What is Pheromone Difference between hormones and pheromone Types of glands (exocrine and endocrine) exocrine gland its origin and example Types of exocrine gland (I—II—III) function of exocrine glands distribution of exocrine glands

1. PHEROMONES

2. Lecture contents
1-What is Pheromone
2- Difference between hormones and pheromone
3-Types of glands (exocrine and endocrine)
4- exocrine gland its origin and example
5- Types of exocrine gland (I—II—III)
6- function of exocrine glands
7- distribution of exocrine glands

3. PHEROMONES: -
A pheromone is a secretion that, if passed to another individual
of the same species, causes it to respond, physiologically or
behaviorally, in a particular manner.
- Pheromones are thus concerned with signaling between
individuals of the same species and are therefore often
important in sexual behavior and in regulating the behavior and
physiology of social and sub-social species. It is probably true
that pheromones are used in communication by at least some
species in all the insect orders.

4. Many pheromones are perceived as scents by olfactory
receptors and affect the recipient via the central nervous
system. In other cases, pheromones are ingested by the
recipient. These may be perceived by the sense of taste,
exerting their effects via the central nervous system, or the
pheromone, once ingested, may be absorbed and influence
biochemical reactions within the recipient. Pheromones that
affect behavior directly through the nervous system are called
releaser pheromones; those that affect metabolism are known
as primer pheromones

5. PHEROMONES
Hormones, secretion of endocrine glands, are concerned with regulation within the
organism. Other chemical substances are concerned with communication between
organisms.
Chemicals with an intraspecific function are called pheromones; those with an
interspecific function are often called allelochemicals. Some chemicals can serve both
functions, even in one insect. Most pheromones and allelochemicals are produced by
ectodermal glands secreting to the outside of the body.
Pheromones represent an intraspecific communication among members of the same
species.
Allelochemicals, produced by individuals of one species, modify the behavior of
individuals of a different species (i.e. an interspecific effect).
Glands producing chemicals for interspecific communication usually have reservoirs
while most pheromone glands do not. Pheromones used for marking, however, are
usually stored in a reservoir. Many chemicals used for defense are stored within the
body and are not secreted.

6. Exocrine and Endocrine Glands
There are two types of glands: exocrine and endocrine. Exocrine
glands discharge their products via aperture or ducts into the
external world or lumens of various viscera, for example, the
reproductive tract or the alimentary canal.
Endocrine glands are typically ductless, and their secretions are
usually released directly into the hemolymph.

7. Exocrine glands:-
Exocrine glands may be single cells or small aggregates of secretory
cells. A single secretory cell, for example, one that secretes a toxic
substance, may contain an intracellular ductile and may also be
associated with another cell, a ductule cell, that forms a duct for the
transfer of secretions from the gland cell to the outside. More
complex glands may be formed as invaginated masses composed of
large numbers of cells that secrete their products into a common
lumen with a single aperture that may in turn open into a common
duct(e.g. Salivary glands)

8. Further, complex glands may be associated with a
separate, but attached, reservoir in which large
amounts of secretion can accumulate(e.g. Salivary
reservoirs in many insects ).
Externally, fine hairs may be associated with a gland
opening or gland duct opening. Such hairs may aid in
rapid dispersal of the secretion products, such as one
involved in chemical communication between
individuals.

9. Exocrine glands are generally of ectodermal origin and are
found widely scattered over the insect body. The specific
location of a given gland is often correlated with its function.
For example, salivary glands are typically derived from the
labial segment of the insect head during embryogenesis,
although in the fully formed insect, they are usually located in
the thorax on either side of the foregut.
Glands associated with the reproductive system are closely
connected with the internal genital organs.

10. Exocrine glands fall into three classes.
Class I gland cells have the outer plasma membrane produced
as a microvilli or parallel lamellae which may abut directly
onto the cuticle, but are often separated from it by a space in
which their secretion presumably accumulates. The cuticle
above the cells is usually unmodified and it is presumed that
the secretion reaches the external surface of the cuticle via
the pore canals and epicuticular filaments.
They have no reservoir. Class I cells are often involved in
pheromone production and the pheromone is released
directly following its synthesis.

11. Class II gland cells are derived from epidermal cells, but
have no direct contact with the cuticle, nor do they have
a duct. They are only known from the sternal glands of
termites.
Class III glands are also below the epidermis but
connect with the exterior by a duct. The distal surface of
the gland cell is developed into microvilli which
surround a cavity.

12. The lining of the duct leading to the outside is
continuous with the epicuticle on the outside of the
body. Internally it projects into the cavity of the gland
cell and it is perforated forming a structure called the
end apparatus. The duct is produced by a separate cell.
In some cases, the glands open into an epidermal
invagination which may then serve as a reservoir in
which the pheromone of social Hymenoptera where
larger quantities of pheromone are produced.

14. Functions of the Exocrine glands:-
Functionally (i.e., based on secretion), exocrine
glands can be placed into four major categories with
the specific types of glands fitting into one or more of
these groups:-
Defense – Intraspecific communication- Building
structural materials – Transport of Materials in the
liquid state.

15. Distribution of pheromone glands:-
In many female Lepidoptera, the glands producing the male sex
attractant pheromone lie beneath an intersegmental membrane of the
posterior abdominal segments, usually between segments 8 and 9.
It is often ventral in position, but in some species, it is dorsal and in
others, it occurs as a ring all around the body.

16. Many male Lepidoptera have pheromone-producing glands
which are often associated with structures used for pheromone
dispersal. Male Noctuidae produces an aphrodisiac pheromone
in special glands, called Stobbe‫’׳‬s glands, in the second
abdominal segment. Each gland consists of several glandular
cells which are greatly enlarged in the adult, each enclosing a
large central cavity continuous with the base of a hair. After
enclosing, the fluid in the cavity is discharged into the hair,
which is tubular and ends at the base of a brush of scales.

17. Male cockroaches have glands producing an aphrodisiac pheromone
beneath the tergites of certain abdominal segments. The gland cells open
at the surface of the cuticle through small ducts, sometimes in association
with tufts of long setae which possibly assist in dispersal of the
pheromone.
In Aphids, the alarm pheromone is produced by glands associated with
the cornicles, while the sex pheromone of the female is released from
glands on the hind tibiae in some species.
The hindgut produces pheromones associated with aggregation in bark
beetles.
The oviposition marking pheromone of the fruit fly is produced in the
posterior midgut. This is one of the few examples of a pheromone not
produced by glands derived from ectoderm