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05.03 Detritivore Feeding Guilds

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Bugs 101: Insect-Human Interactions

阿尔伯塔大学

4.8（16 個評分） | 5.3K 名學生已註冊

Of all the animals on earth, which are the strongest for their size? What about the fastest? Who were the first animals to evolve flight? Insects take all of these titles and more! As the most abundant animals on the planet, insects and other arthropods affect our lives in so many ways. From beneficial interactions like pollination and biological pest control, to the transmission of life threatening diseases; this course will teach you about the big ways that these little arthropods impact our lives. In Bugs 101: Insect-Human Interactions, you will be plunged into the diverse (and sometimes alien) world of arthropods to learn how they work, what they do, and how insects and humans interact every day. After completing this course, you will be able to: Describe the evolutionary relationships between insects and their arthropod relatives Inventory major groups of insects and their diversity Demonstrate evolutionary adaptations that make insects successful Discuss insect biology and human-insect interactions Evaluate positive and negative interactions between insects and humans Propose practical and symbolic roles insects play in human societies

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Biology, Entomology, Science, Ecology

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4.8（16 個評分）

5 stars
15 ratings
2 stars
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MA

Aug 07, 2019

Its really a very interesting course to learn the basic knowledge of different type of insects and their interaction with the humans as well.

VI

Aug 13, 2019

A study which is highly enjoyable and useful for professionals

從本節課中

Module 05: Insects as Decomposers

Without decomposers, dead trees and leaves would pile up in forests, and we would be walking knee deep in dung and animal carcasses. Insect decomposers help to recycle these materials and many others back into the earth, recycling the nutrients to be used by other organisms again. This module unearths the importance of these decomposers to our ecosystem, and even discusses some ways these insects can be used to help solve crimes.

05.03 Detritivore Feeding Guilds17:44

教學方

Dr. Maya Evenden
Professor of Entomology

腳本

[MUSIC]

Detritivore feed on many kinds of organic material from plant

fragments to animal matter such as skin, feathers, and even dung.

When different types of arthropods feed on similar organic material they

can be grouped, into what is known as a feeding gilt.

Let's examine some of the detritivore feeding gilts,

including xylophages, coprophages, and necrophages.

Cellulose is a large, complex polysaccharide or

sugar molecule found in the cell walls of plants.

It is an important structural component of plants, and

is the most abundant carbohydrate on Earth.

It is therefore not surprising that many insects have evolved the capacity to

use cellulose through the consumption of wood,

a substance relatively low in nutrients other than cellulose and lignin.

These insects are collectively called xylophages.

While some insects feed on and

damage live trees, many wood feeders specialize on dead and decaying trees.

Wood-feeding insects, such as carpenter ants, termites, and many

beetles play an important role in breaking down dead wood in forest ecosystems.

However, the same insects that are important nutrient recyclers in forests

can also feed on man made what instructors potentially causing major damage.

But how exactly do these insects feed on wood?

Most xylophagous insects have close symbiotic interactions with

gut microbes to help them digest the tough cellulose.

Termites, for example,

have particularly well-developed endosymbiotic fauna in their hindguts.

That being said, some insects, including many termite species, and

certain cockroaches, can produce cellulose degrading enzymes of their own.

Microbes in the hindgut of many termites breakdown the complex sugars found in wood

into simpler sugars that can be metabolized by the termite host.

Cellulose in particular is broken down into short chain fatty

acids that the termites use for nourishment.

The endosymbiotic community is complex, and

includes bacteria, archaea, and proteus, all housed in the termite hindgut.

Because the cuticular are lining of the hindgut is shed at each mold,

the symbionts are lost when the insect molds.

To deal with this, termites transfer microbes between nest mates

through a process known as trophallaxis.

This microbe exchange occurs between individuals in the colony

either through mouth to mouth feeding on specialized fluids or

by feeding on hindguts secretions.

Termites use the ladder method for symbiotic exchange.

Take note though,

that termite truthful axis is an exchange of special hindgut secretions, and

should not be confused with dung feeding or coprophagy which we will discuss next.

Vertebrate dung is a rich source of nutrients for insects to tried force.

Insects that consume dung are called coprophages, and

includes species such as dung beetles and many flies.

By consuming organic waste, coprophagous detritivores help

move nutrients back into the soil where they can be taken up by plants.

Maggots of dung flies, house flies, and blow flies, commonly feed on dung.

The adult fly's of these groups are particularly well adapted to locate fresh

piles of excrement that are suitable over position substrates.

Eggs or larvae are deposited onto the freshly laid dung.

Rapid colonization of the dung while it is still fresh is particularly important for

juveniles, so that they obtain enough nutrients from it

to complete development before the dung dries out.

