Midterm II Flashcards
What features distinguish Osteichthyans from other fishes?
- Unique pattern of dermal bones surrounding the jaw and brain case
- Presence of maxilla, premaxilla, and dentary
- Dermal bones form palate
- Dermal head bones attach to pectoral girdle (can form operculum)
- Branchiostegal rays in the floor of the gill chamber (used for suction)
- A gas-containing structure used for buoyancy or respiration (such as a swim bladder or lung)
What are the differences between Ray fins and lobe fins?
Ray finned fish ancestors presumably had similar fins to sharks with scapulacoracoid with basal and radial pterygiophores and finally fin rays. Current actinopterygii have lost most of the pterygiophores.
Ancestral Sarcopterygii had monobasal fins made of only bones (no real rays). Modern sarcopterygii (such as the tetrapodomorphs) have an asymmetrical fin skeleton closely resembling the ancestral pattern
Describe the basic features of sarcopterygii
Have primitive scale types called cosmine, made of dentine-like material. Have massive tooth plates with enamel for crushing invertebrates. Arose and radiated in devonian
What are the living types of sarcopterygii? What is the evolutionary significance of these animals? Which group is the sister group to tetrapods?
Tetrapoda, dipnoi (lung fishes) and actinisita.
The lobe fin’s bone structure is very similar to that of a tetrapod limb (gave way to tetrapod limbs). The locomote using the same opposite movement of front and hind limbs that tetrapods do.
Dipnoi, based on molecular evidence, were found to be the sister group to tetrapods
Describe the extant Dipnoi. What is special about the African Lungfish?
Dipnoi are distinguished by the loss of tooth-bearing dermal bones (maxilla, premaxilla, dentary) and fusion of palatoquadrate and chondrocranium. Have an autostylic jaw, tooth plates, choanae (nasal cavity opens to oral cavity) and fused dorsal, caudal, and anal fin.There are three types of lungfish: South American, African, and Australian. All are either facultative or obligate air breathers.
African lungfish live in flood plains where they experience a wet and dry season. During the dry season they estivate: bury into the sand and form a mucous cocoon around themselves, waiting out until the wet season.
What characterizes actinistia? Compare and contrast extinct and extant actinistia
Actinistia have lobe fins, a three lobed tail and a conservative morphology.
Miguashaia - Oldest fossil. Devonian.
Dipluris - Jurassic. Has characteristic extra lobe on caudal fin
Holophagus
Rebellatrix - Described in 2012, using fossils from Rockies. Has a very different curved caudal fin, typical of high speed swimmers.
Extant coelocanths are seen very rarely, live in caves, and have a diphycercal (bones extend through the whole length) tail, an unrestricted notochord, are ovoviviparous and lecithotrophic, have a tapetum, cosmine scales, and an electrosensory organ in the snout. They include Latimeria chalumnae, found in 1938 and Latimeria menadoensis, found in 1998.
List all the groups of actinopterygians from ancestral to derived, with a brief description of each
Polypterids (bachirs and reed fish) have many miniature dorsal fins, ganoid scales, a ventral lung, and an ancestral fin form.
Paleonisciforms were the early ray finned fishes. They had a single dorsal fin and survived until the Mesozoic.
Acipenseriforms (sturgeons) have no dermal or endochondral bone, have armour-like “scutes” along body, and are suction feeders. Eggs were traditionally used for caviar. Also includes paddlefish, which have a paddle-like Ampullary rostrum.
Lepisosteiforms (garpikes) are lurking predators with a derived crocodilian-like mouth. Their green eggs are toxic and their swim bladders are modified as lungs.
Amiiformes (Bowfins) are the sister group to the teleosts. They are very derived and have cycloid scales, mobile maxilla, Heterocercal tail, and extensive dermal bone.
Teleosts are the most derived and consist of most fish in the world
Describe the life cycle of the American eel. What type of life cycle is this?
Eggs are laid in the Sargasso Sea and the leptocephalus larva is born. These drift on the current into rivers where they develop into small glass eels. It is in these rivers where they grow and mature until they eventually become adult silver eels.
This is a catadromous life cycle.
What is the function of pharyngeal jaws?
The teeth on pharyngeal jaws allow for further breakdown of plant tissue.
However, they can be used by predators. The moray eel has mobile pharyngeal jaws with sharp teeth for grasping prey to be pulled into the mouth
Discuss Elopomorpha
Includes the primitive teleost Tarpon and the Anguilliformes (true eels). Eels have no pelvic girdle or pelvic fins. All eels have the same larval form, the leptocephalus larva.
