Fishes Lecture Flashcards
Cyclostomata synapomorphies
Circular mouth
Single median nostril
Branchial basket
Velum
Rasping tongue supported by cartilage (lingual cartilage)
Myxiniformes anatomy and ecology
Degenerate eyes
Barbels
Single semicircular canal situated at an angle
Vary in gill slits
Single median fin
Direct development
Petromyzontiformes anatomy and ecology
2 dorsal fins
Caudal fin
Eye
Pineal eye
Buccal funnel
2 semicircular canals
Indirect development (larval stage)
Ectoparasitic
Anadromous
Myxiniformes metabolism and tonicity relative to environment. Why?
Low metabolism, osmoconformers. Cannot support active transport needed to have a different tonicity relative to their surroundings
Petromyzontiformes metabolism and tonicity relative to environment. Why?
Higher metabolism, osmoregulators. Are able to support active transport between environment and tissues
What can you infer about the Petromyzontiform kidney?
Used to help osmoregulate
Why is it important for Petromyzontiformes to be osmoregulators?
Relative salt concentration between tissues and environment changes between life stages. Juveniles are found in fresh water and must transport salt into their tissues and vice versa for adults
What traits do gnathostomes have that cyclostomes do not?
Paired fins and limbs
Increase in metabolism
Larger forebrain (receives more sensory info)
3 semicircular canals
Lateral paired gills rather than midline
Mineralized tissues (bones, teeth)
Paired nasals
Jaws
Describe the development of paired nasals in gnathostomes
In gnathostomes, the nasohypophyseal plate has split into two nasal placodes and the adenohypophyseal placode. This splitting allowed the mandibular mesoderm to migrate farther into the head along with the mandibular neural crest cells to form the upper and lower jaws
What is developmental bias/constraint? Give an example
Due to development, not all morphological variation is equally probable.
Ex. mandibular mesoderm could not migrate with neural crest cells due to nasohypophyseal plate in Cyclostomata, so it was unlikely for them to develop two nasal passages
What are the developmental contributors to the vertebrate skull?
Neural crest cells and the mesoderm + neural crest cells
What type of cell is an osteocyte?
A cell that makes bone
What type of cell is an osteoblast?
A cell that makes osteocytes
What type of cell is an osteoclast?
A cell that destroys osteocytes
What are the bone types of the vertebrate skull?
Dermal bone and endochondral bone
What is endochondral ossification?
The process of developing bone from existing cartilage
What are the developmental contributors, bone types, and functions of the chondrocranium?
Neural crest cells + mesoderm, endochondral bone, functions as a brain case
What are the developmental contributors, bone types, and functions of the dermatocranium?
Neural crest cells, dermal bone, functions as the covering of the brain case and palate of the mouth
What are the developmental contributors, bone types, and functions of the splanchnocranium?
Neural crest cells, endochondral bone, supports gill arches and throat plus helps in the formation of jaws
Where is dermal bone found in the vertebrate skull?
Dermatocranium
Where is endochondral bone found in the vertebrate skull?
Chondrocranium and splanchnocranium
What is the biggest difference in the ventilation structures of a Lamprey and a Hagfish?
Hagfishes have a nostril that connects to the oral cavity. The nostril of a Lamprey does not connect to its oral cavity.
What happens in the development of Cyclostomes that causes them to not form jaws?
The nasohypophyseal placode blocks the migration of of mandibular tissue toward and around the mouth.
What do the premandibular/mandibular mesoderm form from?
Neural crest
Where does Hox gene expression stop?
Stops at the anterior end of the mandibular arch. Only present posterior to the jaws.
What is the purpose of barbels in Hagfish?
Used for sensation of water currents and food
What is unique about Hagfishes compared to Lampreys?
Hagfish do not have any neural arches and Lampreys do
What is the difference in gill position between Cyclostomes and Gnathostomes?
-Cyclostomes have gills that are MEDIAL and the gill arches (support) are LATERAL.
-Gnathostomes have gills that are LATERAL and gill arches (support) that are MEDIAL.
Where is the Nasopharyngeal duct located in Hagfishes?