In some cases, small forensic fly species such as the lesser dung flies

will take advantage of another species ability to locate and

access dung piles by hitching a ride on a larger coprophagous insects.

There are several groups of beetles that feed on dung though the most

well-known are probably the dung beetles in the family scare a bad day.

You may be familiar with these beetles from their prominence

in Egyptian mythology, or their starring role in some movies.

We will learn more about the place of insects, and mythologies, and

pop culture in module 12.

Some adult dung beetles gather the excrement and form it into a ball,

sometimes working in pairs.

The ball is rolled to a suitable location where it is buried, and

used as a deposition site for the females eggs.

The larvae that hatch,

feed on the dung supplied by the parents in the nest chamber.

Some adult dung beetles will also feed on fecal material, but only on the fluids and

finest particulate matter, or on associated microbes.

The dung burying behavior of these beetles protects their food from competitors,

predators, and unfavorable climatic conditions.

Rather than making a nest some dung beetle species

will blur directly into the dung pile to lay their eggs.

Many species of dung beetle also exhibit by parental cooperation as both male and

female beetles work together to build a nest, and provide food, and protection for

the offspring.

For some dung rolling species, the production of the dung ball can

even serve as a sexual display to attract mates looking for a big pile of poop.

Some species of dung beetles have evolved an alternative strategy

rather than gathering and preparing their own dung.

These beetles are kleptoparasites that take advantage of

nests prepared by other dung beetles.

Coprophagous are important recyclers of the nutrients and fecal material.

They are particularly important in the management of pastoral farming ecosystems

where the dung of cattle and

other livestock needs to be rapidly transformed into usable nutrients.

If dung is left on the ground too long, it can impede plant growth through lack of

light or nutrients, and seriously deteriorate pasture land.

This in turn limits the available grazing area.

Some researchers have suggested that dung beetles may help

produce parasite infestations in livestock

by removing fecal material that could otherwise incubate parasitic worms.

Furthermore, dung beetle activity may also suppress the breeding success

of pest difference flies due to intraspecific competition for resources.

Let's hear from Dr. Kevin Floate, an expert from Agriculture and

Agri-Food Canada on the decomposition of dung and other fecal factoids.

>> Some of research scientist with Agriculture and Agri-Food Canada, and

I study different topics of Entomology.

Insects can play a very large role in dung decomposition,

but overall there's other factors that are equally one point.

For example, if you have fresh cattlemen, you're on a pasture and

a sudden rainstorm that can essentially wash the pattern within a matter of hours.

Birds will forage in dung looking for insects or

seeds, and they will shred a cow pie very quickly.

You can imagine a dung pat which gets deposited in the wintertime,

it may persist for years.

So most of the insect colonization occurs within the first hours,

maybe the first two weeks after the dung is deposited.

And if nothing's colonized during that period, probably nothing will colonize.

So it depends a lot on when the dung path is deposited on the pasture.

It depends on what the animal might have been treated with, so most live duck or

cattle for example, are treated with some sort of a parasiticide product.

Depending on what parasiticide is used, residues appear in the dung,

which in effect activity in the dung insects.

And consequent have implications for

how quickly those insects can breakdown the dung.

Any factors affecting insect activities, so if the pie deposited at night

time versus day time, and the shade versus full sun, again, time of the year.

It also would depend on what insects species are present where the dung

pies positive.

So one of these groups we call detritivores, and

these are beetles that are attracted to fresh dung to feed, but

they don't actually lay their eggs in dung.

They come in they feed they disappear, their larvae we're developing cropland or

rich organic soils.

And then we have another group, I refer to these as a dwellers.

So these are dung beetles, the adults will arrive at a fresh pie.

They'll dig and tunnel into the fresh pie made lay an egg,

and that egg will hatch into larva, and

the larvae will develop in the pie as it sits on the surface of the soil.

We have another group called the Rollers down here.

And as you might expect from the name, these adults will come into a fresh pie,

and adults will actually remove a bit of the manure, and form it into a ball.

And then working as a pair of male and

female, they'll push that ball of manure away from the pie.

Some distance it could be a matter of inch centimeters,

or a meter, or more, and then buried underground.

In the tunnel where they bury a manure, they'll lay an egg.

So that was not a catches into larva.

The larva has already food supply, and it'll feed on the bereavement year.

And then we have another group called tunnellers here in the bottom, and

the tunnellers are very similar to the rollers.

It's the adult that arrives at the fresh dung pie, and

adults will rip apart the pie, and make it into small balls mirror.

And then they tunnel directly beneath where the pious sitting into the ground.

They'll bury them in your in the tunnels and then lay an egg, and

when the egg hatches the larva has something to eat.

They can rip apart a pie and spread it within a matter of hours or days.

