Download PLP 3104

PLP 3104
Fundamentals of entomology
Internal systems of
an insect
Dr. Lau Wei Hong
Department of Plant Protection
Faculty of Agriculture
UPM
Digestive system
http://philschatz.com/biology-book/resources/Figure_28_04_06.png
Foregut (stomodeum)
Digestive system
Mouth
• Mandibles break down food into small pieces. Enzymes excreted from the
mouth salivary glands will help in breaking down food and also add
moisture.
Pharynx
• Peristalsis (rhythmic muscular contractions of the gut wall).
Crop
• Temporary food storage, digestion may occur as a result of salivary
enzymes.
Proventriculus
• Tooth-like denticles that grind food particles.
http://entomology.osu.edu/~bugdoc/Ent101/101Anatomy/101Anatomy_Pics/gut.TIF.JPG
Stomodeal valve
• Regulates the flow of food from the stomodeum to mesenteron.
1
Midgut (mesenteron)
Digestive system
Gastric caecum
• Finger-like projection (2-10), provide extra surface area for
secretion of enzymes or absorption of water.
Ventriculus
• Primary site for enzymatic digestion of food and absorption of
nutrients.
• Microvilli (microscopic projections): increase surface area for
nutrient absorption.
• Peritrohphic membrane: protects the digestive cells without
inhibiting absorption of nutrient molecules.
Pyloric valve
• Regulates the flow of material from mesenteron to
proctodeum.
Hindgut (proctodeum)
Malpighian tubules
• long, spaghetti-like structure
• Excretory organs: remove nitrogenous wastes
(principally ammonium ions, NH4+) from hemolymph.
• Toxic NH4+ is converted to urea and then to uric acid
by a series of chemical reactions.
Ileum, colon, rectum and anus
• Homeostasis, regulating the absorption of water and
salts from waste products in the alimentary canal.
https://sp.yimg.com/xj/th?id=OIP.M1313a80ce124374e0efa7e65292d66cdH0&pid=15.1&P=0&w=300&h=300
Respiratory system
•
RS is responsible for:
1. Deliver sufficient O2 to cells
2. Remove CO2 (waste product of cellular respiration)
•
Insects breathe passively through special openings in the
side of cuticle called spiracles. 1 pair of spiracles per body
segment of thorax and abdomen.
•
These opening lead the O2 through a complex system of
tubes called trachea.
•
Valve: muscle that regulates air flow, contract to close
spiracle, relax to open spiracle.
2
Respiratory system
•
Spiracle
•
•
Tracheole:
special cells at the end of each tracheal branch, provides a thin, moist
interface for exchange of gasses between atmospheric air and a living
cell.
– Valves
– Hairs that filter out dust as the air enters
•
– O2 dissolves in the liquid and then diffuses into the cytoplasm of an adjacent
cell.
– CO2 diffuses out of the cell and body through the tracheal system.
Taenidia:
– Cuticle that winds spirally through the membranous wall.
– Prevents tracheal tube collapse under pressure.
– Gives tracheal tubes the ability to flex and stretch.
•
Air sacs:
– Store a reserve of air.
– Fill and enlarge as insect breaks free of the old exoskeleton and expands a
new one – molting.
Circulatory system
• Open system: blood is not contained within a system of
vessels.
• Hemolymph (blood) consists of 90% plasma (liquid) and 10%
hemocytes (cells).
• Functions:
– Transport of nutrients and hormones
– Storage of substances (amino acids)
– Water reservoir
– Hydrostatic pressure for movement
– Protection from foreign organisms that have invaded body
(immunological function) – phagocytosis and
encapsulation.
http://blog.inceptsaves.com/files/2011/03/Trypanophobia.jpg
How does hemolymph move
throughout the insect body?
• Only one vessel is present in the insect circulatory system:
the dorsal vessel.
• The dorsal vessel acts as the heart (in the abdominal region),
pumping hemolymph forward into the anterior region (in the
head and thorax), where it acts as the aorta and dumps the
hemolymph into the head.
• It flows posteriorly and is returned to the heart via ostia, which
are small slits in
the heart region
of the dorsal
vessel designed
for hemolymph
uptake.
NERVOUS SYSTEM
Nervous
• What happen when you attack the
fly?????
• 3 components
– 1)brain
central
– 2)ventral nerve cord
nervous system
– 3)peripheral nervous system (extend outside
the central nervous system to serve the limbs
and organs
• Each of the components consists millions
of neurons
3
WHAT IS A NEURON?
http://1.bp.blogspot.com/-EmcKLvxRm-Y/TbBAyh1nH4I/AAAAAAAAAOI/LLkE0dpGLh8/s1600/insect-diagram.jpg
Categories of neurons
Afferent (sensory) neurons
– bipolar or multipolar cells
– dendrites associated with sense
organs or receptors.
