Mollusks have well developed body organs that are used in the respiratory, circulatory and nervous systems. The stomach-foots include snails, limpets and abalones, which have shells. Slugs and nudibranchs are also stomach-foots, but do not have shells.
A few stomach-foots are found on land. The Many-Plated or Chitons The many-plated or chitons class Polyplacophora have eight plates and look like pill-bugs but pill-bugs are not chitons.
Chitons crawl along rocks looking for food usually algae. A chiton uses its radula tongue to scrape algae off rocks. It also has very hard teeth that are also used to scrape algae of rocks. These teeth are hard enough to etch glass! Embedded within their shells are primitive "eyes" that can detect light. Chitons are very, very slow moving. During a year, a chiton may move only ten feet! The Bivalves The bivalves class Bivalvia are very well known. They include clams, mussels, oysters and scallops.
Though structured similarly to other mollusks, a cephalopod nervous system far surpasses the nervous systems of their closest molluscan relatives—the California sea slug has about 18, neurons while the common octopus, Octopus vulgaris , has roughly million neurons in its brain. Humans have many more, just under billion , but a cephalopod is on par with dogs and some monkeys since they also carry about two-thirds of their neurons in their arms, not their head.
Unlike humans and other mammals, the cephalopod brain will grow one and a half times its original size from the moment of birth to adulthood. With intelligence comes the ability to learn. Scientists first realized cephalopods had a talent for learning after the publication of a groundbreaking study by a German researcher named Jakob von Uexkull in Uexkull starved a group of octopuses for fifteen days and then presented them with hermit crabs carrying anemones on their shells.
The famished octopuses readily attacked the hermit crabs, though after a few stings from the anemones they soon avoided the crabs altogether. Early studies found an octopus can be trained to perform specific behaviors using food rewards and shock punishments, showing they are capable of making associations. When presented with a foreign but harmless object they will initially explore and investigate, but after consecutive introductions, they quickly lose interest, a sign they remember the object and its now unremarkable nature.
Surprisingly, though, octopuses are not the best when it comes to tackling mazes—they fail to even remember a simple sequence of turns. Levers are also tricky for octopuses and, for the most part, tests trying to teach octopuses to feed themselves using a lever mechanism have been unsuccessful.
It may come as a bit of a surprise that although they are reclusive and solitary creatures, octopuses may be able to learn from one another. In a study, scientists trained a group of octopuses to discriminate between two colored balls. Choosing a red ball elicited a tasty snack while choosing a white ball elicited an unpleasant shock. As this group of octopuses learned to associate color with reward and punishment, a second group of octopuses was allowed to observe from separate tanks.
Next, these observers were given the choice—red or white. Without reward or punishment, the second group chose the red ball more quickly than the initial group. Playing behavior is also attributed to intelligent organisms like mammals and some birds, but recent studies suggest octopuses may also like to have a little fun. A study at the Seattle Aquarium found that two of ten octopuses squirted water at weighted pill bottles, pushing the bottles against a filter current.
After waiting for them to float back the octopuses squirted them again, almost like bouncing a basketball. A study suggested that octopuses will play with blocks as well.
Sometimes referred to as the chameleons of the sea, a cephalopod can change the color and texture of its skin in the blink of an eye. Some use this skill to blend into their environment as masters of disguise, while others purposefully stand out with a flashy display. They change texture by controlling the size of projections on their skin called papillae , creating surfaces ranging from small bumps to tall spikes.
A study on cuttlefish found that once the papillae extend they become locked in place, enabling the cuttlefish to effortlessly hold their textured disguise while expending minimal energy. The color transformations are made possible by thousands of pigment-filled cells that dot the entire body, called chromatophores.
Within each chromatophore is an elastic, pigment-filled sac that is connected and controlled by several muscles and nerves. When the muscles contract the sack expands, revealing vibrant pigments—reds, browns, and yellows. When the muscles relax, the sack shrinks back down, hiding the pigment. The iridophores lie directly beneath the chromatophores and are responsible for displays of metallic greens, blues, gold, and silver. In combination, these color and texture changing techniques allow a cephalopod to mimic almost any background.
Experiments by Roger Hanlon show cuttlefish expertly mimicking mottled textures, stripes, spots, and a black and white checkerboard! Certain cephalopods have even mastered the ability to impersonate other animals, a self-defense tactic called mimicry.
