Marine Invertebrates of Bermuda Caribbean Reef Squid (Sepioteuthis sepioidea) By Kelly M. McKay Dr. James B. Wood - Editor Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Taxononmy


Phylum: Mollusca
  Class: Cephalopoda
    Order: Teuthida (Squid)
      Family: Loliginidae

Squid are members of the phylum Mollusca, which also contains clams, oysters and mussels, and are members of the order Teuthida which contains octopus and cuttlefish. Members of the family Loliginidae are powerful swimmers, have a diamond-shaped fin at the rear end of the mantle membrane and resemble cuttlefish in their outward appearance (Sugiyama et al., 1980). Due to this resemblance, in Bermuda, Sepioteuthis sepioidea is often referred to as Cuttle or Scuttle (Boycott, 1965). The body of the Caribbean Reef Squid (Sepioteuthis sepioidea) is widened and flattened, with adult females reaching a dorsal mantle length of at least 120mm and adult males at least 114mm.

Habitat


Sepioteuthis sepioidea, much like its common name suggests (Caribbean Reef Squid), can be found in tropical and sub-tropical waters ranging from Bermuda to Florida through the West Indian Islands and from Cozumel to Venezuela along the Caribbean (Boycott, 1965). S. sepioidea can be found in depths ranging from just under the surface down to 100 meters and from open waters to the shoreline; location is often dependent on each individual's level of growth and development as well as the time of day (Moynihan and Rodaniche, 1982). Newly hatched S. sepioidea are 'semiplanktonic,' spending the majority of the time near the surface or directly underneath floating vegetation, but during turbid (murky) water conditions, can be found at depths up to 2 meters below the surface. They occur both near the shore and in channels between islands. Older, not yet mature Caribbean Reef Squid have different habitats, often congregating in shallow turtle grass beds during the daytime and usually staying between 25 to 30cm from the surface. At night, though, squid at this growth stage can be found near the bottom, close to the substrate. Medium-sized and adult Caribbean Reef Squid, before reaching the fully mature breeding stage, occur in many habitats, though usually avoiding turle grass, because of the hindrance it causes in movement. Squid at this development stage are found over a great diversity of sandy and coral bottoms and have been found to travel distances between Caribbean San Blas Islands (Moynihan and Rodaniche, 1982). At night they remain offshore, while during the day they remain predominantly closer to shore. Courting and breeding adults, those that are fully mature, are typically concentrated on coral reefs and in water up to 8 meters deep during the day; at night, however, they prefer deeper, open water (Moynihan and Rodaniche, 1982). During spawning, S. sepioidea inhabits shallow waters (Sugiyama et al., 1980).

Also dependent on Caribbean Reef Squid habitat ranges is global location. Around the San Blas Islands of the Caribbean, Sepioteuthis sepioidea are found ranging from the mainland shore to the outermost islands, with their population estimated at tens of thousands of individuals (Moynihan and Rodaniche, 1982). In Bermuda, the Caribbean Reef Squid is found on rocky and sandy substrates and in well-lit waters. The exact vertical distribution in Bermuda is unknown, but it is thought to range from 10 to 100 meters (Boycott, 1965). Compared with other squid species, overall S. sepioidea keeps nearer the bottom substrate (Boycott, 1965).

Ecology


The behavior of an animal depends, among other things, on the kinds of information collected by its sense organs and organization of the brain (Hanlon and Messenger, 1996). Caribbean Reef Squid exhibit various behaviors, some of which are unique to the species and some of which are common to most other cephalopods. The life history of Sepioteuthis sepioidea is very detailed and specific. In spawning, female Caribbean Reef Squid lay seven to eight eggs in a row within an egg capsule and deposit such capsules on the substrate (Moynihan and Rodaniche, 1982). Egg capsules are common among other squid and resemble pods of plants; the amount of eggs present in each capsule is usually more abundant in other species of squid, and is species specific. After hatching from the capsules, the juveniles reach maturity in approximately 6 months (Moynihan and Rodaniche, 1982). The juvenile's first feeding age is between 10 to 15 hours after hatching and the first food type is mysid shrimp (Boyle, 1987), with older Caribbean Reef Squid showing a preference of consuming young fish over copepods, amphipods (beach hoppers), crustacean larvae and polychaetes (LaRoe, 1971). Juveniles grow approximately .7mm per day (Boyle, 1987). Adult Caribbean Reef Squid feed on shrimp and smaller fish, usually only a few centimeters long, including such fish as the Dusky anchovy (Anchova lyopesis), a schooling sarding, the Dwarf Herring (Jenkinsia lamprotaena) and hardhead silversides (Antherinomorus stipies). Shrimp are captured when the squid descends to the sand, uses its arms to disturb the substrate and flushes out the prey (Hanlon and Messenger, 1996). Tricky hunting tactics are used by S. sepioidea to capture prey. At night, the Caribbean Reef Squid may stalk its prey, perhaps using lures. The squid usually hunt in disguise by mimicking sargassum weed; this involves making postural, textural and chromatic adjustments while associating itself with clumps of weed (Moynihan and Rodaniche, 1982). There is no sign of cooperative hunting in the Caribbean Reef Squid, though an individual may alert another individual if prey is near (Moynihan and Rodaniche, 1982). Most hunting is done actively at night, though feeding may occur during the day, as the result of waiting for prey to pass by (Moynihan and Rodaniche, 1982). Once captured, fish are brought to S. sepioidea's mouth, bitten behind the head and held in the arms until eaten. Flesh and internal organs are devoured, while the head, tail, vertebral column and ribs are discarded usually in one piece (Boyle 1987). Sepioteuthis sepioidea have also been observed storing prey while eating (Cowdry, 1911).

