Ampullae of Lorenzini (sg.: ampulla) are electroreceptors, sense organs able to detect electric fields. They form a network of mucus-filled pores in the skin of cartilaginous fish (sharks, rays, and chimaeras) and of basal bony fishes such as reedfish, [1] sturgeon, [2] and lungfish. [1] They are associated with and evolved from the mechanosensory lateral line organs of early vertebrates. Most bony fishes and terrestrial vertebrates have lost their ampullae of Lorenzini.
Ampullae were initially described by Marcello Malpighi and later given an exact description by the Italian physician and ichthyologist Stefano Lorenzini in 1679, though their function was unknown. [3] Electrophysiological experiments in the 20th century suggested a sensibility to temperature, mechanical pressure, and possibly salinity. In 1960 the ampullae were identified as specialized receptor organs for sensing electric fields. [4] [5] One of the first descriptions of calcium-activated potassium channels was based on studies of the ampulla of Lorenzini in the skate. [6]
Ampullae of Lorenzini are physically associated with and evolved from the mechanosensory lateral line organs of early vertebrates. Passive electroreception using ampullae is an ancestral trait in the vertebrates, meaning that it was present in their last common ancestor. [7] Ampullae of Lorenzini are present in cartilaginous fishes (sharks, rays, and chimaeras), lungfishes, bichirs, coelacanths, sturgeons, paddlefishes, aquatic salamanders, and caecilians. Ampullae of Lorenzini appear to have been lost early in the evolution of bony fishes and tetrapods, though the evidence for absence in many groups is incomplete and unsatisfactory. [7]
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Each ampulla is a bundle of sensory cells containing multiple nerve fibres in a sensory bulb (the endampulle) in a collagen sheath, and a gel-filled canal (the ampullengang) which opens to the surface by a pore in the skin. The gel is a glycoprotein-based substance with the same resistivity as seawater, and electrical properties similar to a semiconductor. [8] [3] [9]
Pores are concentrated in the skin around the snout and mouth of sharks and rays, as well as the anterior nasal flap, barbel, circumnarial fold and lower labial furrow. [10] Canal size typically corresponds to the body size of the animal but the number of ampullae remains the same. The canals of the ampullae of Lorenzini can be pored or non-pored. Non-pored canals do not interact with external fluid movement but serve a function as a tactile receptor to prevent interferences with foreign particles. [10]
The ampullae detect electric fields in the water, or more precisely the potential difference between the voltage at the skin pore and the voltage at the base of the electroreceptor cells. [11] [12] [6]
A positive pore stimulus decreases the rate of nerve activity coming from the electroreceptor cells, while a negative pore stimulus increases the rate. Each ampulla contains a single layer of receptor cells, separated by supporting cells. The cells are connected by apical tight junctions so that no current leaks between them. The apical faces of the receptor cells have a small surface area with a high concentration of voltage-dependent calcium channels (which trigger depolarisation) and calcium-activated potassium channels (for repolarisation afterwards). [13]
Because the canal wall has a very high resistance, all the voltage difference between the pore of the canal and the ampulla is dropped across the 50 micron-thick receptor epithelium. Because the basal membranes of the receptor cells have a lower resistance, most of the voltage is dropped across the excitable apical faces which are poised at the threshold. Inward calcium current across the receptor cells depolarises the basal faces, causing a large action potential, a wave of depolarisation followed by repolarisation (as in a nerve fibre). This triggers presynaptic calcium release and release of excitatory transmitter onto the afferent nerve fibres. These fibres signal the size of the detected electric field to the fish's brain. [14]
The ampulla contains large conductance calcium-activated potassium channels (BK channels). Sharks are much more sensitive to electric fields than electroreceptive freshwater fish, and indeed than any other animal, with a threshold of sensitivity as low as 5 nV/cm. The collagen jelly, a hydrogel, that fills the ampullae canals has one of the highest proton conductivity capabilities of any biological material. It contains keratan sulfate in 97% water, and has a conductivity of about 1.8 mS/cm. [14] [11] All animals produce an electrical field caused by muscle contractions; electroreceptive fish may pick up weak electrical stimuli from the muscle contractions of their prey. [6]
The sawfish has more ampullary pores than any other cartilaginous fish, and is considered an electroreception specialist. Sawfish have ampullae of Lorenzini on their head, ventral and dorsal side of their rostrum leading to their gills, and on the dorsal side of their body. [15]
Ampullae of Lorenzini also contribute to the ability to receive geomagnetic information. As magnetic and electrical fields are related, magnetoreception via electromagnetic induction in the ampullae of Lorenzini is possible. Many cartilaginous fish respond to artificially generated magnetic fields in association with food rewards, demonstrating their capability. Magnetoreception may explain the ability of sharks and rays to form strict migratory patterns and to identify their geographic location. [16]
The mucus-like substance inside the tubes was thought in 2003 perhaps to function as a thermoelectric semiconductor, transducing temperature changes into an electrical signal that the animal could use to detect temperature gradients. [17] A 2007 study appeared to disprove this. [18] The question remained open, [19] and in 2023 it was predicted that the ampullae of Lorenzini in sharks would be able to detect a temperature difference of 0.001 Kelvin (a thousandth of a degree). An artificial sensor using the same principle is able to detect a difference of 0.01 Kelvin. [20]
Chondrichthyes is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or bony fish, which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates.
