Glossary of Terms
Scientific terms translated
Abiota = non-living features of the environment, which can impact upon living organisms (Compared to "Biota")
Abyssopelagic Zone = aka Abyssal Zone, referring to the 2nd deepest layer of the ocean (between the "Hadalpelagic Zone" and "Bathypelagic Zone") from 4000 - 6000m depth
[Ocean] Acidification = a process related to "climate change" whereby excess atmospheric carbon dioxide dissolves into the ocean, causing a drop in pH into acidic levels
Acoustic telemetry = scientific method to study shark movement by fitting them with electronic tags
Adelphophagy = see "Embryophagy"
Aggregation = when sharks form a group because environmental conditions (such as prey availability, temperature, salinity etc.) drive them to do so (In comparison to a "Social group")
Agonism / Agonistic display = any behaviour related to conflict or competition, including fighting, threat, defence, flight, freezing, avoidance and appeasement (See also "Threat display")
Alopiidae = family of sharks, order Lamniformes (aka Thresher sharks)
Amphistylic jaw suspension = primitive jaw morphology found in "Hexanchiformes", where upper jaw is attached to the "Chondrocranium" by ligaments, with limited support from cartilage. Hiders jaw protrusion and limits gape compared to "Orbitostylic" and "Euhyostylic jaw suspension"
Ampullae of Lorenzini = jelly-filled pores on the snout of "elasmobranchs" which are used to sense electromagnetic fields during hunting and navigation
Anal fin = "Median fin" on underside of a shark, near the "Cloaca", absent in the majority of "Squaliform" sharks
Angling = recreational and/or competitive (not commercial) shark fishing, using a rod and line. Once quite destructive, today sharks are commonly released unharmed and anglers contribute enormous amounts of data to scientific research
Anguilliform swimming = swimming via eel-like undulations of the whole body. Most inefficient mode of swimming employed by relatively sedentary species (Opposed to "Carangiform" and "Thunniform swimming")
Apex predator = a predator at the top of a food chain; occupying the highest trophic level, with natural predators (See also "Mesopredator")
Aplacental viviparity = aka yolk-sac viviparity, see "Ovoviviparity"
Aplesodic pectorals = where radial cartilage extends into less than half of the pectoral fins, making them more flexible and less supportive (As opposed to "Plesodic pectorals")
Anoxic = term used describe area of water devoid of any oxygen (See also "Hypoxic")
Barbel(s) = sensory projections from near the nose / mouth in some shark species, used to detect prey
Bathypelagic Zone = aka the Midnight Zone, depth layer in the ocean between 1000 - 4000 m deep, with very little light penetration (lying between the "Abyssal zone" and the "Mesopelagic Zone"
Batoids = skates and rays, close relatives of sharks, characterised by relatively flattened body, ventral placement of gills and different fin morphology
Behavioural osmoregulation = movement to actively seek out site with preferred salinity range, minimising energetic costs associated with osmoregulation
Behavioural thermoregulation = movement to actively seek out site with preferred temperature range
Benthic = bottom-dwelling, living on/close to substrate (As opposed to “Pelagic”)
Biota = all living members of the environment, including flora and fauna (Compared to "Abiota")
Brachaeluridae = family of sharks, order "Orectolobiformes" (aka Blind sharks)
Breaching = leaping completely out of the water, seen in great white sharks, basking sharks, thresher sharks and mako sharks
Buccal pumping = method of respiration, whereby the shark pumps its mouth open and closer to force oxygenated water over the gills, therefore does not need to keep swimming in order to breathe (As opposed to "Ram ventilation")
Bucklers = thorn-like scales along the back and tail of skates
Bycatch = when non-target marine creatures are unintentionally caught during commercial fishing, an especially large threat to many shark species, responsible for largest volume of global shark mortality
Carangiform swimming = relatively efficient swimming method, used by active species, characterised by undulating only the back half of the body (Opposed to "Anguilliform" and "Thunniform swimming")
Carcharindiae = family of sharks, order "Carchariniformes" (aka Requiem sharks)
Carchariniformes = order of sharks (families 1. Carcharindiae, 2. Scyliorhinidae, 3. Triakidae, 4. Sphyrnidae)
Carnivore = an animal that feeds on other animals (See "Herbivore" and "Omnivore")
Cartilage = resilient, flexible tissue which forms the skeleton of sharks, less mineralised and lighter than bone (creating buoyancy), and lacking nerves or blood vessels
Catch-all fishing = commercial fishing operations composed of multiple gear-types (See "Gill net", Long-lining" and "Trawling"), to target a wide range of commercially valuable marine species for human consumption (As opposed to "Targeted fishing")
Caudal fin = aka the tail fin, provides propulsion for swimming
Caudal peduncle = region on a sharks body from the base of the second dorsal fin to the start of the caudal fin
Ceratotrichia = soft, unsegmented, flexible cartilage composed of keratin, providing support to the outer regions of a sharks fins, valued for shark fin soup
Cetorhinidae = family of sharks, order "Lamniformes" (aka Basking sharks)
Chlamydoselachidae = family of sharks, order "Hexanchiformes" (aka Frilled sharks)