Pug-nosed eels are typically scavengers but can use jaws to eat their way into the flesh of bottom dwelling fish (also have been shown to eat blood).
Eels live all over the world, especially in deep sea. The deep see eels include the gulpers and swallowers.
Discuss trends in jaw mobility within the Actinopterygii, using specific examples.What are the feeding advantages of this adaptation?
Early actinopterygians had amphistylic jaws that snapped shut with the help of a small adductor mandibulae muscle. Later neopterygians such as Amia Calva have a mobile maxilla with teeth on it that swings down, creating suction and stopping prey from escaping. Primitive teleosts such as Tardon would have a mobile maxilla that swings forward, creating a circular opening in the mouth with a fold of skin behind the maxilla to hold food in. More advanced teleosts such as the African cichlid Fish have a protrusible premaxilla (pushed out by maxilla) with folds of skin creating a circular gape for maximum speed and suction
Discuss aposematism and mimicry in amphibians.
Aposemitism occurs when organisms have bright colouring to advertise the fact that they are poisonous or taste gross.
It is possible for non-toxic animals to mimic the colouration or pattern of toxic species to avoid predation
What are the scientific names of soft rayed and spiny rayed fishes. Distinguish morphologically between “soft rayed” and “spiny rayed” euteleosts. Use as many characteristics as possible.
Spiny rayed fishes - Acanthopterygians. Soft-rayed fishes -
Dorsal fins: spiny rayed fishes have one spiny fin and one soft fin
Pelvic fins: are located more anteriorly in spiny rayed fishes
Cross-sectional shape: spiny rayed fishes are elongated and round, soft rayed fishes are flattened and narrow
Swim bladder: Connected to gut in soft rayed, separate in spiny rayed
Scale type: Soft rayed have cycloid scales, spiny rayed have ctenoid (spiky) scales
Discuss locomotion in fishes. Specifically mention thrust and drag
In order to move underwater, the fish must move its body back and forth, with most of the thrust coming from the fish pushing backwards on the water. Two types of drag act on a fish: frictional/viscous drag (caused by friction between body and water) and inertial drag (caused by pressure differences). Viscous drag is worse when there is a higher surface area but lower when there are no scales. Inertial drag is sensitive to the shape of the body. Streamlined shapes produce less inertial drag.
Discuss how the aquatic medium shapes the sensory systems of fishes
Underwater the lens of the eye must be spherical to allow for the cloudy light to be focused properly. At great depths, other senses must be finely tuned since there is no light.
Some fishes have phenomenal olfactory senses. Often these fishes are predators who rely on their senses other than sight to find prey?
The lateral line system is used to sense pressure changes in the water around the fish (sensing the movement of animals they may not see).
The inner ear is derived from the lateral line system and plays a big part in sensing the fish’s acceleration and place in space.
A lot of fishes can also detect electrical impulses of other fishes. Some can even create their own electricity (electric “eel”)
Mechanoreceptors are the basic receptors in several sensory systems of fishes.
Explain the structure and function of these receptors in each system (lateral line and receptors of the membranous labyrinth).
Hair cells in the neuromasts consist of one large kinocilium and tiny little stereocilia, embedded in the cupular matrix. The cupula deflects the hair cells, triggering nervous signals to quickly be sent, and when the cupula is bent in the opposite direction, there is a reduction in the firing rate of the nervous signals, allowing complex sensory information to be understood.
Each chamber of the inner ear contains an otolith, which is resting on sensitive hair cells. When the otolith moves (which occurs during acceleration and stopping of the fish), the hair cells detect this and send a signal to the brain to prevent confusion. This system also senses static equilibrium.
What evidence exists to support the view that the inner ear is derived from the lateral line system?
- Receptors are identical - hair cells
- Receptors are derived from same embryonic tissue (neuroectoderm)
- Endolymphatic duct in sharks connects to surface, remnant of surface origin
- Ear sinks below surface during embryological development
How do fish take advantage of the fact that water is a reasonably good conductor ofelectrical signals? Discuss the processes of electrogenesis, active and passive electroreception, electrolocation and electrocommunication.
Some fishes generate electricity to shock predators and prey. Whereas others generate electricity to communicate. Some predators, such as sharks, can sense the electrical impulses of others.
Electrogenesis - Achieved through modified muscle cells filled with electrocytes stacked in series. These electrolytes can have currents transmitted through them.
Passive electroreception: Detects low frequency electrical signal.