The mimic octopus is the pinnacle of shape-shifting wizardry. It appears to imitate up to 15 different animals that we know of. Faced with a pesky damselfish it buries six of its arms in the sand leaving just two strategically placed and colored to look like the venomous banded sea snake a predator of the fish.
It can also cruise along the sand like a flat, banded sole fish or swim up in the water column like the venomous, spiny lionfish. Light is created through a chemical reaction that produces light energy in the body of the animal, similar to how fireflies flash on a hot summer night.
A catalyst called luciferase sets off the light producing substance called luciferin. The result is an eerie glow, startling flash, or syncopated blinking. Bioluminescence serves more than just a pretty display. The concentration of photophores on the bottom side of some squid suggests the light is used as a camouflage technique called counterillumination; the bright light protects the squid from lurking predators below by allowing it to blend in with light coming from the surface of the water.
But for the cephalopods that want to stand out, light is used to lure prey or flash as a warning for predators. The dazzling light displays of the firefly squid during mating season off the coast of Japan are quite the sight to see at night, though scientists are unclear whether the purpose of the light is to attract mates, deter predators, or something yet to be discovered.
One of the most exciting light displays is performed by the vampire squid. Deep ocean dwellers, vampire squid rely on three types of light organs. Each of the eight arms is tipped with several simple light organs, tiny photophores dot the skin, and a third, more complex pair of light organs with photoreceptors sit near the fins. When startled, luminescent clouds of mucus are emitted from the arm-tip light organs, leading scientists to think the glowing display is a defense mechanism.
While some cephalopods, like the vampire squid, are able to produce light on their own, for others lighting up requires a bit of help. The bobtail squid relies on a bacterium called Vibrio fischeri , and will selectively allow this bacterium to grow within its photophores.
At birth, a young bobtail squid lacks the bioluminescent bacteria and must find the light producing microbes in the water column. Once one bacterium successfully enters the photophore it multiplies by the hundreds of thousands, a colonization that spurs the full development of the photophore.
Vibrio fischeri is a common bioluminescence partner with some other cephalopods that owe their glowing skills to the microbe. In a stressful situation, a cephalopod has one final defense tactic. Almost all cephalopods have an ink sac, a bladder that can suddenly release a plume of dense, black ink. When startled or attacked by a predator the ink jet works like a smokescreen, a distraction, or a cephalopod look-a-like that the predator attacks instead which allows the real cephalopod to make a quick escape.
The ink can also act as a warning cue to other cephalopods. In the presence of ink the California market squid will begin to swim, and the Caribbean reef squid will initiate camouflage coloring. The Japanese pygmy squid has figured out how to use ink to hunt for shrimp , rather than just hide from predators.
It squirts a few quick puffs in the direction of the shrimp and then darts through the ink to grab its meal. The ink is potentially used as a way to both hide from the prey and to distract the shrimp from noticing the incoming attack. For most cephalopods, sex is a once in a lifetime event—both the male and female die shortly after mating.
A male sometimes initiates the interaction with a courtship display meant to attract and woo the female, though for most octopuses there is little foreplay. If successful, the male will use his hectocotylus, a specialized arm, to deposit sperm packets called spermatophores on or in the female. The story of how the name hectocotylus came to be is a tale of mistaken identity. Turns out, it was actually a male cephalopod arm, but the name stuck.
In the paper nautilus, the hectocotylus detaches completely during sex and remains inside the female—this is what Cuvier mistook as a worm.
Fertilization varies from species to species and in some cases the female holds on to the hectocotylus in a specialized pouch and fertilizes the eggs as she lays them. In some squid and cuttlefish , mating occurs in mass gatherings and the males compete for access to the female as she spawns. In the European squid, Loligo vulgaris , smaller males will skirt around the edges of the spawning ground and display patterns similar to a female, rather than challenge the dominant male.
If a female octopus lives near the ocean floor, once her eggs are fertilized, she will scout out a shelter to lay her eggs and attach them to the ceiling or walls in long strings. While most octopus mothers spend less than a few months watching over their brood, one deep-sea octopus, Graneledone boreopacifica , holds the record for the longest time spent watching over her eggs—over four and a half years! The long egg development time is most likely a response to the relatively cold environment of the deep sea.