Chondrichthyes = class cartilaginous fishes; including sharks, rays and chimaeras (see "Holocephali"), with cartilaginous skeletons, skin of dermal denticles, 5-7 gill slits lacking boney covering, nostrils on underside (few exceptions), internal fertilisation using claspers and cloaca, revolver dentition, urea for osmoregulation, lacking swim bladders and boney scales,
Chondrocranium = cartilaginous structure protecting and providing support for the brain and sensory organs in sharks, made of single, unsutured structure
Chumming = aka burleying, the act of attracting sharks to a boat by tossing liquidated fish tissues and oil into the water to create an odour plume
CITES (Convention on International Trade in Endangered Species of Flora and Fauna) = an international agreement between governments, to ensure that international trade in specimens of wild animals and plants does not threaten their survival
Cladodonts = earliest known true sharks, which arose around 150 million years ago and were killed off in the Great Permian extinction e.g Cladoselache, Xenacanthus, Falcatus (See also "Hybodont")
Clasper[s] = aka mixopterygia, modified fins of male sharks, used as reproductive organs to transfer sperm during mating (See also "Cloaca")
Classical conditioning = a learning process whereby an animal learns to associate one stimulus with another, e/g the sound of a bell with food (see also "operant conditioning")
Climate Change = term used to describe the anthropogenically driven change in global climate, caused by excess Greenhouse gas emissions, predicted to cause rising sea levels, shifts in ocean cycling, and ocean "Acidification" and "Deoxygenation"
Cloaca = female reproductive opening for mating and also for defecation (See also "Clasper")
CMS (Convention on Migratory Species) = aka The Bonn Convention, international agreement that aims to conserve migratory species within their entire range, rather than via legislation in every separate country
Cognition = the mental process of gaining knowledge and adapting behaviour, through thought, experience and the senses
Conspecific = another individual of the same species (As opposed to "Heterospecific")
Continental shelf = rim of continent covered by sea, from coast to 200 m depth, where seafloor begins to slope down to deepsea planes
Continental slope = part of seafloor sloping down from border of continental shelf at 200 m, down to deepsea planes of 4000 m depth
Continuous breeding = year-round breeding with no resting phase between pregnancies, where females develop eggs throughout pregnancy in preparation for the next mating. Characteristic of "Viviparous" sharks with minimal maternal input, eg. deep-sea "Squaliforms" (As opposed to "Seasonal" and "Punctuated breeding")
Convergent evolution = the process whereby organisms which are not closely related, independently evolve similar traits, as they adapt to similar environments or "Niches"
Countershading = fading of skin pigmentation from dark on the "Dorsal" side to light on the "Ventral" side, making the animal more difficult to see in the water
Crepuscular = an animal appearing or active in twilight; just before the sun goes down, or just after the sun rises
Delayed oviparity = aka retained oviparity, reproductive method whereby eggs are laid some time after internal fertilisation and therefore spend a relatively short period developing outside of the mother, and are a relatively costly investment to the female (Opposed to "Immediate oviparity")
[Ocean] Deoxygenation = a process related to "climate change", whereby rising sea surface temperatures causes oxygen to escape from seawater
Dermal denticles = aka "Placoid scales", plate-like scales which form shark skin, evolved from teeth
Display = a stereotyped behaviour pattern, modified by natural selection, to convey information, usually among "conspecifics" or within social groups
Dissection = the examination of internal structures of an animal, in order to better understand its anatomy
Dominion = an area where an individual exhibits elevated dominance and aggression towards others, but does not attempt to expel them
Dorsal = referring to the back of an animal (As opposed to "Ventral")
Dorsal fin(s) = "median fins" on the back of a shark, which act as a keel (improving manoeuvrability and preventing tipping from side-to-side whilst swimming). Presence / loss of 2nd dorsal fin can be used to identify relatedness of shark species
Dredging = commercial fishing method whereby heavy apparatus are dragged along the ocean floor to extract valuable bottom-dwelling species (See "Trawling")
Dynamic lift = type of upwards force created by fins whilst swimming (As opposed to "Static lift")
Echinorhinidae = family of sharks, order "Squaliformes" (aka Bramble sharks)
Echinorhiniformes = order if sharks (family 1. Echinorhinidae)
Ecosystem = a community of interacting organisms and their physical environment
Ectothermy / Ectotherm = an animal which does not raise its internal body temperature above that of its surroundings (As opposed to "Endothermy"
Elasmobranch / Elasmobranchii = aka Euselachii, subclass; collective term for sharks and rays, named for arch-shaped gills
Embryophagy = form of "Intrauterine cannibalism" whereby unborn pups eat their siblings in the womb
Embryotrophy = reproductive method unique to tiger sharks, where unborn pups are enclosed in sacs of fluid which provide them nutrition