Sepioteuthis sepioidea are remarkable for their calm demeanors and extensive social interactions. Except in courtship, attacks of overt fighting between individuals are rare within established groups (Moynihan and Rodaniche, 1982). S. sepioidea are usually found in groups called shoals; these groups are a social assembly for rest, defense, foraging, courtship, mating and spawning (Hanlon and Messenger, 1996). Within a shoal, dominanat hierarchies are present, with there being a subtle relationship between members based on size; smaller individuals often give way to larger individuals and when an individual is needed to confuse, distract or intimidate a potential predator, larger individuals often react (Moynihan and ROdaniche, 1982). Within shoals, duties are assigned. 'Sentinels,' vigilant individuals with attuned senses watch for predators and alert the group when a danger approaches. Usually, there are sentinels facing in all directions at one time (Moynihan and Rodaniche, 1982). These sentinels watch for such predators as the Mutton Snapper (Lutjanus alanis),the Purplemouth Moray Eel (Gymnothorax vicinus) and the Spotted Snake Eel (Ophichthus ophis), depending on global location (Moynihan and Rodaniche, 1982). Also within shoals, social fidelity is maintained loosely, often lasting only days, as opposed to weeks or months in other species (Hanlon and Messenger, 1996). In Little Cayman Island, it was observed that S. sepioidea spends approximately 64% of the day resting in shoals, with the rest of the day and nighttime divided between avoiding predators, in courtship and in moving to and from feeding areas; much of the time these shoals are arranged in linear positionings (Hanlon and Messenger, 1996). Different squid species can often be found mixed within the same shoal. Sepioteuthis sepioidea has been seen mixed with Loligo plei in Panama, the Bahamas and the Cayman Islands (Moynihan and Rodaniche, 1982). There is also a common association between the Caribbean Reef Squid and two species of Goatfishes, the Yellow Goatfish (Mulloidichthus martinicus) and the Spotted Goatfish (Pseudupeneus maculatus). While the Goatfishes forage on the substrate for small invertebrates and plants, the squid hover near them. The relationship between the two is not fully clear, but it is thought the squids are acting as sentinels, keeping watching to alert the fish of any danger. The benefit of the squid interaction, though, is unknown (Moynihan and Rodaniche, 1982).

Much like other cephalopods, the Caribbean Reef Squid has the ability to change skin color and patterns; this is accomplished by the brain directly controlling th chromatophores (Hanlon and Messenger, 1996). Color and pattern change can be used for a variety of reasons. From defense, to courting and hunting, S. sepioidea shows a variety of ritualized patterns which may be linked with specific behaviors. Pattern changes often occur during hunting, with a particular body pattern persisting through the attack or with it changing in different sequences; the different stages of attacking prey are not strictly associated with certain patterns (Moynihan and Rodaniche, 1982). Some Caribbean Reef Squid have been seen imitating parrotfish, swimming backward with its arms and tentacles held together while displaying two eye spots (Hanlon and Messenger, 1996). In defense, juvenile Caribbean Reef Squid may imitate blobs of their own ink, while older individuals may express diematic behavior, the sudden appearance of bold light or dark chromatic components, usually accompanied with the spreading of the arms, webs or fins to create the illusion of largeness (Hanlon and Messenger, 1996). At least 40 body patterns can be observed in defensive situations (Byrne et al., 2003). Skin patterns shown in the Caribbean Reef Squid include: bars, belly stripe, dark arms, yellow flecked, speckled belly, streaks, zebra coloration and golden eyebrows, where the brow ridge turns a metallic gold. The pattern seen most frequently is finely mottled medium brown above, and clear light brown or whitish below (Moynihan and Rodaniche, 1982). Aside from changing pattern to avoid predators, squid may jet away quickly, for long distances, usually in a tight shoal and may do so with or without inking (Moynihan and Rodaniche, 1982). During courtship, males often show zebra display with shimmering chromatophores to exhibit vigor (Hanlon and Messenger, 1996). Many othe squid have the ability to bioluminesce; Sepioteuthis sepioidea, though, does not possess this ability (Moynihan and Rodaniche, 1982).

