What class are cartilaginous fish found under and which orders do this class include?
Order Chimaeriformes (subclass Holocephali)
What characters link all Chondrichthyes together?
Placoid scales or dermal denticles
Claspers on male pelvic fins
Spiral valve intestine
Replaceable teeth, usually
What is the species name of dogfish sharks? Order? Family? Characteristic traits?
Subclass Elasmobranchii Order Squaliformes Family Squalidae
Species: Squalus acanthias
Single spine in front of both dorsal fins; white spots along sides; no anal fin\
What are the identifiable shark external anatomy?
Nostril, in which water flows into and enters nasal sac
Ampullae of Lorenzini, small pits covering large areas of skin near the mouth and nose below the sharks snout, detecting weak electrical fields
dermal denticles: placoid scales that are structured like small teeth, which are shed and grow as the shakes does
first dorsal fin: stabiliser
lateral line: sensory hair cell clusters (neuromasts) and small water-filled canals, lie immediately beneath the skin on a shark' head and extends along sides of body
second dorsal fin: assists in thrust and helps stabilisation, preventing rolling from side to side as it swims
caudal fin: heterocercal in sharks
anal fin: aid in stabilisation
pelvic fin: in males, have rod-like extension on inner edge used for internal fertilisation
pectoral fin: used for lift during swimming, for turning, and as stabilisers as they resist pitch caused by heterocercal tail lift
gill slits: usually five but may have six or seven; chimeras have one
teeth: found in rows that fall out and is replaced by new teeth that move forward in little as 24h; chimeras only have large permanent grinding tooth plates
jaws: loosely connected by ligaments and muscle to the skull and are high mobile where snout bends up and out and jaws move forward and protrude and move back in and under snout; chimeras have cranially fused upper jaw
What are the traits of a male chimera required to be IDed for lab?
Head clasper -- absent in females
Eye Spine on first dorsal fin
Elongate second dorsal fin
Upper lobe of caudal fin
Lower love of caudal fin
Claspers on pelvic fins
Where are spiracles and nares found on rays and skates?
Spiracles are right behind eyes on the dorsal side. When resting on the bottom, the large spiracles pull water from dorsal surface in through it's gills and out its ventral gill slits.
Nares are anterior of ventral mouth, and pulls water in through nares into mouth.
Where are claspers found and what are they used for?
Found in Chondrichthyes, inner base of pelvic fins in males of all species and groups.
Claspers are used for internal fertilisation and are evident in very young and immature individuals.
How do copulatory organs differ in Chimaeridaes than other Chondrichthyes families?
Males have head (cephalic) claspers or tentaculum and have pelvic claspers on the inner pelvic fins but are bifid or each are divided into two, producing an appearance of distally of four claspers.
What are the components of the common urogenital system found in both male and female Chondrichthyes?
kidneys: used for osmoregulation where urea is kept inside of shark blood so that osmotic pressure equals that of sea water and therefore no gains or losses of water occurs
rectal glands: tube-like rectum extensions controlling salt concentration within the body; excess salt is excreted into the rectum
archinephric ducts: females = drain into cloaca through urinary papilla; males = transports urine and sperm and forms the seminal vesicle caudally
accessory urinary ducts: generally absent in females; drains caudal kidneys and found dorsal to seminal vesicles
What are the components of Chondrichthyes male genital system?
TESTES: dorsal to liver lobes in which male gametes are formed
EFFERENT DUCTULES: small tubes carrying sperm from testes into kidneys
EPIDIDYMIS: head kidney collects sperm \
VAS DEFERENS: highly coiled tube that carry sperm to seminal vesicle
SEMINAL VESICLE: enlarged section of vas deferens which adds secretions to sperm
SPERM SAC: small invaginated sacs of the seminal vesicle that receives sperm and seminal secretions
SIPHON: a cranially closed sac that produces secretion expelled with aid of claspers during mating
What are the female genital system components found in Chondrichthyes?
OVARIES: two cream coloured organs dorsal to liver where eggs move into body cavity and into oviducts when ready to be fertilised
OVIDUCTS: two dorsalaterally elongated tubes that share common opening to body cavity (OSTIUM)
SHELL GLAND: at the cranial end of oviducts that secretes shell around group of eggs, is reservoir for sperm storage, and in which eggs are fertilised within as they pass through
UTERUS: enlarged caudal end of the oviduct, in which fertilised eggs develop
What is a characteristic of the Family Rajidae?
Lay egg cases -- are OVIPAROUS -- which contain one to a few young inside. Egg cases are species specific.
How is blood pumped in Chondrichthyes (and nearly all other fishes)?
Heart is situated on ventral side directly behind gills and blood is pumped FORWARD from the heart and UPWARD through the gills and circulates through the upper part of the body and ultimately back down to the heart.
By pumping blood up from the ventral part of the body, gravity as well as pressure is used to being blood back to the heart.
Describe the blood flow through the various parts of a Chondrichthyes heart from the body to the lungs using a diagram.
6) Body➡1) Sinus venosus➡2) Atrium➡3) Ventricle➡4) Conus Arteriosus➡5) lungs↖6) Body
Verbally describe the GENERAL flow of blood found in fish.