Endothermy / Endotherm = an animal which raises its internal body temperature higher than the surrounding environment (As opposed to "Ectothermy"), differs from "Mesothermy" as temperature is maintained within a homeostatic range (See also "Regional endothermy")
Epipelagic Zone = aka Sunlight zone, shallowest layer of the ocean, which light can penetrate, from the surface up to 200m depth (above the "Mesopelagic Zone")
Euhyostylic jaw suspension = highly evolved jaw morphology found in the "Batoid" , where there are no connections (via either ligaments or articulation) between the "Chondrocranium" and upper jaw, and jaws are supported entirely by cartilage. Allowing extreme upper jaw to protrusion and wide gape, compared to "Amphistylc", "Orbitostylic-" and "Hyostylic jaw suspension")
Euryhaline = able to export a wide range of salinities (As opposed to "Stenohaline"), rare in "Elasmobranchs"
Euselachii = see "Elasmobranchii"
Extant = living species (As opposed to "Extinct")
Extinct = species with no living individuals (As opposed to "Extant")
Facultative parthenogenesis = the ability of some sexually reproducing animals to switch to asexual reproduction. May be linked to "Inbreeding"
Family = a term used describe a group of "Genera" in taxonomic classification
Fecundity = the number of offspring which can be produced by a female throughout her life, often relatively low in sharks
Fish Aggregation Device (FAD) = device used in commercial fishing, (especially "Purse seine" fishing), to encourage fish into a tight group, making them easier to catch. Previously non-destructive to sharks, modern, complex raft designs have increased shark "Bycatch"
[Shark] Fishing = extracting sharks from the marine environment for human consumption of fins, meat and/or liver oils (See "Gill net", "Longlining", "Purse seine", "Trawling"). Can be commercial (large scale for sale on the global market) or subsistence (for use by the fisher to feed their family) (Not to be confused with "Finning")
[Shark] Finning = wasteful and cruel type of commercial shark fishing where fins are removed and the rest of the carcass is discarded at sea. Now illegal in many countries
Fitness = an individual's ability to survive to reproductive age, find a mate, and produce offspring
Following behaviour = copulation behaviour seen in some species, male following female with snout less than 30cm from tail
Galeomorphs = superorder, galeomorph sharks (Orders 1. Heterodontiformes, 2. Orectolobiformes, 3. Lamniformes, 4. Carchariniformes) (As opposed to "Squalomorphs")
Gaping = an "agonistic" behaviour of slow, exaggerated opening of the jaws conspicuously wider than normal
Genetic bottleneck = when the genetic diversity of a population is reduced due to "Inbreeding", making a species vulnerable to disease
Genus (pl. Genera) = a term used describe a group of species in taxonomic classification, referring to a set of closely related or similar species
Ghost fishing = discarded, lost, or abandoned, fishing gear in the marine environment, which continues to entangle and potentially kill marine animals, smother habitat (such as reefs) and act as a hazard to navigation
Gill(s) = slit-like openings on each side of a shark near the head, used to extract oxygen from water for respiration
Gillnet = commercial fishing method, utilising a net which entangles in fish gills (In contrast to a "Purse seine"), difficult to untangle sharks caught as "Bycatch", so can lead to "Post-release mortality"
Gill rakers = small cartilaginous projections from the gill arch, which form a finger-like sieve, used in filter-feeding
Gnathostome = term used to refer to any and all fish (including sharks) with an articulated jaw
Golden Age of Sharks = period 300 - 360 million years ago (during the Carboniferous) when sharks were the dominant fish in the ocean and their biodiversity was incredibly high
Gravid = carrying eggs or young, aka pregnant
Hadalpelagic Zone = aka Deep-Sea Trenches, the deepest layer of the oceans (below the "Abyssopelagic Zone") at depths of 6000m or more
Hemiscyllidae = family of sharks, order ""Orectolobiformes (aka Bamboo and Epaulette sharks)
Herbivore = an animal that feeds on plants (See "Omnivore" and "Carnivore"
Heterocercal tail = tail with upper and lower caudal lobes of differing size and/or shape (As opposed to "Homocercal" or "Hypocercal tail")
Heterodont dentition = jaws have teeth of different shapes (As opposed to "Homodont dentition"
Heterodontidae = family of sharks, order ""Heterodontiformes (aka Horn sharks)
Heterodontiformes = order of sharks (family 1. Heterodontidae)
Heterotroph = organisms which rely upon consuming other organisms (plants and/or animals) for nutrition (See "Trophic level")
Hexanchidae = family of sharks, order "Hexanchiformes" (aka Cow sharks)
Hexanchiformes = order of sharks (families 1. Hexanchidae, 2. Chlamydoselachidae)
Histotrophy = where embryos of "Viviparous" species, are nourished by the secretion of mucous (known as histotroph) from the lining of the mother's uterus. Relatively costly to mother compared to "Lecithotrophy" and "Limited histotrophy" (See also "Lipid histotrophy" and "Placental viviparity")
Holocephali = aka chimaeras, close relatives of sharks and rays, now a small group, but which were once very biodiverse
Homeostasis = the maintenance of a constant internal environment within the body, despite fluctuating external conditions. In sharks this includes the maintenance of internal temperature, and salt, ion and water levels in the body
Homocercal tail = tail with symettrical upper and lower caudal lobes (As opposed to "Heterocercal" and "Hypocercal tails")
