Chapter 3 -Early Vertebrates Flashcards Preview

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Flashcards in Chapter 3 -Early Vertebrates Deck (34):

(Myxinoidea - Hagfish) - External Features

- Elongated, scaleless, and pink or purple in color
- Large mucus glands that open through the body wall to the outside (to deter predators)
- Single terminal nasal opening that connects to the pharynx


(Myxinoidea - Hagfish) - Skeletal

- Have a cranium, but lack vertebrae


(Myxinoidea - Hagfish) - Sensory

- Only one semicircular canal on each side of the head
- Rudimentary eyes with thick skin


(Myxinoidea - Hagfish) - Feeding and Digestion - Morphology

- Mouth is surround by six tentacles (barbels) (how you can tell the difference between Hagfish and Lamprey)
- Two horny plates in the mouth that have sharp tooth like structures


(Myxinoidea - Hagfish) - Feeding and Digestion - Behavior

- Primarily scavengers
- Feed in large numbers
- They can tie a knot in their tail to situate prey for feeding
- A mucoid sac envelopes the food, enzymes digest it, and waste gets secreted within the sac


(Myxinoidea - Hagfish) - Excretory

- Body fluids are the same as the environment (iso-osmotic)
- Primitive kidney with no collecting ducts


(Myxinoidea - Hagfish) - Respiratory

- 1-15 external gill openings
- External gill opening is posterior, almost mid-body (enables them to breathe while burrowed head first in the sand)


(Myxinoidea - Hagfish) - Cardiovascular

- Large blood sinus
- Low blood pressure
- True heart with 3 chambers
- Accessory hearts (help pump blood) in the liver and tail (one of the only vertebrates that still have accessory hearts)
- Aneural hearts - the pumping rhythm of the heart is intrinsic instead of being controlled by the CNS
- Red blood cells that contain hemoglobin
- Note: True heart and red blood cells containing hemoglobin are features that are derived characteristics for Craniata (everything from Hagfish on, have these features)


(Myxinoidea - Hagfish) - Reproduction

- Sex ratio 100:1 females to males
- Some species are hermaphoditic
- Eggs are oval (~1cm long) and encased in a tough, clear covering that is secured to the bottom of the ocean floor by hooks


(Myxinoidea - Hagfish) - Development

- No larval stage (direct development)
- Embryos do possess the neural crest


(Myxinoidea - Hagfish) - Ecology

- Distirbution: Nearly worldwide, except polar regions
- Habitat: Deep oceanic water inhabitants that burrow into the sand
- Some species live in colonies and tend to live and breed locally


(Extinct, Jawless, Soft Bodied Fish - Myllokumingia and Haikouichthys)

- Characters of both
- Fossils found from the Early Cambirum in China
- Small (~3cm), fish-shaped
- Cranium
- W-shaped myomeres (vertebrate feature)
- Dorsal fin and ribbon like ventral fin
- Paired sensory structures in the head
- Segmental structures flanking the notochord

- Characters of just Haikouichthys
- Lamprey-like cartilaginous gill supports


(Petromyzontoidea: Lampreys) - External Features)

- Similar in size and shape to Hagfish
- Single nasal opening


(Petromyzontoidea: Lampreys) - Skeletal - Arcualia

Primitive cartilaginous elements that are the precursor to true vertebrates


(Petromyzontoidea: Lampreys) - Sensory

- Two semicircular canals
- Eyes are large and well-developed


(Petromyzontoidea: Lampreys) - Feeding and Digestion - Morphology

- Round mouth
- Oral hood- fleshy funnel, which is studded with horny conical spines
- Protrusible tongue-like structure
- Oral gland secretes an anticoagulant
- Digestive tract is straight and simple


(Petromyzontoidea: Lampreys) - Feeding and Digestion - Behavior

- Parasitic on other fish
- Some species have non-feeding adults


(Petromyzontoidea: Lampreys) - Excretory

- Chloride cells in the glands and well-developed kidney regulate ions, water, and waste