Caribbean Reef Squid females exhibit sexual selection, possessing the choice of whether or not to accept a male as a spermatophore donor. Squid fertilization occurs internally but usually with a minimal amount of physical contact between the female and the male. The male transfers a spermatophore to a particular area on the body surface of a female, the female decides if she wants to accept the spermatophore and if she does, she fertilizes herself. If she decides against it, the spermatophore is discarded (Moynihan and Rodaniche, 1982). Sexual activities occur throughout the day and peak right before dark, with courtship occurring immediately following an interaction with a predator (Hanlon and Messenger, 1996). After spawning once or a short series of times, all or most adults die, a cycle called semelparity (Moynihan and Rodaniche, 1982).

Recent Research


The Caribbean Reef Squid has recently been the subject of much neurological and sensory research. In a 1999 study by Arrieche, the optic gland of Sepioteuthis sepioidea was researched and described at different sexual maturity stages. Because the reproductive organs in S. sepioidea are significantly different at different sexual maturity stages and because the gland, which consists of secretory cells, blood vessels, nerve cells and support cells, has a similar function to the hypophosis, which controls sexual development in vertebrates, the Caribbean Reef Squid was chosen. The optic gland hormone of the Caribbean Reef Squid is species specific and is associated with the multiplication of reproductive cells; the fine structure of the gland suggest that there are various other functions associated with it. For this study, both male and female squid were examined at different sexual maturity stages using Transmission Electron Microscopy (TEM) to compare cell changes throughout the lifecycles (Arrieche, 1999). It was found that at the the juvenile maturity stage the optic gland is almost undifferentiated from the cerebral brain tissue, possessing a reddish color in individuals with a larger dorsal mantle length. Also, the reproductive organs in males tended to increase with a larger dorsal mantle length as well as the optic nerve cells at different stages showing different organelle abundances. In the juvenile and immature stages, numerous cellular mitochondriae were present and the endoplasmic reticulum was thin and dispersed in the cytoplasm. In reproductive male individuals, though, the secretory cells were nearly absent and the endoplasmic reticulum was dilated (Arrieche, 1999). Results such as these show the vast potential of the functions of the squid's internal systems. The changes in abundances of cellular organelles and the correlating relationships in the male squid's mantle length with reproductive organ size, show that hormones and chemicals have a great impact on the changes within the squid. Further research needs to be done, though, to better assess the functions of the optic gland.

The Caribbean Reef Squid neural Giant Axon has also been the subject of extensive research. In a study by Rosenthal and Bezanilla (2002), the action potentials were recorded from four temperate to tropical species of squid, including Sepioteuthis sepioidea, to determine which physiological properties contribute to temperature adaptation in the giant axon. Highly temperature sensitive, the squid giant axon is used to determine basic mechanisms of excitability. In comparing the four squid species axon responses, the study found that the action potential (of the giant axon) has a falling phase whish differs among all the species tested and correlates with the thermal environment of the species; the colder climate squid experienced a slower action potential. Other findings include that the action potential's rising phase in the Caribbean Reef Squid is relatively slow compared to that of the other species studied, and that the conduction velocity of the giant axon of the Caribbean Reef Squid, at all temperatures, is slower than the other species' (Rosenthal and Bezanilla, 2002). This separation in the resuls of Sepioteuthis sepioidea gives it unique qualities that also should be further researched.