– carry information toward the central
nervous system.
• Nerve cell
• For information transfer
• Composed of
– 1) dendrite (enter the cell
body)
– 2) cell body (nucleus found)
– 3) axon( leaving the body)
• Repeating unit of neuron form a
nervous system
• Individual nerve cells connect
with one another through
special junctions, called
synapses.
Efferent (motor) neurons
– unipolar cells
– conduct signals away from the central
nervous system
– stimulate responses in muscles and glands.
A
D
A
D
BRAIN
Interneurons
– unipolar cells (often with several collaterals
and/or branching axons) that conduct signals
within the central nervous system.
• Nerve cord to the head is the BRAIN
• 3 pairs of ganglia region:
– 1)protocerebrum: associated with vision; they
innervate the compound eyes and ocelli.
2)deotocerebrum: pair lobes with sensory
pathway to antennae
– 3)tritocerebrum: lobes with connective to 1st
ganglion of ventral nerve cord
4
VENTRAL NERVE CORD
• 1) subesophageal ganglion
– innervates mandibles, maxillae, and labium,
hypopharynx, salivary glands, and neck
muscles.
• 2) thoracic ganglia
– ) control locomotion by innervating the legs
and wings.
• 3) abdominal ganglia
http://1.bp.blogspot.com/-EmcKLvxRm-Y/TbBAyh1nH4I/AAAAAAAAAOI/LLkE0dpGLh8/s1600/insect-diagram.jpg
– control movements of abdominal muscles.
PERIPHERAL NERVOUS SYSTEM
ENDOCRINE SYSTEM
1) neuron of sensory organs (sensory
neuron)
2) neuron attached to muscles (motor
neuron)
• Function of insect nervous system critical
in insect control
consists of those glandular cells, tissues,
and organs whose products (hormones)
supplement
the
rapid,
short-term
coordinating functions of the nervous
system.
HORMONE
• Chemical signal sent from cells in one part
of an organism to cells in another part (or
parts) of the same individual.
• Chemical messenger
• Produced in very small quantities, but
cause big changes in their target cells.
• Effect may be stimulatory (pencetus) or
inhibitory (perencat).
http://cronodon.com/images/ant_glands_v2.jpg
5
Categories of hormoneproductin cells in insects
1) Endocrine glands -- producing hormones and releasing them
into the circulatory system.
2) Neurohemal organs -- store their secretory product in a special
chamber until stimulated to release it by a signal from the nervous
system (or another hormone).
3) Neurosecretory cells -- specialized nerve cells (neurons) that
respond to stimulation by producing and secreting specific chemical
messengers. - a link between the nervous system and the
endocrine system
Endocrine glands
• the largest glands are found in the
prothorax: PROTORACIC GLANDS (A)
• Produce ecdysteroids/ molting
hormones(ECDYSONE)
• stimulate synthesis of chitin and protein in
epidermal cells for MOULTING PROCESS
• Once reaches adult stage, its prothoracic
glands wither (kering/kecut):
(A)
• never molt again.
(A)
4) Internal organs -- hormone-producing cells are associated with
organs like ovaries and testes, the fat body, and parts of the
digestive system
Neurohemal organs
Neurosecretory cells (D)
• 1) CORPORA CARDIACA (B)
– Release prothoracicotropic hormone (PTTH)
– Only release PTTH when received signal from
brain.
• 2) CORPORA ALLATA (C)
– manufacture juvenile hormone (JH),
– Inhibits the development of adult characteristics
during the immature stages
– promotes sexual maturity
(B)(C)
during the adult stage.
• found in clusters, both medially and laterally in the
insect's brain.
• specialized nerve cells (neurons) that respond to
stimulation by producing and secreting specific chemical
messengers. Functionally, they serve as a link between
the nervous system and the endocrine system
• secrete brain hormone.
(D)
(D)
(D)
(B)(C)
Internal organs
• Ovaries and testes
– produce gonadal hormones: to coordinate
courtship and mating behaviors.
•
Ventral ganglia in the nervous system
– eclosion hormone that helps an insect shed
(tanggal) its old exoskeleton
– bursicon hormone: that causes hardening
and tanning of the new one.
http://www.dinkuminteractive.com/wp-content/uploads/2011/05/End.jpg
6