Between the nostril cavity and the pharynx
What type of ventilation do adult Lampreys use?
Tidal ventilation
What parts make up the Lamprey mouthparts?
-Hood (for sucking)
-Longitudinal lamina (biting)
-Transverse lamina (rasping)
Are the mouth structures of a Lamprey mineralized?
No, they are keratinous
What part of a fish would a parasitic Lamprey attack and why?
The gills, because they are easily accessible and have high blood flow
What is the function of the lateral line in fishes?
Canals with openings that are innervated used to detect water currents
What osmoregulatory challenges does a freshwater teleost face?
An environment that is hypotonic to the fish. Na and Cl are actively transported into the fish and the fish produces copious amounts of dilute urine
What osmoregulatory challenges does a marine teleost face?
An environment that is hypertonic to the fish. Na and Cl are actively transported out of the fish and small amounts of concentrated urine are produced.
What two structures are homologous across all Gnathostomes?
-Hyoid arch
-Jaw arch
What are the 3 dimensions of swimming?
-Pitch (up and down)
-Yaw (left and right)
-Roll (circular)
How does a heterocercal tail affect a fishes swimming?
It pushes the fish upwards
How are the fins made during development?
Somites migrate into the limb buds to form fins/limbs
What part of the cranium never forms in Chondrichthyans?
Dermatocranium. Only the Chondrocranium and Splanchonocranium form.
What is the lower jaw known as in Chondrichthyans?
Meckel’s cartilage
What are the 3 types of jaw suspension?
-Autostylic (palatoquadrate is fused to chondrocranium)
-Amphistylic (upper jaw is connected to chondrocranium by a ligament)
-Hyostylic (jaws are rotated under the chondrocranium)
If a Chondrichthyan has teeth that are flat, what can be assumed about their predation strategy?
These teeth are using for crushing, so the fish likely eats hard foods such as , clams, molluscs, or crustaceans
What type of jaw suspension do Chimaeras (Holocephali) have?
Autostylic
What is the function of Ampullae of Lorenzini?
Electroreception: they are the modified parts of the lateral line system that are primarily sensitive to electrical fields and help in hunting down prey.
What two clades make up Elasmobranchii?
-Selachii (sharks)
-Batoidea (skates, rays, sawfishes)
What two groups make up Selachii?
-Galeomorphii (typical sharks)
-Squalomorphii (dogfish, greenland shark, sawshark, angel shark)
What is significant about Sawsharks?
They underwent convergent evolution with sawfishes (both have similar rostrums)
What is significant about angel sharks?
They underwent convergent evolution with Batoidea (similar pectoral fins and depressed body shape)
How can you tell an angel shark apart from a Batoid?
Batoids have pectoral fins that are fused to their heads. Angel sharks have pectoral fins that are separate from their heads.
How can you tell the difference between a sawfish and a sawshark?
Sawfish (Batoidea) have ventrally positioned gills, while sawsharks (Selachii) have laterally positioned gills
What is the type of jaw suspension seen in batoids?
Amphistylic
What is the structure of placoid scales?
-Innervated in the inner core of pulp
-Dentine layer
-Enameloid layer
What thermoregulation strategy do sharks use?
Regional heterothermy
What is the countercurrent heat exchange system called?
Rete mirabile
Where is the warmed blood sent to in sharks?
-Swimming muscles
-Eyes (visual acuity)
What type of fertilization do all sharks have?
Internal fertilization
What does a thin tooth shape indicate about a sharks prey?
The shark likely eats other fish
What does a wide, triangular tooth shape indicate about a sharks prey?
The shark likely eats mammals
Why is shark conservation difficult?
Because sharks are K-selected species that mature slowly and invest lots of resources in few offspring.
Are sharks more dependent on electrical cues or olfactory cues?
Electrical cues. Olfactory cues are used at greater distances
How do basking sharks and other filter-feeders collect food?
They have filtration pads in their gills that collect food particles while allowing water to pass through
What is the coracomandibularis?
A muscle in sharks that allows them to pull back and down on their lower jaw while the hyoid arch stretches the jaw outwards
What temperature of water has the highest O2 concentration?
