Integument of fish, amphibians, reptiles Flashcards by Emma Davies

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

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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

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what does lamprey skin look like

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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

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Fish epidermis of (shape) epithelium
(usually) often protected by ___

stratified cuboidal, mucopolysaccharide mucous cuticle

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fish epidermal glands present

mucous, granular

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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

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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)

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what do granular and mucous glands in the minnow look like

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Most extant bony fish have ___

overlapping scales

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Histological section of skin layers of a juvenile
steelhead trout with overlapping scales

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dermis of fish

fibrous connective tissue, scales

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fibrous connective tissue of fish

Fibrous Connective Tissue – increases
strength and resists deformation (rippling) in skin due to drag

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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

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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

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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

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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

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Cosmoid Scales or Dermal Armor (most primitive)
who has them

Taxa – only in fossil Ostracoderms, Placodermi, Sarcopterygii

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Cosmoid Scales or Dermal Armor (most primitive)
layers

Layers = enamel + cosmine (dentin) + spongy bone + lamellar bone

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Cosmoid Scales or Dermal Armor (most primitive)
bone

Spongy bone is more open and has spaces/cavities
– Lamellar bone is dense, in layers

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Ostracoderm Cosmoid Scale: Enamel from ___ – ___ in origin

ameloblasts, ectodermal

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Placoid (Dermal Denticles) Scales:
who

Taxon – Chondrichthyes (evolved from cosmoid type)

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Placoid (Dermal Denticles) Scales: layers

Layers = enamel + thick dentin + pulp cavity (bone absent)

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Placoid (Dermal Denticles) Scales: what does it look like

Spiny tip of “triangular” scale pierces epidermis

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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

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

Integument of fish, amphibians, reptiles Flashcards

(79 cards)