For some squids that live in the open ocean, the eggs are spawned in gelatinous masses that then drift within the water column. The discovery of a mass squid graveyard off the coast of California indicates that once the female squid successfully reproduce, they die and sink to the bottom of the ocean to over 3, feet 1, m where they become food for deep-sea scavengers.
Upon hatching, the tiny, baby cephalopods become planktonic, meaning they live in the water column. Many hatchlings are already adept predators and will actively pursue prey. Little is known about the early life stages of specific species due to difficulties in identifying the very small young. A cephalopod is a strategic and cunning predator. Divers know that a telltale sign of an octopus den is a collection of empty crab shells littered on a rocky bottom. Carnivorous predators, all cephalopods have evolved special tools to help eat their prey.
They rely on a sharp beak that chops their prey into bite-size pieces. Inside the beak, a tongue-like radula is lined with tiny teeth which can push food down into the digestive tract or act like a drill to bore holes in shellfish.
In many cephalopods, not just the notoriously deadly blue ringed octopus , a salivary gland produces a paralyzing toxin that immobilizes and digests prey upon being bitten. The cephalopod esophagus runs through the brain, requiring food to be sufficiently pulverized so it can fit through the narrow space. The digestive tract also includes a stomach, which further mashes the food, and a caecum where some nutrients are absorbed.
Often, cephalopods are voracious consumers. A study of the California two-spot octopus found that an 80 percent decline in the octopus population spurred a percent explosion of their prey populations, gastropods snails and slugs and hermit crabs. They devour everything, even crabs, and lobsters, and oysters, and all shellfish. Some oceanic cephalopods participate in daily movements, called diel vertical migrations.
The cover of night allows them to hunt at the surface without the threat of predators seeing them. Once the sun comes up they make their way down to deeper, darker water. Although a formidable predator in its own right, the soft bodies of squid, octopus, and cuttlefish are delectable meals for other predators.
Birds also eat cephalopods. Albatrosses will plunge up to 32 feet 10 meters deep to snatch a squid beneath the waves. Scientists often find the tough beaks of squid and octopus in the stomachs of sperm whales and seals. Sperm whales that wash ashore can even have large sucker scars along their body, indicating the whales engage in epic battles with giant squid while eating them.
People have enjoyed eating cephalopods since ancient times. According to Paul Bartsch , Curator of Mollusks at the Smithsonian Museum of National History in the early s, the Greeks and Romans considered all kinds of octopus to be a delicacy.
In Rome, they would stuff the cavity within the body full of spices, cut off the arms, and bake it in a pie. During preparation, chefs refused to use iron knives claiming that the metal left an unsavory taste and would instead use special bamboo knives.
The Greeks, too, enjoyed octopus, and often sent one as a gift to parents the fifth day after a child was born, the naming day. One comedic Greek story tells the tale of Philoxenus of Cythera, a particularly greedy man. One night, Philoxenus desired an elaborate meal, which subsequently included a massive, three-foot octopus as its main dish.
Upon consuming all eight arms by himself, the man fell ill and required the attention of a doctor. In many places around the world, octopus, squid, and cuttlefish are common menu items at the dinner table. Over 4 million metric tons of cephalopods are fished from the ocean every year, the same weight as 27, adult whales. Squids make up a good chunk of the catch, accounting for about 75 percent of that total. In several areas like the Gulf of Thailand, evidence of squid fishing can even be seen from the international space station.
Squid fishermen string hundreds of bright lights from their boats at night to attract plankton, a powerful lure for squid that follow their prey to the surface where they are then caught by the fisherman. But octopuses and cuttlefishes are also culinary favorites. A United Nations Food and Agriculture Organization report found that roughly , metric tons of octopus were fished the previous year, and in recent years cuttlefishes have had similar totals. Cephalopod ink itself is the featured ingredient in Italian risotto nero and Spanish arroz negro.
In Asia where there is a prominent cephalopod fishery, the ink is also used in traditional medicine, having exhibited antimicrobial properties. There is also great interest in its use in anticancer drug development.
Cephalopods reproduce rapidly and so overfishing is often less of a problem than it is with finfishes. Most shallow water species are active visual predators with vigorous metabolic activity and sophisticated behaviors see between others Hanlon et al.