Homodont dentition = jaws with teeth of the same shape (As opposed to "Heterodont dentition"
Hunch display = "Agonistic" behaviour exhibited by sharks, part of series of stereotyped movements preceding aggressive attack, featuring raised snout, arched back, lower pectoral fins and exaggerated swimming movements
Hybodonts = group of shark ancestors which arose after the extinction of the "Cladodonts" during the Great Permian extinction and gave rise to modern sharks (See also "Neoselachians)
Hyostylic jaw suspension = jaw morphology found in most Elasmobranchs and all bony fishes, where there loose ligament and cartilage connection between the jaw and "Chondrocranium", allows jaw protrusion and gape more than "Amphistylic" and "Orbitostylic", but less than and "Euhyostylic jaw suspension"
Hypocercal tail = unusual tail morphology found in angel sharks, where lower caudal fin lobe is larger then the upper, causing head elevation (As opposed to "Heterocercal" and "Homocercal tails")
Hypoxia / Hypoxic = term used to describe an area of water which is extremely low in dissolved oxygen (See also "Anoxic")
Idiosphere = the volume immediately surrounding an individual that it will defend if broached without appropriate signalling or permission
Immediate oviparity = aka single oviviparity, reproductive method whereby eggs are laid very quickly after internal fertilisation, so spend a long time developing outside of the mother, vulnerable to predation (Opposed to "Delayed oviparity)
Inbreeding = when closely related species breed together, leading to a "Genetic bottleneck"
Innate = knowledge or behaviours present since birth, which does not require learning or experience (Sometimes referred to as instinct)
Intrauterine cannibalism = when unborn pups feed on their siblings and/or unfertilised eggs (See "Adelphophagy", "Embryophagy", "Oophagy"
Internal fertilisation = reproduction through insertion of the male sex organ into female genitalia (compares to external fertilisation, aka spawning, used by most fish)
IUCN (International Union for the Conservation of Nature) = organisation assessing abundance of species of wild animals to assign them to an extinction risk category on the "Red List" of threatened species
Jaw closing = an "agonistic" behaviour of non-forcefully bringing the jaws together
[the] Jaws Effect = term coined by Dr C. Neff to describe the pervasive fear of sharks (leading to revenge cullings and inadequate conservation measures) in the wake of the 1975 blockbuster movie
[the] Jurassic Split = now inaccurate term previously used to describe the moment when sharks and rays diverged, originally thought to be some 200 million years ago (during the Jurassic period), now known to have occurred some 270 million years ago
Juvenile = a young animal which has yet to reach sexual maturity
Keystone species = a species which is critical to an ecosystem, without which the system would collapse completely
Klinotaxis = side-to-side motion of the head in response to stimulation (commonly a smell), allowing orientation and movement towards the stimulus by alternating exposure of sensory receptors on either side of the body (See also "Tropotaxis")
K -Selected life history strategy = term use describe species (including all sharks) which are slow growing, mature late in life and have low fecundity, meaning they are slow to recover from population declines (As opposed to r-Selected life history strategy")
Lamnidae = family of sharks, order "Lamniformes" (aka Mackerel sharks), including only known "Endothermic" shark species
Lamniformes = order of sharks (families 1. Lamnidae, 2. Mitsukurinidae, 3. Megachasmidae, 4. Cetorhinidae, 5. Alopiidae, 6. Odontaspididae)
Lateral keel = prominent ridges along the sides of some sharks, which provide stability when swimming at high speeds
Lateral line = sensory organ running parallel along each side of a fish's body, capable of detecting water displacement and changes in pressure
Lecithotrophy / Lecithotrophic = form of "Ovoviparity" where developing embryos receive nutrition exclusively from yolk. Relatively less costly to the mother compared to "Matrotrophy". Similar to "Oviparity"
Lekking = when individuals of one sex (commonly males) group to perform mating rituals, displaying competitively to the opposite sex their readiness to mate and value as a breeding partner
Limited histotrophy = when embryos of "Ovoviviparous" sharks are nourished via mucoid secretions from the mother's uterine wall. Relatively, costly to mother compared to "Lecithotrophy", but less costly than "Histotrophy"
Lipid histotrophy = when embryos of "Viviparous" species are nourished with uterine milk without direct connection to the uterine wall (In comparison to "Placental viviparity". See also "Histotrophy")
Longlining / Long-line fishing = commercial fishing method utilising a line with multiple (sometimes thousands) of baited hooks at regular intervals. Relatively less destructive method than "Gill nets", with reduced "Post-release mortality of sharks caught as "Bycatch"
Looping = an "Agonistic" display of swimming in a spiral loop
Marine Protected Area (MPA) = an area managed to protect marine ecosystems, processes, habitats, and species, which can contribute to the restoration and replenishment of resources for social, economic, and cultural enrichment
