Sea hares are gastropods without hard shells, using their specialized ink as their main defensive mechanism instead. Their ink has several purposes, most of which have a chemical basis. For one, the ink serves to cloud the predator's vision as well as halt their senses temporarily. In addition, the chemicals in the ink mimic food. Their skin and digestive tract are toxic to predators as well. [1] They are also seen to change their feeding behaviours in response to averse stimuli. [2]
The diet of sea hares enables them to gain the chemicals present in their ink and determine the color of their ink. [1] [3] They have adapted over time to feed mainly on seaweed and algae as without their specific diet they will be left without ink [1] and fall prey to predators. The species they feed on determine the strength of their chemical defense. Individuals that feed on red algae, such as plocamium, were found to have better defense than those that fed on green algae, like ulva lactuca. [3]
The ink and opaline glands produce ink and opaline respectively; these two substances are mixed in the cavity and expelled towards the predator. The ink and opaline are highly concentrated with free amino acids and ammonium; they are responsible for the response of the predators since predators have receptive sites for them. [4] The ink and opaline has been demonstrated to stimulate appetitive and ingestive behaviours, though opaline differs in the sense in that it inhibits ingestion. [5]
Phagomimicry is the defensive behaviour in which expelled chemicals mimic food, deceiving some organisms to eat it instead. In the case of sea hares, the ink produced deceives their predators to attack their ink instead of pursuing the sea hare. This is possible because of the chemicals present in sea hares' ink mixture. The ink and opaline contains high levels of amino acids and ammonium, present in their predators' food. As a result, predators are deceived into attacking the mixture and feeding on it. [4] This gives the sea hare an opportunity to escape. This reaction has been observed in some lobsters. [5] [6]
The chemicals produced also affect the nervous system of the predators. [5] The ink produces an averse response in some predators. For instance, sea anemones shrivel up when they come in contact with the Ink. [6]
Nudibranchs belong to the order Nudibranchia, a group of soft-bodied marine gastropod molluscs that shed their shells after their larval stage. They are noted for their often extraordinary colours and striking forms, and they have been given colourful nicknames to match, such as "clown", "marigold", "splendid", "dancer", "dragon", and "sea rabbit". Currently, about 3,000 valid species of nudibranchs are known.
The California sea hare is a species of sea slug in the sea hare family, Aplysiidae. It is found in the Pacific Ocean, off the coast of California in the United States and northwestern Mexico.
The order Aplysiida, commonly known as sea hares, are medium-sized to very large opisthobranch gastropod molluscs with a soft internal shell made of protein. These are marine gastropod molluscs in the superfamilies Aplysioidea and Akeroidea.
Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails that, over evolutionary time, have either entirely lost their shells or have seemingly lost their shells due to having a significantly reduced or internal shell. The name "sea slug" is often applied to nudibranchs and a paraphyletic set of other marine gastropods without apparent shells.
Aplysiidae is the only family in the superfamily Aplysioidea, within the clade Anaspidea. These animals are commonly called sea hares because, unlike most sea slugs, they are often quite large, and when they are underwater, their rounded body shape and the long rhinophores on their heads mean that their overall shape resembles that of a sitting rabbit or hare. Sea hares are however sea snails with shells reduced to a small plate hidden between the parapodia, and some species are extremely large. The Californian black sea hare, Aplysia vaccaria is arguably the largest living gastropod species, and is certainly the largest living heterobranch gastropod.
Aplysia is a genus of medium-sized to extremely large sea slugs, specifically sea hares, which are a kind of marine gastropod mollusk.
A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. These pools typically range from a few inches to a few feet deep and a few feet across. Many of these pools exist as separate bodies of water only at low tide, as seawater gets trapped when the tide recedes. Tides are caused by the gravitational pull of the sun and moon. A tidal cycle is usually about 25 hours and consists of one or two high tides and two low tides.
Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.
A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea hares (Aplysiomorpha), and sap-sucking sea slugs (Sacoglossa).
Mesograzers are defined as small invertebrate herbivores less than 2.5 cm in length, and can include juveniles of some larger species. The feeding behaviour of these small invertebrate herbivores is what classifies them as mesograzers. They are commonly found abundantly on Microalgae, seagrass beds, giant kelp, and coral reefs globally, since these are their main food sources and habitats. Their foraging behaviour is grazing on the organism they are living on, where there are typically masses reaching tens of thousands of mesograzers per meter of habitat. They experience predation from micro-carnivorous fish that help regulate the population of kelp and other common food sources of mesograzers by controlling the population of mesograzers; consequently, grazing is an important process linking aquatic vegetation to higher trophic level. Mesograzers show important top-down effect on marine communities, depending on the diversity and presence of predators. Mesograzers are typically overlooked in scientific research however their foraging effects have been suggested to have extreme effects on the population of their common food sources. They both positively and negatively affect macroalgal performance and productivity through grazing on algal, or through removing epiphytes. Mesograzers typically exist in spaces lacking enemies by inhabiting, therefore consuming, marine vegetation which are defended against more mobile, larger consumers through chemical defenses.
