Fishes and Amphibians Flashcards
Living my jawless fishes are known as …
And include what species?
Cylcostomata
(Round mouth)
Hagfish
Lampreys
What is a fish?
Aquatic vertebrate will gills, appendages in the form of fins (if present), and usually the skin is covered in scales
Fish vs fishes
Fish refers to one or more individuals of a species
Fishes refers to more than one species
What species with fish like names are not actually fish
Jellyfish, starfish, crayfish, shellfish
Specific challenges of aquatic environment
-water is 800 times denser than air
-most fished adjust to salt and water balance of environment
-gills extract oxygen from water (water has 1/20th of the oxygen in air)
Clade Cyclostomata specific adaptations for hagfishes and lampreys
Hagfish: knot tying and slime
Lamprey: parasitism, best building
When did Cyclostomata appear
Ancient fishes that hbu exchanged little over 400-450 my
External characterisitcs of jawless living fish
-body is slender and eel like
-skin naked (no scales)
-caudal fin
-pore-like hill openitna
-distinct head: tripartite Brian encoded in cartilaginous skull
What do jawless fish not have?
Jaws, paired nostrils, paired fins, mineralized tissues (bone, teeth)
Hagfish and lamprey internal characteristics
-adults have notochord
-rudimentary vertebral elements (cartilage)
-pharyngeal muscles power gills for respiration
-keratinized “teeth” structures on tongue or oral hood (lamprey): not real teeth
Nostril in hagfishes and lamprey
Nasohypophyseal opening
One nostril that contains olfactory epithelium to smell. The opening for the nostril connects to the pharynx, so that hagfishes CNS breathe through their nostril!!!
In lampreys too( but does not connect to pharynx so lampreys cannot breathe through nostril
Posterior to the nasal sac in hagfishes is the ______
Adenohypophysis (anterior pituitary)
Barbel
Whisker like sensory organ in hagfish
Lamprey features not present in hagfish
Dorsal fun
Eyes are more developed in lamprey (pineal eye)
Habitat of Hagfish
Marine, worldwide
Deep water
What are hagfishes overfished for
Eel leather or food
Hagfish feeding
Scavengers: large numbers of hagfish are quickly attracted to the smell of dead or dying fishes or other animals (whales), enter body of animal.
Use keratinized “teeth” on tongue to rasp bits of flesh from prey
Tie into knot
How do hagfish escape capture
- Tie themselves in knots for leverage to heal press or escape
- Slime!!!! To choke prey. Scrape off with knot after (produces from muscles glands)
Hagfish slime parts
-70-200 slime glands secrete mucin (mucous) and protein threads, each contained in separate cells
-when they contact water, Mucin absorbs water and threads unfurl to bind mucin into continuous mass of slime
How do hagfish reproduce
-not much known: don’t reproduce in captivity
-females outnumber 100 to 1, some are heterotrophic
-females produce yolky eggs that attach to the bottom of sea
-eggs take 5 months to hatch into hagfish: no larval stage
Latin name for lampreys means what?
Rock licker
Petromyzontiformes
Lifestyle of lampreys
Anadromous
Live as adults in oceans or large lakes, ascend rivers and streams to breed, then die
Lamprey feeding
Most are parasitic (adults)
-use suction of oral hood to attach to host
-sharp keratinized teeth and rasping tongue drill hole
-oral gland secretes anticoagulant
-don’t kill host, but leave weakened
How do lamprey respirate
Flow through ventilation: applies to larva and adult not attached to prey: draws water into mouth and pumps out through gills
Tidal ventilation: when attached to host, acquire oxygen by moving water in and out of gills
Characteristics of non-parasitic lamprey
-small (<20cm)
-inhabit small streams
-poorly developed teeth
-brief adult period (<6 months)
-don’t feed as adults
-spawn, then die
Northern Brook lamprey
3 Manitoba species of lamprey
-chestnut (parasitic)
-silver (parasitic)
Both above about 35cm
-northern brook (non parasitic)
Lamprey nest building and spawning
-male begins building nest, and is joined by the female
-use oral hood to life rocks, and vibrations to remove debris
-female lays eggs and male fertilize
-monogamous
-die after spawning
How do male Lamprey attract females and mate with them
-Male dorsal adipose ridge tissue that heats up 0.3° when female is present: Rope tissue
-pheromone to attract females to area
-Thermogenic secondary sex characterisitc
-males rub rope tissue over females abdomen and if she agrees she will rub her Urogenital pore against the tissue in return.
