General facts of parasitic nematodes:- Pin worm, giant round worm, whip worm, pork worm, hook worm

Enterobius sp.

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Common name: Pin worm/thread worm/ seat worm

Disease: Enterobiasis (symptoms:- itching in the preanal area)

Host: Human

Habitat: Small intestine

Infective stage: Eggs

Transmission: Ingesting eggs

Parasitic adaptations: Small, sticky, translucent eggs, cuticle

Enterobiu sp -Life cycle 

Trichuris trichuira

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Common name: Whip worm/tap wrom

Disease: Trichuriasis ( Symptoms: Diarrhea, anemia)

Host: Human

Habitat: Colon

Infective Stage: Embryonated eggs

Transmission: Ingesting eggs

Parasitic adaptations: Long slender tapered body, cuticle

Trichinella sp

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Common name: Pork worm

Disease: Trichinosis (Symptoms: nausea, diarrhea, vomiting, fever)

Host: Human, pig, bear, rat

Habitat: Intestine

Infective stage: Cysts (larva)

Transmission: Eating uncooked pork, 

Parasitic adaptations: Long slender body, cuticle

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Ascaris sp

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Common name: Giant round worm

Disease: Ascariasis (Symptoms: Diarrhea, cough, nausea)

Host: Human

Habitat: Intestine

Infective stage: Embryonated eggs ( containing larva)

Transmission: Ingesting eggs

Parasitic adaptations: Long slender body, cuticle, lipid cover around the eggs which is resistant to abrasion and chemicals

Ancylostoma sp

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Common name: Hook worm

Disease: Protein deficiency, anemia, cough

Host: Human, cat

Habitat: Intestine

Infective stage: Filari form larva

Transmission: Penetrating the intact skin of the host

Parasitic adaptations: Dental plates in mouth, slender body, cuticle

Plant senescence in brief

Senescence

Senescence is an important program in which the function of a cell/tissue/whole plant naturally leads to its death.

Senescence involves in plant aging.

When tissues senesce they produce enzymes which can recycle the “expensive” materials and reroute the sub-units to somewhere else that growth takes place.

Overall senescence

·         Occurs in the whole plant.

·         Death takes place right after flower and setting.

·         When the flower dies the whole plant dies too.

·         Ex: Asteraceae ( Sun flower)

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Top senescence

·         After the growth season the part above the ground dies remaining the underground part that can grow for several years.

·         Therefore a rhizome is present.

·         Ex: Weed, Grass

       

Deciduous senescence

·         In dry seasons like winter and summer, the leaves falls and trunk remains.

·         Leaves fall due to avoid the heavy transpiration occurs in the dry season.

·         Ex: Deciduous plants

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Progressive senescence

·         Older parts die due to the senescence and the new organs and tissues continue their development.

·         Ex: Green trees

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As above mentioned, senescence can occur in cells as well as tissues.

Cell senescence

·         Can be described according to the senescence in cell membrane and organelle level.

Senescence in cell membrane

Lipid phase change

·         Plasma membrane has the fluid mosaic structure.

·         This structure changes as the liquid crystalline state changes into the solid-gel state.

·         Therefore the membrane gets inflexible and hard.

Degradation and preoxidation of lipids

·         Lipid content gets decreased.

·         It occurs as the lipid synthesis decreases and lipase content increases.

·         Phospholipase, lipoxygenase, MDA and active O₂ content increase.

Increase in Phospholipase activity

·         Mainly the activity of Phospholipase D takes place in plants.

Biomembrane degradation and leakage

·         The equilibrium of ions breaks down.

·         Metabolisms get disordered.

Senescence in organelle level

·         Ribosomes and RER break down.

·         Chloroplasts collapse and mitochondrion cristae are swollen.

·           As the vacuoles break down, all the toxics inside them is released to the cell plasma.

·         Therefore the autophagy takes place and the senescence of organelles activates.

Population dispersion

Dispersion is the pattern of spacing among the individuals within the population. Basically there are three patterns.

-          Clumped dispersion

-          Uniform(regular) dispersion

-          Random dispersion

Clumped

·         Commonest pattern that can observed in populations.

·         Individuals are bunched into groups within the population.

·         This is mainly results from the response to the unevenly distributed resources in their environment.

·         Also there are positive interactions between the individuals.

·         This supplies many advantages to the population such as protection from predators, reproduce and increase the population size and decrease the energetic cost of moving to do work.

Uniform

·         Individuals are uniformly spaced within the population.

·         Mainly results from the competition for resources.

·         Therefore there are aggressive interactions between the neighbours.

Random

·         Individuals are randomly spaced within the community.

·         Not that much common in nature.

·         This occurs as there are no strong interactions between the individuals.

·         They show neutral interactions.

Moulting and cuticle formation of insects

Hormones such as Ecdysone and bursicon play an important role during the events in moulting.

Apolysis

·         Epidermal cells divide and change their shape.

·         These cells separate from the inner surface of the old endocuticle and leave out the sub-cuticular space.

·         This space is consisting of moulting fluid, proteinase and chitinase.

·         These enzymes are inactive in this stage.

Formation of the epicuticle

·         Cuticulin is deposited below the moulting fluid and above the epidermis.

·         This forms the new Cuticulin layer.

·         Inner protein epicuticle is deposited under the Cuticulin layer.

Deposition of new procuticle

·         Deposition of procuticle occurs beneath the Cuticulin layer.

·         After the deposition enzymes in the moulting fluid activate and digest the old endocuticle.

·         Only a thin layer of the old endocuticle is left out.

·         This layer is called as Ecdysial membrane. These lines are located in the median lines of head and thorax.

·         Weak lines appear along this Ecdysial layer.

·         Wax secretion occurs on to the surface of the new cuticle.

Ecdysis

·         Moulting fluid and digested old endocuticle are absorbed.

·         Intake of the air and muscular contractions cause the insect’s body to swell.

·         This leads the old exoskeleton to split open along the weak lines.

·         Insect draws itself out.

·         All parts of the old cuticle are shed.

·         This old cuticle is called as cast skin.

Expansion of the new procuticle

·         New cuticle is soft and pale.

·         At this moment new procuticle expands before it hardens.

Hardening and darkening of cuticle

·         Hardening of the cuticle is known as sclerotization.

·         This forms sclerites which are rigid plates of exoskeleton.

·         It also darkens the cuticle. This is known as tanning.

Deposition of the new endocuticle

·         New endocuticle deposits after the moulting and tanning.