also, when these sepiidae roam they usually only venture 90-550 meters which means they do not tend to stray from their known ecosystem unless for mating. They play the very important role of consumers in their ecosystems as they eat a wide variety of prey. They also have the ability to be flexible in their ecological niche when resources become scarce as they can move from eating crustaceans and fish to gastropods, nemertean worms, polychaetes, and even other sepiids. However, they are not the top predator because, as mentioned previously, sharks, dolphins, large fish, seals, and even whales prey on them.
At first glance, Sepiids might appear to slide right into a common slot for the oceanic food pyramid, however upon further inspection we see that Sepiids are particular in their location and do not really identify as Secondary, Tertiary or even necessarily Top consumers. Much like other cephalopods, their diet is specific when it comes to size. Smaller and more underdeveloped Sepiids will stick to a more euryphagous diet of crustaceans and mollusks but over time they will grow and develop more advanced hunting techniques. With larger body mass comes a larger diet so this is why we see older Sepiids expanding their diets. Anything they can catch and outsize has a likely chance of becoming food. Whether that be crustaceans like crabs, lobsters and shrimp, or smaller fish, often including octopus and worms. Sepiids will typically and quite often change their chromatophores based on what they are hunting, and since they are generalist hunters, they can come in a wide variety of hunting patterns. Primarily using their longest extendable tentacle, Sepiids will use it almost as if it were a spear. Catching fast-moving prey as it moves past. The beak is used for prey with harder exteriors like crustaceans but the bite is also equipped with an immobilizing toxin for more troublesome prey like octopus and squirming fish.
Most sepiids can withstand a wide range of climate conditions. Most species are found in shallow water where there is more solar energy with a higher productivity rate, but the species is also capable of surviving in deeper, dark waters as deep as 2,000 feet. Additionally, the species prefers to inhabit the warm, tropical low latitude waters around the equator, but are diverse enough to survive in the productively lower habitats of deep waters. The Sepiidae typically spend their winter months in the deep waters, and migrate to shallow waters of coasts to breed in the spring in summer seasons. The species is likely to benefit from the seasonal water currents found in many of the Earth’s largest oceans. The species can ride the Benguela, Peru, and California currents to bring them towards the warmer tropical waters for mating season, and can ride the North Pacific current as well as the North and South Equatorial currents back to colder, deep waters after they have mated.
This unusual biogeographic pattern of the Sepiids covers much of the world but excludes the Americas. The great distances between environments in these locations lead to the divergent evolution between species. This explains the great number of species mentioned above and the vastly diverse adaptations suited for the many different environments. Species that spread from colder waters to warmer coastal areas lost the ability to cross the cold water regions due to their temperature and depth and became unable to mate with the other species of Sepiids.
However, there are a few species of shallow water Sepiids that have the habit of following seasonal migrations. During the spring and summer they remain in inshore waters, but during the fall and winter months they move to depths of 100m to 200m. For these species, most of their time is spent burrowing in the sand during the day and prowling the sea floor at night for food. Also, when these sepiidae roam they usually only venture 90-550 meters which means they do not tend to stray from their known ecosystem unless for mating. They play the very important role of consumers in their ecosystems as they eat a wide variety of prey. They also have the ability to be flexible in their ecological niche when resources become scarce as they can move from eating crustaceans and fish to gastropods, nemertean worms, polychaetes, and even other sepiids. However, they are not the top predator because, as mentioned previously, sharks, dolphins, large fish, seals, and even whales prey on them.
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