This document provides an overview of mammalian characteristics and diagnostic features. It discusses various skin glands found in mammals like mammary glands, sweat glands, scent glands, and details their structure and function. Hair characteristics are also described, including hair structure, color variation, and sensory modifications. Finally, horns and antlers are summarized, distinguishing between true horns, antlers, and rhinoceros horns.

1. M . S C Z O O L O G Y P A R T I I
B Y
MaMMalian
CharaCteristiCs
NAVEED AKHTAR
NAVEED AKHTAR
ASSISTANT PROFESSOR OF ZOOLOGY
ASSISTANT PROFESSOR OF ZOOLOGY

2. Lecture#1
Skin Glands and Hairs

4. Introduction
 The basic structural plan of the mammalian
characteristics was inherited from the mammal like
reptile (order therapsida) about 200 MYA
through synapsid lineage
 The key to the mammalian success was the ability to
 The key to the mammalian success was the ability to
respond environmental stimuli than archosaurian
 When first mammal appeared in the triassic period,
no show further skeletal modifications of therapsid
body plan
 The most important development was articulation of
the dentary/squamosal

5.  The first character to be developed in the therapsid was
endothermy
 Mammals have three to six fold capacity of energy production
than do reptiles and a standard metabolic rate 8-10 times
higher
 Relative to the body size, internal organs of the mammals are
 Relative to the body size, internal organs of the mammals are
larger than reptiles
 Mitochondrial surfaces of the major body organs of the heart,
brain and kidneys are greater ensuring endothermy
 Lungs surface area also facilitate in high absorption of oxygen
 High absorptive area of the digestive track also facilitate
endothermy

7. Diagnostic Characters of Mammals

9. Soft Anatomy
 SKIN GLANDS
 1. Mammary Glands
 Mammalain skin contains different types of glands
not found in other vertebrate groups
 Most important on is Mammary Gland
 Most important on is Mammary Gland
 These gland provide nourishment to young during
postnatal period
 Mammary glands consist of comp[lex system of
ducts that reach outside through prominence called
nipple or teats

13. Conti…..
 During the late pregnancy, epithelium of the ducts is
stimulated by the endocrine secretions especially
estrogen and progesterone
 Secretary epithelium divide rapidly and produce milk
after birth
after birth
 Secretion of the anterior pituitary gland release
Prolactin and Growth Hormones that stimulate
production of milk
 Composition of the milk varies from species to
species of mammals

14.  Cow's Milk contain 85% of water, the dry weight
contains 20% protein, 20% fats and 60% sugars
mainly lactose along with vitamins and salts
 Milk of those mammals that show very rapid growth
of young contain high amount of Protein and Fat
of young contain high amount of Protein and Fat
 Example:
 Seals milk contains 15 times high fat and 5 times
high protein as compared to cow’s milk

15. Cow Milk Composition

16.  Sucking develop strong pair bond between mother
and young, also its time of the rapid learning
especially for mammals having complex foraging and
social behaviors that prepare them for adult
independent life
independent life
 Some males can lactate like females, proving once
again how little we know about the lives of bats.
 The lactating males are Dayak fruit bats
(Dyacopterus spadiceus) found in parts of
southeast Asia, especially Borneo

17. The only male mammal to lactate

18.  They just lactate like Galactorrhea in human females
(Racey et al., 2009)
 Suckling Variation in Mammals
 Monotreams
 Most mammals suck milk through nipples projections
 Nipples are lacking in monotreams and they young suckle
 Nipples are lacking in monotreams and they young suckle
from the tufts of hairs on mammary area
 Aquatic Mammals
 Aquatic mammals belong to order cetaceans including
Dolphin, Whale and Porpoises have muscle that force milk in
young mouth , an adaptive radiation in aquatic animals with
no lips
 https://www.youtube.com/watch?v=n79nj6J2cqg

19.  The number of nipples vary in mammals from two in
many kinds of mammals to 19 nipples in opposum ,
Marmosa

20.  2. Sweat Glands
 Provide evaporative cooling to maintain
thermoregulation
 Also eliminate some waste materials
 Evening distributed on surfaces of most mammals,
 Evening distributed on surfaces of most mammals,
but in some restricted to some body parts
 In humans, ungulates, sweat glands are only present
on feet or venter (abdomen)
 Sweat glands are completing lacking in cetaceans
cetaceans
 some bats and rodents also lack sweat glands