Mate choice = when choice of a reproductive partner is non-random, but rather based on favourable traits. Commonly "female mate choice" (when female chooses male), but also sometimes "male mate choice" (when male chooses female) or "mutual mate choice" (when both male and female choose each other) (See also "Sexual selection")
Matrotrophy / Matrotrophic = form of reproduction where developing embryos gain nutrition from the mother. Costly to the mother compared to "Lecithotrophy"
Mechanoreception = sensory ability to detect displacements in water (See "Lateral line")
Median fins = unpaired fins along the centre line of a sharks body, which provide stability, eg. "Dorsal fin(s)" and "Anal fin"
Megachasmidae = family of sharks, order "Lamniformes" (aka Megamouth sharks)
Megalodon = common name used to refer to an enormous, extinct shark species Otodus / Carcharocles megalodon
Mermaid's purse = slang term used for shark / ray egg cases (See "Oviparity")
Mesopelagic Zone = aka Twilight Zone, relatively shallow depth layer in the ocean, from 200 - 1000 me, where light can easily penetrate (between the "Epipelagic Zone" and "Bathypelagic Zone")
Mesopredator = a mid-ranking predator (below the "Apex predator") in the mid- "trophic levels", which typically preys on smaller animals
Mesothermic / Mesotherm = a relatively rare form of "Endothermy" whereby an organism elevates its body temperature above that of the environment using metabolic heat, but has little to no control to maintain a specific temperature range
Microplastics = extremely small pieces of plastic debris from the breakdown of discarded consumer products and industrial waste
Mitsukurinidae = family of sharks, order "Lamniformes" (aka Goblin sharks)
Mixopterygia = See "Claspers"
Monophyletic group = a group of organisms which have all evolved from a common ancestor
Mouthing = hunting and/or investigative behaviour; whereby shark grasps an object in it’s mouth briefly, releasing it without removing flesh
Multiple paternity = when a female carries offspring from more than one father at once (See also "Polyandry")
Myliobatiformes = order of rays including stingrays, eagle rays, devil rays and mobula rays
Nares = aka nostrils, channels that lead into the olfaction organs
Natal site = place of birth (often referred to in terms of "Philopatry")
Natural selection = the process whereby organisms better adapted to their environment tend to survive and produce more offspring
Negative buoyancy = when an animal is heavier than surrounding water and tends to sink. In sharks this is counteracted by their oily liver, light skeleton, lift generated by fins when swimming and, in some species, by gulping air from the surface (See also "Neutral buoyancy", "Dynamic-" and "Static lift")
Neonate = a new-born animal
Neoselachii / Neoselachian = subcohort of the "Euselachii", modern sharks and rays, including the "Squalimorphs", "Galeomorphs" and "Batoids"
Neutral buoyancy = when an animal is neither more or less buoyant than surrounding water, and hangs in the water column without sinking or floating (See also "Negative buoyancy")
Niche = aka ecological niche, the position of a species within an ecosystem and its ecological role within that system
Nictiting membrane = whitish membrane which can be drawn across the eye to for protection, present only in "Carcharhiniformes"
Noise pollution = anthropogenic sound (from drilling, seismic surveys, shipping, and using radar and sonar) which causes disturbance in the marine environment
Nursery habitat = area where juvenile marine animals live during the first months of life because the area offers ample food and/or protection from predators (See also "Philopatry")
Nutrient translocation = the movement of nutrients from one location to another, for example, from a feeding site to a defecation site
Odontaspididae = family of sharks, order "Lamniformes" (aka Sandtiger sharks)
Omnivore = an animal that eats a variety of food of both plant and animal origin (See "Herbivore" and "Carnivore")
Ontogeny / Ontogenetic = the developmental history of an organism
Oophagy / Oophagus = aka "Intrauterine cannibalism", when embryos feed on unhatched eggs while still inside the mother's uterus (See also "Adelphophagy")
Operant conditioning = learning process whereby an animal learns to associate an action with either a positive (reward) or a negative (punishment) response (See also "Classical conditioning")
Orbitostylic jaw suspension = evolutionarily quite advanced jaw morphology, where the short orbital process of upper jaw buttresses the jaw. Provides intermediate protrusion and gape compared to "Amphistylic" and "Euhyostylic jaw suspension"
Order = a term used describe a group of "Families" in taxonomic classification
Orectolobidae = family of sharks, order "Orectolobiformes" (aka Wobbegongs)
Orectolobiformes = order of sharks (families 1. Orectolobidae, 2. Rhincodontidae, 3.Stegostomatidae, 4. Parascyllidae, 5. Hemiscyllidae, 6. Brachaeluridae, 7. Ginglymostomatidae)
Osmoregulation = the maintenance of stable ion, salt and water concentrations within the body ("Homeostasis"), by counteracting the natural tendency for water to diffuse from areas of high to low salt ie. by stopping the loss of water in very saline environments and stopping movement of water into the body in less saline water
Otolith[s] = carbonate structures in the ears of fish, which can be used to estimate age. See also "Stataconia"
Oviparous / Oviparity = egg-laying reproduction where embryos are nourished by egg yolk (As opposed to "Ovoviviparity" and "Viviparity")