Other current research is focusing on the unique color changing patterns of Sepioteuthis sepioidea; a model of visual skin displays in the Caribbean Reef Squid has recently been constructed using Adobe Photoshop. This graphic model, which represents both dorsal and lateral views of the squid, shows variations in skin (visual) patterns between males and females ranging different age groups as well as displays such as camouflage patterns (Byrne et al., 2003). In order to obtain the information employed for this model, field study was conducted off the coast of the Caribbean Island, Bonaire, for an extensive period of time. The model was made in a way much similar to actual squid skin displays, using basic background colors and areas of the body where they overlay distinct patterns (Byrne et al., 2003). This model will be made publicly accessible via CephBase (link at bottom of page) in the near future, and works by clicking together combinations of layers to present known Caribbean Reef Squid skin patterns. Coloration models possible include pale background, blue-green eyebrows, brown stripes, male and female zebra patterns and mid-dorsal line representations, all of which have been observed and may be linked to distinct squid behaviors. This graphic representation provides nomenclature on the level of patterns and displays, as well as units and components (Byrne et al., 2003), and is a step in common understand and compiling of the data concerning Sepioteuthis sepioidea.

There are many interesting aspects in the life of the squid species Sepioteuthis sepioidea, many of which deserve, but have not yet received, adequate research. It has been suggested that the Caribbean Reef Squid has its own 'language,' with visual signals constituting a vocabulary and syntax (Moynihan and Rodaniche, 1982). This suggestion exvokes many responses in the scientific community and poses such questions as, "do signals provoke different responses?"(Hanlon and Messenger, 1996), "are combinations of patterns designed for particular reasons?" and "can individuals 'converse' with one another?" (Moynihan and Rodaniche, 1982). Answers to such questions may lead to important revelations in squid society and behavior. Though limited knowledge is known on the various forms of visual signaling, much more research needs to be done to show the wide-ranging implications it can have. Perhaps the one answering these questions could be you!

Commercial Importance


Members of the Loliginidae family are regularly consumed by humans because, despite their elastic muscles, are considered 'soft and tasty.' Sepioteuthis sepioidea, though, are not usually consumed (Sugiyama et al., 1980). There are many cases in which small individuals of Loliginidae are consumed fresh, such as Loligo japonica in southeast Asia, the Californian Doryteuthis off the coast of the western United States and the recent find of the abundant Loligo edulis off the coast of New York (Sugiyama et al., 1980). Loliginidae squid are often dried in perparation for consumption; Sepioteuthis lessoniana is used for both Biko and Fukuro forms of dried squid. In the drying process of Biko, the base of the squid's fins are pierced with a bamboo skewer, thus opening holes. In the drying process of Fukuro, the epidermis and fins of the squid are removed to stimulate drying (Sugiyama et al., 1980). S. sepioidea are mistakenly caught year-round by dragnets and by those angling for shrimp and fish (Sugiyama, et al., 1980). In Bermuda, accidently caught squid are utilized by the local fishermen for bait (Wood, 2004). In the commercial fishing industry, the mistaken catches of the Caribbean Reef Squid are often a bother to the fishermen, though, because of their lack of commercial use. In a listing of worldwide commercial cephalopods, Sepioteuthis sepioidea was not mentioned (Boyle, 1987). Aside from being relatively commercially unimportant, they also are not particularly detrimental to any commercial industries.

Bermuda Laws


There are no Bermuda Laws concerning the Caribbean Reef Squid.

Personal Interest


The ocean is a dark, mysterious place. In many ways, it's like another world. When I was younger, I liked to imagine all the different animals that could be found in the deep ocean; I pictured huge, dinosaur-like creatures floating and jetting around, whipping from here to there, chasing and eating each other. A child's imagination is a wonderful thing. I grew up with a love for the ocean, but once I got a little older, I abandoned my dreams of huge, mysterious creatures in the dark abyss. When I was about fifteen, though, I stumbled on a book about the Giant Squid, and my fascinations with the other-worldliness of the oceans returned. I found myself so intrigued with the creature, I would read books upon books on the animal, seemingly not being able to get enough of it. How wonderful, I thought, it would be to see a Giant Squid or to be able to swim with one. Unfortunately, opportunaties like that are extremely rare, with most human-Giant Squid encounters happening when the squid is dead...so I chose the next best thing!

I decided to research Sepioteuthis sepioidea, the Caribbean Reef Squid for this webpage, because of my fascination with Giant Squid. I figured, 'hey, if I can't have the large scale, why not go for the smaller version?!' Sometimes the best things come in the smallest packages! Researching the animal has proven to be just as interesting as the Giant Squid (though not as entertaining as imagining the Giant Squid's habitat). In recalling what I read on the Giant Squid, despite the limited knowledge the world has of them, I found some similarities between the Caribbean Reef Squid and Architeuthis (Giant Squid).

Most humans are fascinated with the mysterious, myself included. I like to imagine, wonder and hypothesize about that which I do not know. Sometimes, though, the most amazing things can be found right before your eyes. S. sepioidea is a great creature, possessing so many unique characteristics that I find myself in awe (if only I could visually change my colors and patterns, I wouldn't have to color my hair!).