On the other hand, mesopelagic and deep-sea cephalopod species have been less well-studied and their feeding strategies and behaviors are not well known. Cephalopods show a significant negative relationship between metabolism and minimum habitat depth Seibel et al. As showed by Seibel et al. These cephalopods live both in epipelagic waters as subadults and deep-sea when adults and do not follow the negative relationship between minimum depth and metabolic rate showed for most cephalopod species studied.
The example illustrate that phylogeny is also an important factor when considering metabolic rates of individual species Seibel and Carlini, The following text seeks to briefly review recent advances on cephalopod predation and identify the main gaps in knowledge on this aspect of cephalopod biology and behavior.
Here, we aim to briefly account for the wide spectrum of morphological, behavioral, and physiological features that cephalopods use to meet their energetic needs through predation and food intake. Along this journey we will identify possible gaps in knowledge, thus providing a short guide for future studies.
The physiology and sensory processing capabilities of cephalopods are adapted to all marine environments. Animals looking for diverse prey needed to meet energetic requirements; metabolic energetic needs that change dramatically according to the ontogenetic state, the habitat they live in and life cycle stage.
A variety of feeding behaviors have been recorded in association with diverse feeding strategies for review see Hanlon and Messenger, ; but see also Rodhouse and Nigmatullin, , and such richness is accompanied by a sophisticated set of sensory systems review in: Budelmann, ; Wells, ; Budelmann et al.
This developed sensory system allows them to achieve sophisticated behaviors to detect food, avoid predators and communicate between congeners in a way comparable to vertebrates. Photo-, mechano-, and chemoreceptors provide support for the collection of information about their potential prey.
Table 1. Biological and behavioral adaptations utilized by cephalopods for the sake of their predatory behavior. Probably one of the most striking features of cephalopods is their developed eye, superficially resembling that of teleost fish. It has a single nearly spherical lens with a graded refractive index, the ability to accommodate the len and a similar capacity for eye movement, showing an example of convergent evolution Packard, The use of an adjustable pupil to control the amount of light entering the eye distinguishes the cephalopods' eye from their fish counterpart and the light-evoked pupillary constriction in cephalopods is among the fastest in the animal kingdom Douglas et al.
Among the few exceptions is the deep-sea cirrate octopod Cirrothauma murrayi , whose eye lacks lenses and the optic lobes are simply organized Aldred et al. Most cephalopods studied have a single type of rhodopsin as a visual pigment, suggesting they are blind to color Messenger et al. They can achieve spectral and color discrimination by exploiting chromatic aberration and pupil shape Stubbs and Stubbs, , but this system could work for only a narrow range of visual tasks Gagnon et al.
The giant Architeuthis and the colossal Mesonychoteuthis squids have the largest eyes in the animal kingdom, however their characteristics suggest they are mainly used for detecting and identifying bioluminescent waves generated by sperm whales during their dive into the deep, thus protecting them from potential predation, rather than detecting prey at long distances Nilsson et al. The importance of the visual system to locate prey is also reflected in the ability for aerial capture, such as, when Sepia officinalis is able to attack and capture prey shown above the water surface by an experimenter Boletzky, The complexity of the visual system of cephalopods is also achieved through extra-ocular light perception capabilities, providing an intricate network of sensory devices on their skin see also Kingston et al.
In addition, cephalopods are sensitive to polarized light and polarization vision serves to enhance the detection and recognition of prey. Sensory capabilities are not limited to vision.
Cephalopods have sensory receptors that form the lateral line system, which detects gentle water currents and vibrations. Ciliated primary sensory hair cells, sensitive to local water movements, are arranged in epidermal lines located on the arms, head, anterior part of dorsal mantle and funnel e. In fact, cuttlefish are able to catch small shrimp in the darkness and behavioral experiments showed they use the epidermal lines to detect prey Budelmann et al.
Distant chemoreceptor organs such as, olfactory organs and rhinophores, further provide additional sensory capabilities. Olfactory organs are paired, oval shaped organs situated on either side of the head, ventrally behind the eye and near the mantle edge.