Ovoviviparous / Ovoviviparity = aka Aplacental viviparity aka Yolk-sac viviparity reproduction whereby fully developed young hatch from an egg within the uterus and are birthed soon after, embryos are nourished by yolk and not supplied nutrients via placenta (As opposed to "Oviparity" and "Viviparity") (See also "Immediate-" and "Delayed oviparity")
Paired fins = fins found symmetrically in twos, corresponding to the fore and hind-limbs in mammals, eg. "Pectoral ins" and "Pelvic fins" in sharks
Palatoquadrate protrusion = forward extension of the upper jaw, causing it to separate from the cranium and which may bare the upper teeth. Exaggerated in the goblin shark - extending their reach when hunting prey
Parascyllidae = family of sharks, order "Orectolobiformes" (aka Collared Carpet sharks)
Parthenogenesis = when a female spontaneously switches to asexual reproduction and produces offspring without a male
Parturition = the process of giving birth to offspring
Parturition habitat = environment where females give birth to their young
PAT Tag = aka Pop-Up Archival Tag, type of electronic tag, used to study movement, which automatically detaches from the shark for data download
Pectoral fin(s) = "Paired fins" found on the either side of a sharks body (homologous to the fore-limbs in mammals), used for orientation and to create "Dynamic lift" (See "Pitch" and "Roll"), and for communication in "Agonistic displays". Can be either "Plesodic" or "Aplesodic"
Pelagic = living in open water (As opposed to “Benthic”)
Pelvic fins = "Paired fins" located on the underside of a shark (homologous to the hind-limbs in mammals), which prevent "Roll" and control "Pitch"
Periocardio-peritoneal canal = space connecting area around the heart to the rest of the abdomen, aiding in heart function and important for avoiding heart compression
Philopatry = the tendency of animals to return / remain near a particular site / area, sometimes returning to a remarkably specific location even after extended, long-distance migrations
Photophore = a light-producing organ in the skin
Phytoplankton = microscopic "Planktons" floating in the water column, which produce energy via photosynthesis, rather than ingestion of other organisms (See also "Zooplankton"). Vital food source for many marine animals at low "Trophic levels"
Pineal organ / Pineal gland = organ located near the brain, involved in photoreception independently from the eyes, by receiving light through the top of the head. Produces melatonin to maintain a circadian rhythm
Pitch = up and down angle-of-swimming in the water (See also "roll" and "yaw")
Pit organs = unspecialised sensory cells on the top and sides of the head, around the spiracles, and along the trunk and tail, which detect external water movement
Placental viviparity = reproduction whereby live young are birthed after having been nourished with uterine milk directly via a placenta-like structure connected to the mother's uterine wall. Very costly to the mother compared to other reproductive methods (As opposed to "Lipid histotrophy", "Aplacental viviparity". See "Viviparity")
Placoid scales = See "Dermal denticles"
Plankton = small or microscopic organisms (mostly diatoms, protozoans, small crustaceans, and the eggs and larval stages of larger animals) drifting in the water column. Vital food source for many marine animals at low "Trophic levels" (See also "Phytoplankton" and "Zooplankton")
Plesodic pectorals = evolutionarily advanced pectoral fin morphology, where radial cartilage spreads into more than half of the fin, making them stiffer (As opposed to "Aplesodic pectorals")
Poikilothermic / Poikilotherm = an organism with a variable body temperature that tends to fluctuate with the temperature of its environment
Polyandry = when one animal mates with multiple partners and becomes pregnant with several different fathers (aka "Multiple paternity")
Polyphyodont dentition = aka "revolver dentition", whereby an animals teeth are continually replaced throughout life
Post-release mortality = death after release from a fishery due to injury / stress / infection / behaviour changes
Precaudal pit = small notch before the caudal fin in some species of sharks which increases tail flexibility
Principal population = main breeding population of migratory sharks (As opposed to "Accessory population")
Prismatic calcified cartilage = form of shark cartilage which is hardened by calcium to make the bones more resilient to stress at certain regions
Pristiophoridae = family of sharks, order "Pristiophoriformes" (aka Saw sharks)
Pristiophoriformes = order of sharks (family 1. Pristiophoridae)
Punctuated breeding = reproductive method where female is pregnant (often for 1 year or more) and are then dormant for an extended period to recover time, making for long reproductive cycles. Common in "Viviparous" sharks where maternal input is high eg. dusky sharks (As opposed to "Continuous" or "Seasonal breeding")
Punting = form of locomotion used by skates, where bi-lobed pelvic fins are used to crawl along the benthos
Pup = term used to describe shark offspring
Purse seine = commercial fishing method targeting dense schools of fish, utilising a basket-shaped net that surrounds them from all sides. Relatively non-destructive method, except when including a "Fish aggregating device", which increases shark "Bycatch" (See also "Longlining" & "Gillnet")
Rajiformes = order of rays commonly known as skates
Raking = an agonistic behaviour of forcefully striking of the upper jaw teeth against a "Con-/ Hetero-specific", causing injury to the receiver