References

Arrieche, D (1999) Ultrastructure of the optic gland of the squid Sepioteuthis sepioidea (Cephalopoda:Loliginidae). Instituto de Investigaciones en Biomedicinia y Ciencias Aplicadas.

Boycott, BB (1965) A comparison of living Sepioteuthis sepioidea and Doryteuthis plei with other squids and with Sepia officinalis. Journal of Zoology: 344-351.

Boyle, PR (ed.) (1987) Cephalopod Life Cycles: Volume II Comparitive Reviews. London: Academic Press, pages 54, 78, 207, 254.

Byrne, RA, Griebel U, Wood, JB, Mather A (2003) Squid say it with skin: a graphic model for skin displays in Caribbean Reef Squid (Sepioteuthis sepioidea). Berliner Parabiol. Abh 03:29-35.

Cowdry, EV (1911) The color changes of Octopus vulgaris. University of Toronto Studies, Biological Series No. 10: 1-53.

Hanlon, TH, Messenger JB (1996) Cephalopod Behavior. UK: Cambridge University Press, pages 12-171.

LaRoe, ET (1971) The culture and maintenance of the lolinginid squids Sepioteuthis sepioidea and Doryteuthis plei. Marine Biology: 9-25.

Moynihan M, Rodaniche AF (1982) The behavior and natural history of the Caribbean Reef Squid Sepioteuthis sepioidea. With a consideration of social, signal and defensive patterns for difficult and dangerous environments. Advances in Ethology: 1-151.

Rosenthal JC, Bezanilla F (2002) A comparison of propogated action potentials from tropical to temperate squid axons: different durations and conduction velocities correlate with ionic conductance levels. Journal of Experimental Biology. 205:1819-1830.

Sugiyama M, Kousu S, Hanabe M, Okuda Y (1980) Utilization of Squid. Tokyo: Koesisha Joseikaku Company Limited, pages 17-18, 131-133.

Links

Sepioteuthis sepioidea from The Cephalopod Page
In Search of the Giant Squid

Marine Invertebrates of Bermuda Carribean Reef Squid (Sepioteuthis sepioidea) By Justin Anderson Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Taxononmy


Phylum: Mollusca
  Class: Cephalopoda
    Order: Teuthida
      Family: Loliginidae

Sepioteuthis sepioidea, commonly called the Caribbean Reef Squid, is a member of the Phylum Cephalopoda, along with octopii, cuttlefish, and the nautilus (Pechenik 2000). As members of the Order Teuthida, squid are the most heterogeneous and extensive cephalopod taxon (Ruppert et al. 2004).


Habitat




Abstract
Sepioteuthis sepioidea (more commonly the Caribbean Reef Squid) live in particular habitats based upon growth and developmental stages. These stages include newly hatched, small, adult, and pre-breeding squid. While newly hatched squid are “semiplanktonic,” adolescent to adult individuals use jet propulsion in locomotion. This jet propulsion can be slow or rapid, depending upon the situation. Caribbean reef squid are largely piscovorous, waiting for their prey during the day and hunting at night. Powerful arms and tentacles help in bringing prey to the mouth. In hunting, S. sepioidea may employ a number of techniques including raising arms, hiding tentacles, bending tentacles into a v-pattern, and twistingly confusing prey. During the day, these creatures remain in shoals and at night, they scatter. Fishes are primary squid predators. And, in response, squid will cautiously weigh their options and may ink or employ camouflage through rapid color changing techniques. Squid are also semelparous and possess distinct courting behavior. A study by Arrieche (1999) allowed for developmental tracking using optic gland size increase over time. In addition, squid are commercially valuable as a food source and bait. And, although predatory towards fish, they do not seem to have any significant impact upon fish population nor are they endangered despite overfishing in many species including S. sepioidea.

Habitat preferences can be linked to growth and development (Moynihan and Rodaniche 1982). In order to examine these varying preferences, Sepioteuthis sepioidea is divided into four life cycle categories: newly hatched, small, medium and large (adult). Each stage corresponds to an ecological and social phase.

Newly hatched individuals are “semiplanktonic” and are only seen during the day (Moynihan and Rodaniche 1982). Generally, they are found near the surface of moderately deep waters about 0.2 to 1.0 m below the surface and 1 to 10 m from the seafloor. At times they may be near or under floating vegetation. Bottom content in these areas has little effect on locations at this stage.

