LECTURE 18 - 'Fishes' part 2 Flashcards
1
Q
What are the two superclasses of fish?
A
- Cyclostomes (jawless vertebrates - only fish)
- Myxinoidea and Petromyzontoidea
- Gnathostomata (jawed vertebrates, including tetrapods)
2
Q
What are the synapomorphies in Gnathostomata?
A
- Jaws
- Paired pectoral and pelvic fins with girdles
3
Q
(IN VERTEBRATA) What are Gnathostomata?
A
- Jaws
- 60, 000 species
- 99% of living vertebrates
- Two main extant grouping: CHONDRICHTHYES (cartilaginous fishes) and OSTEICHTHYES (bony fishes)
4
Q
What are the characteristics of the class Chondrichthyes?
A
- Skeletons made of cartilage rather than bone (no bone marrow, so red blood cells produced in the spleen)
- Paired fins
- Placoid scales (‘dermal teeth’) - typically oriented in one direction
- No swim bladder
- 5 -7 pairs of gills
5
Q
(IN CHONDRICHTHYES) What are Holocephali?
A
- Subclass Holocephali
- 31 species
- e.g., ratfish, elephant fish
- Marine, benthic
- Feed by crushing molluscs with plate-like teeth
- Upper jaw fused to cranium
- No stomach - move food directly into the intestine
- Single gill opening per side
- Sometimes have venomous spines
- Excellent night vision
6
Q
(IN CHONDRICHTHYES) What are Galeomorpha?
A
- Subclass Galeomorpha
- ~300 species
- e.g., tiger shark, hammerhead shark
- Marine, often pelagic
- Often (but not always) carnivorous
- Anal fin always present
- Usually lack fin spines
- Teeth are embedded in multiple rows directly within the gums
- Cannot swim backwards
- Non-carnivorous sharks employ filter feeding with gill rakers - long filaments that form a sieve
- Different species have independently evolved different strategies for filter feeding (e.g., ram vs. suction)
- Whale sharks are the largest extant fish species (18m), but feed on some of the smallest prey
7
Q
(IN CHONDRICHTHYES) What are Squalomorpha?
A
- Subclass Squalomorpha
- 91 species
- E.g., dog fish, basking shark
- Marine, usually deep water
- Lack an anal fin and nictitating membrane
- Fin spines
- Filter feeding Squalomorpha: the basking and megamouth sharks
- Basking sharks filter up to 2000 tons of water per hour by pusing water through the gills while swimming
- Megamouth sharks filter feed by actively sucking water through their gills
8
Q
(IN CHONDRICHTHYES) What are Batoidea?
A
- ~600 species
- e.g., skates and rays
- Usually (but not always) benthic
- Mostly marine, but few freshwater
- Swim with enlarged pectoral fins
- Ventral gill opening
- No anal fin
9
Q
What are the characteristics of the superclass Osteichthyes?
A
- Largest group of vertebrates in existence today
- 45 orders, 435 families, 27,000 species
- Skeletons composed of bone tissue
- Two main extant groupings: ACTINOPTERYGII (ray-finned fishes) and SARCOPTERYGII (lobe-finned fishes and tetrapods)
10
Q
(IN OSTEICHTHYES) What are Actinopterygii?
A
- Ray-finned fishes have fins that are webs of skin supported by bony or horny spines (“rays”), as opposed to fleshy lobed fins (like Sarcopterygii)
- Fins attach directly to the proximal or basal skeletal elements
- Make up the dominant class of vertebrates (99% of fish species)
- Ubiquitous in both marine and freshwater environments
11
Q
(IN OSTEICHTHYES - IN ACTINOPERYGII) What are Polypteriformes?
A
- 11 species
- Bichirs (also called ropefish and dragonfish)
- Restricted to freshwater in Africa
- Unique dorsal fin spines
- Ganoid scales
- Able to breathe air using a pneumatic duct connected from their foregut to the gas bladder
- Prey on fish and invertebrates
12
Q
(IN OSTEICHTHYES - IN ACTINOPTERYGII) What are Acipenseriformes?
A
- 25 living species
- Sturgeons and paddlefishes
- Restricted to coastal and freshwater habitat in the Northern Hemisphere
- Skeleton is mostly cartilaginous but does contain bones
- Ganoid scales
- Morphological characteristics have remained relatively unchanged since the Triassic
- Long-living and late maturing
- Largest freshwater fish (up to 7.5m and 1500kg)
- Most valuable fish in the world due to production of caviar
13
Q
(IN OSTEICHTHYES - IN ACTINOPTERYGII) What are Lepisosteiformes?
A
- 7 species
- Gars, garpikes
- Fresh and brackish water in North and Central America
- Heavily armoured with ganoid scales (used as arrowheads by First Nations)
- Able to breathe air using vascularized swim bladders - can take gulps of air to allow them to persist in oxygen poor waters
- Ambush predators of smaller fish and crabs
14
Q
(IN OSTEICHTHYES - IN ACTINOPTERYGII) What are Amiiformes?
A
- Just a single species: bowfin
- Freshwater habitats within North America, although fossil deposits suggest they were previously widespread in South America, Europe, Asia, and Africa
- Cycloid scales (more similar to those found in Teleosts)
- Long undulating dorsal fin
- Like gar, able to breathe air using a vascularized bladder/lung, permitting life in hypoxic waters
- Ambush predators of fish and aquatic invertebrates
15
Q
(IN OSTEICHTHYES - IN ACTINOPTERYGII) What are Teleostei?
A
- Infraclass
- Largest infraclass in the class Actinopterygii, wit the other two being Holostei (garfish and bowfins) and the paraphyletic Chondrostei (sturgeons and birchirs)
- ~26,000 species, 448 families, 40 orders (~96% of all fish species)
- Main difference to other bony fish is their jaw bones, which have movable maxilla and premaxilla - make it possible to protrude their jaws outwards from the mouth