Cold water
What conditions influence salinity?
-Currents
-Depth
-Temperature
-Glacial input of fresh water
-Halite deposits
What zone of the ocean contains the most diversity of fishes?
The photic zone (0m-1000m)
Where is there more deep sea diversity and why?
There is more deep sea diversity near the poles due to the rich oxygen content of the cold waters
What is the purpose of countercurrent flow in the gills?
To maximize oxygen pickup
How does average oxygen intake vary with lifestlye?
Oxygen intake will increase depending on if the fish is typically a fast swimmer, average swimmer or bottom-dweller.
How do fast swimming fish increase their oxygen intake?
They use ram ventilation by constantly swimming with their mouths open
What are two other features that can be seen in fast swimming fish?
-Higher number of secondary gill lamellae
-Greater gill area
What types of muscles are associated with aerobic and anaerobic activity?
Aerobic: Red muscle
Anaerobic: White muscle
What limits the size of gill area?
Osmotic flux - If the gill area is too large, too much water will be lost to the surroundings
What is the function of the operculum?
A bony flap that sits over the gills and controls the pressure and pumps water over gills
How does the dual pump system in gills work?
Water enters through the mouth (oral valve) and into the buccal cavity during the suction phase. The water then flows over the gill curtain when the opercular cavity undergoes suction. The oxygen-depleted water is then pushed out through the opercular cavity.
What is characteristic of the secondary lamellae when the gills are used for air breathing?
The become stiffer so they don’t collapse in the air. The 2nd and 4th gill arches also bear big bushy structures.
What additional structure do air-breathing fish often have?
An out-pocket from the gut tube known as the lung/gas bladder (ancestral)
In air breathing fishes (such as the Bichir), what does the lung structure look like?
It is spongy and has a high surface area for gas exchange
How can the power required to swim be reduced?
-Streamline tail and make it rigid
-Thin webs of skin for maneuverability
-Increase the amplitude of waves along body
-Modify the base of the tail (caudal peduncle)
What are the two components of drag that affect swimming?
-Friction drag (viscosity of water)
-Pressure drag (turbulence created by tail movement)
What are the 3 main approaches to feeding?
-Swim over and bite (ram feeding)
-Suction feeding
-Filtration
Ratfish and chimaeras are part of which group?
Holocephali
Rays and skates are part of which group?
Batoidea
Sharks are part of which group?
Selachii
Sharks and rays share this group
Elasmobranchii
List the chondrichthyan synapomorphies
Calcified cartilage
Placoid scales
Unique mode of dental replacement
Ampullae of Lorenzini
Pelvic claspers (males)
What are the building blocks of the chondrichthyan skeleton? What about their composition makes them different from our skeletons?
Skeleton composed of tesserae (plates), which assemble to make hollow structures. Compared to our bones, they are missing calcium hydroxyapatite
Explain the similarities and differences between placoid scales and human teeth
They are ectodermal organs housing a pulp cavity, dentine, and enamel, much like our teeth. The only difference is that they lack calcium hydroxyapatite
What is a tooth whorl?
The teeth of chondrichthyans start far back in the jaw and move forward as they develop, eventually replacing the teeth being currently used, like a conveyor belt
What is different about the composition of chondrichthyan teeth and human teeth?
Chondrichthyan teeth lack calcium hydroxyapatite and have replaced it with fluorapatite, which is similar in structure
What is the order of senses in which chondrichthyans can detect prey?
- Olfaction (smell)
- Mechanoreception (movement, turbulence)
- Vision (sight)
- Audition (sound)
- Electrical fields
- Physical contact
True/False? Ampullae of Lorenzini are found solely in chondrichthyans
False. Monotremes (echidnas and platypus) use an analogue to search for food in dirt and water
What do the Ampullae of Lorenzini require for proper function?
Water, which is a better electrical conductor than air
What is the function of the Ampullae of Lorenzini?