The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial cells, known as hair cells, which respond to displacement caused by motion and transduce these signals into electrical impulses via excitatory synapses. Lateral lines play an important role in schooling behavior, predation, and orientation.
An electric fish is any fish that can generate electric fields, whether to sense things around them, for defence, or to stun prey. Most fish able to produce shocks are also electroreceptive, meaning that they can sense electric fields. The only exception is the stargazer family (Uranoscopidae). Electric fish, although a small minority of all fishes, include both oceanic and freshwater species, and both cartilaginous and bony fishes.
The black ghost knifefish is a tropical fish belonging to the ghost knifefish family (Apteronotidae). They originate in freshwater habitats in South America where they range from Venezuela to the Paraguay–Paraná River, including the Amazon Basin. They are popular in aquaria. The fish is all black except for two white rings on its tail, and a white blaze on its nose, which can occasionally extend into a stripe down its back. It moves mainly by undulating a long fin on its underside. It will grow to a length of 18"-20". Only a fish for those with large aquariums, minimum 100 gallons.
Electroreception and electrogenesis are the closely related biological abilities to perceive electrical stimuli and to generate electric fields. Both are used to locate prey; stronger electric discharges are used in a few groups of fishes to stun prey. The capabilities are found almost exclusively in aquatic or amphibious animals, since water is a much better conductor of electricity than air. In passive electrolocation, objects such as prey are detected by sensing the electric fields they create. In active electrolocation, fish generate a weak electric field and sense the different distortions of that field created by objects that conduct or resist electricity. Active electrolocation is practised by two groups of weakly electric fish, the Gymnotiformes (knifefishes) and the Mormyridae (elephantfishes), and by Gymnarchus niloticus, the African knifefish. An electric fish generates an electric field using an electric organ, modified from muscles in its tail. The field is called weak if it is only enough to detect prey, and strong if it is powerful enough to stun or kill. The field may be in brief pulses, as in the elephantfishes, or a continuous wave, as in the knifefishes. Some strongly electric fish, such as the electric eel, locate prey by generating a weak electric field, and then discharge their electric organs strongly to stun the prey; other strongly electric fish, such as the electric ray, electrolocate passively. The stargazers are unique in being strongly electric but not using electrolocation.
Magnetoreception is a sense which allows an organism to detect the Earth's magnetic field. Animals with this sense include some arthropods, molluscs, and vertebrates. The sense is mainly used for orientation and navigation, but it may help some animals to form regional maps. Experiments on migratory birds provide evidence that they make use of a cryptochrome protein in the eye, relying on the quantum radical pair mechanism to perceive magnetic fields. This effect is extremely sensitive to weak magnetic fields, and readily disturbed by radio-frequency interference, unlike a conventional iron compass.
Ocean Guardian is the manufacturer of Shark Shield shark repellent devices. The Ocean Guardian electronic devices create an electromagnetic field to deter shark attacks and are used by surfers, scuba divers, snorkelers, spearfishers, ocean kayak fishers, swimming areas off boats and for ocean fishing. It is considered one of the few electrical devices on the market that has performed independent trials to determine its effectiveness at deterring shark attacks, Whilst it is noted the Shark Shield technology does not work in all situations, modelling research from Flinders University in 2021 indicated that the proper use of personal electronic deterrents is an effective way to prevent future deaths and injuries, and estimated that these devices could save up to 1063 Australian lives along the coastline over 50 years.