(Petromyzontoidea: Lampreys) - Respiratory

- Seven pairs of gill pouches open just posterior to the head k
- Tidal ventilation - water is both drawn in and expelled out through the gill slits (most fish use a flow-through ventilation (through mouth - out gills))
- Velum - a flap that prevents the water from flowing out of the respiratory tube into the mouth


(Petromyzontoidea: Lampreys) - Cardiovascular

- Accessory hearts are lost


(Petromyzontoidea: Lampreys) - Reproduction - Anadromous

Live as adults in oceans or big lakes and ascend rivers and streams to reproduce


(Petromyzontoidea: Lampreys) - Reproduction - Semelparous

Reproduces a single time before it dies


(Petromyzontoidea: Lampreys) - Reproduction - Nesting

Males and females make a nest together


(Petromyzontoidea: Lampreys) - Reproduction - Eggs

Females produce hundreds to thousands of eggs, which are ~1mm in diameter and lack a protective covering


(Petromyzontoidea: Lampreys) - Development

- All have larvae (ammocoetes) that hatch in about two weeks
- 7-10 days after hatching, ammocoetes (6-10mm long) leave the nest and currents carry them downstream to quiet banks of the river or stream
- Larvae spends 3-7 (17?) years burrowed into sand as a filter feeder
- Once the larvae reach 10 cm in length, it begins metamorphosis into a parasitic juvenile
- Migration back to adult habitat doesn't occur until the spring following metamorphosis
- Adult stage last for 1-2 years


(Petromyzontoidea: Lampreys) - Ecology

- Distribution: Cooler waters in the northern and southern hemisphere
- Habitat: Adults in oceans and big lakes. Larval stage in streams and rivers.


(Petromyzontoidea: Lampreys) - Human Interaction

- Petromyzon marinus, the sea lamprey, was indigenous to Lake Ontario, but became an invasive species to other great lakes through the Welland canal


(Extinct Jawless Fish: Conodontia) - Vertebrate Characters

- Myomeres
- Notochord
- Cranium
- Large eyes


(Extinct Jawless Fish: Conodontia) - Unique Characters

- Conodont elements - small spine-like structures composed of apatite that are similar in their microstructure of dentine and thought to be tooth-like structure


(Extinct Jawless Fish: Conodontia) - Derived Characters

- Covering of dermal bone
- Cerebellum in the hindbrain
- Olfactory tract connecting the olfactory bulb to the forebrain
- Lack jaw, but some had movable mouth plates
- Most have midline dorsal fin (HUGE DEVELOPMENT)


Basic Gnathostome Design Characteristics

- Jaws formed from the mandibular gill arch.
- Gill skeleton consists of jointed branchial arches and internal gill rakers
- Hypobranchial musculature
- Two distinct olfactory tracts leading to two distinct nostrils
- Three semicircular canals in the inner ear
- Conus arteriosus in the heart
- Horizontal septum divides the epaxial and hypaxial portions of the muscles
- Vertebrae now have a centra and ribs
- Most have a well-developed heterocercal caudal fin


What new behaviors did jaw allow?

- New feeding behaviors
- Allows for digging holes
- Create nests with pebbles and vegetation
- Grasp mates during courtship or juveniles during parental care


Extinct Jawed Fish: Placoderms

- Bony Shield
- Covered 1/2-1/3 of anterior portion of their bodies
- Head and trunk portions were separated by a mobile joint

- Primarily marine, but also lived in freshwater and estuaries (area between freshwater and saltwater)
- Myomeres are weakly W shaped and are not separated by a horizontal septum
- 7 intrinsic eye muscles (most gnathostomes have 6)
- Nerve lack myelin sheaths
- Semidentine - type of cellular hard tissue in their dermal bodies
- Internal fertilization
- Primarily bottom dwellers


Extinct Jawed Fish: Acanthodians

- Stout spines anterior to their well-developed dorsal, anal, and paired fins
- Up to six pairs of ventrolateral fins
- Early forms were marine, but the clade is mostly freshwater
- Slender bodies with a basic fusiform shape and hetercercal caudal fin
- Habitat was midwater (not bottom dwellers)
- Shark-like teeth