To detect electrical fields produced by the movement of prey
Describe the path an electrical current would take to reach the ampullae of Lorenzini starting from the snout of the predator
Electrical current would enter through the pores on the snout, then travel down the lateral line canal to the ampullae
What are pelvic claspers used for? Why are they only found in males?
Males use claspers to insert sperm into the cloaca of females for reproduction
True/False? All chondrichthyan reproduction is internal
True
What are the synapomorphies and apomorphies of chimaeras?
Synapomorphy:
Operculum (gill cover)
Apomorphies:
Cephalic claspers (pelvic claspers found near the head)
Swim by pectoral fin flapping
Narrow tail
Why would swimming with pectoral fins be beneficial to chimaeras?
It produces almost no sound
Chimaeras are benthic. What does this mean?
They live near the bottom of the ocean
What is the synapomorphy of Elasmobranchii?
External gill slits
What are the synapomorphies and apomorphies of Batoidea?
Synapomorphy:
Mouth and gill slits are ventrally positioned
Apomorphies:
Dorsoventrally flattened
Fused head and pectoral fin
Why are the teeth of Batoidea flat?
They are used for crushing rather than slicing
What are the synapomorphies and apomorphies of Selachii?
Synapomorphies:
Heterocercal tail
Fatty liver
Which direction does a heterocercal tail push the organism?
Up and forward
What are some mechanisms in which Selachii use to control their net movement?
Upwards facing snouts lift the head up
Fatty liver can control upwards or downwards movement by altering fat content
When a Selachii wants to move downwards in the water column, how will its physiology change?
It will decrease the quantity of fat in the fatty liver
When a Selachii wants to move upwards in the water column, how will its physiology change?
It will increase the quantity of fat in the fatty liver
How do fish protrude their jaw to suck prey in?
-The maxilla and premaxilla are forced forward by the hyomandibula
-The mandible is forced down
-Branchiostegal rays are used to manipulate pressure in the mouth
-A negative pressure is created causing the food to be sucked into the fishes mouth
What structures have been lost in a typical teleost fin?
-Basals
-Most of the radials
What is the Weberian Apparatus and what group is it seen in?
-Seen in Teleostei
-It is specialized elements of the cervical vertebrae and ribs that transmit vibrations from the swim bladder to the inner ear
What group contains 40% of all fish diversity?
Euteleostei
What reproductive strategy do ray-finned fishes use?
Oviparity
What adaptations can be seen in mesopelagic fish?
-Large eyes
-Silver skin (makes then hard to see by predators)
What is the hunting style of deep sea predators?
Sit and wait
-Too expensive to actively hunt
-Usually have very large mouths
-Can expand gut
What is the reproductive strategy of Actinistia?
They are ovoviviparous
What is the lung like in Actinistia?
The lung is filled with fatty tissue because coelacanths rarely ever surface
What structure did coelacanths lose?
Maxilla
What structures did Dipnoins lose?
Maxilla and premaxilla
What type of jaw suspension do Dipnoins have?
Autostylic (palatoquadrate is fused to braincase)
What are two ancestral traits that Dipnoins have?
-Cartilagenous notochord
-Cartilagenous brain case
What type of teeth do Dipnoins have and what are they used for?
They have teeth on their palate fused into ridges. Used for crushing hard objects
What type of jaw suspension do Holocephali have?
Autostylic/Holostylic
What is an autostylic jaw suspension?
The upper jaw is fused to the brain case, which limits mobility of the lower jaw
What type of jaw suspension do elasmobranchs have?
Hyostylic
What is a hyostylic jaw suspension?
The upper jaw is not fused with the braincase, allowing for a higher degree of jaw mobility
What are the two types of chondrichthyan ventilation?
Ram and buccal pumping
Describe ram ventilation
The mouth is always open. Water comes through the mouth and spiracle and leaves through the gills
Describe buccal pumping
The chondrichthyan will take a gulp of water, close the mouth, and pump the water out through the gills using buccal muscles
True/False? An organism that uses buccal pumping cannot use ram ventilation
False. Buccal pumpers can achieve both types of ventilation
True/False? An organism that relies on ram ventilation can use buccal pumping. I just chooses not to
False. Primary ram ventilators lack buccal muscles, so they cannot use buccal pumping
Why is countercurrent gas exchange the most efficient gas exchange mechanism available for fishes?
