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Zoology 224 > Quiz #1 > Flashcards

Quiz #1 Flashcards

1
Q

Chondrichthyes teeth

A
  • Non-rooted teeth develop deep within skin as “tooth whorls”
  • Continuously replaced
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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%)
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3
Q

What vertebrates do you find pleurodont teeth in?

A
  • Ancestral

- Some fishes, amphibians, some lizards

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4
Q

What vertebrates do you find acrodont teeth in?

A
  • Most fishes, some lizards

- Predators

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5
Q

What vertebrates do you find thecodont teeth in ?

A
  • Crocodiles, mammals

- Embedded in sockets with mineralized cementum

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6
Q

What kind of teeth do most vertebrates have?

A
  1. Homodont - simple cones, all similar

2. Polyphyodont - continuously replaced

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7
Q

What are the types of teeth in mammals?

A
  1. Heterodont - variable structure and function

2. Diphyodont - 2 sets of teeth (humans)

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8
Q

Synapomorphies of gnathostomata

A
  • Jaws with non-replaceable teeth
  • Autostylic jaw suspension
  • Weakly developed myomeres
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9
Q

Synapomorphies of eugnathostomata

A
  • Teeth (deep-rooted and/or replaceable)
  • Amphistylic jaw suspension
  • Myomeres with epaxial and hypaxial
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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)
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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
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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
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13
Q

Mineralized endoskeleton structure

A
  1. Hagfish, lampreys, early ostracoderms: Cartilage
  2. Derived ostracoderms, placoderms: Mineralized cartilage and perichondral bone
  3. Chondrichthyes: Calcified cartilage and remnant perichondral bone
  4. Osteichthyes: Perichondral and endochondral bone
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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
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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)
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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
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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

Zoology 224 (10 decks)

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