Integument of fish, amphibians, reptiles Flashcards
features of amphioxus skin
keratin?
simple or stratified
shape
do they have pigment cells
no keratin, simple columnar or cuboidal epithelium, no pigment cells, simple dermis
lamprey skin features
keratin?
scales?
simple or stratified?
shape?
is it more complex than amphioxus?
no keratin, no scales, stratifies cuboidal, it is more complex than amphioxus
what does lamprey skin look like
skin of bony fish
ex?
mucous cuticle?
stratified or simple?
shape
keratin?
Skin of a Bony fish (a teleost) – note, mucous cuticle
present, stratified cuboidal epithelium, non-keratinized
Fish epidermis of (shape) epithelium
(usually) often protected by ___
stratified cuboidal, mucopolysaccharide mucous cuticle
fish epidermal glands present
mucous, granular
fish mucous glands, unicellular and multicellular
Unicellular – abundant, decrease turbulence & drag, protection
from microbes or parasites, osmoregulation (reduce water loss),
aestivation (protective mucous “cocoon” in Dipnoi)
* Multicellular – large with duct, produce copious, thick slime (i.e.
hagfish) to counter act predation by other vertebrates
fish granular glands - unicellular and multicellular
Granular - produce alkaloids (toxins) and other chemicals
* Unicellular – in Lamprey & several Actinopterygii, triggered by
injury, function as an alarm to warn others of predators
* Multicellular – not as common, found in several Actinopterygii &
Sarcopterygii, are “poison” glands often associated with fin spines, can
produce alarm substances in some species (i.e. catfish spines)
what do granular and mucous glands in the minnow look like
Most extant bony fish have ___
overlapping scales
Histological section of skin layers of a juvenile
steelhead trout with overlapping scales
dermis of fish
fibrous connective tissue, scales
fibrous connective tissue of fish
Fibrous Connective Tissue – increases
strength and resists deformation (rippling) in skin due to drag
fish - The ordered ___ strands of
the stratum compactum keeps
skin ___ but tight so that
surface ___ does not occur,
which would induce turbulence
collagen , flexible, wrinkling
evolutionary origins of scales
Uncertain if first vertebrates had dermal scales or not – hagfishes may
be closest living representative of the earliest ancestral craniate line and
they lack dermal scales
2 major hypothesis for scale origin in first vertebrates
Were small filter feeders or scavengers, many larger invertebrate
predators existed at the time, dermal armor provided protection
– Lacked bony internal skeleton, dermal armor provided calcium
storage needed for normal functio
trends in bony scale evolution
Reduction in size (width) of scale – especially in tail region
– Decreased number of layers within the scales
– Decreased thickness of scale
– Lighter, giving animal flexibility
Cosmoid Scales or Dermal Armor (most primitive)
who has them
Taxa – only in fossil Ostracoderms, Placodermi, Sarcopterygii
Cosmoid Scales or Dermal Armor (most primitive)
layers
Layers = enamel + cosmine (dentin) + spongy bone + lamellar bone
Cosmoid Scales or Dermal Armor (most primitive)
bone
Spongy bone is more open and has spaces/cavities
– Lamellar bone is dense, in layers
Ostracoderm Cosmoid Scale: Enamel from ___ – ___ in origin
ameloblasts, ectodermal
Placoid (Dermal Denticles) Scales:
who
Taxon – Chondrichthyes (evolved from cosmoid type)
Placoid (Dermal Denticles) Scales: layers
Layers = enamel + thick dentin + pulp cavity (bone absent)
Placoid (Dermal Denticles) Scales: what does it look like
Spiny tip of “triangular” scale pierces epidermis
Placoid (Dermal Denticles) Scales: describe placement
isolated scales, scales covering entire body, nearly absent in some rays
Placoid Scales of Shark - most consider placoid scales to be homologous to our ___
teeth
where is ameloblast from and purpose
form ectoderm, deposits enamel
where Is odontoblast from and its purpose
neural crest, deposits dentin
what is the differentiation of ameloblast vs odontoblast determined by
epithelium
histology of dentin vs enamel
Ganoid (Rhomboid) Scales: who
Taxa – fossil & a few living Actinoptergii (gar, sturgeon, a few
others) and fossil Sarcopterygii
Ganoid (Rhomboid) Scales: layers
Layers (derived) = enamel (ganosine) + thin lamellar bone (no
dentin)
Ganoid (Rhomboid) Scales: what do they look like
Small, equal sized scales with little overlap
Ganoid (Rhomboid) Scales: feature
Protective, but flexibility is limited