The oxygen diffusion gradient between the water and blood vessel is constant, so the amount of oxygen moving from the water to the blood is maximized
The efferent gill artery goes towards or away from the gills?
Away
The afferent gill artery goes towards or away from the gills?
Towards the gills, carries deoxygenated blood
What about the structure of the gills maximizes oxygen uptake?
Tree-like formation - lots of surface area, and countercurrent exchange
Describe chondrichthyan osmoregulation
They are osmoconformers but still regulate salt and water intake. They take in some water and salt with food, the gills absorb water and excrete urea, the rectal gland secretes salt ions, and the kidneys excrete copious urine and some urea
Describe chondrichthyan reproduction
Internal fertilization using pelvic or cephalic (Holocephali) claspers
What is oviparity?
Laying eggs that mature into babies
What is viviparity?
Live birth
True/False? Placentals are the only group that have placentas
False. Some viviparous chondrichthyans also use placentas
What is ovoviviparity?
The egg hatches inside the mother and is born as a live fetus
What evolutionary consequences does ovoviviparity come with?
Depending on the species, some chondrichthyans cannibalize their littermates while still in the womb
What is a trophic cascade?
A form of top-down regulation where a keystone species is removed from the population and the next trophic level down thrives, so the level below that dies
Why are sharks hard to conserve?
They take a long time to mature, they need lots of resources, long lifespans, they invest energy in their young, small fecundity, reproduce biannually (one every two years), long gestation period
What are the synapomorphies of Osteichthyes?
Lepidotrichia
Bony operculum
Teeth on dermal bone
Outpocket of stomach
What are lepidotrichia?
Bony segments that extend outwards to support the fin made from endochondral bone
What is chondrichthyan fin support called?
Ceratotrichia
True/False? Any dermal bone situated on top of endochondral bone can form teeth
True
What is a physostomas outpocket important for?
The development of the lungs
What does a physoclistous outpocket develop into?
Swim bladder
What ventilation structures are similar between chondrichthyans and osteichthyans?
Gill arches, gill septum, and gill filament
What are the two types of stomach outpocket in Osteichthyes?
Physostomous and physoclistous
What ventilation structures are unique to chondrichthyans relative to osteichthyans?
Spiracle, gill slit, 5 gill arches
What ventilation structures are unique to osteichthyans relative to chondrichthyans?
4 gill arches, operculum, gill opening
Explain the dual-pump ventilation system
Step 1: Mouth is open, operculum is closed, both buccal cavity and opercular cavity have negative pressure
Step 2: Mouth closes, operculum is still closed, positive pressure in buccal cavity and negative pressure in opercular cavity force water past gills
Step 3: Mouth is still closed, operculum opens, positive pressure in buccal cavity and opercular cavity force water past gills and exhausted water out, respectively
What effects on metabolism does the dual-pump ventilation system have?
Less energy spent keeping the mouth open for ram ventilation so this system is more efficient, allowing for a higher metabolism
Does the osteichthyan electrical sensory system differ much from the chondrichthyan sensory system?
No, not significantly
Which organ is most important for the development of the electricity-discharging organ found in electric eels? Why?
The lateral line, as the electric organ in many different species is found along this system
Describe a marine telost’s osmoregulation
Drinks water, loses ammonia and water passively and chloride ions actively through gills, excretes small amounts of concentrated urine, ammonia, some urea, and divalent ions
Describe a freshwater telost’s osmoregulation
Gets some water and salt with food, passively absorbs water and sodium ions and passively loses ammonia and actively pumps in chloride ions through gills, kidneys reabsorb salt and excrete lots of dilute urine, ammonia, and some urea
What is a marine telost’s overall goal in order to osmoregulate?
Keep excess ions out and water in
What is a freshwater telost’s overall goal in order to osmoregulate?
Keep ions in and excess water out
What does ammoniotelic mean? Are marine or freshwater telosts ammoniotelic?
