Know your islands
Caribbean Reef Squid (Sepioteuthis sepioidea) live in the ocean waters of Florida, Bahamas and the Caribbean.
Squid are commonly found in groups of about four to 30 in the shallows associated with reefs.
It lives in waters to approximately 100 meters. The habitat of reef squid changes according to the squid’s stage of life and size.
The small squid typically gather together in shallow turtle grass near islands and remain within two meters from the surface to avoid bird predators.
They also do not dwell on the ocean floor because of possible snapper predation.
At night however, they often will swim to deeper waters and hunt with older, larger squid. When mating, adults are found near coral reefs in shallower depths.
Squid are in the Class Cephalopoda and are molluscs: they are closely related to the cuttlefish and octopus and more distantly to the snails, clams, oysters, and sea slugs.
Like all squid, Caribbean Reef Squid have eight arms and two longer tentacles that flow behind their body as they swim by expelling water from a mantle cavity with a water-jet action. All 10 appendages of the squid are “fixed to its head” and are arranged in a circle around the mouth. Compared to the overall body, squid’s eyes are strikingly large.
The have the largest eye to body ratio in the entire animal kingdom.
All are carnivores that have a pair of powerful, beaklike jaws to crush or tear food. Squid are voracious eaters typically consuming 30 per cent to 60 per cent of their body weight daily. Prey is caught using the end of the long tentacles which are then pulled towards the mouth supported by the shorter arms. They consume small fish, other mollusks and crustaceans.
The colouring of a Caribbean reef squid is a generally a mottled medium green to brown on the dorsal side and clear, light brown, or whitish on the ventral side.
A distinct white line runs longitudinally on the dorsal side. These animals are social creatures often found in small groups that communicate through a variety of complex signals.
Both cuttlefish and squid communicate by controlling the pigment in their skin. This strategy is used as a defence to confuse predators and to communicate between members of a shoal. Caribbean Reef Squid are believed to display nearly 40 different patterns. Colours are produced by chromatophore organs, part of the muscular system, controlled directly by the brain. Retreating squid near the protection of the reef will often turn dark brown or reddish in colour to match their surroundings.
On average, squid shoals are attacked several times during the daytime, by such predators as Bar and Yellow Jacks, Cero Mackerels and groupers.
Members of a shoal typically form a line with larger individuals, acting as sentinels, stationed at each end and near the middle.
When approaching danger is detected, the shoal typically forms into a tight school and jets away as a group. Like other cephalopods, Caribbean reef squid are semelparous; that is, they die after reproducing.
Females lay their eggs then die immediately after. The males, however, can fertilize many females in a short period of time before they die. Females lay the eggs in well-protected areas scattered around the reefs.
In terms of conservation, there are several reasons that Cephalopods are rarely listed as threatened or endangered (nationally or internationally).
The primary reason squids, octopuses, and cuttlefish have not received much attention for conservation issues is because not enough is known about the species to know whether or not they are threatened. Cephalopods have no conservation status under The United States Endangered Species Act, IUCN, or CITES.
Protect Cayman’s Marine Life! For more information, to share your knowledge or if you would like to get involved with the many activities in the National Trust’s Know Your Islands Program, please visit www.nationaltrust.org.ky, or call 949-0121.The weekly column from the National Trust is submitted by Marnie Laing, Education Programs Manager at the Trust.
Last week’s answer: Red Bats are very rare; they roost alone in foliage and are the only bats known to commonly give birth to more than one pup at a time.
Trivia question: Name one local marine mollusc that has become rare because of over-collecting.
Look for the answer in next week’s feature!