In virtually all fishes, the heart is a SINGLE TWO-CHAMBERED PUMP (vs a four-chambered pump in tetrapods). Deoxygenated blood is pumped forward from the SINGLE VENTRICLE to the GILLS where O2 and CO2 are exchanged. The oxygenated blood then passes to the tissues, where it loses oxygen, and eventually returns to the hear where it enter through the SINGLE ATRIUM.
What is the difference between the heart of Chondrichthyes and that of Atinoptyerigians?
Chondricthyes has a CONUS ARTERIOSUS which pumps blood from the VENTRICLE--> GILLS.
- CHONDRICHTHYES: BODY to.... 1) Sinus Venosus 2) Atrium 3) Ventricle 3) CONUS ARTERIOSUS .....to GILLS
Actinoptyerigians have a BULBUS ARTERIOSUS (vs a CONUS ARTERIOSUS).
- ACTINOPTYERIGIANS: BODY to.... 1) Sinus Venosus 2) Atrium 3) Ventricle 4) BULBUS ARTERIOSUS .....to GILLS
How many heart chambers are there in Chondrichthyes/other fish?
Conforms to a general four-chamber-in series where blood enters the SINUS VENOSUS, then to the SINGLE ATRIUM, followed by the VENTRICLE, and through the CONUS ARTERIOSUS (Chondrichthyes) or BULBUS ARTERIOSUS(other fish).
Explain the function and form of the 4 heart chambers found in Chondrichthyes and contrast it to that of an Actinoptyergian.
SINUS VENOSUS: a THIN-WALLED TRIANGULAR sac that lies dorsal and slightly posterior to the ventricle, which collects venous blood from the body and passes it one way to the....
ATRIUM: a THIN-WALLED, LIGHTLY MUSCLED SINGLE-CHAMBERD sac that lies anterior to the sinus venosus(1) and dorsal to the ventricle (3), which pumps blood into the ventricle (3) and has atrioventricular valves that stop backflow from ventricle to atrium when ventricle contracts.
VENTRICLE: a THICK-WALLED (highly muscled) SINGLE CHAMBERED sac that pumps blood directly to the gills then through to the body.
CONUS ARTERIOSUS: a THICK-WALLED TUBE extending from the ventricle to the ventral aorta, that contains numerous SEMILUNAR VALVES that prevent back-flow into ventricle, and EXPANDS during VENTRICLE CONTRACTION and CONTRACTS after VENTRICLE COMPLETES CONTRACTION, and as a result evens out blood pressur reaching the thin-walled gills.
Actinopterygians have a BULBOUS ARTERIOSUS
Describe the branchial gill structure found in Chondrichthyes.
GILL FILAMENTS are PAIRED but are ATTACHED to each other by way of the GILL RAY or the GILL SEPTUM.
The gill ray/septum is attached internally with the GILL ARCH.
The GILL RAKER is found on the inside of the GILL ARCH.
Each half of the gill filament pair of is called a DEMIBRANCH.
The pair of filaments is called a HOLOBRANCH.
The GILL ARCH/GILL SEPTUM connects directly to the skin separating the gill slits in Chondrichthyes.
Half a pair of gill filaments is known as?
A single pair of gill filaments is known as what?
What is the difference between Chondrichthyes branchial structure versus an Actinopterygian's
In sharks, rays and chimeras, the gill filaments are separated from each other by the GILL SEPTUM and each septum is connected to the skin that separates each gill slit. The gill septum is connected internally to the gill arch which in turn makes up the gill raker.
In Actinopterygians, the gill septum is small and the pair of gill filaments are not separated from each other by a fold of skin.
What are Placoid scales?
Found in sharks and rays (and early/extinct chimaeras) and NO OTHER FISHES.
Composed of a vascular inner core of pulp, a middle layer of DENTINE and a hard enamel-like outer layer of VITRODENTINE.
Are often referred to as DERMAL DENTICLES.
They do not increase in size as the fish grows, instead new scales are added.
Differentiate between placoid scales and dermal denticles.
Different name for the same thing: is a scale that is composed of a vascular inner core of pulp, a middle layer of dentine and a hard enamel-like outer layer of vitrodentine.
How do dermal denticles look like?
Consists of a flattened rectangular base plate embedded in the fish and variously developed structures (spines, etc) which project posteriorly on the surface, giving many species a rough texture.
Placoid scales vary between species.
They do not increase in size as the fish grows, instead new scales are added.
What are differences in placoid scale shape and density between slow moving (car sharks, nurse sharks) and fast moving (blue shark) Chondrichthyes species?
Denticles are designed to minimize friction with water, where faster moving species have denticles that are designed to direct water flow along the fish body and allow the fish to slip more smoothly within water.
What is the underlying trait within Elasmobranches (Sharks & Rays) with respect to teeth form and function?
Teeth are constantly being lost and replaced, simultaneously i.e. are on a conveyer belt.
The palatoquadrate (or upper jaw) of Elasmobranches projects forward and down when feeding, and pulls backward and up when drawing in prey.