Their possible role in prey detection is poorly understood. Water containing food odor shrimp is detected by S. Increased ventilation rates in response to prey chemicals was described for Eledone cirrhosa Boyle, ; and positive chemotaxis for Octopus maya during Y-maze experiments, with amino acids alanine, proline , nucleotids ATP , and crab extract functioned as excitants, while betaine and taurine functioned as arrestants Lee, The rhinophores of Nautilus are paired organs located below each eye and open to the exterior by a narrow pore.
They are similar to the olfactory organs but are significantly larger Basil et al. In addition, cephalopods have contact receptors in the tentacles, sucker rims, and lips; known to allow sensing of a broad spectrum of chemical and mechanical signals. Sucker receptors are more elaborated in octopus.
There are about 10, chemoreceptor cells in a single sucker of an octopod, but only about are present in the sucker of a cuttlefish Budelmann, The food searching habit of benthic octopods see below Speculative pounce , that make extensive use of the arms and suckers exploring rocks and crevices, may justify this marked difference. In contrast, cuttlefish use their arms mostly for manipulating their prey Chichery and Chichery, Contact receptors located in lips of octopus and cuttlefish are more advanced in structure and organization than those of squid.
As cuttlefish and octopus are more sedentary and benthic than pelagic squid, they may rely more on tactile and chemical stimuli Emery, Chemical receptors in cephalopods help them to locate prey and also to avoid unwanted prey. Cuttlefish were able to learn that a prey is not acceptable food, to recognize and to avoid it and, as a result, to choose a usually non-preferred prey when necessary Darmaillacq et al.
Hatchling cephalopods are of relatively large size, ranging from 0. Preference for prey at hatchling when previously exposed during the latest embryonic stages Darmaillacq et al. In this species, the development of learning and predatory behavior is observed during late embryonic and early juvenile development. This occurs simultaneously with the maturation of the vertical—subvertical lobe tracts of the brain, allowing the animals to maintain a prey in the frontal field during predatory pursuit Dickel et al.
Then, during the first 3 months of life, feeding hierarchy has been reported for the same species Mather, ; Warnke, A comprehensive review on this behavioral development is provided by O'Brien et al. On the other hand, in the juvenile holobenthic octopuses O. Juvenile octopuses selected crabs as prey when individuals had previously been fed shrimp earlier in life. This could be the result of innate biological processes Portela et al.
In squids, brain developmental differences can be found when observing the relatively large Loliginid Sepioteuthis lessoniana hatchlings, with a subvertical lobe of especially complicated domain structure, which may reflect an active predatory behavior Shigeno and Yamamoto, In comparison, the minor development of higher motor centers of the small ommastrephid Todarodes pacificus hatchlings, suggests these animals are not active predators at this time but perhaps suspension feeders after hatching Shigeno et al.
The first food and feeding strategy of the ommastrephid paralarvae before they start to actively feed on zooplankton is an unresolved question that merits further research O'Dor et al. Diet of planktonic cephalopods in the wild is poorly understood Passarella and Hopkins, ; Roura et al.
Roura et al. Stable isotope ratios allowed discrimination of specific feeding strategies during ontogenesis and accumulations of metals as cadmium and mercury also reflected the ontogenetic stage in five species of cephalopods Chouvelon et al.
Externally, strong morphological changes during early life are recognized in some cephalopod groups, particularly in oegopsid squids and merobenthic octopods, associated with different habitats and feeding modes during early life. Ontogeny of prey capture develops progressively, from a simple type after hatching to an adult-like capture behavior involving structures such as, tentacles and hooks, which are absent or poorly developed in larval forms Sweeney et al. In young ommastrephid squids, the fused tentacles forms the proboscis and its functionality, supposedly related to food capture, remain an open question that again needs future research Uchikawa et al.
In loliginid squids, ontogeny of prey capture develops progressively, from a simple type after hatching to an adult-like capture behavior involving tentacles after 1 month of age in Doryteuthis opalescens raised with copepods Chen et al.
In merobenthic octopods, a positive allometric arm growth takes place during planktonic life, probably helping the animal to capture benthic prey after settlement.
At the same time animals lose the oral denticles of the beaks, of which the trophic function remains unclear Villanueva and Norman, However, observations on the external digestion and initial ingestion process in the pymy squid Idiosepius paradoxus , suggest that oral denticles may be used to detach the semidigested flesh from the exoskeleton of the crustacean prey Kasugai et al. The early development of the muscular, protein-rich arm crown in merobenthic octopods is related to the decrease in lipid content of the animal, due to the relative decrease of the visceral mass, where lipids are abundant.