Ramming = an "Agonistic" display where a signaller uses it’s snout to forcefully strike a receiver, often causing retreat
Ram ventilation = method of respiration, whereby the shark swims forwards to keep oxygenated water running over the gills (As opposed to "Buccal pumping")
Recruitment = term used to describe juvenile animals surviving to maturity and becoming a part of the adult population
Rectal gland = small organ responsible for maintaining osmotic "Homeostasis", by eliminating excess sodium and chloride ions which diffuse into a shark's body from salt water (See "Osmoregulation")
Red List [of Threatened Species] = List of wild species threatened with extinction, produced by the "IUCN"
Red muscle = highly vascularised, slow-twitch muscle used for slow, cruising swimming in sharks. Contractions generate heat in sharks with "Regional endothermy" (As opposed to "White muscle")
Regional endothermy = "Endothermy" limited to only certain areas of the body, such as vital organs like the eyes, brain and muscles. Found in "Lamniform" sharks
Repetitive aerial gaping (RAG) = an agonistic behaviour (potentially due to frustration) consisting of rhythmic, exaggerated opening and closing of the jaws above the water surface, known only in white sharks
Retia mirabella = countercurrent heat-exchangers found in sharks of the "Lamniform" family, which are responsible for "Endothermy"
Rheotaxis = the ability to orient with or against the current, thanks to the detection of water flow
Rhincodontidae = family of sharks, order "Orectolobiformes" (aka Whale sharks)
Rhinopristiformes = order of rays including wedgefish, guitarfish and sawfish
Revolver dentition = "Polyphyodont dentition", teeth embedded into gums (rather than jaw, as seen in bony fish) and are continuously replaced throughout life
Roll = body positioning on a horizontal plan in the water (See also "Pitch" and Yaw")
Rostral teeth = hardened tooth-like structures projecting from the extended rostrum in sawfish and sawsharks
Rostrum = the snout of a shark, which projects out from the head
r -Selected life history strategy = term used to describe species, like rabbits, which grow quickly, reach maturity at a young age and have high "Fecundity" (As opposed to "K-Selected life history strategy")
Salinity = amount of salt dissolved in seawater
Scavenger = an animal which exploits food which available (due to another predator's hunting or natural mortality) without hunting the prey themselves
Scyliorhinidae = family of sharks, order "Carchariniformes" (aka Cat sharks)
Seasonal breeding = when reproduction is limited to certain times of year. Common in "Ovoviviparous" sharks and rays (As opposed to "Continuous" or "Punctuated breeding")
Secondary lamellae = sites of gas exchange (oxygen in and carbon dioxide out) in the "Gills"
Sexual dimorphism = differences between males and females of a species, including differences in size, colour or behaviour
Sexual Selection = "natural selection" occurring due to preferences of sexual partners for certain features (See also "Mate choice"). Jokingly called 'survival of the sexiest'
Siphon sac = male reproductive organ in sharks, which fills with seawater to flush sperm into the female during mating
Species = a term used in taxonomic classification, referring to a group of individuals which are capable of reproducing together
Sperm storage = reproductive strategy employed by females of some species, where viable spermatozoa are stored for an extended period of time after mating, so the female can become pregnant at a later date
Sphyrnidae = family of sharks, order "Carchariniformes" (aka Hammerhead sharks)
Spiracle(s) = a pair of vestigial gill slits behind the eye of some sharks, used to provide oxygenated blood directly to the eye and brain through separate vasculature
SPOT Tag = aka Smart Position or Temperature Transmitting Tag, type of electronic tag, used to study movement, which transmits data via satellite
Spyhopping = a shark raising a portion of its face out of the water, in order to clear the eye/s from the surface to inspect objects
Squlidae = family of sharks, order "Squaliformes" (aka Dogfish sharks)
Squatinidae = family of sharks, order "Squatiniformes" (aka Angel sharks)
Squatiniformes = order of sharks (family 1. Squatinidae)
Squaliformes = order of sharks (families 1. Squlidae, 2. Echinorhinidae)
Squalomorphs = superorder, squalomorph sharks (Orders 1. Hexanchiformes, 2. Squaliformes, 3. Pristiophoriformes) (As opposed to "Galeomorphs")
Squatinomorphii = superorder, squatinomorphs (Orders 1. Squatinomorphes)
Stable isotope analysis (SIA) = scientific method using stable isotopes of carbon, nitrogen and sulphur accumulated in shark tissues, to determine what they have eaten in the past and where they source prey, used to determine "Trophic level"
Static lift = upwards force generated by buoyancy of a sharks body (As opposed to "Dynamic lift)
Statoconia = "Otoliths" of sharks, which differ to that of bony fish as they do not lay down ,concentric annual growth rings
Stegostomatidae = family of sharks, order "Orectolobiformes" (aka Zebra sharks)
Stenohaline = only able to survive a narrow salinity range (As opposed to "Euryhaline"), common in "Elasmobranchs"
Stomach contents analysis = scientific study of the feeding habits of fish and other animals based upon analysis of stomach contents
Sub-adult = an animal which has advanced beyond the "Juvenile" stage and is close to, but has yet to reach sexual maturity