Teeth size and shape vary among species depending on their diet.
What are the 4 major components of Chondrichthyes sensory system?
SIGHT: Eyes in various sizes depending on species and ecology.
SMELL: Nares directs water across the olfactory sacs in order to increase sense of smell
WATER DISPLACEMENT/PRESSURE/DIRECTION: Lateral line system stretching down sides from gills to tail, consisting of hollow tube openings out into skin at perforated scales, allowing sense of movement within surrounding waters. Found in most fish and amphibians.
ELECTRORECEPTION & TEMPERATURE GAUGE: Ampullae de Lorenzini composes a specialized part of the lateral line in Chondrichthye head region (and other primitive fishes ex sturgeons/paddlefish). Ampullae de Lorenzini detect weak magnetic fields produced by other fishes, at least over short ranges and are found on both VENTRAL and DORSAL part of the shark's SNOUT.
What is the form and function of the Chondrichthyes liver?
Two large lobes of the liver connected by the median lobe, which consists of high fat concentrations and aids in floatation in water.
Chondrichthyes do not have a swim bladder.
Name and describe the 8 Chondrichthyes body cavity structures required for lab.
ESOPHAGUS: short and wide, connecting between the pharynx to the stomach
STOMACH: J-shaped organ which has a cardiac portion near the heart and a limb portion after the bend of the stomach, ending at the PYLORIC SPHINCHTER which restricts stomach and intestine flow
DUODENUM: short section immediately caudal from the stomach that receives liver secretions (bile) from the bile duct
LIVER: has three lobes, two large and one small; gall bladder is found within the smaller lobe of the liver (median lobe)
PANCREAS: Ventral pancreas located on the ventral surface of the duodenum and dorsal pancreas which is long and thin located behind the duodenum and extends to the spleen
SPIRAL INTESTINE: Crainally located fromt he duodenum, distinguished by extensive network of arteries and veins over surface, with internal funnel shaped folds i.e. spirals which greatly increases surface area of intestine
RECTUM: short end portion of the digestive tract between the intestine and the cloaca, which stores solid waste
SPLEEN: caudal to the stomach and proximal to the spiral intestine, associated with the circulatory system
What are gill rays?
Cartilaginous spines that support the interbranchial septa i.e. gill septum.
What are the gill arches?
the main skeletal framwork of each gill where gill rays/septa and gill rakers extend from opposite sides of these arches.
What are gill rakers?
cartilage- supported projections from the gill arches that face the pharynx, which protect the gills by screening them from food particles in water which are then diverted backward toward the esophagus.
Where is the dorsal skeletogenous septum located?
the dorsal part of the epaxial musculature, which separates the epaxial muscle fromt he skin.
What is the epaxial musculature?
the dorsal portion of the two major muscle sections of a fish, which is separated from the hypaxial musculature by the horizontal skeletogenous septum.
What does the horizontal skeletogenous septum do?
Divides the epaxial and hypaxial musculature from each other.
What is the hypaxial musculature?
the lower, ventral portion of the two muscle sections of a fish, separated from the epaxial/dorsal musculature by the horizontal skeletogenous septum.
Where is the lateral line, with respect to musculature within fish?
along the horizontal skeletogenous septum
What are myosepta?
The tissue connections that hold myomeres -- separate muscle fibres -- together
What are myomeres?
The separate muscle fibres that are arranged in W-shapes (not in Myxinidae or Petromyzontidaes) that aid in movement of the fish.
What are the semi-circular canals and their functions?
They are a pair -- within Chondrichthyes -- of three bones on each side of the brain that act as the inner ear of the shark involved in BALANCE, HEARING, and possibly MAGNETIC ORIENTATION.
Found in chambers below the small holes in the cartilaginous brain case with small clear tubes inside these holes located posterior and lateral to each side of the brain
Fine tubes/holes at the rear of the brain associated with the semicircular canals
What are the 7 major components of the Chondrichthyes brain, in order from posterior to anterior?
MEDULLA OBLONGATA: elongated region of the brain that extends from behind the cerebellum and is continuous with the spinal chord, and is involved with reception of major trunk nerves.
CEREBELLUM: a large, median, oval mass, whose cranial end overhangs the optic lobes, and whose dorsal section is demarcated by shallow grooves into four sections and involved with motor/muscle functions of the body.
OPTIC LOBES: paired bulbous lobes that lie behind the cerebrum/cerebral hemispheres and slightly in front of and below the cerebellum, responsible for visual information processing.
CEREBRAL HEMISPHERES/CEREBRUM contains the olfactory lobes...
OLFACTORY LOBES: located in the front portion of the cerebrum, where olfactory information is processed.
OLFACTORY BULBS: paired bulbs that form the most cranial portion of the brain and are lateral enlargements in contact with the olfactory sacs and receive primary olfactory neurons coming from the olfactory epithelium.
OLFACTORY SACS: the sensory organs with which smells within water is detected and sent to the connected olfactory bulbs where information is sent into the olfactory lobes of the cerebrum.
With respect to the Elasmobranches brain, what are three important considerations to take into account?