During planktonic life, the octopus feeding behavior is that of a visual predator. The presence of prey increases the turning rate and reduces the swimming speed in O. At the other end of early life is senescence, a period coincident with the end of the single reproductive period characteristic of this group of semelparous molluscs.
Chichery and Chichery found in aging S. In addition, they suggested that visual capacities were also affected during the aging process by reducing the attention mechanisms and also the maintenance of the predator's visual tracking behavior, concluding that the low interest in the prey shown by senescent cuttlefish may be related to the deterioration of the basal lobe and the decreasing visual input. The progressive loss of appetite in both senescent male and female octopuses is fairly well documented see review by Anderson et al.
In the brooding O. Interestingly, in the brooding female Octopus filosus , Wodinsky found that removal of optic glands made them cease brooding, start feeding again, and live longer than normal. This surprising behavior after removal of these glands has not been studied in other cephalopod species. Crustaceans are present in nearly all the cephalopod diets studied to date. Teleost fish and molluscs complement their energetic needs in different proportions, depending on the species, habitat, and ontogenetic stage see reviews of Nixon, ; Rodhouse and Nigmatullin, Why crustaceans seem to be an indispensable prey in the diet to sustain suitable growth for cephalopods under culture conditions, and particularly for their young stages, is a subject of current debate Iglesias et al.
Large protein and amino acid content in the diet are required to maintain positive growth, at least in shallow water cephalopod species characterized by vigorous protein metabolism and showing a relatively low quantity of lipids in their body composition.
However, phospholipids, cholesterol, and long-chain polyunsaturated fatty acids PUFA , all of them abundant in marine crustaceans, seem to play an important role. Particularly, the n-3 PUFA, due to their high demand for cell membrane synthesis where they are incorporated, due to the inability of cephalopods to synthesize them Monroig et al.
In addition, the elemental composition of natural food strongly suggests that cephalopod paralarvae and juveniles must require a food rich in copper Villanueva and Bustamante, This fact is probably related to the haemocyanin requirements for oxygen transport, as copper is the dioxygen carrier of haemocyanin typical of crustaceans and molluscs.
Again, marine crustaceans seem to play a pivotal role in the diet of cephalopods, also considering that diet of a species can change from different locations depending on the prey availability and abundance Leite et al. This species is able to fuel its low metabolism mainly on detritus Hoving and Robison, On the other hand, as an extreme comparative example, the Giant Pacific octopus Enteroctopus dofleini and Octopus cf insularis occasionally feeds on large marine birds Anderson and Shimek, , and attacks and bite damage to the skipjack tuna Katsuwonus pelamis and yellowfin tuna Thunnus albacares inside purse seine nets have also been described for the jumbo squid Dosidicus gigas Olson et al.
These species are extreme examples showing the adaptive capacity of cephalopod species to obtain energy from the different marine habitats in which they live.
In addition, when resources are scarce or when the density of congeners is high, cephalopods can choose cannibalism as a feeding behavior. Cannibalism is common in most cephalopod species whose diet has been studied, an uncommon characteristic in the animal kingdom which may be related to their high metabolic demands.
In addition to visual stomach content analysis, recent tools are being used as trophic indicators and tracers in food chain pathways including stable isotope Lorrain et al.
Until food satiation is obtained, cephalopods explore their environment looking for food. Known modes of hunting in cephalopods include ambushing, luring, stalking and pursuit, speculative hunting and hunting in disguise, among others Table 2 , described in detail by Hanlon and Messenger Behavioral observations on foraging cephalopods in their natural habitat usually come from shallow-water environments, mostly on cuttlefishes and octopuses using scuba diving.
A variety of behaviors have been recorded and mimicry has been observed during octopus foraging Forsythe and Hanlon, ; Hanlon et al. The sequences of foraging behavior in shallow water octopuses usually showed characteristics of a tactile saltatory searching predator, as well as a visual opportunist Leite et al.
Using acoustic techniques, coordinated school behavior during foraging was recorded at night in shallow water for jumbo squid D. They were observed using ascending, spiral-like swimming paths to emerge from extremely dense aggregations Benoit-Bird and Gilly, Table 2. Comparison between different hunting strategies adopted by some species of cephalopods and vertebrates not an exhaustive list. Behavioral studies of predation in the laboratory are more detailed and abundant.