Small sized individuals can be found both near islands and in wide channels between islands (Moynihan and Rodaniche 1982). At this stage, the young have shorter fins and are not often found close to shore as often as older squid. Although they tend to float passively, they still have the ability to swim strongly against a current when necessary.

Larger individuals have longer fins and are less planktonic (Moynihan and Rodaniche 1982). Longer fins allow them quicker and more efficient swimming capabilities. Adults habitually dwell in shallow turtle grass flats that are close to islands during the daytime. In these areas, depth ranges from a few centimeters to 2 m. Smaller adults attempt to keep a certain “safe” distance from the surface compared to larger individuals.

In pre-breeding stages, S. sepioidea avoids the shallow depths of turtle grass flats, due to a limit in shallow water on maneuverability (Moynihan and Rodaniche 1982). Breeding individuals are also very attracted to coral and will reside in the reefs. In general, average adults tend to prefer open water conditions at night and inshore conditions during the day (Moynihan and Rodaniche 1982).

Ecology


General Introduction and Characteristics
Members of the Order Teuthida (squids) have an internal and uncalcified shell (Pechenick 2000). Eight arms and two retractile tentacles (Morton and Yonge 1964) envelop the head, which has advanced eyes with lenses. Squids have an adapted radula for feeding and are commercially important. Specifically, S. sepioidea has a soft and silvery gray body but in the Bermuda area is browner colored. The animal also turns pale when agitated with often distinctly visible black blotches (Thomas 2003).

Primarily abundant in the tropical western Atlantic (Moynihan and Rodaniche 1982), squid are both major predators and a major food source for larger fishes, marine animals, and birds (LaRoe 1971). And, like other cephalopods, S. sepioidea are fast growing, semelparous, and have a short life span (Moynihan and Rodaniche 1982). Also, individuals travel in large, organized groups by day and scatter more at night at night, mainly due to the visual cues of schooling (Hurley 1978).

Movement
While newly hatched squid are “semiplanktonic” (Moynihan and Rodaniche 1982), adolescent to adult individuals use jet propulsion in locomotion (Pechenick 2000). To move, the squid will use mantle muscles to eject water from its funnel. Contraction of thick circular muscles in the mantle will force water through the funnel of the squid. Depending on the direction the squid wants to move in, the funnel is positioned opposite the desired direction of movement.

Squid can also jet slowly or quickly. Slow jetting is a general form of movement when the squid is free of danger (Pechenik 2000). The animal will jet quickly in response to immediate attack or danger. In this instance, the funnel is pointed toward the anterior end of the squid, propelling it quickly in a posterior direction.

Squid tend to move farther from shore when water is murky (sediment or disturbance), diluted by heavy rainfall, or overly warm from intense sunlight (Moynihan and Rodaniche 1982). Such a characteristic causes a great deal of diversity in population size and density in a particular area. Sepioteuthis sepioidea squid observed at the San Blas Islands along the Caribbean coast or eastern Panama were more abundant during the late spring and summer months (April to July) than in the winter months (November to February).

Predators
S. sepioidea squid observed in the Caribbean (Moynihan and Rodaniche 1982), are largely piscovorous and wait for their prey to approach them during the day. At night, they are more active hunters. Captured prey are generally a few centimeters long, depending upon the size of the squid. In feeding, fish are transported to the mouth by the arms where they are bitten behind the head and secured until eaten. These arms are lined with sharp hooks, corresponding to adapted sucker-rings (Verrill 1882). The tip of the arms have a cluster of smoother suckers, while the clubs at the ends of the longer tentacles have both connective tubercles and smooth suckers. The squid will feed on the flesh and internal organs of the fish but discard the head, tail, vertebrate column, and ribs.

In hunting, S. sepioidea will employ a number of techniques (Moynihan and Rodaniche 1982). Individuals may raise their central upper arms to lure potential curios predators. Another method, presently exclusive to S. sepioidea, involves hiding their tentacles from the vision of their prey until the time to attack comes. At this time, tentacles are rapidly extended past the limit of the longest arms. Also, squid can bend their tentacles in a hooking v-pattern to aid in capturing smaller prey. In addition, upon approaching food a squid may twist and spiral its tentacles in hopes of confusing its prey.

During the day, S. sepioidea lives in large and organized groups (Moynihan and Rodaniche 1982). This species does not cooperatively drive its prey but may compete with one another for food at times. They remain closely bunched and will strike at prey generally one at a time then fall back into line with the group. However, S. sepioidea will exhibit cannibalistic activity (Woods, J.B. BBSR). When ready to feed, they have been observed anchoring themselves, dormantly, by the arm tips on the seafloor bottom and wait for the appearance of its prey (Moynihan and Rodaniche). The fish captured are primarily sardines, dwarf herring, false prichard, red, and hardhead silversides. Other prey include shrimp, mysids, and mollies (CephBase 2004).