Active Electroreception: Generate a weak EOD which is then detected. Achieved by Ampullary organs and tuberous organs.
Electrolocation: Used in weakly electric fishes for navigation and communication. EOD is detected by tuberous organs and impulses from other fish detected by Ampullary organs.
Electrocommunication: EOD’s can give information about the sex, species and identity of a fish. Female fishes prefer longer EODs, so sexual selection drives that
How do cartilaginous and bony fish maintain a constant internal environment in marine and freshwater environments? Are some fish more tolerant of salinity changes?
Freshwater fish - hyperosmotic (tendency to gain water)
Saltwater fish - hyposmotic (tendency to lose water)
Kidney helps regulate water and salt balance by altering glomerular filtration rate and tubular respiration/secretion: freshwater fish secrete dilute urine and saltwater fish excrete lots of sodium.
There are two main types of salinity tolerance: Euryhaline, meaning that the organisms are tolerant to a wide range of salinities (salmon, eels, catfish), and stenohaline, meaning that the organisms have a small range of salinity tolerance (tuna, goldfish).
In what form are nitrogenous wastes excreted in various vertebrate groups? Give examples of ammonotely, ureotely and uricotely.
Excreting nitrogenous wastes primarily as ammonia is called ammonotelism, primarily as urea is called ureotelism, and primarily as uric acid is called uricotelism.
Most bony fishes are ammonotelic.
Mammals (including humans) are primarily ureotelic. Urea is synthesized from ammonia and is less toxic.
Reptiles (including birds) are primarily uricotelic. It is a semisolid waste (very little water is lost) and takes more energy than the other two.
How are fish gills adapted to extract the maximum amount of oxygen from the water?
There is a steep concentration gradient for the Oxygen exchange, a large surface area with a thin exchange surface, and a one way flow of water. The anti-parallel flow of the blood and water allows for maximum oxygen exchange to occur.
Why is it that accessory respiratory structures are best developed in tropical fishes? Describe, with specific examples, the various accessory means of respiration using atmospheric air.
Because there is very little oxygen in warm water.
Gut breathing - the stomach can be used as a site for gas exchange. An air bubble is taken into the body and then absorbed into the walls of the stomach.
The mouth can be used for air breathing, where an air bubble is held between the highly vascularized surfaces on the top and bottom of the mouth (this same process can occur in the pharynx as well).
The interior body wall can be used for gas exchange.
The labyrinth organ can be used for gas exchange.
The mudskipper uses it’s skin and operculum chamber.
Finally, the most important gas exchange structure, the lung.
Are lungs a recent product of bony fish evolution? Briefly describe the evolutionary history of lungs.
Lungs are not a recent development in body fishes. They go back all the way to the bichirs and lungfishes, two of the oldest clades of Osteichthyes.
Lungs arose both ventrally and dorsally. It arose dorsally before gars, carp, and perch. In carp and perch it is a hydrostatic swim bladder (physostomous in carp and physoclistous in perch), whereas in gars it is an aerial respiratory organ.
Lungs arose ventrally before bichirs, lungfish, and tetrapods as an aerial respiratory organ. In bichirs it is nonalveolar, contrasting with tetrapods and lungfish. Lungfish have a simple glottis and tetrapods have a guarded one.
What selective advantages favoured the fish-tetrapod transition to a terrestrial existence? Discuss the evolution of tetrapods based on fossil evidence of elpistostegid osteolepiforms. Include specific evidence based on the morphology and presumed lifestyle of Panderichthyes and Tiktaalik.
Because there weren’t many predators on land during the Devonian, the selective advantage of life on land was high. The juveniles would have less predators, there was less competition for food, and it allowed for basking onshore.
The elpistostegalians are considered the sister group of tetrapods. Two important organisms in this group are panderichthys and Tiktaalik.
Panderichthys had a dorso-ventrally flattened body, a broad, flat snout, eyes pointing ahead, no dorsal or anal fins, and a tail that is not designed for speed in water. It likely lived in shallow water.
Tiktaalik was a bit more derived. It had an elbow joint, broadly overlapping ribs (for supporting body on land), probably had lungs, but it also had gills as well. Tiktaalik actually had what could be considered a neck (no operculum or suprascapular), which was likely used to snap at prey items that were on land.
Looking at the fossil evidence of the elpistostegalians, you can see the gradual transition from fish to tetrapod. The fins slowly to develop into limbs with elbows and no fin rays. The ribs become more prominent, able to support the animal’s body. The eyes migrate to the top of the head and the body is dorso-ventrally flattened.