The predatory strategy is part of a series of body and locomotory patterns. The visual attack is executed with great accuracy leading to a final strike, a sequence described in cuttlefishes Messenger, and identified in different species Lolliguncula brevis , Jastrebsky et al. During the attack, raised arms and dynamic skin patterns are part of these sophisticated behavioral sequences utilized presumably to deceive the potential prey and facilitate capture.
Raised arms are expressed during predation when the cuttlefish has located its prey and is approaching it to reach a position suitable for attack. Arms I appear extended vertically upwards Messenger, , p.
In some cases, arms II may also be similarly raised. Raised arms are generally dark and may sway to and fro. Messenger suggests that this peculiar posture and swaying movement of the arms may act as lures, directing the prey's attention away from the tentacles.
Chromatic pulses and rhythmic passing waves as been described as dynamic skin chromatic patterns of cephalopods during hunting displays. Chromatic pulses are known in cuttlefishes and also in squids and octopuses and consist of a single band of color contrast sweeping across part of the predator in a particular direction. Rhythmic passing waves are known in cuttlefishes and octopuses, involving the movement of rhythmic bands across the predator in a constant direction see How et al.
The most accurate description of full attack response of octopuses e. The chromatic, postural, and locomotor components i. The full attack is only one example of the variety of predatory behaviors.
A full gradient of locomotor patterns appear to be exhibited. As reviewed by Borrelli et al. The animal moves along the substrate aided by the suckers of the central half of the arm, while the arms push or pull, depending on their position, to facilitate the direction of movement; this crawling may imply several arms Finn et al. Crawling is adopted by octopuses to explore their surroundings and approach sites that they eventually explore for prey capture. On the other hand, speculative hunting or speculative pounce is characteristic of several octopus species see for e.
Every 1—2 m it makes a speculative pounce, covering a rock, a clump of algae, or a small area of the bottom with its web. In addition, cephalopods use different tools to enhance prey capture.
For example, disguise strategies using ink during predation, has been reported recently by Sato et al. These pygmy squid use ink during prey attacks in two modes: releasing ink between themselves and the prey and then attack through the ink cloud, and also releasing ink away from the prey and attacking the prey from another position.
Another tool used in the darkness is the dinoflagelate bioluminescence, employed by Euprymna scolopes and S. During foraging under culture conditions, it is remarkable that cuttlefish Sepia pharaonis are able to identify the amount of prey available, discriminate prey numbers, and the following prey selection, all depending on their satiation state Yang and Chiao, When cuttlefish detect a prey, they perform a well-known three-stage visual attack sequence of attention, positioning, and seizure Hanlon and Messenger, Observing conspecifics during prey capture, these events do not seem to improve their predation techniques Boal et al.
Venom is used by cuttlefishes and octopods to kill the prey and for muscle relaxation. Octopuses bored holes in the carapace, the eye or the arthrodial membrane of crustaceans Grisley et al.
The selection of the preferred area to inject the cephalotoxin in the crab seems to be a combination of factors related to prey and octopus size. For example, large octopuses use eye puncture less frequently than small individuals Grisley et al. Prey handling in octopus eating bivalves showed different combinations of pulling and drilling feeding behaviors.
The injection of the cephalotoxin into the bivalve and gastropod prey is associated with drilling. Drilling occurs by the combined action of radula and salivary papilla Nixon, A combination of drilling and pulling behaviors has been reported for preying on bivalve and gastropod prey Runham et al. Octopuses hold the prey within the proximal part of the arms so, they cannot use vision during most prey handling period, probably choosing the most energetic, cost effective feeding behavior based on previous experience Anderson and Mather, In the field, other factors may influence the bivalve selection and feeding mode.
In addition to pulling and drilling, shell crushing has been reported as a feeding behavior for the deep-sea octopod Graneledone preying on gastropods, a behavior that may be favored due to their relatively larger beaks in comparison with those of shallow water octopods Voight, It is remarkable that the elevated diversity of cephalopod hunting behaviors, almost matches the strategies adopted by vertebrate predators Table 2.
Both taxa are so diverse and remote in their phylogenetic traits, but clearly there are cases of functional and behavioral convergence during evolution.
