internal physiology of fishes
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Internal Physiology of Fishes. Chapter 8. Feeding. Most fishes are carnivores. plankton feeders demersal feeders open water predators Bony fishes – teeth can be found in jaw, roof of the mouth, on gill rakers, and in pharynx Cartilaginous fishes – teeth only on jaw margin. - PowerPoint PPT PresentationTRANSCRIPT
Internal Physiology of FishesChapter 8
FeedingMost fishes are carnivores.
plankton feedersdemersal feedersopen water predators
Bony fishes – teeth can be found in jaw, roof of the mouth, on gill rakers, and in pharynx
Cartilaginous fishes – teeth only on jaw margin
Gill rakers & arches
Digestive Systemmouthpharynxesophagusstomach
J-shaped or elongated
intestineanterior pyloric
caeca secretes digestive enzymes
receives inputs from pancreas and liver
spiral valvecloaca/anus
Circulatory System
Fish have a two-chambered heart.Deoxygenated blood is pumped to the gills where
gas exchange occur.
Circulation and Heat ExchangeMost fish are
poikilothermic.Few large sharks and
bony fish can maintain core body temperature slightly higher than their environment.
rete mirabile (‘wonderful net’)
adaptation for inhabiting colder waters
Respiratory AnatomyFish exchange O2 and CO2 through paired
gills.
Cartilaginous fishes Bony fishes
Respiratory Anatomy – Cartilaginous vs. Bony Fishes
Cartilaginous FishesMost swim continuously.First pair of gill slits is
modified into spiracles.Usually 5 gill slits – may
have 6 or 7.
Bony FishesHave a single common gill
chamber.Covered by an operculum
Respiratory AnatomyCovered by an
operculumGill archesGill filamentsLamellae
Gas exchange occurs by simple diffusion
Countercurrent system of flow
Osmoregulationregulation of the
body’s internal salt balance
Bony fish Body fresher than
seawater Drink seawater Salt excreted by
kidney Small amount of urine Chloride cells
Cartilaginous fish Rectal gland Urea in blood Absorb water through
gills
Nervous SystemFish possess a central nervous system,
consisting of a brain and spinal cord.
Variation exists. Proportional size of the lobes reflects the predominant movement and feeding behaviors of particular species. (i.e. the largest area of the lamprey brain is the cerebellum and medulla which indicates the fishes reliance on grasping with its jaw and attaching to its food).
Fish SensesSmell – use sensory cells in olfactory sacs on both
sides of the head. Each sac opens to the nostrils or nares.
During dissection, note the large portion of the forebrain devoted to smell particularly in the shark.
Fish SensesTaste – Taste buds can be found on the
mouth, fins, skin, lips, and barbels of fish.
Fish SensesSight – used by most fishes
Unlike terrestrial vertebrates, fish eyes focus by moving the lens closer or farther away from the subject
Shallow water species have color vision● Sharks and deeper
water species may have little color vision, but see best in contrasting light situations
● Some have a nictitating membrane that can cover the eye from the bottom to reduce brightness or offer protection
Fish SensesTouch – fish possess a lateral line consisting
of canals in the skin and in the bone or cartilage of the head that connect to neuromast cells that are sensitive to vibration.
Fish SensesHearing – perceive sound
waves with their inner earsUse fluid filled canals on
either sides of the brainSome fish amplify sounds
using their swim bladderInvolved in balance – use
ear stones or calcified otoliths that rest on sensory hairs
Fish Skeleton
Shark Skeleton
ReproductionSexes are usually separate.Some fish are hermaphroditic, but usually
still reproduce with other individuals.Some fish are sequential hermaphrodites –
individuals begin life as one gender and later change into the other.
Sexually dimorphic sockeye salmon (male on bottom)
Simultaneous HermaphroditesFish in the Salmon and Sea bass families.
Protygynous sequential hermaphroditism
Protandrous sequential hermaphroditismInitial phase: initial males and females
Terminal phase: males
Fish Reproductive AnatomyJawless and bony fish – separate urogenital
opening for urination and gamete releaseCartilaginous fish – duct leads from
reproductive organ to the cloaca
http://www.marinebiodiversity.ca/shark/english/skull5.htm
Reproductive behaviorTiming of reproduction controlled by sex
hormones released into blood stream.In response to maturation of gametes or to
environmental cuesPotential mates come together.CourtshipFertilization – may be internal (most
cartilaginous fish) or external (most bony fish)
Some fish tend eggs or brood nests (usually males)
Early Development Oviparous – large number of immature eggs
are laid at a single time. Larval fish hatches quickly, but still retains and absorbs yolk sac.
Ovoviviparous – female retains eggs inside her reproductive tract for protection
Intrauterine cannibalism
Viviparous – produce embryos that absorb nutrients through the walls of the mother’s reproductive tract
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