- Cycloid & Ctenoid (Elasmoid) Scale: who
– Taxa – modern Actionpterygii & Sarcopterygii show independent origins of cycloid scales (derived from ganoid scale type)
- Cycloid & Ctenoid (Elasmoid) Scale: layers
– Layers of thin acellular, fibrous bone
- Cycloid & Ctenoid (Elasmoid) Scale: features and where
Light weight, but protective
– Overlap, improved flexibility
– Body covered, nearly absent in some
Skin of a Bony fish (a teleost) – note, ___
present
mucous cuticle
is dentin and enamel present in cosmoid
yess
is enamel and dentin present in ganoid
enamel yes, dentin no
is enamel and dentin present in cycloid or ctenoid
neither
inside out theory teeth of scales
Inside-out – Teeth first. Conodonts, which are ancient, have
teeth. So teeth came first. Others argue that conodont teeth are
unlike other vertebrate teeth, so they “don’t count
outside in teeth vs scales theory
Outside-in– Scales first. Used as protection and then they
moved inward to pharyngeal region and mouth – lots of fish have
pharyngeal teeth. Based on ostracoderms and placoderms, true
vertebrates with large dermal plates but no teeth. Additionally,
cosmoid scales are chemically more like our modern teeth.
do we really know if teeth became before scales
no
what are pharyngeal teeth
think trypaphobia but with flat round teeth instead
Lamprey “teeth” made of ___, not
___ to scales
keratin, homologous
three layers of epidermis in amphibian integument
stratum basale, transitional layer, status cornuem
amphibian - very thinly keratinized ___ epithelium
stratified squamous
amphibian straum corneum is a
Very thin apical layer
of keratinized cells
glands in amphibian epidermis
Multicellular glands predominate
purpose of mucous in amphibians
mucus important for respiration
histology of amphibian skin
are there pigment cells in the epidermis of amphibians
yes
purpose of microvilli in amphibian skin
Microvilli for increased surface
area for gas exchange, mucus
very important for this process
reptile integumentary
Highly keratinized stratified squamous epithelium
3 layers of reptile integument
Stratum basale (germinativum) – basal layer of cuboidal cells,
mitotically active
– Intermediate zone – composed of recently divided cells in various stages
of development, becoming keratinized
– Stratum corneum– apical layer, heavily keratinized = keratin scales
dermis of reptile integument
Stratum Laxum, Stratum Compactum. Connective tissue w/small bones
(osteoderms, gastralia) in some, such as savannah monitors, crocodilians.
skin replacement in reptiles
Crocodilians – wear & tear
– All snakes – shed all at once
– Most lizards – shed in pieces
what did reptiles invent
Reptiles “invented” claws
gastrula in reptiles
Gastralia composed of dermal bone,
expands to form plastron (bottom) in turtle
what are beaks made of
keratin
Reptiles have three types of chromatophores- pigment producing cell of neural crest origin
Melanophores
– Lipophores
– Iridophores
- Mutations affecting pigment production result in types of ___.
albinos
Mammals and birds only have one type of chromatophore, the ___
melanocyte
dermal melanophore
located in the upper dermis
epidermal melanophores
lower epidermis
melanophores Synthesize and contain black-brown pigment known as ___
(___), can be found as ___ (red-brown)
melanin (eumelanin), pheomelanin
Melanosomes (packages of melanin) are moved within the melanophore to give ___
different appearances.
Birds & mammals only have melanocytes, a specialized melanophore, evolved ___ in the two lineages
independently
if melanosomes are aggregated (together), what color in the cell
light (if spread out, cell is dark)
what are chromatophores mediated by
endocrines
in mammals and birds, melanocytes produce melanosome, whichh transfer to
keratinocytes
where are melanocytes found in bird s and mammals
stratum basale of
mammalian epidermis
lipophores in reptiles have two cell types
xanthophores and erythrophores produce fat
soluble pigments
xanthophores
Xanthophores produce yellow to orange pteridines, also retain
yellow to reddish carotenoids from diet
erythrophores
produce red pteridines
reptile iridophores
Do not produce pigment, contain crystalized of purines –
typically guanine, hypoxanthine, & adenine in reptiles
purines in reptiles
Types of purines and orientation of the crystals determines how
the light is reflected – appearing green, blue, or red =
“structural colors”
where are iridophotes located
Concentrated where melanophores are absent, may play role in
blocking UV rays