Cephalopod ink is a dark-coloured or luminous ink released into water by most species of cephalopod, usually as an escape mechanism. All cephalopods, with the exception of the Nautilidae and the Cirrina, are able to release ink to confuse predators.
The spotted sea hare is a species of sea slug in the family Aplysiidae, the sea hares. It reaches a length of up to 20 cm (7.9 in) and is found in the northeast Atlantic, ranging from Greenland and Norway to the Mediterranean Sea.
Aplysia vaccaria, also known as the black sea hare and California black sea hare, is a species of extremely large sea slug, a marine, opisthobranch, gastropod mollusk in the family Aplysiidae. It is the largest sea slug species.
Chemical defense is a strategy employed by many organisms to avoid consumption by producing toxic or repellent metabolites or chemical warnings which incite defensive behavioral changes. The production of defensive chemicals occurs in plants, fungi, and bacteria, as well as invertebrate and vertebrate animals. The class of chemicals produced by organisms that are considered defensive may be considered in a strict sense to only apply to those aiding an organism in escaping herbivory or predation. However, the distinction between types of chemical interaction is subjective and defensive chemicals may also be considered to protect against reduced fitness by pests, parasites, and competitors. Repellent rather than toxic metabolites are allomones, a sub category signaling metabolites known as semiochemicals. Many chemicals used for defensive purposes are secondary metabolites derived from primary metabolites which serve a physiological purpose in the organism. Secondary metabolites produced by plants are consumed and sequestered by a variety of arthropods and, in turn, toxins found in some amphibians, snakes, and even birds can be traced back to arthropod prey. There are a variety of special cases for considering mammalian antipredatory adaptations as chemical defenses as well.
Pain in invertebrates is a contentious issue. Although there are numerous definitions of pain, almost all involve two key components. First, nociception is required. This is the ability to detect noxious stimuli which evokes a reflex response that moves the entire animal, or the affected part of its body, away from the source of the stimulus. The concept of nociception does not necessarily imply any adverse, subjective feeling; it is a reflex action. The second component is the experience of "pain" itself, or suffering—i.e., the internal, emotional interpretation of the nociceptive experience. Pain is therefore a private, emotional experience. Pain cannot be directly measured in other animals, including other humans; responses to putatively painful stimuli can be measured, but not the experience itself. To address this problem when assessing the capacity of other species to experience pain, argument-by-analogy is used. This is based on the principle that if a non-human animal's responses to stimuli are similar to those of humans, it is likely to have had an analogous experience. It has been argued that if a pin is stuck in a chimpanzee's finger and they rapidly withdraw their hand, then argument-by-analogy implies that like humans, they felt pain. It has been questioned why the inference does not then follow that a cockroach experiences pain when it writhes after being stuck with a pin. This argument-by-analogy approach to the concept of pain in invertebrates has been followed by others.
Pterygophora californica is a large species of kelp, commonly known as stalked kelp. It is the only species in its genus Pterygophora. It grows in shallow water on the Pacific coast of North America where it forms part of a biodiverse community in a "kelp forest". It is sometimes also referred to as woody-stemmed kelp, walking kelp, or winged kelp.
Phagomimicry is a defensive behaviour of sea hares, in which the animal ejects a mixture of chemicals, which mimic food, and overwhelm the senses of their predator, giving the sea hare a chance to escape. The typical defence response of the sea hare to a predator is to release two chemicals - ink from the ink gland and opaline from the opaline gland. While ink creates a dark, diffuse cloud in the water which disrupts the sensory perception of the predator by acting as a smokescreen and as a decoy, the opaline, which affects the senses dealing with feeding, causes the predator to instinctively attack the cloud of chemicals as if it were indeed food. This ink is able to mimic food by having a high concentration of amino acids and other compounds that are normally found in food, and the attack behaviour of the predator allows the sea-hares the opportunity to escape.
Aplysioviolin is a purple-colored molecule secreted by sea hares of the genera Aplysia and Dolabella to deter predators. Aplysioviolin is a chemodeterrent, serving to dispel predators on olfactory and gustatory levels as well as by temporarily blinding predators with the molecule's dark color. Aplysioviolin is an important component of secreted ink and is strongly implicated in the sea hares' predatory escape mechanism. While the ink mixture as a whole may produce dangerous hydrogen peroxide and is relatively acidic, the aplysioviolin component alone has not been shown to produce human toxicity.
Aplysia gigantea is a species of sea slug, a shell-less marine gastropod mollusk in the family Aplysiidae. The species was first described in the Journal of the Malacological Society of Australia in 1869. A. gigantea is also known more commonly as the sea hare due to their posterior chemosensory tentacles resembling a hare's ear. A. gigantea is the largest known species in Australia of the opisthobranch genus. The species is known to have toxic effects on terrestrial organisms, particularly domestic dogs. Exposure to this species with dogs has been associated with the development of neurotoxicosis, with symptoms ranging from respiratory distress to tremors, muscle fasciculations, and seizures.
Isotealia antarctica, the salmon anemone, is a species of sea anemone in the family Actiniidae. It is found in the southern Atlantic and Pacific Oceans and the waters around Antarctica. It is a filter feeder and opportunistic predator.