In neritic and epipelagic cephalopods, vision is probably the main sense utilized for prey detection and capture. As light intensity decreases in deep-sea environments, low temperature reduces the metabolic demands and predator-prey distance changes Seibel et al. In this environment, the mechanoreceptor structures in the arms, tentacles, and filaments increase in number and complexity.
These metabolic and morphological changes considered to be closely related with the prey selected by deep-sea cephalopods result in feeding strategies that are more diverse in the deep-sea that previously believed. The cirrate octopods are characterized by the possession of paired filamentous cirri along the arms, of diverse length according to families, which are interspersed between a single row of suckers, and are thought to have a sensory function involved in prey detection and capture.
Cirrates feed mainly on small-sized organisms with low swimming speeds including amphipods and polychaetes Collins and Villanueva, For S. The knowledge of the diet of deep-sea squids needs further research. A comprehensive review of the main prey found in stomachs of deep-sea squids has been provided by Hoving et al. As suggested by Young et al. The deep-sea squid Grimalditeuthis bonplandi is an extreme example: its tentacles have a very thin and fragile elastic stalk, whereas the clubs bear no suckers, hooks, or photophores.
It is unknown how these tentacles are used to capture and handle their prey, as they consist on cephalopods and crustaceans Hoving et al. Also the mesopelagic Spirula spirula feeds mainly on detritus and zooplankton Ohkouchi et al. As mentioned above, cephalopods do not necessarily predate exclusively on live prey. Some cephalopod species are collected in large numbers from the wild using baited traps such as, Nautilus Dunstan et al. Recent development of the cephalopod culture techniques review in Iglesias et al.
The first feeding period usually requires live crustacean prey, particularly for the delicate planktonic stages, although planktonic octopuses are able to detect, capture and ingest inert particles from the water surface Marliave, or descending in the water column Villanueva et al.
A successful semi-humid squid paste-bound gelatine has been developed to feed O. The training phase from feeding on live prey to inert food shows the behavioral adaptions and learning capacities of these animals under laboratory conditions.
As an example noted by Nabhitabhata and Ikeda , S. The same behavioral adaptions and prey capture modes are observed in S. In this review, we surfed through a number of important topics that require further research and possibly a dedicated effort.
Research on cephalopod predatory strategies is needed in a variety of fields, from behavior to ecology. Studies of feeding behavior, nutrition, and feeding requirements are critical in order to develop the nascent cephalopod aquaculture of key species, particularly from early young stages. Studies on nutritional requirements are only at the beginning. The role of lipids on the early growth and survival of shallow water species seems more important than previously supposed and research is also needed in that field Navarro et al.
As this number increases in the future, new larval and juvenile predatory behavioral strategies will mostly likely be described. Similarly, the future study of deep-sea and oceanic cephalopod forms will provide further instances of novel, undescribed receptors, organs, behaviors, and modes of prey detection and capture in cephalopods Hoving et al.
In addition, whether our knowledge on diet richness of a given cephalopod species in the wild is affected or not by research effort remains to be explored; data we presented above may represent only a starting-point. The variability of conformation of cephalopod beaks and their functional relation with possible prey-items is another possible challenging avenue of research Franco-Santos and Vidal, ; Franco-Santos et al.
Some aspects, such as, the hormonal control over feeding in cephalopods are practically unknown Wodinsky, Interactions with other species such as, intraguild predation when species compete simultaneously for resources and interact as prey and predator , is another aspect that may need further attention in cephalopod science. The interaction between shallow water octopus and juvenile lobster is potentially an example of intraguild predation involving interference competition for refuge Butler and Lear, but cannibalism see above may also be seen under this framework.
Interaction with other species, as well as competition for spatial and feeding resources will probably be modified with global change. A representative example is the case of the jumbo squid D. During the daytime, jumbo squids dive to the depth, suppressing metabolism in the oxygen minimum zone, an energy saving strategy in hours of prey limitation in shallow waters Rosa and Seibel, The expected climate change expansion of deep-water hypoxia and the warming and acidification of surface waters will concentrate both prey and predators, with unknown effects on D.
The expected variation in climate change and ocean acidification has been shown to induce complex changes in chemoreception and prey detection, including altered cue detection behaviors in some marine organisms.
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