home / ethogram menu / Aquatic Invertebrates /
Species: Squid (Loligo pealei)
Use: Body patterning behavior
Authors: Roger T. Hanlon, Michael R. Maxwell, Nadav Shashar, Marine Resources Center, Marine Biological Laboratory, Woods Hole, Ellis R. Loew, Department of Biomedical Sciences, Cornell University, & Kim-Laura Boyle
Methods: NA
Publications/Presentations: R.T. Hanlon, M.R. Maxwell, N. Shasher, E.R. Loew, K. Boyle (1999). An ethogram of Body patterning Behavior in the Biomedically and Commercially Valuable Squid Loligo pealei off Cape Cod, Massachusetts.
Light Chromatic Components
Clear: Is retraction of all or most chromatophores, thus rendering the animal translucent in clear water or white murky water. In clear water, when viewed against a sand bottom or laterally against the aquatic background, the translucence renders the squid cryptic, or camouflaged, and often the Dorsal iridophore splotches are expressed simultaneously. Internal organs, such as the red accessory nidamental gland in females, are often visible. In murky water, Clear appears bright white in most lighting circumstances (i.e., the brightness surpasses the albedo of greenish water, producing a whitish color). In the immediate vicinity of egg beds, the white form of Clear seems to function as an intraspecific signal to repel other squids; a squid displaying this component is almost always engaged in mate guarding, egg laying, or agonistic bouts.
White arms/head: This results from variable retraction of chromatophores on the head and arms. This component sometimes preceded all white (or clear) in intraspecific encounters: thus, it appears to be a milder signal of alarm repellant to approaching squids. White head/arms is most common in paired females near eggs and is seen when unpaired males approach.
White dorsal stripe: This is retraction of chromatophores along a dorsal mantle that is otherwise dark: the stripe may be short or long. It has been seen in consort males when an intruder male approaches.
Accentuated testis: This is a male-only component shown when the chromatophores directly above the testis are retracted while the squid mantle is otherwise dark, thus accentuating the whiteness of the organ. This component was seen frequently in single or mate-paired males when reproductive behavior was actively occurring in the school.
Accentuated oviducal gland: This is a female-only component analogous in form and function to Accentuated testis in the male. This was often seen in females paired with consort males.
Dorsal mantle collar iridophores: These are on the anteriormost portion of the mantle, and they appear as bright yellow or pink iridescence; this component tends to produce disruptive coloration by breaking up the longitudinal aspect of the squidÕs body.
Dorsal iridophore splotches: These occur on the dorsal mantle and head. They are distinctive yellow or golden color, and they help to produce general camouflage.
Iridescent arm stripes: These extend most of the length of the first three pairs of arms. These are usually expressed lightly during camouflage in the Clear pattern, but during agonistic encounters they can be expressed very brightly (see color illustration in Hanlon, 1982).
Iridescent sclera: This is the bright silver iridescence on the backÊ (or sclera) of the eye; squids have the ability to obscure this with chromatophores with the Shaded eye component.
Dorsal iridophore sheen: This is somewhat rare and is only noticeable from the side. Its function is unclear but may aid camouflage in open water by disrupting the body shape.
Polarized arms: These are highly polarized reflections that create the most conspicuous component of polarization.
Skin surface polarization: This results from the difference in refractive indexes between the squidÕs body and the water, so that light reflected from any area of the skin may be partially polarized.
Polarized eyes: These result from reflection by iridophore cells that surround the eye.
Polarized dorsal sheen: The dorsal mantle occasionally reflects light that is partially polarized, resulting in Polarized dorsal sheen.
All dark: This is the opposite of Clear: all or most chromatophores are expanded to some degree. The maximal expression of All dark produces an overall deep brown coloration; it is characteristic of alarmed squids. However, the chromatophores need not be maximally expanded, and thus there are ranges of darkness. Often squids are in a ÒnormalÓ or ÒbasicÓ coloration that is roughly between Clear and All dark, producing an overall amber body pattern.
Dark arms/head: This is variable in expression and is opposite to White arms/head. It is seen typically in mating pairs and may represent a mild state of alarm.
Dark head: This is expansion of all the chromatophores around the head of the animal (but not the arms), causing the head to appear almost black. This component is frequently seen in mate pairs near the egg mop and probably represents a low-grade alarm signal.
Dark dorsal stripe: This extends halfway or fully down the mid-dorsal mantle. Seen mainly on calm squids, it apparently aids camouflage because it covers some of the bright organs such as the testis, oviducal glands, and ink sac.
