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ZOOL403 > Chondrichthyes > Flashcards

Chondrichthyes Flashcards

1
Q

Chondrichthyes include

A

sharks, skates, rays, chimeras
- Mostly marine, some freshwater, few both
- 1,300 spp

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2
Q

Chondrichthyes Synapomorphies

A

1) Calcified cartilage (in plates called “tesserae”)
2) Replacement teeth
3) Placoid scales (“mini teeth”)
4) Ampullae of Lorenzini (sense electric fields)
5) Pelvic claspers on males

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3
Q

Calcified Cartilage - in plates of “tesserae”

A
  • Skeletons are entirely cartilage
  • Sharks don’t have dermatocranium
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4
Q

Replacement teeth

A
  • Continuously replaced teeth that are replaced about the same time they become dull
  • Movement of replacement teeth is a conveyor belt, teeth move forward and flip up
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5
Q

Placoid scales - “Mini teeth”

A
  • Have an internal structure of teeth unlike other bony fish
  • Structures vary over the body of a shark and different species.
  • Have hydrodynamic function, helps deal with drag by holding layer of water near skin
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6
Q

Ampullae of Lorenzini

A
  • Organ that senses electric fields
  • Inside pores = jelly that is electrically conductive and then tube/cells that senses signals
  • Used for looking for prey (muscles/things buried) and align mouth onto prey for eating
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7
Q

Pelvic claspers on males

A
  • Part of the reproductive system
  • Modified pelvic fin
  • Groove along side where sperm travels, only use 1 clasper at a time during reproduction
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8
Q

Holocephali

A
  • Chimaeras (ratfishes or ghost sharks)
  • Deep water, bottom dwellers (eat shelled stuff)
  • Swim by flapping pectoral fins (“underwater flight”)
  • Narrow tail
  • Operculum - covers gills so there’s a single opening (instead of gill silts), ventral
  • Cephalic clasper (males) - forehead extension, spiky protection, reproductive positioning
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9
Q

Elasmobranchii

A
  • Sharks, skates, rays
  • Name means “plate gills” - have gills with dividing sheet of tissue in between, leads to 5-7 silts
  • Most have 1 gill/branchial arch
  • Spiracle (cart fish only), hole into pharynx on cranial + dorsal side, respiratory
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10
Q

Elasmobranchii: Selachii

A
  • Sharks
  • Variety of feeding modes: swimming predators (bitting or ramming), filter feeders (special case of ramming), benthic feeders (suction)
  • Tend to have heterocercal tails = functional consequences -> creates forces move forward + up, problem of staying upright when swimming, counteracted by swimming with head up, tail down
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11
Q

Elasmobranchii: Batoidea

A
  • Skates and rays
  • Dorsoventrally flattened
  • Can be in water column (flapping swim) or benthic (undulation swim)
  • Mouth and gill slits on ventral side
  • Same swimming pattern as sharks
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12
Q

Autodiastylic suspension (ancestral)

A
  • 2 major connections
  • One connection is cranial and ventral to eye on palatoquadate
  • Other connection is caudal and ventral to eye on palato quadrate
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13
Q

Holostyly suspension

A
  • New 2nd association is between the hyoid arch and the mandibular arch (b/w and just caudal to palatoquadrate and Meckel’s cartilage (lower jaw) connection)
  • Connection that was caudal to the eye is gone
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14
Q

Holostyly in real skulls

A
  • Sharks and rays - jaws can protrude, palatoquadrate can swing forward
  • Chimaera - no protusion, palatoquadrate fused to skull
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15
Q

Amphistyly - considered a variation on holostyly

A
  • 3rd connection posterior to eye
  • More common among extinct spp
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16
Q

Cartilaginous fishes use a variety of senses

A
  • Scent, vision, hearing
  • Electroreception
  • Pressure sensing (lateral line and also on head)
17
Q

Sensory systems are used in a stereotyped sequence

A

1) Olfactory
2) Lateral line
3) Vision + hearing
- Electro + mechano (lateral line + touch)

18
Q

Ventilation

A
  • Water flows into mouth or spiracle, over gills, and out slits
  • O2 exchange also skin but v little %
  • Ram ventilators - must continuously swim (open ocean spp)
  • Or have a pumping system (most sharks)
19
Q

Fishes use counter-current oxygen exchange

A
  • Water and blood flow in the opposite directions, max extraction: >90%
  • Over the entire length of secondary lamellae
20
Q

What advantage does countercurrent exchange have over concurrent?

A
  • Extracting more O2
  • Less O2 in water than in air
  • Must efficiently extract O2
21
Q

Some species have more secondary lamellae surface area than others. What advantage might this provide, and what kinds of lifestyles would this support?

A
  • More surface area for O2 exchange/diffusion
  • More active lifestyles
22
Q

Cartilaginous fishes are osmoregulators

A
  • Actively control salt amounts in body
    Managing water:
  • Total salt content = total salts in seawater (no water movement)
  • Retain urea, stabilized with TMAO (helps prevent urea from negatively affecting body tissues)
    Managing salts:
  • Less Na+ and Cl- in body than seawater, so salts diffuse in
  • Rectal gland: connected to intestine, extracts Na+ and Cl- and secretes into intestine for excretion
23
Q

Cartilaginous fishes use internal fertilization, via pelvic claspers

A
  • Cloaca: shared opening to gut and reproductive tract (on female for internal fertilization, males also have one)
24
Q

Cartilaginous fishes use 3 incubation strategies

A

1) Oviparity
2) Viviparity
3) Ovoviviparity

25
Q

Oviparity

A

Standard egg-laying

26
Q

Viviparity

A
  • Live birth
  • Embryo attaches to uterine wall and has umbilical cord (mammals)
27
Q

Ovovivparity

A
  • Combination of oviparity and viviparity
  • Lays eggs internally, hatch internally, then live birth
  • Siblings may attack each other internally, also eat unfertilized eggs
28
Q

Cartilaginous fishes (esp sharks) are vulnerable to overfishing

A
  • Often apex predators
  • Slow birth and growth rates (few offspring produced at one time) = replacement rates are very slow
  • Indirect consequences to loss of sharks -> food chain/trophic levels affected

ZOOL403 (13 decks)

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