Food selection is of greatest important to the survival of young squid (LaRoe 1971). In isolated studies, newly hatched squid were very selective in choosing prey but flourished upon large amounts of mysid crustaceans. Juveniles and adults also capture small planktonic animals (copepods) and small arthropods (Moynihan and Rodaniche 1982).

Prey
Predators of the squid S. sepioidea are abundant, varied, and generally fishes (Moynihan and Rodaniche 1982). Out of the 28 cephalopod-feeding fishes, five are lutjanids, four are pomadasyids, four are serranids, three are scombrids, two are priacanthids, and two are sphyraenids. Of these however, only five showed more than ten percent squid content in their stomachs, none of which were of the species S. sepioidea (Moynihan and Rodaniche 1982).

Squid will not immediately attempt escape when alarmed by predators (Moynihan and Rodaniche 1982). Rather, they will wait and cautiously calculate their options. This factor is largely due to their highly developed brains, a distinguishing, although not exclusive, characteristic compared to other mollusks. The squid brain is a nerve ring with closely packed ganglia surrounding the esophagus. Sensory input from the eyes, statocyst, and olfactory epithelium are processed in the two cerebral ganglia (Ruppert et al. 2004).

In instances of rapid escape, Sepioteuthis sepioidea, like other squid, will often ink in response to any form of alarm. (Moynihan and Rodaniche 1982). The ink, an agitation pheromone (Huffard and Caldwell 2002), functions as a distractive decoy, forming a thick cloud and taking a long time to clear. This allows ample time for predatory escape.

Reproduction
Squid reproductive patterns have developed based upon a year round mating strategy (Arkhipkin et al. 2000). For this reason, the population is divided into several groups that help to maintain species survival by remaining protected in larger numbers.

Prior to mating, the male will pursue the female in order to protect her from other males (Arnold 1965). While males and females are physically distinguishable by smaller males and a more rounded posterior margin of the mantle in females, the sexes also behave differently during the courtship process. Generally, an aggressive male will begin the courting ritual by selecting a specific female and swimming parallel to her. As he swims, he is rapidly fluttering his fins and changes to a pale reddish color that is accentuated on his ventral surface. Initially, the female rarely responded to these actions by the male. When the female does eventually return attention to the male, she will also swim parallel to the male, showing her own unique courtship patterns formed by chromatophore contraction. At this point, the male changes to a dark brown color banded across the mid-dorsal section of the mantle. While initially avoiding aroused courting males, females will eventually pick a mate based upon no particular preference (Arnold 1965).

During early stages of courtship, groups are comprised of one female and several competing males (Moynihan and Rodaniche 1982). Following courtship, when the female selects a male, individuals separate into pairs. The female lays her eggs in clusters on coral crevices. Being a semelparous species, the parents die shortly after the eggs are laid.

Recent Research


Arrieche (1999) examined the ultrastructure of the optic gland of the squid Sepioteuthis sepioidea. The optic glands in cephalopods can be found at the posterior edge of the optic brain tract as two oval organs. They consist of main or secretory cells, blood vessels, nerve cells, and support cells. Physiologically, they control sexual development, control ovary protein synthesis, stimulate gonadal mitosis, mating habits, feeding, and longevity. The ultra structures examined by Arrieche (1999) were in the cases of both sexes at different sexual stages and were viewed using a Transmission Electron Microscope in hopes of comparing secretory cell changes.

Morphological characteristics, such as mantle length and reproductive organs, in S. sepioidea are excellent indicators of what stage of sexual maturity and individual has reached (Arrieche 1999). However, some squid were found at the same stage of development with different mantle lengths. And, although several squid species structure were more difficult to observe, S. sepioidea possesses an ideal structure in that its optic gland has some distinct features in addition to normal cephalopod characteristics. Organelle abundance differed in secretory cells between sexual stages. And, results showed a consistent increase in optic gland diameter in both sexes (Arrieche 1999).

It was not possible to study females, however, during spawning or post-spawning stages due to a stage of committed care for eggs until hatching followed by a short resting and brooding period (Arrieche 1999). This period was eventually followed by death in the animal.