Ventral mantle stripe: This is a thin, distinct line of fully expanded chromatophores. The function of this component is uncertain, but it is seen commonly on mating pairs and on males during mate guarding.
Mantle margin stripe: This is a dark line running along the fin insertion. It was seen most often as a mild reaction to disturbance or alarm during agonistic bouts, and was usually expressed in conjunction with ventral mantle stripe, Fin spots, and weak Lateral flame.
Dark arm stripes: These are variable, being expressed either along the third pair of arms or along pairs 1,2, and 3. This uncommon component wasÊ seen on a female that also expressed Dark fins just before a male mated her, and as another mating pair bumped into them.
Fin spots: Are a collection of small circular and oval dark spots scattered across the fins. This component is seen mostly during agonistic bouts or rarely when an aggressive male comes close by.
Arm spots: These are small and occur at the base of the third arms, the second arms, or both. This component is seen on males during mate guarding and at the early stages of agonistic encounters: it probably constitutes a low grade of alarm.
Infraocular spot: Appears directly in front of the eye and has variations, including a circular shape that looks like an eye ring.
Bands: Are variable, and may occur on the fins, head or arms. First reported by Stevenson (1934), this component is seen typically in calm, bottom-sitting squids and functions as disruptive coloration to break up the longitudinal outline of the squid.
Shaded eye: Is a transverse head bar of expanded chromatophores that may aid crypsis by covering the bright Iridescent sclera of the eyes.
Dark fins: Occur when all fin chromatophores are expanded maximally: it is not common but has been seen on females that are alarmed.
Dark posterior mantle: Is similar to Dark fins, but the mantle chromatophores are expanded: it may be the next stage of alarm after Dark fins.
Shaded testis and shaded oviducal gland: Are selective expansion of chromatophores over the testis or oviducal gland. Both are often indistinct and serve to mask these bright white organs, thus aiding crypsis.
Red accessory nidamental gland: Can be seen through the translucent mantle and occurs only in fully mature females, so it may be a part of communication even though it is internal. Since it turns red only upon attainment of full sexual maturity, it may be a sign of female sexual maturity or even receptivity.
Lateral mantle spot: This is a female-only component expressed as a small intense dark spot of chromatophores near the anterior fin insertion. It coincides roughly with the position of the Red accessory nidamental gland, and the two may function together in some way. The lateral mantle spot is seen only when the female is paired with a large consort male, and could indicate either receptivity or rejection.
Lateral blush: This is a female-only component expressed unilaterally as a diffuse dark area on the lateral mantle. It may be comparable to a variety of similar components shown by female squids, and it may function as a repellant to courting males (Hanlon and Messenger, 1996).
Weak lateral flame: This is a male-only component produced by longitudinally oriented rows of partly expanded chromatophores. It is seen during low-grade agonistic contests.
Raised arms: Is the unilateral or bilateral raising of the first pair of arms, which may be light or dark, and is seen in both males and females on the mating grounds. This component appears to be a signal of alarm during agonistic contests. It was previously reported by Arnold (1962, 1990).
Splayed arms: Is a posture in which all eight arms are spread and flattened on the horizontal plane. This posture is expressed by both sexes but is most common in males that use it to guard female mates they are escorting to egg mops.
Raised and splayed arms: Are a combination of the previous postures in which the arms are all splayed except for the first pair, which is raised: it is a strong signal of alarm used when a rival male approaches closely.
Drooping arms: In a swimming squid is a posture in which all the arms appear relaxed and hang downward.
Flared arms: Is a rare posture in which all of the arms are held stiffly outward in a radial manner; it is seen during highly aggressive agonistic encounters between two males, and during mate guarding.
Inking: Is the expulsion of ink mixed with mucus, either in small puffs or as a large dense cloud (Hanon et al., 1994).
Jetting/fleeing: Inking is often followed by this, which is a rapid jet-propulsed escape used in avoidance of both predators and conspecifics. Females often jet from males that try to swim with them or copulate with them.
Chasing: This occurs when one squid actively pursues another, usually in forward swimming. In most cases a male is pursuing another male at the conclusion of an agonistic bout.
Bottom sitting: Occurs when a squid rests on the substrate.
Egg touching: Consists of contacts with an egg mop by both males and females. Contact ranges from brief, exploratory touches to embraces of an egg capsule with all of the arms. Females usually lay eggs on existing egg mops, and touching may be a way of assessing the egg-laying substrate. Males commonly touch eggs, and touching is often followed by highly aggressive bouts (Hanlon, 1996), suggesting that the eggs provide a visual, tactile, or perhaps chemosensory stimulus.