Both are ammoniotelic. This means that they excrete raw ammonia
Describe the general reproductive strategy of osteichthyans
Rely on external fertilization and are thus oviparous
What does gonochoristic mean?
It means the organism stays the sex it was since birth
What is sequential hermaphrodism? Provide two examples
All members of a species start as a sex and can develop into another as they mature or are exposed to environmental pressure
Ex: Protandrous hermaphrodism in clownfish. All start as male and develop into female if no females present
Ex: Protogynous hermaphrodism in bluehead wrasse. May either start as male or female but develop into a male once mature
What is simultaneous hermaphrodism?
The organism possesses both male and female reproductive organs and can reproduce through asexual reproduction if in isolation
What does endothermy mean?
Relies on metabolism and other mechanisms to maintain body temperature
What does ectothermy mean?
No mechanisms for thermoregulation
What does homeothermic mean?
Body temperature must stay within a specific range for the organism to live, and thus is unable to function without homeostasis
What does heterothermic mean?
Body temperature may fluctuate without serious consequences so is able to function without homeostasis
What is an example of a heterothermic ectotherm (fish)?
Most fish, as their gills are always exposed to water with ever-changing temperatures
What is an example of a homeothermic ectotherm (fish)?
Some fish that possess anti-freeze proteins
What is an example of a heterothermic endotherm (fish)?
Tuna, sharks, and swordfish have axial tissues dense in mitochondria that keep the organism warm through constant movement
What is an example of a homeothermic endotherm (fish)?
Opah uses its kidney to generate heat
True/False? Osteichthyans have semicircular canals for orientation sensation
False. They have Neuromast organs that contain hair cells for vestibular sensation
What are the synapomorphies of Sarcopterygii?
Cosmine in scales
Intracranial joint
Fleshy-finned limbs with a single basal bone at the base of the fin
True/False? The scales of Sarcopterygii contain cosmine, which is unique to this group
True
What is the main role of the intracranial joint?
Allows some movement of the premaxilla for feeding
How do osteichthyans feed?
Gape-suction feeding creates negative pressure in their mouths so when they open their mouths, everything in front of them gets sucked in
True/False? Propulsion by fleshy-lobed fins is mainly powered by the fin rays themselves
True
Where are the basal elements situated?
Between the pelvic/pectoral girdle and radials
Where may basal bones be found in Sarcopterygii?
Throughout the midline of the fin
Which groups make up Sarcopterygii?
Actinistia (Coelacanths), Dipnoi (lungfishes), and Tetrapods
What separates Rhipidistia from Actinistia?
Rhipidistia has divided atria
A divided atrium allows for what?
Multiple circuits (systematic and respiratory)
What is a Lazarus taxon?
An organism which was previously thought to be extinct that has been discovered to still be living
What is an apomorphy of Actinistia?
The loss of the maxilla
What are the apomorphies of Dipnoi?
Loss of both premaxilla and maxilla
Loss of the intracranial joint
Autostylic
Teeth fused into plates for crushing
What impacts do lampreys have on the economy?
Fisheries situated on the great lakes are prone to losing fish due to fast-growing lamprey populations, as they are parasitic to fish
Describe the hyomandibula bone placement in each of the three jaw suspension types. How does this effect jaw movement?
Holostylic: dorsal and caudally positioned relative to lower jaw; limited jaw movement
Amphistylic: caudally positioned relative to lower jaw; able to push lower and upper jaws to extend outwards
Hyostylic: Caudally positioned relative to upper jaw; allows for extreme extension of upper jaw
What about the splanchnocranium differs between Chondrichthyes and Osteichthyes?
Chondrichthyes: exclusively endochondral bone
Osteichthyes: endochondral and dermal bone
What is the major theme for the synapomorphies of Cyclostomata?
Parasitic characteristics, no paired characteristics
What is meant by the branchial basket?
Medial gills on Cyclostomata
What are primary and secondary lamellae?
They make up the gill filament
Why do caudate larvae not require pedicellate teeth?
Use gape-suction feeding to eat, so teeth not needed
What does anadromous mean?
Migrates to fresh water to spawn
