Fishes Flashcards
Form
Types of scales
- Placoid scales
- Ganoid scales
- Cycloid & Ctenoid scales
Types of scales
Placoid scales
- Small, conical, toothlike structures
- Typical of chondrichthyes
- Modified to teeth in sharks
Types of scales
Ganoid scales
- Diamond shape
- Early bone fishes and living gars
Types of scales
Cycloid & Ctenoid scales
- Arranged in overlapping rows
- Typical of teleost fish
Adaptations for buoyancy
- Swim bladder
- Never stop swimming (tuna)
- No need to buoyancy (abyssal fish)
- Asymmetrical tail (provides lift)
- Large livers with squalene (particularly buoyant lipid)
Adapations for buoyancy
Swim bladder
- Gas-filled organ
- Volume adjusted for neutral buoyancy
- Volume of gas can be adjusted as fish moves up and down water column
Respiration
- Most fish use gills
- Some fish also have lungs
Respiration
Gills
- Composed of thin filaments covered with an epidermal membrane folded repeatedly into plate-like lamellae to increase SA for gas exchange
- Located in the pharyngeal cavity
- Covered with an operculum in bony fishes
Osmotic reguation
- Maintenance of balance of fluids
- Freshwater = hyperosmotic regulators
- Marine = hypoosmotic regulators
Osmotic regulation
Adaptations of hyperosmotic regulators
- Scales and mucous protect the fish
- Water pumped out by kidneys
- Salt-absorbing cells in the gill move salt from water to blood
Osmotic regulation
Adaptations of hypoosmotic regulators
- Salt-secretory cells in the gills move salt out of the body
- Salt is voided with faeces or excreted by the kidney
Taxonomy
Agnatha
* Hagfishes
* Lampreys
Chondricthyes
* Sharks, rays, & chimeras
Osteichthyes
* Actinopterygii (Ray-finned fishes)
* Sarcopterygii (Lobe-finned fishes)
Agnatha
No vertebrae or jaw
Hagfishes
* Environment
* Nutrition
* Sensory
* Defense
Agnatha
- Marine
- Scavengers & predators (not parasitic)
- Keratinized plates on tongue to rasp bits of flesh from its prey
- Poorly developed eyes
- Keenly developed sense of smell & touch
- Produce slime as a defence mechanism
How do lamprey feed?
Agnatha
Use tooth-like plates of keratin for rasping a hole, through which fluids & tissues are sucked
Chondrichthyes
Sharks, rays, chimeras
- Cartilaginous fishes (no bone)
- Placoid scales
- No swim bladder
- Asymmetric hetercercal tail provides lift
- Large livers with squalene
Osteichthyes: General charactersitics
- Bony fish (bone replaces cartilage)
- Gas-filled pouches branches from oesophagus
- If pouch used for gas-exchange = lungs
- If pouched used for buoyancy = swim bladder
Osteichthyes
Ray-finned fishes
- Actinopterygii
- Symmetrical homocercal tail
- Gills and swim bladder
Osteichthyes
Lobe-finned fishes
- Sarcoptergii
- Lungfish and coelacanths
- Ancestor of tetrapods
- Lobe fins with a single bone that articulates with rest of body
- Diphycercal tails
- Lungs and gills
Lobe-finned fishes
Lungfishes
- Breathe with gills and lungs
- Can live out of water for extended periods of time
Lobe-finned fishes
Coelacanths
- Living fossils
- 80 million years of
morphological stasis
Reproduction in fishes
- Mostly dioecious
- external fertilization
- oviparous
- r-selected
Patterns of reproduction: Pelagic marine teleosts
- minute, buoyant, transparent eggs
- Eggs hatch into larvae as they float in the ocean
Patterns of reproduction: Near-shore and benthic fish
- Larger eggs, with more yolk
- Non-buoyant, adhesive
- Eggs are buried, attached to vegetation, deposited in nests
- Many benthic fish guard their eggs (male)
Unusual reproduction: Clown fish
Sequential hemaphroditism
* Group consists of a breeding pair (one male, one female) and a number of undifferentiated fish
* If the female dies, the adult male becomes female, and one of the smaller, undifferentiated fish takes his place
Unusual reproduction in fishes: Amazon molly
Asexual parthenogesis
* Egg is diploid when it is laid
* No meiosis
* Male sperm from a related species may be required to stimulate the egg
* Offspring are clones of the mother
* All female species