-male then wraps around her tightly, bites onto her head and locks into her by tying a knot with tail.
-both release sex cells together and fall into nest
Lamprey life cycle steps
- Large number of small eggs hatch, larvae leave nest at 1cm long and burrow into sand (Ammocoetes)
- Ammocoetes live sedentary in fresh water burrows and filter feed for 3-7 years
- Metamorphosis: over two months, become parasitic
- Parasitic growing stage: emerge as small (13cm) adults. Lasts 1-3 years and they feed on large fish
- Reproduce and die in streams
Sea lamprey effect on Great Lakes
-originally only in eastern lakes, but human made canals connected them to all 5 of the great lakes
-negative effect on native fish species starting 1930 and still today
-Trout population diminished
Sea lamprey control methods
Larvacides: chemicals to reduce larvae in spawning streams
Possibility of using pheromones to attract females away from males or trap them
Most modern day fish, except the lampreys and hagfish are part of the Clade called _________
Gnathostomata
Jawed vertebrates
Conodonts
Soft-bodied animal with mineralized teeth (high proportion of hydroxyapatite, which gives harness to teeth)
Extinct jawless fishes
When were conodonts around
300mya
Ostracoderms characteristics
Groups of jawless fish
-Dermal armours (exoskeleton) in form of large plates that cover head and sometimes the pectoral region or covered a portion of the body
-jawless
-more derived forms had paired pectoral fins (no paired pelvic fins)
Ostracoderms time period
-orodovician (period followed the Cambrian until end of the Devonian)
Mass extinction at end of Devonian wiped them out
Placoderms
-plate like dermal armour covering the front 1/3 to half of the body
-paired pelvic and paired pectoral fins
-lower jaw resembles jawed vertebrates
-inner ear with 3 semicircular canals
-external organs (clasper)
-presence of an external reproductive organ (internal fertilization)
Example species of Placoderms
DUNK
Are placoderms true Gnathostomes
Yes - bones forming upper had are homologous to bones in gnathostome jaw
When did placoderms go extinct
End of Devonian in mass extinction
Evolution of the jaw
- Basal gnathostomes: placoderms. Lower jaw resembles gnathostomes
- More derived placoderms: have a maxilla and pre maxilla bones in upper jaw
- Cartilaginous fishes (lost bony skull)
- Crown gnathostomes: include ray-finned and lobe-finned fish (includes tetrapods)-retain bony skull and these are refined
Phylogeny of early vertebrates
- Cyclostomata: lamprey and hagfishes: evolutionary oldest extant vertebrates
- Conodonts: jawless, with mineralized teeth, long fossil record into Mesozoic
- Ostracoderms: jawless, abundant; extinct by end of Devonian
- Placoderms: jaws, abundant until end of Devonian
Advantages of paired fins
-thrust, steering and stability in three dimensions
-tail fin-> primary thrust
-Anal and dorsal fins->lessen rotation or side to side swing
-pectoral and pelvic -> control vertical tilt; act as brakes, occasional thrust
Dermal bone
Ossification of cells of skin with no cartilaginous precursor
-forms exoskeleton
-head shield or scales of ostracoderms
-most of our skull plates
Endochondral bone
-Begins as cartilage, then ossifies
-forms Endoskeleton
-vertebrae of bony fish and tetrapods
-fin or limb bones in fish or tetrapods
Are fin rays dermal or Endochondral
Dermal
Jaws enabled what?
