ichthyology intro Flashcards
how many extant fish species are there and why
> 35,400
- Very big environment - ca. 70% Earth’s surface is covered by water
- Fish are old
- Fish are paraphyletic
how many species are freshwater
> 13,000 spp
5 layers of ocean depth
Epipelagic surface to 200m
Mesopelagic 200m to 1,000m
Bathypelagic 1,000m to 4,000m
Abyssopelagic 4,000m to 6,000m
Hadal Below 6,000m
what’s the deepest part of the ocean called and how deep is it
mariana trench - 11km
why do no fish exist in the deepest 25% of the oceans (deeper than 8,400 m)
Hydrostatic pressure can have severe effects on protein formation - Tri-methylamine N-oxide (TMAO) stabilises proteins - TMAO concentration increases in fish tissues with increasing depth
why are fish so old
Longer to adapt
what are jawless vertabrates called and what classes are in there
Agnathans
- Class DIPLORHINA (Double nostril - all extinct)
- Class CEPHALASPIDOMORPHI (previously known as Monorhina or single nostril) - most extinct, 48 extant spp.
what orders are apart of Agnathans
- Order Petromyzontiformes – lampreys (Class MYXINI (also have a single nostril) - most extinct )
- Order Myxiniformes - hagfish, 88 extant spp.
lamprey characteristics
- Mainly freshwater
- Most are ectoparasites
- Some have adult life in sea, returning to freshwater to breed -> anadromy (anadromous)
what is anadromy (anadromous)
have adult life in sea, returning to freshwater to breed
what is Diadromy (diadromous)
migration between freshwater + seawater
The principal feeding and growing biome differs from the reproductive biome
what is Catadromy (catadromous)
fish that live in freshwater and return to sea to breed
hagfish characteristics
- All marine, benthic scavengers
- No adhesive sucker, but rasping ‘tongue’
- Only vertebrate with blood isotonic to seawater
- No vertebrae!
- Famous for producing slime – v effective defence
what are vertebrates with jaws called
Natha
what does a Hypothetical intermediate condition of a fish jaw include
- Premandibular arch
- Mandibular arch (upper portion + lower portion)
- Hyoid arch - remains as hyoid arch –> difference between fishes + tetrapods is how this arch is associated with the cranium (hanging off or attatched)
- Pharyngeal clefts remain as gill slits
what’s the Premandibular arch
frontal arch - lost through evolution
what’s the Mandibular arch and the upper and lower portion
becomes biting jaws
- upper portion = palatoquadrate cartilage
- lower portion = Meckel’s (or mandibular) cartilage
what’s the Hyoid arch
remains as hyoid arch –> difference between fishes + tetrapods is how this arch is associated with the cranium (hanging off or attatched)
main difference between fishes + tetrapods
how the hyoid arch is associated with the cranium (hanging off or attatched)
what are Pharyngeal clefts
remain as gill slits
what parts of the hypothetical intermediate condition of a fish do Chondrichthyans posses
- Hyoid arch suspends hyomandibular arch from cranium – no direct contact – jaws are mobile
-upper part = palato-quadrate
-lower part - ceratohyal - 1st gill slit becomes Spiracle
how is the hyoid arch associated with the cranium in fishes + tetrapods
fishes = not fused to the skull (mobile)
tetrapods = fused to skull
what is Amphistyly
- Primitive condition, all from fossil record
- Support from autostyles and hyomandibular arch
- Acanthodii and Placodermi
what is Holostyly/Autostyly
- Palato-quadrate fused to skull
- Dipnoans, chimaeras, tetrapods
what is Hyostyly
- Support from Hyomandibul
- Jaw not directly connected to skull
- typical Chondrichthyes
2 subclasses in Class Chondrichthyes (sharks & rays)
- Sub-class ELASMOBRANCHII (1,279* extant spp.)
Sharks, Skates, Rays - Sub-class HOLOCEPHALI (55 extant spp.)
Chimaeras
how many orders are in Sub-class ELASMOBRANCHII and what are the main ones
13 orders
- CARCHARINHINIFORMES (304 spp.)
cat sharks, hammerhead sharks…
Includes Family CARCHARHINIDAE (requiem sharks; 59 spp.)
- LAMNIFORMES (16 spp.)
Mackerel sharks (threshers, makos, basking, tigers, white)
- MYLIOBATIFORMES (257 spp.)
Sting rays, devil rays
- RAJIFORMES (311 spp.)
Rajid skate and rays
Chondrichthyes characteristics
- cartilaginous fish
- 1,334 extant spp
- no bone
- spiracle
- no operculum
- no swim bladder
- ampullae of Lorenzi
- spiral valve
- placoid scales (denticles)
- internal fertilisation
Osteichthyes characteristics
bony fish
- 33,969 extant spp
- true bony skeleton
- no spiracle
- operculum covering gills
- swim bladder
- no electro receptors
- no spiracle valve but pyloric caecae
- overlapping scales
- mostly broadcast spawners
2 classes of Osteichthyes (bony fishes)
- Class SARCOPTERYGII (8 spp.) - lobe-finned fish
Actinistia - coelacanths (2 spp.)
Dipnomorpha - lungfish (6 spp.) - ACTINOPTERYGII (33, 920 extant spp.*) - ray-finned fish
Subclass CHONDROSTEI (sturgeons, paddlefish…)
Infraclass HOLOSTEI (bowfins, gars…)
Infraclass TELEOSTEI (96% of all living fish)
what are “Lower” teleosts and “higher” teleosts called
“Lower” teleosts = euteleosts
“higher teleosts” = neoteleosts
lower teleosts characteristics
- soft fin rays
- 1 dorsal fin (maybe adipose)
- low pectoral fins
- horizontal pectoral fin base
- abdominal pelvic fins
- pelvic fins with numerous rays
- scales usually cycloid
- swimbladder often physotomous
higher teleost characteristics
- may also have spiny fin rays
- 1 or more dorsal fin
- higher pectoral fins
- pectoral fin base angled towards vertical
- pelvic fins thoracic or jugular
- pelvic fins with less rays
- scales usually ctenoid
- swim bladder physoclistous
