11 Insect Metamorphosis

Dr. PARVISH PANDYA’s presentation

“Metamorphosis inInsects”

A presentation compiled from various sources by

Dr. PARVISH PANDYA,Zoology Dept. Bhavan’s College, Andheri.

Dr. PARVISH PANDYA’s presentation

Sites from which presentations have been downloaded and later editted. I am indeed thankful to them for their kindness and support :http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.htmlhttp://faculty.pnc.edu/jcamp/parasit/parasit.htmlhttp://www.amnh.org/rose/hope/creatinghope/http://www.biology.eku.edu/SCHUSTER/bio%20141/POWERPOINT%20NOTES/Intro%20to%20Protozoa_files/fullscreen.htmhttp://www.biosci.ohio-state.edu/~zoology/eeob405/http://www.tulane.edu/~wiser/protozoology/pwpt/http://www.iep.water.ca.gov/suisun/photos/wildlife.htmlhttp://www.uta.edu/biology/marshall/2343/http://www.uta.edu/biology/faculty/faculty.htmlhttp://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htmhttp://bio.fsu.edu/http://www.aw-bc.com/http://www.nhm.org/http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/

It is very easy to find mistakes in these presentations…..I request you to kindly rectify them and supply me the modifications needed at parvishpandya@yahoo.comThanks a lot and have fun in teaching & learning Zoology….

Dr. PARVISH PANDYA’s presentation

Insect metamorphosis

“change in form”

Dr. PARVISH PANDYA’s presentation

Dr. PARVISH PANDYA’s presentation

Dr. PARVISH PANDYA’s presentation

Entomological Terms

Stadium: period of time between successive molts

Instar: the insect itself between two successive molts

Stage: principal divisions in life cycle (egg, larva, nymph, pupa, adult)

Example: The first instar (first larval stage) lives in wood.

Dr. PARVISH PANDYA’s presentation

Simple Metamorphosis1. Ametabolous (“no”)

wingless as adults; silverfish, collembola

2. Hemimetabolous (“incomplete”)aquatic nymphs that do not resemble adults; mayflies, dragonflies, etc.

3. Paurometabolous (“gradual”)nymphs and adults live in same habitat; proportions differ; bugs

Dr. PARVISH PANDYA’s presentation

Metamorphosis

LarvaeYoung very different from adults

Holometabolous

Nymphs (land)Naiads (water)

Specific number of molts

Paurometabolous

instarslarvae look like adults, just smaller

Ametabolous

Young calledAppearanceType

Dr. PARVISH PANDYA’s presentationAmetabolous Incomplete Complete

Dr. PARVISH PANDYA’s presentation

“Simple”

“Complete”

Dr. PARVISH PANDYA’s presentation

Dr. PARVISH PANDYA’s presentation

Metamorphosis• ancestral condition – ametamorhic• continue molting after sexual maturation• indeterminate no. molts

Thysanura

Dr. PARVISH PANDYA’s presentation

Hemimetabolous Development• “incomplete” metamorphosis• final molt - wings and genitalia• some with non-feeding reproductive stages

Incomplete metamorphosisIn mayfly

Dr. PARVISH PANDYA’s presentation

Review Metamorphosis

Dr. PARVISH PANDYA’s presentation

Dr. PARVISH PANDYA’s presentation

Complete Metamorphosis

(Holometabolous)Wings develop internally.egg, larvae, pupa, adultbeetles, butterflies, fleas, flies, bees, etc.

Dr. PARVISH PANDYA’s presentation

Dr. PARVISH PANDYA’s presentation

B is for Butterfly

Though the butterfly hasn’t a notionOf how to accomplish eclosionIt always takes placeWith exquisite grace,Gymnastics, and later, slow motion

Dr. PARVISH PANDYA’s presentation

Holometabolous Development• resting stage between larval instars and adult• the ultimate innovation why so successful?• hypothesis: multiple niche exploitation• relative stage-specific selection• non-feeding reproductive stages

pupa

Dr. PARVISH PANDYA’s presentation

Pupation• larval tissues are partly - entirely destroyed• replaced by growth of imaginal disks

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a-Ecdysone

Corpus alatum

Prothoracicgland

Juvenilehormone

Tobaccohornworm

Dr. PARVISH PANDYA’s presentation

See Elzinga, p. 133

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Commercial silkworm, Bombyx mori

Normal Development

Corpora allataremoved(less JH)

Dwarf pupaand adult

Corporaallataremoved(less JH)

Very smallpupa and adult

Corpora allata

implant (more JH)

Giants

6

Dr. PARVISH PANDYA’s presentation

Hypermetamorphosis

• Occurs in parasitic insects where firstinstar seeks out the host, and once in the host, molts into a less active larva.

• Examples: Coleoptera: MeloidaeColeoptera: Rhipiphoridae

Strepsiptera (twisted-wing parasites)A few Diptera and Hymenoptera

Dr. PARVISH PANDYA’s presentation

Intermediate Types of Metamorphosis

A. Thrips: larva, prepupa, pupa, adult

B. Whiteflies: 1 instar (active and wingless), 2-3 instars (sessile and scale-like), 4 instar, adult

C. Male scale insects: 1 instar (crawler), subsequent instars, pupa, adult (winged)

Dr. PARVISH PANDYA’s presentation

Hypothesis: larval stage (holometaboly) resulted from altered hormonal control of embryogenesisTrumen and Riddleford ’99. Nature 401: 447-452• Ecdysteroids and Juvenile Hormones• obs. JH absent during embryo formation in ametabolous and hemimetabolous insects• -> developing embryo resembles adult• holometabolous insects: early appearance of JH suppresses some adult-directed growth

Dr. PARVISH PANDYA’s presentation

Blattodea

Diptera

MantodeaIsoptera

PsocopteraPthirapteraHemiptera

Thysanoptera

Plecoptera

Orthoptera

Dermaptera

Phasmida

Odonata

Ephemeroptera

Thysanura

323 mya290245

20814665

1.64oldest fossil

Paleoptera

Apterygota

Neoptera

hemimetabolous

ametabolous

holometabolous

Strepsiptera

NeuropteraRaphidiopteraMegalopteraColeoptera

Mecoptera

Siphonaptera

Trichoptera

Lepidoptera

Hymenoptera

Dr. PARVISH PANDYA’s presentation