21.  Types of Sweat Glands
 There are two kinds of sweat glands:
 Eccrine glands secrete a watery fluid that, if
evaporated on the skin’s surface, draws heat away
from the skin and cools it.
from the skin and cools it.
 Eccrine glands occur in hairless regions, especially
the foot pads, in most mammals, although in horses
and most primates they are scattered over the body
 They are either reduced or absent in rodents, rabbits,
and whales

22.  2. Apocrine glands
 Apocrine glands are larger than eccrine glands and
have longer and more convoluted ducts.
 Their secretory coil is in the dermis and extends deep
into the hypodermis.
into the hypodermis.
 They always open into a hair follicle or where a hair
once was
 Apocrine gland development occurs near puberty
and is restricted (in the human species) to the axillae
(armpits), mons pubis, breasts, prepuce, scrotum,
and external auditory canals

23.  In contrast to the watery secretions of eccrine
glands, apocrine secretions are milky fluids, whitish
or yellow in color, that dry on the skin to form a
film
 Apocrine glands are not involved in heat regulation.
 Apocrine glands are not involved in heat regulation.
Their activity is correlated with certain aspects of
the reproductive cycle.

24.  3. Sebaceous Glands
 A sebaceous gland is a microscopic exocrine gland in
the skin that opens into a hair follicle to secrete an oily or
waxy matter, called sebum, which lubricates the hair and
skin of mammals
skin of mammals
 In humans, sebaceous glands occur in the greatest number
on the face and scalp, but also on all parts of the skin except
the palms of the hands and soles of the feet. In the
eyelids, meibomian glands, also called tarsal glands, are a
type of sebaceous gland that secrete a special type of sebum
into tears

26.  4. Scent Gland /Musk Glands
 Scent glands are exocrine glands found in
most mammals. They produce semi-
viscous secretions which contain pheromones and
other semiochemical compounds. These odor-
other semiochemical compounds. These odor-
messengers indicate information such as
status, territorial marking, mood, and sexual power
 The odor may be subliminal—not consciously
detectable

27.  The even-toed ungulates (Artiodactyla) have many
specialized skin glands, the secretions of which are
involved in semiochemical communication
 These glands include the sudoriferous glands (located on
the forehead, between the antlers and eyes),
the preorbital glands (extending from the
medial canthus of each eye), the nasal glands (located
the preorbital glands (extending from the
medial canthus of each eye), the nasal glands (located
inside the nostrils), the interdigital glands (located
between the toes), the preputial gland (located inside the
foreskin of the penis), the metatarsal glands (located
outside of the hind legs), the tarsal glands (located inside
of the hind legs), and the inguinal glands in the lower
belly or groin area.

29.  Deer musk is a substance with a persistent odor,
obtained from the caudal glands of the male musk
deer.
 Although more commonly referred to as "musk", the
term itself is often used to describe a wide variety of
term itself is often used to describe a wide variety of
"musky" substances from other animals such as
the African civet ("civet musk") or various synthetic
musks whose compound exhibits some character of
deer musk.

30.  These glands are various used for attracting mates,
marking territories, communication during social
interactions, and protection

31. 2. Hair
2. Hair
 Mammals body is covered with hairs, a character not
no structural homolog with other vertebrate group
 Hair were perhaps developed in the therapsids
before loss of the scaly covering lost
This is also evident is mammals like armadillos
 This is also evident is mammals like armadillos
having scaly or body tail, hair projects from the
scales
 Hair Structure and Modification in Mammals
 Hair consist of the dead epidermal cells that are
strength by the keratin, a tough protein

32. Conti….

34.  Cold water are insulated by hairs and blubber
 Some mammals like whale and porpoise hairsless
and prefect to live warm environment or have
alternative adaptations like thick layer of
subcutaneous Blubber
subcutaneous Blubber
 Hairs are sparsed (‫)ﻣﻨﺘﺸﺮ‬ on mammals like elephants ,
hippopotami and have surface area to volume ratio
adjusted for heat adjustment