Active foraging
Supported higher levels of activity
Predators to capture prey that are larger than themselves
Upper and lower jaws develop from _____
Hyoid develops from
Pharyngeal arch (Mandibular arch)
2nd arch (hyoid arch) and helps brace jaws
Jaws and nostril development in Cyclostomes and Gnathostomes
Single nasohypophyseal placode blocks migration of Mandibular tissue around mouth
-one opening and placode for nose and anterior pituitary
Separation between 2 nasal palcodes and hypophyseal placode
-gives room for Mandibular cells to migrate and form upper jaw
The fossil record supports the hypothesis that jaws cannot develop until ……
Two nostril have formed with a separation in the location of the anterior pituitary
Need 2 nasal openings and separated anterior pituitary
Why did jaws arise
- Enable animals to prey on large and active animals
- Improved ventilation- changes in Mandibular arch made it possible for fish to close their mouths. Closure of the mouth may have been an early step in creating a “double-pump” system of hill ventilation still used in jawed fishes today.
Chondrichthyes
Cartilaginous fishes
-ancient group appearing before Devonian
-living forms are highly derived
-about 1200 extant species in 2 lineages
2 lineages of Chondrichthyes
Elasmobranchii: sharks, skates, rays
Holocephali: chimeras
Elasmobranchii skeleton, and teeth, and body covering
-cartilaginous skeletons with crystalline calcium including the skull: chondrocranium
-loss of dermal bone:
-teeth and placoid scales: thick tough mineralized scales known as placoid scales or dermal denticles. Teeth evolved from the dermal placoid scales
Elasmobranchii respiration
Gills to absorb oxygen from the water
-5 full slits on both sides of the body
-spiracle: water pumped into small hole behind eye as another way for water to enter body.
Elasmobranchii and an _______ mouth
What helps Elasmobranchii locomotion
-fusiform shape: streamline body and placoid scales reduce drag
-heterocercal tail: vertebral column extends into dorsal lobe of tail
-enormous oily bodies in liver reduce density as sharks otherwise sink due to heavy body and no gas bladder
How do Elasmobranchii deal with their loss of teeth
Teeth replacement
-Polyphyodont: continual teeth replacement.
-sharks replace teeth every 8 days
-Tooth whorl: conveyer belt of new teeth ready to go behind current teeth
Jaw suspension and profusion of Elasmobranchii
-hyostalic jaw suspension: derived form of jaw suspension in which the upper jaw moves independently of the cranium
Advantage: animal expands and protrudes jaw giving it ability to catch larger prey
Gaelomorphii shark: Whale shark
-up to 19m in length: largest non-mammalian vertebrate
-mostly filter feeder of Plankton
-
Galeomorphi shark: Hammerhead Shark
-distinct head serve to enhance directional sensitivity of neuromasts (lateral line) and electro receptors in ampullae or olfaction
-grow more than 6M
Gaelomorphii sharks: walking sharks
-walk around on sea floor bottom on search of small crustaceans or fish
Squalomorphii sharks: Greenland shark
-longest life expectancy of vertebrates at 392 years
-reach sexual maturity at 150 years
-can grow larger than 6.5m
-slow swimmer with presumed slow metabolic rate
Squalomorphii shark: cookie cutter shark
-<50cm long
-deep water
-feeds by biting pieces of flesh of sharks, tuna and dolphins
_____% of Elasmobranchii are….
Skates and rays
Habitat and body form of rays and skates
-sea floor life
-dorsal-ventral flattened body: enlarged pectoral fins for locomotion
-mouth and gills on ventral side, spiracle on dorsal side
-flattened teeth for crushing crustaceans, molluscs and echinoderms
Skates vs rays
Skates:
-rounder body
-long, thick tail with two dorsal fins and one caudal fin
-oviparous (egg laying)
Rays:
-kite body shape
-thin, whip lash like tail
-fins replaced by enlarged serrated, venomous barbs
-viviparous
Holocephalli: the chimeras unique traits
-live in deep water
-dense concentration of mechano and electro receptors on head and rostrum to detect prey
-3 pairs of continuous growing flat tooth plates
-mixed diet of crustaceans, echinoderms and fishes