Quiz #1 Flashcards
1
Q
Chondrichthyes teeth
A
- Non-rooted teeth develop deep within skin as “tooth whorls”
- Continuously replaced
2
Q
Osteichthyes (bony fish and descendants) teeth
A
- Teeth develop beneath skin –> rooted
- Become embedded in dermal bone
- Homologous to dermal bone and chondrichthyan scales
- Enamel and dentine hardest vertebrate tissue known (>90% mineralized with hydroxyapatite (CaP); bone ~70%)
3
Q
What vertebrates do you find pleurodont teeth in?
A
- Ancestral
- Some fishes, amphibians, some lizards
4
Q
What vertebrates do you find acrodont teeth in?
A
- Most fishes, some lizards
- Predators
5
Q
What vertebrates do you find thecodont teeth in ?
A
- Crocodiles, mammals
- Embedded in sockets with mineralized cementum
6
Q
What kind of teeth do most vertebrates have?
A
- Homodont - simple cones, all similar
2. Polyphyodont - continuously replaced
7
Q
What are the types of teeth in mammals?
A
- Heterodont - variable structure and function
2. Diphyodont - 2 sets of teeth (humans)
8
Q
Synapomorphies of gnathostomata
A
- Jaws with non-replaceable teeth
- Autostylic jaw suspension
- Weakly developed myomeres
9
Q
Synapomorphies of eugnathostomata
A
- Teeth (deep-rooted and/or replaceable)
- Amphistylic jaw suspension
- Myomeres with epaxial and hypaxial
10
Q
Generalized gnathostome synapomorphies
A
- Pelvic fin and girdle
- Three semicircular canals
- Vertebrae with neural and haemal arches
- Joined arches and gill rakers
- Hypobranchial musculature
- Two olfactory bulbs and two nostrils
- Spiracle
- Conus arteriosis (4th heart chamber)
11
Q
Chondrichthyes synapomorphies
A
- Calcified cartilaginous endoskeleton (ancestors had bone)
- Loss of dermal skeleton
- Tooth whorls
- Placoid scales
- *-Unsegmented fin rays (ceratotrichia)
- Claspers on male pelvic fins
12
Q
Osteichthyes synapomorphies
A
- Endochondral endoskeleton
- Lung/swim bladder
- Terminal mouth opening
- Dermal mouth bones with rooted teeth
- Bony ganoid scales
- *-Segmented fin rays (lepidotrichia)
- Bony operculum
- Otoliths in inner ear
13
Q
Mineralized endoskeleton structure
A
- Hagfish, lampreys, early ostracoderms: Cartilage
- Derived ostracoderms, placoderms: Mineralized cartilage and perichondral bone
- Chondrichthyes: Calcified cartilage and remnant perichondral bone
- Osteichthyes: Perichondral and endochondral bone
14
Q
Teeth
A
- Chondrichthyes and (extinct) Acanthodians: Non-rooted tooth whorls within skin; continuously replaced
- Osteichthyes: Teeth develop below skin (rooted); become embedded in dermal bone; with replacement teeth
15
Q
Scales
A
- Chondrichthyes: Placoid scales (remnants of bony dermis; dentine surrounded by “enameloid”; enameloid with ectodermal and mesodermal elements; reduces drag; reduced/absent in some bottom-dwelling skates and rays)
- Osteichthyes: Ganoid scales (ancestral), heavy enamel over inflexible bone; Elasmoid scales (derived), loss of enamel, dentine, and inflexible bone, flexible bone with thin (or no) enamel
- Scales retained in most bony fishes, some with loss of scales (e.g., catfish, eels, swordfish)
16
Q
Fin rays
A
- Chondrichthyes have “ceratotrichia” (horny rays): Develop from unsegmented, keratinized rods, epidermal; some with spines from modified placoid scales (e.g., stingrays)
- Bony fish have “lepidotrichia” (scale rays): Develop from bony scales, many segmented and paired bony elements; highly flexible; some have inflexible spines from single scale or thickened ray (may be poisonous); strong selection for or against spines depending on whether or not there are predators
17
Q
Synapomorphies of elasmobranch (chondrichthyan group)
A
- Multiple gill openings
- Pectoral fin openings
- Hyostylic jaw suspension
- Pectoral fin support
- Vertebral centra
- Ventral mouth
- Changes in nervous system, cranium, and gill arches
18
Q
Holocephali (Chimeras, ratfishes, or rabbitfishes)
A
- ~50 marine species in three families
- Fleshy operculum over four gills (one gill opening visible)
- Loss of spiracle and absence/reduction of scales
- Loss of tooth whorls, broad crushing tooth places (“durophagous” dentition - secondary autostylic jaw suspension called “holostylic”)
19
Q
Three groups of Neoselachii (extant elasmobranchs)
A
- Multiple gill openings
- Galeomorphi
- Squalomorphi
- Batoidea
20
Q
Galeomorphi
A
-Anal fins
-~400 species
-Open water (larger sharks, very active predators)
E.g., great white, thrasher, hammerhead
21
Q
Squalomorphi
A
- Sharks
- No anal fin
- ~160 species
- Benthic
- E.g., dogfish, angel
22
Q
Batoidea
A
- Skates and rays (~640 species)
- Ventral gill openings
- Dorso-ventrally flattened
- Durophagous dentition (good for crushing)
- No anal fin
- Reduced scales
- Benthis and pelagic
23
Q
Characteristics of skates
A
- Thick tail with dorsal and caudal fin
- Some skates with electric tail
- Oviparous (egg layers)
24
Q
Characteristics of rays
A
- Whiplike tail with bars instead of fins
- Sting rays and bat rays with venomous spines
- Viviparous (live birth)
25
Q
Characteristics associated with predaceous nature of chondrichthyes?