Substrate = the earthy material at the bottom of a marine habitat, like dirt, rocks, sand, or gravel
Subterminal mouth = common morphology in sharks, where mouth is on the underside of the head (As opposed to "Terminal mouth")
Swim bladder = organ in bony fishes (not found in sharks), which provides "Neutral buoyancy"
Tail slapping = an agonistic behaviour consisting of whip-like lashing of the tail at/near the surface, hitting or directing splashes towards a competitor, known in white sharks and sandtiger sharks
Targeted fishing = commercial fisheries utilising specially designed gear (e.g. "Gill net", "Long-lining", "Purse seine", "Trawling") to catch a specific commercially valuable species (As opposed to "Catch-all fishing"
Term size = length at birth
Terminal mouth = morphology found only in frilled, angel, whale and megamouth sharks, where mouth is situated on the tip of the snout (As opposed to "Subterminal mouths")
Tesserae = highly mineralised plate-like tiles, coating the surface of "tessellated cartilage" in the "Chondrichthyan" skeleton
Tessellated cartilage = highly mineralised cartilage found in the vertebral column and jaw of "Chondrichthyans"
Thermal niche expansion hypothesis = the theory that "Endothermic" sharks, like great whites, are more broadly distributed than "Endotherms", thanks to their wide "Thermal tolerance"
Thermal tolerance = temperature range in which an animal can survive without suffering heat or cold shock, and subsequent cellular damage
Threat display = communicates an individual’s ill ease at the close presence of another and often remind the recipient of the signaller’s ability to inflict harm, with the goal to force the competitor to flee without resorting to fighting, so gaining access to a resource, without risk of personal injury
Thunniform swimming = most efficient form of swimming used by extremely fast species, where propulsion comes by only moving the tail, not the body (Opposed to "Anguilliform" and "Carangiform swimming")
TMAO (Trimethyl Amine Oxide) = an organic compound which is a by-product of protein metabolism. Actively retained in the body of sharks (along with "Urea") to raise the internal osmolality to be equal to that of surrounding seawater for "Osmoregulation"
Tonic Immobility = a state of paralysis which can be induced by flipping a shark on its back or overloading the electromagnetic sense (See also "Ampullae of Lorenzini")
Torpediniformes = order of rays including the electric rays and sleeper rays
Total length (TL) = standard measure used to describe the size of sharks, measured from the tip of the "Rostrum" in a straight line to the tip of the upper "Caudal fin"
Trawling = commercial fishing method whereby a net is dragged behind a moving vessel, either at the surface, mid-water or at the bottom (Not to be confused with "Dredging")
Triakidae = family of sharks, order "Carchariniformes" (aka Smoothhound sharks)
Tribasic cartilage support = three types of cartilage (named proterygium, mesopterygium and metapterygium) which support the pectoral fins sharks, but allow greater flexibility than ancestors had
Trophic cascade = an ecological phenomenon triggered by the addition/removal of a species into the food chain, which results in dramatic changes to the ecosystem structure
Trophic level = organisms within an ecosystem which occupy the same level in a food chain (See "Primary producer", "Heterotroph", "Mesopredator", "Apex predator")
Tropotaxis = orientation by simultaneous comparison of olfactory stimuli from paired receptors (See "Klinotaxis").
UNESCO World Heritage Site = an area or site with outstanding value to humanity, which is protected and maintained for future generations to enjoy
Upwelling = the process of seawater rising from depth to replace surface waters with cooler, more productive (aka nutrient-rich) water
Urea = an organic compound which is a by-product of protein metabolism. Actively retained in the body of sharks (along with "TMAO") to raise the internal osmolality to be equal to that of surrounding seawater for "Osmoregulation"
Vagility = ability of offspring to disperse away from their birth site
Ventral = referring to the underside of an animal (As opposed to "Dorsal")
Vertebral band analysis = method used to estimate the age of a shark by counting the annual/biannual deposition of a new band of cartilage over the skeleton
Vesicles of Savi = tactile receptors that sense vibrations, used for prey detection by some "Batoids"
Vitellogenesis = the accumulation of milk into egg yolk, as an energy storage for developing embryos
Viviparous / Viviparity = reproduction birthing live young (As opposed to "Oviparity" and "Ovoviviparity")
White muscle = fast-twitch muscles which generate rapid bursts of speeds in sharks (As opposed to "Red muscle")
Wobbegong = common name for a group of "Orectolobiform" sharks, characterised by ray-like flattened bodies and impressive camouflaging
Yaw = direction of movement from left to right on a horizontal plane (See also "pitch" and "roll")
Yolk-sac viviparity = See "Ovoviviparity"
Young-of-the-Year (YOY) = juvenile animals born within the last year
Zooplankton = mixture of many different types of "Plankton" animals, ranging from microscopic (mainly diatoms, protozoans, small crustaceans, and the eggs and larval stages of larger animals) up to large animals like jellyfish. Vital food source for many marine animals at low "Trophic levels" (See also "Phytoplankton")