Whereas you can have a lot of dwellers coming in, but

degradation from dwellers because it's larval feeding can take months.

So you got the little head up here,

you have the three pair of legs at all insects half up here.

But then the rest of this is the abdomen and like the rumen of a cow.

The gut of dung beetles have specialized microorganisms

designed to break down plant fiber.

So different bacteria than you'd find in a cow but the same function.

And that's why dung beetle takes so

long to develop from egg to adult because it's the quality of their diet.

Plant fiber, it's not very nutritious.

Now other insects, for example like flies that are feeding on bacteria for the life

cycle, can go from egg to adult in a week or less, depending on temperatures.

If you have a fresh cow pie on a pasture, the grass beneath that pie cannot be

greater, so it's immediately taken out of grazing as far as the cow is concerned.

And then the nutrients from that manure will leach out into the surrounding area,

and fertilize the grass.

But because there is so

much nitrogen now surrounding that pie, that grass comes up not as healthy.

But as almost a nitrogen rich, almost rank, it's like a green hail

surrounding the pie, cows don't like that grass so they avoided.

So if you look at the amount of dung deposited by one cow on a pasture

during a day, and assume the pies don't overlap each other,

that removes about a meter of forage out of that pasture per cow per day.

We do a lot of our research on native grassland in southern Alberta.

And there are species associate native grassland

that we don't find on team patches.

So patches in which the land has been plowed up and planted to grasses.

I have canton species which strangers are rollers, I love them because they have

a lot of our very, high level paternal care maternal care for their offspring.

>> Animal corpses also called carrion, are nutrient rich resources that can

support a wide diversity of organisms, many of which are insects.

Carrion feeding insects called necrophages convert complex organic

molecules within the carrion into simpler compounds and release them into ecosystem.

Carrion like dung is a short-lived resource which is only available for

brief periods of time.

Therefore, necrophagous insects such as flies and

carrion beetles have evolved to be highly sensitive to odors of decay,

and can quickly find carrion in the immediate area.

A good example of necrophagous insects, or

the carrion beetles in the family Silphidae.

In most carrion beetles, the larvae and adults feed on vertebrate carrion.

However, adult beetles may also feed uncaring and

associated fauna such as maggots and other beetles.

Many carrion beetles have to compete with other necrophagous insects

such as blow flies and flesh flies for resources on large carrion.

Carrion beetle larvae may have a key advantage though.

In some cases, symbiotic mites that are transported by the carrion beetle adults

feed on maggots already present on the corpse reducing competition for

the beetles.

Carrion beetle larvae don't just have to compete with other insects.

Since the beetle larvae takes several days to reach maturity,

they must get all their nutrition from the corpse before colonizing bacteria, and

fungi digested since carrion is very susceptible to microbial decomposition.

To deal with this carrion beetle adults remove the fur or

feathers of their prize and cover the skin of the animal in oral and

anal secretions that contain their own cocktail of symbiotic bacteria and fungi.

These microbes compete with other colonizing microbes for

a place on the cadaver, but do not digest it as actively as the other species.

Instead, by taking up space that other microbes could colonize,

the protective layer of the beetle's microbes prevents

other species from consuming the dead body, helping to preserve the carrion for

long enough for the developing larvae to mature.

The beetle's fluids also contain antimicrobial compounds that can further

stunt the growth of unwanted bacteria and fungi.

There are some species of carrion beetles that specialize on smaller corpses

like dead rodents.

These species tend to exhibit bi-parental care,

which is extremely uncommon in insects.

The beetle pair bury the carrion resource

where the offspring have exclusive access to the food.

A corpse may be 200 times the beetle's size, yet

they can drag it to an excavated chamber up to a meter away.

The parents remain with the larvae as they grow, fending off potential predators,

and feeding on the carrion to regurgitate food for the offspring.

The parent beetles also practice a behavior known as filial cannibalism, in

which the parents kill and consume their larvae in order to regulate brood size.

This ensures that surviving offspring grow and

develop successfully as they receive the lion's share of the nutrients.

Parenting can be tough, but in this case, it may be even tougher for the kids.

Depending on the state of decay and the type of carrion,

the composition of detritivores species changes as different species colonize or

finished development on the carrio.

This is known as ecological succession

which is the change in species composition of a community overtime.

While this concept applies to any ecosystem,

it is particularly predictable in the decay of carrion.

As waves of colonizers appear, they consume their favorite resources and

physically alter the habitat making it attractive to other organisms.

The species present on a dead body at each stage of decomposition

differs depending on geographical area and

environmental conditions because each region has its own carry and fauna.

Nonetheless the broad taxonomic categories of carrion specialists

are similar across the world.

We will discuss the phenomenon of succession in more detail in a future

lesson as we explore it's applications and forensic entomology.

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