INSECT THERMO DYNAMICS

THERMODYNAMICS IN INSECTSSSNAIK

MSC.ENTOMOLOGY TNAU,COIMBATORE

WELCOME

TERMS IN THERMODYNAMICS

• Ectothermal – body temperature depends on heat acquired from the environment.• Endothermal – body temperature depends on heat produced by the animal’s own metabolism.•Heterothermal – body temperature is sometimes determined by the organism’s metabolism (endothermy); at other times it is governed by the environment (ectothermy).

TERMS……………………………..

•Poikilotherm – an animal whose body temperature is variable and dependent on ambient.•Homeotherm – an animal whose body temperature is constant as a result of endothermy

TERMS……………………………..

ARE INSECTS BELONG TO COLD OR WARM

BLOODED ANIMALS ? ?

Insects have been traditionally considered to be poikilotherms (animals which body temperature is variable and dependent on ambient temperature)

The term thermoregulation is currently used to describe the ability of insects, and other animals, to maintain a stable temperature (either above or below ambient temperature) at least in a portion of their bodies by physiological or behavioral means

DEFINITION:

CLASSIFYING THERMAL RELATIONSHIPS

Ambient Temperature Ta

Body

Tem

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Tb

Poikilotherm

Homeotherm

THERMOREGULATION• Thermoregulation refers to the ability to

regulate that body temperature which best serves survival and reproduction and it encompasses numerous conflicting constrains and selective pressures.

• Insects are too small to be able to appreciably elevate or regulate their body temperature by internal heat production although some are large enough and that coupled with their high flight metabolism, could easily cause them to overheat

EXAMPLES • Diamesa sp walks on

glacier ice even its body temperature is chilled to -160 C.

• It is so sensitive to heat

SPHINX MOTH Sphinx moth have thick insulating fur and normally maintain thoracic temperature near 460C during flight over a wide range of ambient temperatures.

To these moths our own normal body temperature of 370 C is almost cool.

INSECT

Heat gain= ambient conditions +metabolic activities

HEAT LOSS

1.Evaporation : Cool- Body. Stationary Insects Humidity And Temperature2.convection: large surface volume ratio –smaller

insects 3. Conduction : less important

Heat loss………………………

THERMOREGULATION

PHYSIOLOGICAL CHANGES

Extreme temperatures are avoided. At temperatures over 44 °C, approaching the upper lethal temperature, larvae of the desert locust, Schistocerca, become highly active.Similarly, movement into an area of low temperature promotes a brief burst of activity.The preferred temperature range is towards the upper end of the normal range of temperatures experienced by the insect and in Schistocerca, for example, extends from 35 to 45 °C with a peak at 40–41 °C

BEHAVOURAL REGULATION

Temperature preference of second stage larva of the desert locust Schistocerca sp.

INSECT SUN ORIENTATION

1.Sun -movement2.Sun -exposing

Examples : grasshoppers, caterpollars , butterflies, flies

PHYSIOLOGICAL REGULATION• During flight, the- heating and avoid

overheating. • Eg: Manduca ke e ps its thoracic

temperature between 38 and 42 °C over a range of ambient temperatures from 12 to 36 °C.

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PHYSIOLOGICAL REGULATION- CONTD….

Warming up-flight -unable - Exception The large dragonfly, Anax, reduces its wing beat frequency from about 35 Hz at an air temperature of 20°C to 25 Hz at 35 °C,

In honeybees-high temperatures-reduced bing beat frequency

PHYSIOLOGICAL REGULATION - CONT

Moths and bumblebees – thoracic heat - abdomen thorax warms up, the heart beats more rapidly and with greater

amplitude. increase the rate of circulation

reduce the efficiency of the heat exchanger. The efficiency of the heat exchanger may be greatly

reduced at high ambient temperatures by the haemolymph being pushed back into the gaster in discrete slugs.

The difference in temperature between the gaster and the air is greater at high temperatures

PHYSIOLOGICAL REGULATION…….

XYLEM-FEEDING INSECTS: • a few Cicada species -increased rate of water

loss at 38 °C -reduce body temperature to as much as 5 °C below ambient.

• The water is lost -active process -pores almost 10 micrometer in diameter - dorsal surface - thorax and abdomen.

• Process: 1.High Water Content 2.Humidity low

COOLING BY EVAPORATIVE WATER LOSS IN DESERT CICADA

PHYSIOLOGICAL REGULATION

Honeybees • 1.foraging - nectar also use evaporative cooling. • 2.head 44 °C, • 3.regurgitates a drop of honey from stomach and

holds it on the mouthparts. • 4 .Evaporation of the drop cools the head and as the• 5. head and thorax are in broad continuity, the

thorax is also cooled.

At high ambient temperatures, honeybees switch from pollen gathering to nectar collecting presumably because pollen gatherers do not have an adequate supply of nectar for cooling (Cooper, Schaffer & Buchmann, 1985)

THERMOREGULATION IN HONEYBEES

SEASONAL VARIATION IN BLACK PIGMENTATION OF THE BUTTERFLY, Colias eurytheme

GRASSHOPPERS THERMOREGULATION

EVAPORATIVE COOLING

Grasshoppers have patches of thin cuticle (known as Slifer’s patches) on the dorsal sides of their thoracic and abdominal segments.