Parallel positioning: Occurs when two animals are hovering or swimming parallel to one another in the same direction, within one body length of each other. Courting pairs maintain this position, and agonistic encounters begin with this movement.
Jockeying and parrying: (males only). Occurs when two males maneuver to get next to a female. As successful paired male will often ward off (or parry) the jockeying movements of the unpaired male in a long sequence of swimming maneuvers.
Fin beating: Occurs in the parallel when two males maneuver themselves so that they are beating their fins against each other. This is a physical and escalated stage of an agonistic context, but it results in no obvious physical damage.
Forward lunge/grab: Is a short, fast movement to bluff or grab another male during agonistic contests. The grab sometimes results in grappling in which the squids attempt to bite each other. It is rare and is the highest escalation of a fight.
Male-parallel mating: Occurs when the male positions himself under the female and grasps her anterior mantle to pass spermatophores into her mantle cavity.
Head-to-head mating: Occurs when a male and female face each other, and the male grasps the femaleÕs arms. Spermatophores are placed in a seminal receptacle below the mouth. (Drew, 1911).
Oviposition: (females only). Occurs when the female extrudes a single egg capsule and affixes it to the substrate or to existing communal egg masses: she does not hold the egg capsule for long.
Basic amber pattern: It is the most common and long-lasting body pattern observed in Loligo pealei, and it occurs while the squids are hovering, gently rocking back and forth, or swimming slowly. ÊÊ
Clear body pattern: The basic amber pattern can grade into a lighter Clear body pattern with expression of the Dorsal iridophore splotches: this is seen both when squids are swimming just above the substrate and when they are in the water column.
Countershading: Another subtle variation of the above tow, in this the chromatophores on the dorsal surfaces of the squid are a rather uniform light expansion (as in Clear or Basic Amber) while the ventral portions of the animal are light (probably with help from the many iridophores in the dermis: see Cooper et al., 1990; Hannon et al., 1990) to eliminate the shadow.
Chronic all dark pattern: The function of this pattern is unknown, but has been observed several times in the natural habitat on many hundreds of calm squids hovering in large schools in the water column.
Banded bottom sitting pattern: This is very common and consists of Bands with Dorsal iridophore splotches and Bottom sitting.
Chronic bright white pattern: This pattern has many variations, but the most common one is seen on mating pairs near the egg beds. Males that are mate guarding are in Clear, Raised arms, White arms/head, Arm spots, and sometimes Dark head. Females that are being guarded are in Clear with Dark head, and sometimes Raised arms. In both cases the testis and the oviducal glands are clearly visible through the mantle.
Very dark: This has two variations. The first is a brief flash to a conspecific or an interspecific threat (e.g., to a person in the laboratory or a fish in the field). The second variation shows several flashes over a 5-s period, producing a strong Deimatic effect that startles or bluffs (see Hanlon and Messenger, 1996).
Blanch-ink-jet Maneuver: May be universal among squids: the animal blanches Clear and jets away (usually backwards, but sometimes forward) while ejecting ink in a pseudomorph that remains in the approximate position from which the squid started the maneuver.
Lateral display: is a complex set of behaviors performed only by males during agonistic contexts. There is some stereotypy, although it is by no means a fixed sequence (see Hanlon and Messenger, 1996; DiMarco and Hanlon, 1997). It begins with Parallel positioning by two males and then includes various visual signals including Arm spots, Infraocular spots, Fins pots, Mid ventral stripe, Weak lateral flame, and Raised and splayed arms. The overall base coloration of the body is bright white: this, because it is Òturned onÓ so quickly as the chromatophores retract when a contest begins, gives the optical illusion of flashing. The ensuing dynamic interaction between the males include flashing and escalation to Fin beating followed by Jockeying on the part of the intruder to get near the female, and Parrying by the paired male to fend off the intruder.
Mate guarding pattern: Is shown by paired consort males that are approached either by paired males or by single large or small males that may be seeking an extrapair copulation. The male hovers directly between his mate and the approaching male, maintaining a bright coloration with Arm spots and maximally Splayed arms: the accentuated testis is often conspicuous, especially if the male goes dark or amber briefly.
Accentuated Testis: Is a single component that can and does act as a body pattern, and it is particularly common on small sneakier males that swim around spawning areas attempting to extrapair copulations. This pattern is often shown with the All dark component, but it may also be paired with Basic Amber.