Chatper 18: Integument of Fishes

Question 1

What is the integument of fishes?

Answer 1

Is composed of an Epidermis, Dermis and Scales of a fish

Question 2

How do you study the hydrodynamics of fishes?

Answer 2

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

Question 3

What is Frictional drag?

Answer 3

Causes by passage of water over skin length of a fish

Question 4

What is a boundary layer?

Answer 4

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

Question 5

What is a Reynolds Number?

Answer 5

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

Question 6

What are adaptations in the fish integument that help increase swimming efficiency

Answer 6

1. 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)
2. 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
3. Mucus: may reduce drag (reduces viscosity of H2O as it flows past body)
4. Schooling behavior: Overall reduction in drag may be achieved (V-Shaped pattern)

Question 7

What special cells provide color in fishes?

Answer 7

Chromatophores
Arise from neural crest and share features with nerve cells

Question 8

What is the molecular mechanism of color change in fishes and the stimuli for the change itself?

Question 9

In bioluminescent fish, what are the mechanisms for producing light?

Question 10

In bioluminescent fish, why do they produce light?

Answer 10

Functions in: obtaining prey (by luminescent predators), evading predators (by luminescent prey), communication (between conspecifics); 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 silouette (lanternfish); Advertisement: 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; Disguise; Others: light organs on head (lit visual field), some melanostomiius combine red sensitive retina w a large, red, postorbital photophore (see nearby prey)

Question 11

What type of fishes produce venom?
and how?

Answer 11

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 Synanceidae: Stonefish, venom glands associated with dorsal, anal, & pelvic spines.
Family Scorpanidae: 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.

Question 12

What is a Goblet cell and what does it do?

Answer 12

in the epidermis; contribute to mucus layer along with granular cells; wrasses (Labridae) & parrotfishes (Scaridae) secrete elaborate mucous coccoon from large goblet cells.

Question 13

What is a Club cell cell and what does it do?

Answer 13

produces alarm secretions

Question 14

What is a Granular cell and what does it do?

Answer 14

A secretory vesicle that contributes to the mucus layer

Question 15

What type of cells do wrasses and parrot fish have that allow them to secrete a mucus to form a large cocoon?

Answer 15

Goblet Cells

(acts as a predator deterrent)
(Parrotfish cocoon has antibiotic properties)

Question 16

What are the four types of scales?

Answer 16

Placoid
Ganoid
Cycloid
Ctenoid

Question 17

Drag is proportional to?

Answer 17

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

Question 18

Why are tuna so fast?

Answer 18

Mainly their peduncle
Streamlined body
Clean surface (shiney smooth no scales)
Flexible finlets
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!

Question 19

What type of scales to tuna have and what do they do?

Answer 19

Coarse scales

roughed or sorselet of scales are more hydrodynamic
Ctenoid scales (spines) protrude through mucus

Roughness of protrusions that bust through boundary layer but encourages layer to remain unaffected thus reducing drag.

Question 20

What few types of fish lack skin pigment?

Answer 20

Cave dwelling –> pale or white
Fish larvae eel leptocephali –> transparent
Zebrafish –> Transparent used in genetic studies often

Question 21

What are 3 characteristics of chromatophores?

Answer 21

Located in Dermis
Arise from Neural Crest
Classified by color

Question 22

What two types of cells are fish colors imported by?

Answer 22

Biochromes - Pigments

Structural color/Schematochtroms- Reflection

Question 23

Chromatophores classified by the color pigment black or brown?

Answer 23

Melanophores

Question 24

Chromatophores classified by the color pigment that are reddish?

Answer 24

Erthophores

Question 25

Chromatophores classified by the color pigment Yellow?

Answer 25

Xanthophores

Question 26

Chromatophores classified by the color pigment White?

Answer 26

Leucophores

Question 27

Chromatophores classified by the color pigment that is mirror-like?

Answer 27

Iridophores

Question 28

Chromatophores classified by more than one pigment?

Answer 28

Compounds

Question 29

What is a pigment and where is it found?

Answer 29

Chemical found in a clumped form inside of organelles

Question 30

Color change depends on?

Answer 30

movement of pigments within chromatophores

Question 31

What causes the short-term and rapid changes of color changes in fishes?

Answer 31

Physiological or neurological control or neutral color changes

Question 32

What causes the long-term changes of color changes in fishes?

Answer 32

Increase in chromatophore numbers of pigment distribution within cells
Morphological color change
(Reef fishes, wrasses, tangs)

Question 33

What is a chromatophore and what does it do?

Answer 33

Irregular cells dendritically branchelike similar to neural cells
that distribute pigment

Center of cell–> skin appears pale

organelles are dispersed through the cell–> Skin takes on color of chromatophore

Question 34

What types of species are found to have Iridophores?

Answer 34

The mirror like color is found in open water species
(Blue shark)
subdermal found on lateral and ventral sides of the body

If parallel to body fish appears silvery
If oriented differently the fish may show a darker color on top and a lighter color below

Question 35

What is a subdermal sheet of iridophores on lateral and ventral sides of the body where 80% of light is reflected?

Answer 35

Stratum argenteum