Cyclostomes and Aquatic Environments Flashcards
What makes a vertebrate?
- Presence of neural tube and braincase
- Neural crest cells
- True heart
- Muscularized pharynx
- Vertebrae
- Somites
- Are animals
- Are chordates with chordates synapomorphies
- Often bigger and more active than chordates
- Have developmental processes that add complexity to their body plans
- Most vertebrates (not cyclostomes): also have mineralized tissues and endo/exoskeletal structures
What are the Cyclostomata characteristics?
- No mineralized tissues (no scales)
- 1 nostril at center of head
- Mouth opens laterally
- Branchial basket without articulations
- Gill tissue on medial side of branchial basket (internal, unlike other vertebrates)
- Velum
- Rasping tongue (teeth) supported by cartilage
- Continuous cartilage
Myxiniformes (Hagfish) characteristics
- Benthic (deep sea, marine)
- Degenerate eyes (remnants leftover, but useless for vision)
- Barbels
- Single median fin includes pre-anal component
- 1 semicircular canal
Semicircular canals detect?
Head movement
- For orientation of the head
- When head moves, liquid in semicircular canals moves around and then moves hair cells that line the canal
- Hair cells translate movement of liquid into nerve messages for brain and then brain tells the body its orientation and how to adjust it
Hagfish Feeding
- Scavengers that live inside carcasses or burrows
- Knotting - leverage (how they bite)
- Slime (feeding mechanism and predatory defence mechanism that suffocates food or pred)
Hagfish Ventilation
Ventilation supports feeding mode:
- Nostril and velum allow water flow to gills when mouth is full
- Also lower metabolic rate while feeding (hypoxia tolerance)
- Multiple hearts - standard, plus more throughout body
Osmoregulation of Marine Fishes
- Water tends to diffuse out and salt tends to diffuse in
Osmoregulation of Freshwater Fishes
- Water tends to diffuse into and salt tends to diffuse out
Hagfish Osmoconform
- Have the same amount of salt in body as seawater (though which salts differ)
- Therefore don’t need to move H2O
- Also have special cells in gills
Hagfish Reproduction
- Up too 100F:1M
- Few, large eggs with hook structure (anchoring to seafloor, unknown for sure)
- Direct development - no larval stage (unusual for fishes)
Petromyzontiformes (Lampreys) Characteristics
- Life cycle: anadromous (salmon) or potamodromous (salmon but freshwater only)
- Larvae (ammocoetes) are buried in mud
- Adult: swims and migrates, spawns in freshwater
- 2 dorsal fins, 1 caudal fin
- Pair of seeing eyes. pineal eye (third, sensor for light)
- 2 semicircular canals
Lamprey Feeding
Larvae: filter feed
Adult: parasitic or non-feeding (exists only to spawn)
Feeding adults:
- Buccal funnel is covered in keratin teeth (like tongue)
- Latch onto prey and drain up to 10% of host’s fluids/day
Lamprey Ventilation
- Pouch gills
- Larvae or free-swimming adult: flow-through ventilation (velum aids with flow)
While feeding as adult:
- Branchial contraction pumps water in/out
- Velum prevents mixing between pharynx and digestive tract
Lamprey Osmoregulation
Osmoregulators: 1/3 as salty as seawater, cells in gills exchange salts - a set for in, a set for out (since both fresh and saltwater)
Lamprey Reproduction
- Male and female build nest together (buccal funnel -> rock then move rocks)
- Lots of small eggs
