What is a Fish?

Frogfish

Hairy Frogfish

Goosefish

Oarfish

Antlered Sculpin

CowfishCowfish

Blobfish

Coffin Fish

Fangtooth

Lizardfish

Prickly Shark

Umbrella Mouth

Historic definition: Larger animals that

live in the water

Toadfish

Rockfish

Cuttlefish

Starfish

Jellyfish

Shellfish

Crawfish

Phylogenetic definition

: Vertebrates that occupy the

phylogenetic position between cephalocordates (lancelets) and

amphibians

AmphioxusAmphioxusSea LanceletSea Lancelet

PoisonDart Frog

Anatomic Definitions:

Cold blooded vertebrates with gills

and fins

Cold Blooded ?

GillsFin

Feet!

Lamprey

Is this a fin?

Strictly aquatic craniate vertebrates typically with an elongated or somewhat spindle-shaped body  terminating in a broad caudal fin, limbs in the form of fins when present at all, and a 2-chambered heart by which blood is sent through thoracic gills to be oxygenated

Strictly aquatic craniate vertebrates typically with an elongated or somewhat spindle-shaped body  terminating in a broad caudal fin, limbs in the form of fins when present at all, and a 2-chambered heart by which blood is sent through thoracic gills to be oxygenated

Rivulus

Mangrove ForestMangrove Forest

Strictly Aquatic ?

Strictly aquatic craniate vertebrates typically with an elongated or somewhat spindle-shaped body  terminating in a broad caudal fin, limbs in the form of fins when present at all, and a 2-chambered heart by which blood is sent through thoracic gills to be oxygenated

Spindle ShapeBroad Caudal

Strictly aquatic craniate vertebrates typically with an elongated or somewhat spindle-shaped body  terminating in a broad caudal fin, limbs in the form of fins when present at all, and a 2-chambered heart by which blood is sent through thoracic gills to be oxygenated

2 Chambered ?

Aristotle: 384-322 BC

Aristotle’s (Greek philosopher and scientist) definition in “Historia Animalium” 340 BC: To begin with, fishes have a head, dorsal and ventral sides; in the last named situation are placed the belly and viscera; and at the rear fishes have a tail which is continuous and undivided, but not identical in all fishes.  No fish has a neck, or any limb, or testicles anywhere internally or externally and no breasts.  Fish have two peculiarities, gills and fins: they first take in water through the mouth and then expel it through the gills: most fishes have four fins, though the elongated ones, such as the eel, have only two, and these are situated near the gills.  Similarly the various species of gray mullet have two; so has the tape-fish.  Some of the elongated fishes have no fins at all, e.g., the muraena, and their gills are not well articulated like those of other fishes. Of those which have gills, some have coverings on them, though none of the Selachia has any such covering.  All which have this covering have their gills placed at the side; whereas among selachia the broad ones have them down below the ventral surface (examples are the torpedo fish and the ray); the elongated ones have them on the sides (examples are all the dogfish).  The fishing-frog has them placed at the side, and covered, not with a spiny covering as in the non-selachians, but with a covering consisting of skin. Fishes differ from other animals otherwise than in possessing gills. Unlike viviparous land animals they have no hair, and unlike some of the oviparous quadrupeds they have no horny scales, and unlike birds they have no feathers.  Generally they are covered with ordinary scales, though a few are rough skinned, and a very small number are smooth-skinned; to the smooth skinned also belong the conger, the eel, and the tunny. Organs of sensation.  Fishes have none of these, at least none observable, except eyes-neither the organ itself nor corresponding passages for hearing or smell.  But they all have eyes, without eyelashes, though their eyes are not hard.  The whole tribe of fishes is blooded.  Some are viviparous: the scaly ones are oviparous; all the selachia, except the fishing frog, are viviparous.

Aristotle’s (Greek philosopher and scientist) definition in “Historia Animalium” 340 BC: To begin with, fishes have a head, dorsal and ventral sides; in the last named situation are placed the belly and viscera; and at the rear fishes have a tail which is continuous and undivided, but not identical in all fishes.  No fish has a neck, or any limb, or testicles anywhere internally or externally and no breasts.  Fish have two peculiarities, gills and fins: they first take in water through the mouth and then expel it through the gills: most fishes have four fins, though the elongated ones, such as the eel, have only two, and these are situated near the gills.  Similarly the various species of gray mullet have two; so has the tape-fish.  Some of the elongated fishes have no fins at all, e.g., the muraena, and their gills are not well articulated like those of other fishes. Of those which have gills, some have coverings on them, though none of the Selachia has any such covering.  All which have this covering have their gills placed at the side; whereas among selachia the broad ones have them down below the ventral surface (examples are the torpedo fish and the ray); the elongated ones have them on the sides (examples are all the dogfish).  The fishing-frog has them placed at the side, and covered, not with a spiny covering as in the non-selachians, but with a covering consisting of skin. Fishes differ from other animals otherwise than in possessing gills. Unlike viviparous land animals they have no hair, and unlike some of the oviparous quadrupeds they have no horny scales, and unlike birds they have no feathers.  Generally they are covered with ordinary scales, though a few are rough skinned, and a very small number are smooth-skinned; to the smooth skinned also belong the conger, the eel, and the tunny. Organs of sensation.  Fishes have none of these, at least none observable, except eyes-neither the organ itself nor corresponding passages for hearing or smell.  But they all have eyes, without eyelashes, though their eyes are not hard.  The whole tribe of fishes is blooded.  Some are viviparous: the scaly ones are oviparous; all the selachia, except the fishing frog, are viviparous.

Neck ?

Limbs ?

Testes!

In through the Mouth?

Muraena: No Fins?

Ears ?

Smell?Smell?

“Fish are animals with fins and internal

gills in their adult form”

The Biology of Fishes class definition

(Anatomic):

GillIssues(“Internal Gills”)

Why “internal gills” ?

GillsFin

Bichir

Why “in the adult form”?

FinIssues(What is a fin?)

Fin: An organ consisting of a membrane supported by rays, or little bony or cartilaginous

ossicles, and serving to balance and propel an organism in the water

Bony FishCaudal Fin

HypuralBones

Lepidotrichia

Shark Caudal Fin

NeuralArch

HemalArch

DermalRays

Lamprey

Is this a fin?

InternalGills

Fin ?

“Fish are animals with fins and internal

gills in their adult form”

The Biology of Fishes class definition

(Anatomic):

Quizzzz Wednesday

The Biology of Fishes class definition

(Anatomic):

“Fish are vertebrate animals with fins and internal gills in their

adult form”

For the following description of an animal, answer

“Yes, it could be a fish”,

or “No, it cannot be a fish”.

Explain your answer!

Grelb: Found in oceans worldwide including the kelp forests of coastal California, this species, (Grebulon mostracus) , drifts through the seas propelled primarily by ocean currents. They have large triangular fins that they use for steering and for directing themselves toward their favorite food, the jellyfish. Their gills are protected from jellyfish nematocysts by fine gill rakers that line the pharyngeal side of the gill arches.

Mola mola,

Mola mola