The Mormyridae, sometimes called "elephantfish", are a superfamily of weakly electric fish in the order Osteoglossiformes native to Africa. It is by far the largest family in the order, with around 200 species. Members of the family can be popular, if challenging, aquarium species. These fish have a large brain size and unusually high intelligence.
Shark anatomy differs from that of bony fish in a variety of ways. Variation observed within shark anatomy is a potential result of speciation and habitat variation.
The dwarf sawfish or Queensland sawfish, Pristis clavata, is a sawfish of the family Pristidae, found in tropical Australia. This endangered species is the smallest species in its family.
Orectolobus hutchinsi, the western wobbegong, is a species of carpet shark in the family Orectolobidae. The western wobbegong shark is a moderate sized marine shark found off the coast of Western Australia. Its scientific name is Orectolobus hutchinsi, and it was first identified in 1983 by Dr. Barry Hutchins, but was only recently classified, described, and published in 2006. O. hutchinsi is found on the shallow continental shelf in Western Australia from Coral Bay to Groper Bluff. This species is distinct from other wobbegong sharks because the western wobbegong shark has a yellowish brown upper body and darker brown saddles on their backs. Unlike other wobbegong sharks from the same area, the western wobbegong shark does not have white rings or blotches on their backs.
A Knollenorgan is an electroreceptor in the skin of weakly electric fish of the family Mormyridae (Elephantfish) from Africa. The structure was first described by Viktor Franz (1921), a German anatomist unaware of its function. They are named after "Knolle", German for "tuberous root" which describes their structure.
Magnetic shark repellents utilize permanent magnets, which exploit the sensitivity of the Ampullae of Lorenzini in sharks and rays (electrosense). This organ is not found on bony fish (teleosts), therefore, this type of shark repellent is selective to sharks and rays. Permanent magnets do not require power input, making them practical for use in fisheries and as bycatch reduction devices. Sharkbanz, released in 2014, is a wearable commercially available device intended for recreational users. Its manufacturers cite numerous scientific papers which support the effectiveness of permanent magnets in a range of contexts. A field study of a range of shark deterrents in 2018 found that Sharkbanz were ineffective when used in a temperate oceanic setting with berley-attracted Great white sharks.
The following outline is provided as an overview of and topical guide to sharks:
A sense is a biological system used by an organism for sensation, the process of gathering information about the surroundings through the detection of stimuli. Although, in some cultures, five human senses were traditionally identified as such, many more are now recognized. Senses used by non-human organisms are even greater in variety and number. During sensation, sense organs collect various stimuli for transduction, meaning transformation into a form that can be understood by the brain. Sensation and perception are fundamental to nearly every aspect of an organism's cognition, behavior and thought.
The jamming avoidance response is a behavior of some species of weakly electric fish. It occurs when two electric fish with wave discharges meet – if their discharge frequencies are very similar, each fish shifts its discharge frequency to increase the difference between the two. By doing this, both fish prevent jamming of their sense of electroreception.
Most fish possess highly developed sense organs. Nearly all daylight fish have colour vision that is at least as good as a human's. Many fish also have chemoreceptors that are responsible for extraordinary senses of taste and smell. Although they have ears, many fish may not hear very well. Most fish have sensitive receptors that form the lateral line system, which detects gentle currents and vibrations, and senses the motion of nearby fish and prey. Sharks can sense frequencies in the range of 25 to 50 Hz through their lateral line.
Communication occurs when an animal produces a signal and uses it to influences the behaviour of another animal. A signal can be any behavioural, structural or physiological trait that has evolved specifically to carry information about the sender and/or the external environment and to stimulate the sensory system of the receiver to change their behaviour. A signal is different from a cue in that cues are informational traits that have not been selected for communication purposes. For example, if an alerted bird gives a warning call to a predator and causes the predator to give up the hunt, the bird is using the sound as a signal to communicate its awareness to the predator. On the other hand, if a rat forages in the leaves and makes a sound that attracts a predator, the sound itself is a cue and the interaction is not considered a communication attempt.
The electric eels are a genus, Electrophorus, of neotropical freshwater fish from South America in the family Gymnotidae. They are known for their ability to stun their prey by generating electricity, delivering shocks at up to 860 volts. Their electrical capabilities were first studied in 1775, contributing to the invention in 1800 of the electric battery.
The history of bioelectricity dates back to ancient Egypt, where the shocks delivered by the electric catfish were used medicinally.
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