A
- Hyostylic jaw suspension, replacement teeth
- Fusiform/terete (torpedo) shape
- Heterocercal tail
- Placoid scales to reduce drag
- “Ball-bearing” notochord and calcified vertebrae - power swimming
- Buoyancy from oil-filled liver and urea in tissues (no swim bladder)
26
Q
What do most sensory systems in the chondricthyes develop from?
A
-Ectodermal placodes
27
Q
Chemoreception in the chondrichthyes
A
- “Nose with shark attached”
- Large olfactory organs
- Detect one part in 10 billion
- Follow olfactory gradient to prey? - use lateral line system to go up current
28
Q
Lateral line system (mechanoreception or “remote touch”)
A
- All craniates, except adult amphibians and amniotes
- Detects water disturbance and directionality of its source
- Currents, schooling fish, approaching stationary objects, low frequency sounds
- Can detect vibrations from struggling prey (along with inner ear)
- Lateral line system based on neuromast organs (detect direction based on electrical current - hair cells embeddedd in gel (cupula), water movement displaces gel, moves hair cell which leads to nerve discharge)
- Similar to hair cells in fluid-filled semicircular canal
29
Q
Vision in chondrichthyes
A
- Well developed, some with cones (colour vision?)
- Tapetum lucidum for low light levels (amplifies low light levels): Reflective crystal layer behind retina, also in many nocturnal mammals
- Nictitating membrane obscures vision just before contact with prey
30
Q
Electroreception in chondrichthyes
A
- Vertebrate synaponorphy
- Well developed in sharks (on head) and pectoral fins of skates and rays
- Electroreception based on ampullae of Lorenzini: Conductive gel-filled canals ending in modified hair cells of lateral line; detect minute changes in electric fields (and temperature and salinity); used for final location and detection of hidden prey
- Embryos in eggs can detect predators and will stop moving when predator is close
31
Q
Electroreception in other vertebrates
A
- Present in some “primitive” fish, independent in two teleost lineages (osteoglossomorphs and ostariophysi), independent (?) in coelacanths and lungfishes
- Retained in a few amphibians
- Independent in echidnas and platypus
- Some species can modify electric signals they give off (e.g., Mormyridae (elephant fish) modify signals for sexual signaling and foraging)
32
Q
Hammerheads and ampullae of Lorenzini
A
- Use hammerhead as more area for ampullae of Lorenzini
- Use electroreception for navigating - orient to earth’s magnetic field
- Find “seamounts” in open ocean
33
Q
Function of pelvic claspers in male chondrichthyes?
A
- Modified pelvic fin for sperm transfer - facilitates internal fertilization
- May lead to selection for high maternal investment?
34
Q
Variability in maternal investment in chondrichthyes?
A
- Oviparity (45%): Lecithotrophy (all nutrients are from egg/yolk sac)
- Viviparity (55%): Lecitrophy to matrotrophy (level of investment highly variable)
35
Q
Oviparity
A
- Egg laying
- Ancestral
- All nutrients from egg (yolk sac) - “lecithotrophy”
- Six to fifteen month development period
- Most release eggs early but a few retain them until close to hatch
36
Q
Yolk-sac viviparity
A
- Thin-shelled eggs retained in uterus until development
- All nutrition from yolk sac
- Hatch internally late in development
37
Q
Uterine viviparity
A
- Hatch internally early in development - nutrients from mother via extensions of oviduct or gut
- E.g., stingrays and eagle rays
38
Q
Oophagy
A
- Cannibal viviparity
- Mom supplies unfertilized eggs to developing embryos
- ~15 species (great whites, etc.)
- Also seen in poison dart frog
39
Q
Embryophagy
A
- Cannibal viviparity
- First to hatch in each oviduct eats siblings
- Mom also supplies unfertilized eggs
- Litter or one or two large young
- E.g., sand tiger shark
- Similar to “polyovulating mammals” - often in mammals with high mobility - keeps their balance
40
Q
Placental viviparity
A
- Yolk sac develops into vascularized placenta
- Maternal nutrients via bloodstream
- 10% of species
- Complete reliance on placenta in some
- Many marsupials and mammals with yolk-sac placenta
- Placenta in eutherian mammals from different membrane (allantois)
41
Q
Benefits of matrotrophy
A
- Viviparity common in many large species
- Large precocial young: Avoids predation and cannibalism, young are active predators at birth
42
Q
Costs of matrotrophy
A
- Most chondrichthyes have “slow life histories”
- Large body size
- Slow growth
- Long-lived
- Late sexual maturation
- Low reproductive output
- Leaves them vulnerable to overharvest
