In some primitive cartilaginous fishes, such as the spiny dogfish or mud shark ( Squalus acanthias ), there is a terminal nerve numbered zero, since it exits the brain before the traditionally designated first cranial nerve.

The spiny dogfish has the longest lifespan at more than 100 years.

For example, both the spiny dogfish and the Port Jackson shark have spines in their dorsal fins which are capable of secreting poison.

Dissection of a spiny dogfish.

:* Squalidae ( dogfish sharks ), particularly the spiny dogfish ( Squalus acanthias )

Cephalopods, particularly squid, also form an important component of its diet, while smaller sharks such as spiny dogfish ( Squalus acanthias ) and tope sharks ( Galeorhinus galeus ) are rarely taken.

The spiny dogfish, spurdog, mud shark, or piked dogfish, Squalus acanthias, is one of the best known of the dogfish which are members of the family Squalidae in the order Squaliformes.

A mountain of spiny dogfish.

In the recent past the European market for spiny dogfish has increased dramatically, which led to the overfishing and decline of the species.

This drastic increase led to the creation and implementation of many fishery management policies placing restrictions on the fishing of spiny dogfish.

In 2010, Greenpeace International added the spiny dogfish to its seafood red list.

This species feeds on a variety of benthic and pelagic bony fishes, including hake, flounders, rockfishes, lingcod, topsmelt, mackerel, and herring, and on cartilaginous fishes, including elephantfishes ( Callorhinchus ), spiny dogfish ( Squalus acanthias ), young bluntnose sixgill sharks ( Hexanchus griseus ), and ghost catshark ( Apristurus ) egg cases.

The dish can be one of many species of small shark, including the spiny dogfish ( Squalus acanthias ) or the bull huss ( Scyliorhinus stellaris ).

However, the spiny dogfish is now an endangered species due to overfishing, and is classed as Vulnerable on the IUCN Redlist and the North East Atlantic population as Critically Endangered.

Lake Huron has suffered recently due the introduction of a variety of new invasive species, including zebra and quagga mussels, the spiny water flea, and round gobies.

A 2006 study by Canadian scientists has found five species of deep-sea fish – blue hake, spiny eel – to be on the verge of extinction due to the shift of commercial fishing from continental shelves to the slopes of the continental shelves, down to depths of 1600 meters.

Species more or less completely parasitic include the leafless quintral, Tristerix aphyllus, which lives deep inside the sugar-transporting tissue of a spiny cactus, appearing only to show its tubular red flowers, and the genus Arceuthobium ( dwarf mistletoe ; Santalaceae ) which has reduced photosynthesis ; as an adult, it manufactures only a small proportion of the sugars it needs from its own photosythesis but as a seedling it actively photosynthesizes until a connection to the host is established.

The fossil record of spiny lobsters has been extended by the discovery in 1995 of a 110 million year-old fossil near El Espiñal in Chiapas, Mexico.

These forests contain several impressive trees, among them the banyan fig, which can be recognised by its large, spreading aerial roots, and the kapok tree, which has a spiny trunk, large, waxy red flowers and pods full of cotton-like material.

For example, the spiny egg laying anteater ( echidna ) has a highly developed brain, yet is not widely considered to be very intelligent.

The species has been described based on three specimens found in 2001 ; its only known habitat – stands of spiny guadua and ripidocladus spp.

The ruffe also has a large, spiny dorsal fin likely distasteful to its predators.

Serving as a claim in establishing its provenance, it has been suggested that this spiny plant was used for the " crown of thorns " worn by Jesus, though others have suggested Christ's thorn jujube ( Ziziphus spina-christi ).

It has a spreading rosette ( about wide ) of gray-green leaves up to long, each with a spiny margin and a heavy spike at the tip that can pierce to the bone.

The first ( spiny ) dorsal fin on Atlantic Spanish mackerel and cero has a prominent black patch.

The spiny anterior fin has 13 to 15 spines.

In common with all spiny lobsters, the California spiny lobster has two large, spiny antennae, but no large claws on its legs.

The principal type of neuron found in the subthalamic nucleus has rather long sparsely spiny dendrites.

The link rat, Deomys ferugineus, has been traditionally placed in this subfamily, but molecular phylogenetic studies have shown that it is more related to the spiny mice, genus Acomys.

This marsupial has a thick harsh coat but is not spiny.

This engine has special cast-iron cylinder liners cast into the block, which are a spiny type to improve adhesion between the liner and cylinder block.

This building has a large variety of animals including primates, reptiles, birds, and fish Some endangered animals on display are the spiny turtle, Pan's box turtle ( Cuora pani ), Black-breasted Hill Turtle, radiated tortoise, Flat-backed Spider Tortoise, Fiji iguana, Grand Cayman Island Blue Iguana, Bali Myna birds, Black and White Ruffed Lemurs, and Thick-billed parrots.

The first ( spiny ) dorsal on Spanish and Cero mackerel has a prominent black patch.

The short-beaked echidna was commonly called the spiny anteater in older books, though this term has fallen out of fashion since the echidna bears no relation to the true anteaters.

The dorsal and anal fins are divided into anterior spiny and posterior soft-rayed portions, which may be partially or completely separated.

There are two dorsal fins, the first one spiny and the second soft.

The spiny first dorsal fin is normally folded back in a groove, as are its pectoral fins.

The first ( spiny ) dorsal fin and the pelvic fins are normally retracted into body grooves.

* The spiny and soft ray portions of the dorsal fin are continuous, so there is only one long fin instead of two short separate ones as for the wreckfish Polyprion americanus, scup Stenotomus chrysops, rose fish Sebastes marinus, cunner Tautogolabrus adspersus, striped bass Morone saxatilis.

* Compared to a tautog or cunner, its mouth is much larger, also the caudal fin, pectoral fin, and soft portion ( 11 rays ) of dorsal fin as long as spiny portion.

The anterior spines are much longer, giving a concave outline to the spiny part of the dorsal fin.

In eastern freshwater cod the spiny dorsal fin is moderate in height and is partially separated by a notch from the high, rounded soft dorsal fin.

LTD is induced at corticostriatal medium spiny neuron synapses in the dorsal striatum by a high frequency stimulus coupled with postsynaptic depolarization, coactivation of dopamine D1 and D2 receptors and group I mGlu receptors, lack of NMDA receptor activation, and endocannabinoid activation.

This silvery minnow gets its name from the sharp spiny rays in its dorsal fin.

Mastacembelids have a series of well-separated dorsal spines on their back, hence the name of their family, spiny eels.

The first ( spiny ) dorsal fin is entirely colorless and is normally folded back into a body groove, as are the pelvic fins.

All feature a sloped profile, medium-to-large scales, a spiny dorsal fin and a laterally compressed body.

All feature a sloped profile, medium-to-large scales, a spiny dorsal fin and a laterally compressed body.

Zander are often called pike-perch as they resemble the pike with their elongated body and head, and the perch with their spiny dorsal fin.

The silvery John dory ( Zenopsis conchifera ) is typical of the Zeidae, with its scute-covered belly and filamentous spiny dorsal fin.

The first ( spiny ) dorsal fin is black at the front.

Saugers obtain two dorsal fins, the first is spiny and the posterior dorsal fin is a soft-rayed fin.