35.  Hairs are periodically changed along with
pigmentation in mammals
 Molts occur when a juvenile mammal gets its first
adult pelage
Pigmentation and molts allow mammals to be
 Pigmentation and molts allow mammals to be
different colors in different seasons Brown in
summer White in winter leukemism
 Lack of pigment results in albinism recessive gene
blocks pigment formation (don’t confuse with
leukemism) Excess of black pigment is melanism

38.  Most mammals have two kinds of hair Thick, soft
underhair provides insulation Coarse, long guard
hair - protects and provides coloration

42. Adaptive Radiation in Color Pattern of
Mammalian Hair
 The pelage color of small mammals closely resemble
with soil color
 This color pattern help to avoid predators attack
while foraging
 Pelage color also help in thermoregulation
 Pelage color also help in thermoregulation
 For example, pale bodies of Arabian oryx and
Addax both are desert dewlling and pelgae
help in light adjustment

43. Arabian oryx and Addax

44.  Contershading
 Countershading, the widespread tendency of
mammalsto be darker on the side that receives
strongest illumination, has classically been explained
as an adaptation for camouflage
as an adaptation for camouflage

48. The penguin is a drastic example of
countershading

49. Conti….

50.  In humans, hair is shed and replaced throughout life
(although balding males confirm that replacement is not
assured!).
 In the simplest cases, such as foxes and seals, the coat is
shed once every summer. Most mammals have two
shed once every summer. Most mammals have two
annual molts, one in the spring and one in the fall
 Outside the Arctic, most mammals wear somber colors
that are protective. Often the species is marked with
“saltand-pepper” coloration or a disruptive pattern that
helps make it inconspicuous in its natural surroundings

51.  Examples are the spots of leopards and fawns and
the stripes of tigers. Skunks advertise their presence
with conspicuous warning coloration.

52. Sensory Modification of Hairs
 The hair of mammals has become modified to serve
many purposes.
 Bristles of hogs, spines of porcupines and their kin, and
vibrissae on the snouts of most mammals are examples
 Vibrissae, commonly called “whiskers,” are really
 Vibrissae, commonly called “whiskers,” are really
sensory hairs that provide a tactile sense to many
mammals.
 The slightest movement of a vibrissa generates impulses
in sensory nerve endings that travel to special sensory
areas in the brain. Vibrissae are especially long in
nocturnal and burrowing animals

54. Mystacial Pad

56. Protection
 Porcupines, hedgehogs, echidnas, and a few other
mammals have developed an effective and dangerous
spiny armor.
 When cornered, the common North American
porcupine turns its back toward the attacker and
porcupine turns its back toward the attacker and
lashes out with the barbed tail
 The lightly attached quills break off at their bases
when they enter the skin and, aided by backward-
pointed hooks on the tips, work deeply into tissues.

57.  Dogs are frequent victims but fishers, wolverines,
and bobcats are able to flip the porcupine onto its
back to expose vulnerable underparts

59. 3.Horns and Antlers
 Three kinds of horns or hornlike structures are found
in mammals
 True horns, found in ruminants (for example,
sheep and cattle), are hollow sheaths of keratinized
epidermis that embrace a core of bone arising from
epidermis that embrace a core of bone arising from
the skull.
 True horns are not normally shed, usually are not
branched (although they may be greatly curved),
grow continuously, and are found in both sexes.

60.  Horns may be absent from pronghorn antelope
females but, if present, are shorter than those of the
male.
 Antlers of the deer family are branched and
composed of solid bone when mature.
composed of solid bone when mature.
 During their annual spring growth, antlers develop
beneath a covering of highly vascular soft skin called
velvet
 Except for caribou), only males of the species
produce antlers

61.  When growth of the antlers is complete just before
the fall breeding season, the blood vessels constrict
and the stag removes the velvet by rubbing the
antlers against trees.
 Antlers are shed after the breeding season. New buds
 Antlers are shed after the breeding season. New buds
appear a few months later to herald the next set of
antlers.
 For several years each new pair of antlers is larger
and more elaborate than the previous set

62. Annual growth of buck deer antlers

65.  Annual growth of antlers places a strain on the
mineral metabolism, since during the growing
season an older moose or elk must accumulate 50 or
more pounds of calcium salts from its vegetable diet
 The rhinoceros horn is the third kind of
 The rhinoceros horn is the third kind of
hornlike structure. Hairlike keratinized filaments
that arise from dermal papillae are cemented
together to form these structures, which are not
attached to the skull