Chapter 18: Integument of Fishes Flashcards
What is the integument of fishes?
Is composed of an Epidermis, Dermis and Scales of a fish
How do you study the hydrodynamics of fishes?
Digital Particle Image Velocimetry (DPIV)
Using a camera and a laser to monitor the drag-reducing mechanisms by visualizing the wake of a fish.
Neutrally buoyant + Fluorescent spheres
What is Frictional drag?
Caused by passage of water over skin length of a fish
What is a boundary layer?
A thin water layer that surrounds the fish,
which can flow smoothly over the skin in a linear fashion in very small fish, or larger fish if they move slow
What is a Reynolds Number?
A measure of a Boundary Layer Re= LV/v
L= Length of body V = Velocity v= Kinematic viscosity
density of water x length/ Bulk viscosity
Examples
Re small = Less drag and More laminar (linear)
Re larger = More drage, More turbulence
What are adaptations in the fish integument that help increase swimming efficiency
- Tunas & Tuna-like: streamlined body (laminar flow
maintained), clean surface (maintain laminar), body head
straight swimming (most lateral movement con’t to caudal
peduncle), caudal peduncle has flexible finlets (direct flow
across peduncle to minimize separation of boundary layer),
peduncular ??? aid in maneuvering, corselet of scales that
roughness roughen forebody (some tuna, may help
maintain turbulent attached bondary layer) - Coarse Scales: Roughened corselet of scales (tuna,
hydrodynamic roughening of fish skin), ctenoid scales
(spines protruding through mucus coating), rough
protrusions project through boundary layer causing small
vortices to form encouraging a close turbulent layer to
remain attached & drag reduced - Mucus: may reduce drag (reduces viscosity of H2O as it
flows past body) - Schooling behavior: Overall reduction in drag may be
achieved (V-Shaped pattern)
What special cells provide color in fishes?
Chromatophores
Arise from neural crest and share features with nerve cells
What is the molecular mechanism of color change in fishes and the stimuli for the change itself?
Hormonal and neural control
Pituitary gland secretes MSH melanocyte-stimulating hormone
Causing the movement of melanosomes resulting in a change in color
In bioluminescent fish, why do they produce light?
Functions in: obtaining prey, evading predators, communication
CONCEALMENT: Counterillumination- photophore placement/ other luminous tissue in ventral position, enables fish to match light from above( predators from below less likely to make out fish’s silhouette (lanternfish)
ADVERTISMENT: Communication- involving luminescence active in reproduction (midshipmen use for courtship, lanternfish sexual dimorphic patterns of luminous organs), Startle or confuse predators- midshipmen possess venom spine, flash lights to warn predators;
Others: light organs on head (lit visual field), some melanostomiius combine red sensitive retina w a large, red, postorbital photophore (see nearby prey)
What type of fishes produce venom?
and how?
Moses Sole: glands scattered in skin.
Stingrays: stiff & serated edges, venom in epidermis of sheath, when spine is released skin sheath is broken & venom released.
Dogfish & chimaeras: venom glands along dorsal spines.
Catfish: venom glands in skin sheathing dorsal & pectoral spines, family Plotosidae most dangerous, shovelhead catfish of family Pimelodidae.
Toadfish: Family Batrachoididae. Family Synanceiidae: Stonefish, venom glands associated with dorsal, anal, & pelvic spines.
Family Scorpaenidae: venom glands in grooves along dorsal, anal, pelvic spines; pterois- can kill humans (lionfish).
Family Trachinidae: Weaverfish, venomous opercular & fin spines.
Sabertooth blennies: venom glands associated with grooved teeth.
What is a Goblet cell and what does it do?
in the epidermis;
contribute to mucus layer along with granular cells
wrasses (Labridae) & parrotfishes (Scaridae) secrete elaborate mucus cocoon from large goblet cells.
What is a Club cell and what does it do?
produces alarm secretions
What is a Granular cell and what does it do?
A secretory vesicle that contributes to the mucus layer
What type of cells do wrasses and parrot fish have that allow them to secrete a mucus to form a large cocoon?
Goblet Cells
(acts as a predator deterrent)
(Parrotfish cocoon has antibiotic properties)
What are the four types of scales?
Placoid
Ganoid
Cycloid
Ctenoid
Drag is proportional to?
Velocity squared or Drag = V2
A fast fish must exhibit lots of energy to maintain speed
Tuna a fast fish has a lot of mitochondria as its needed
Why are tuna so fast?
Mainly their peduncle
Streamlined body
Clean surface (shiney smooth no scales)
Flexible finlets
Rigid body head nearly straight during swimming
Keel
Drag on flexible fish> 2-5x greater than drag on a rigid fish
Kick and glide to minimize drag
GLIDING FISH 1/3 DRAG OF STEAADILY SWIMMING FISH AT SAME SPEED!