The patches are most extensive on the middle segments of the abdomen.

SOCIAL INSECTS THERMOREGULATION

1.Ants:Social insects regulate the temperature of their nests so that

their larvae develop under relatively constant conditions 1.summer, the older larvae are brought near to

the surface 2.in winter they may be 25 cm or more below

the surface and so avoid the lowest temperatures.

3.On hot days, Formica blocks its nest entrance stopping the entry of warm air.

HONEY BEES:

2.HONEY BEES:1.FANNING: high temperatures, workers stand at the entrance

of the hive fanning with their wings and creating a draught through the nest. effective to keep the temperature of the brood down to 36 °C when the hive is heated to 40°C.

2.EVAPORATIVE COOLING: Water may also be carried into help cool the hive by evaporation.

3.LEAVE :at excessively high temperatures, the bees leave the combs and cluster outside so that further heating due to their metabolism is avoided.

4.CLUSTERING:On the other hand, in winter when there is little or no brood the bees cluster together on and between a small number of combs.

This behavior is seen when air temperature drops below 15 °C, and their metabolic heat maintains the inside of the cluster at 20–25 °C.

LOW TEMPERATURES

1.Flight 2.Survival

FLIGHT• Eupsilia, operate by raising the thoracic temperature to

30°C or above even at an ambient temperature of 0°C. • These moths have a thick insulating hair pile on the

thorax and a well-developed countercurrent heat exchange system for maintaining the thoracic temperature

1.FLIGHT

2.SURVIVAL (COLD HARDINESS)

• Locusta larvae move very sluggishly and do not feed if the temperature is below 20°C but remain alive for many days even at temperatures close to 0°C.

• Galleria g ro w and pupate at 25 °C and above, but at 20°C most larvae die before pupation although some feeding does occur and a few larvae live as long as 160 days.

Freeze tolerance• The supercooling point for most freeze-

tolerant insects is in the range -5 to -10°C,

the caterpillar of Gynaephora groenlandica from Greenland.

• This insect, which freezes at -7 °C, can remain frozen for 9 months and survive temperatures as low as -70°C.

• Glycerol is the most widely occurring cryoprotectant in insects.

Freeze tolerance

Ice nucleating proteins and a lipoprotein are known to occur in the hemolymph of some freeze-tolerant adult beetles and larval Diptera.

Larvae of the golden rod gall fly, Eurosta, lack ice nucleators in the hemolymph, but a similar function is performed by crystals of calcium phosphate in the Malpighian tubules.

the beetle,Phyllodecta, subject to regular nightly freezing, enabling them to feed during the day and retain food in the gut at night.

HIGH TEMPERATURES

ACTIVITY AND SURVIVAL AT HIGHTEMPERATURES

• Periplaneta, for instance, dies at 38 °C at high humidities, but can survive a short exposure of up to 48 °C if the air is dry.

• Drosophila reared at 15 °C and maintained at 15 °C as adults, survive for about 50 minutes in dry air at 33.5 °C, but if they are maintained at 25 °C before they survive for about 130 minutes.

ACCLIMATION

CRYPTOBIOSIS• Cryptobiosis is the term used to describe the state of

an organism when it shows no visible signs of life and metabolism activity is brought reversibly to a standstill.

• Polypedilum (Diptera) In the dry season these pools dry up and the surface temperatures of the rock probably reach 70°C. Active larvae of Po lype dilum die after an exposure of one hour at 43 °C, but if they are dehydrated so that their water content is less than 8% of its original value they can survive extreme temperatures for long periods

TEMPERATURE AND HUMIDITY RECEPTORS

• Most studied insects sense temperature with their antennae: Worker honeybees have about 50 annulus on each antenna, and Periplaneta has about 100.

• In addition to these sensilla, some multiporous olfactory sensilla on the antennae of Periplaneta and Locusta contain a cell that is thermosensitive.

Chapman,R.F. The Insects – Structure and its Function. 1998.P-524

REFERENCESCHAPMAN, R.F. 1982.THE INSECTS: STRUCTURE AND FUNCTION,

3RD ED. HARVARD U.PRESS. CAMBRIDGE. 919PP VINCENT RACE,H.,CARDE RING,T.ENCYCLOPEDIA OF INSECTS.GULLAN,P.J., CRANSTON,P.S.THE INSECTS –AN OUTLINE OF

ENTOMOLOGY.http://en.wikipedia.org/wiki/Chameleonhttp://jeb.biologists.org/www.elsevier.com/locate/jinsphyshttp://www.sciencedaily.com/releases/2006/10/061002214840.htmhttp://entomology.unl.edu/ent801/temp.html

THANK YOU

PRESENTED BY: S.SRINIVAS NAIK ID. NO:13-503-010