Commercial Importance


Many mollusks are important to the commercial fishing industry including clams, crabs, oysters, scallops, mussels, and squid. Squid are caught and prepared as calamari in many restaurants and sold in many stores across the world. Commercially sold squid are about 12 to 16 inches long and are particularly popular in Europe and Japan. Trawling is a primary method of capturing squid. Prior to around the 1970’s, squid were captured primarily by accident by fishermen intending only to capture fish (Rathjen and Voss 1987). However, cephalopod species still remain nearly untouched population wise. About 70 million tons of recorded fishery catch worldwide are cephalopods. The size of the cephalopod population worldwide has been estimated at 2-100 x 10^6 tons, 100-300 x 10^6 tons, and as excessive as 500 x 10^6 tons. Total catch is estimated at 1.5 to 2.1 % of total fishery intake (Rathjen and Voss 1987).

In addition, all species of squid are considerably piscovorous. Although, generally, this as little effect on fish populations, the overpopulation of fish-preying squid might make a difference. They are also used as bait.

Bermuda Laws


No law were found pertaining to Sepioteuthis sepioidea.



Personal Interest


I have always harbored interest in squid and octopuses. Reading fictional stories or watching movies and television shows about the “mysteries” and “terrors” of the deep. It was not, however, until arriving in Bermuda that I really came to appreciate these unique creatures. I remember learning, upon our first trip to the aquarium, all about the intelligence and complexity of squid and octopuses. I found myself wondering, as I stared into one of the tanks at an octopus, what this creature might be thinking and wanted to learn more about it. Over the weeks, throughout my fall semester studying Marine Invertebrate Zoology at the Bermuda Biological Station for Research (BBSR) I came to learn more and more about the behavior, complexity, and intelligence of these animals. I was even provided the opportunity to accompany researchers at BBSR on some squid tagging trips.

Presently, I am conducting my four-week research study at BBSR with James Wood as a guide and advisor. During this time, I will be helping in the tagging of squid, care of those in captivity at the station, and making my own observations of tagged squids on our trips. In my research, I am examining the size variations in observed local squid shoals in Bermuda. Therefore, it seemed only fitting that I choose the specific Caribbean Reef Squid, Sepioteuthis sepioidea, for my Marine Invertebrate Zoology research assignment.

References

Arkhipkin, A., P. Jereb, S. Ragonese. 2000. Growth and maturation in two successive seasonal groups of the short-finned squid, Illex coindetii from the Straight of Sicily (central Mediterranean). Jour. Mar. Sci. 57: 31-41.

Arnold, John M. 1965. Observations of the mating behavior of the squid Sepioteuthis sepioidea. Bull. Mar. Sci. 15(1): 216-222.

Arrieche, Dwight. 1999. Ultrastructure of the optic gland of the squid Sepiotheuthis sepioidea. Rev. Biol. Trop. 47(4): 831-842.

CephBase. Wood, J.B., and C.L. Day. 1998-2004. 14 November 2004 http://www.cephbase.utmb.edu.

Huffard, Christine L., R.L. Caldwell. 2002. Inking in a Blue-Ringed Octopus, Hapalochlaena lunulata, with a Vestigial Ink Sac. Pacific Science. 56(3): 255-257.

Hurley A.C. 1978. School structure of the squid Loligo opalescens. Fishery Bulletin. 76 (2): 433-442.

LaRoe, E.T. 1971. The culture and maintenance of the loliginid squids Sepioteuthis sepioidea and Doryteuthis plei. Mar. Biol. 9(9): 9-25.

Moynihan, Martin, Arcadio F. Rodaniche. 1982. The Behavior and Natural History of the Caribbean Reef Squid Sepioteuthis sepioidea. Germany: Verlag Paul Parey.

Morton, J.E., and C. M. Yonge. (1964). Classification and Structure of the Mollusca. In Physiology of the Mollusca. 1. Wilbur, K.M. and C.M. Yonge (Eds.) New York; Academic Press. 47-57.

Pechenick, Jan A. 2000. Biology of the Invertebrates. Boston: McGraw-Hill Higher Education.

Rathjen, W.F., and G.L. Voss. 1987. The cephalopod fisheries, a review. Cephalopod Life Cycles Vol II. 253-275.

Ruppert, Edward E., Richard S. Fox, Robert D. Barnes. 2004. Invertebrate Zoology. California: Brooks/Cole-Thomson Learning.

Thomas, M.L.H. 2003. The Ecology of Harrington Sound, Bermuda. Bermuda Zoological Society: Bermuda.

Verrill, A.E. 1882. The Cephalopods. Washington: Government Printing Office.



Links

The Cephalopod Page
MarineBio.org
Deep Sea Images