Lecture 14 IB - Exam 3

decomposers

• a decomposer is an organism that breaks down dead or decaying material

• make up essential part of our food chain: all species nourished by death

detritivores

• obtain their nutrients through consumption of detritus: decomposing plants and animals and their waste

define decomposition

process of breaking down organic matter into simpler forms

insect decomposers

• feed on dead or rotten animals or plants

• fall into categories

  • those thet feed on dead or drying plants

  • those that feed on dead animals (carrion)

  • those that feed on excrement (poop)

• include numerous taxa: beetles, flies, termites, ants, wasps, flies, and can rapidly consume a carcass

excrement

• many insect species are attracted to odor of animal excrement

• manure fly and dung beetle adults lay eggs on fresh feces and larvae feed on the organic matter in waste products

dung beetle

• exhibit preference for herbivore manure type that provides necessary nutrients

• search using olfactory cues, then roll dung to be used as brood chamber

• female lays eggs inside, provisions for larval development

• rolling quickly in a straight line is beneficial for reproductive success

dung beetle and milky way

• navigation at night, need compass to prevent going in circles

• beetles able to use polarized light but maintain straight trajectories in absence of moon

• research conducted in planetarium concluded beetles were not using individual stars but bright strip of stars

dead animals

• necrophagy is feeding behavior on carrion of another organism that it did not kill 

• after death, the process of decomposition begins, and insects arrive within minutes

• temporal resource changes overtime, stages become attractive to different species

brachycera

• ecology of brachycera is diverse

• generally feed on soft or liquid food, lack capability to chew

• maggots modified to live within food source

diptera

• large compound eyes, varied mouthparts

• flies associated with decomposing matter have sponging mouthparts

brachycera larvae

• larvae are all legless, maggots

• mouth hooks, limbless, terminal abdominal spiracles

• important in food webs as both prey and decomposers and in medicine

larval ecology in medicine

• maggots can be used in a medical setting for wound healing

• maggot debridement therapy uses larvae to remove necrotic tissue from wounds

wound healing

• larvae can be used for wound treatment through eating necrotic tissue

• larvae have antibacterial properties that can inhibit secondary infections

• movement of maggots helps promote circulation

maggot debridement therapy 

• reduces cost and need for invasive therapy 

• larvae are reared in sterile environment

• larvae placed inside a dressing to restrict larvae escaping

• only feed on necrotic tissue 

maggots living tissue

• parasitic maggots can infect living tissue

• myasis = infestation of a fly species in living flesh

• eggs are deposited on host, larvae hatch and begin to burrow into skin

magots as pests

• livestock pests that also infect humans

• spines on the larvae cause extreme discomfort

• can be removed by obstructing the breathing channel and removing with forceps

livestock pests

• screw worm: cocholiomya sp. 

• larvae infest exposed soft tissues such as wounds

• burrow deeper into tissue when disturbed

• capable of killing an animal through severe tissue damage

• eradicated using sterile insect technique in 1982, but re-emerged 2016

necrophagous insects

• eggs are laid directly on food source

• adults seek site of egg laying on dead flesh and maggots immediately feed

• basic form of parental care, adult ensures nutrition for offspring survival

necrophagy

• necrophagous insects eating dead/decay animal matter

• fundamental role in terrestrial ecosystems

• can be used to determine the time of colonization at a crime scene: forensic application

forensic entomology 

• the application of the study of insects and arthropods to legal issues

• can be applied to different areas of the legal field

  • urban - criminal and civil

  • stored product - civil

  • medico-legal - criminal

medico-legal forensic entomology

• criminal in nature

• related to insects gathered at the scene of a murder, rape, suicide

• investigations observe insects that have arrived to decompose deceased

• cases involving suspicious deaths where insects are found on decomposing corpse

• insect colonizers can be used to estimate time interval between death and corpse discovery, also called postmortem interval or time of colonization (PMI)

what does a forensic entomologist want to know

species of insect at a crime scene

• specific species are found at certain locations at certain times

• the development time of insect at a crime scene

• insects grow at predictable rate and can be used as indication of time

insect succession

succession: pattern of insect colonization as stages of decomposition progress

abundance of taxa, life stages, and the number of individuals at each stage can be obtained from studies

murder investigations

• deals with specific insects arriving at body to lay eggs

• forensic entomologists assess location on body and order of insect appearance

• determining insect colonizers can determine time of colonization in time of death estimates

criminal forensics

• Subset of species (blow flies, dermestid

beetles) are commonly found, and have

been studied extensively in context of

forensic entomology

• Most criminal forensic cases likely to

involve these species, and statistically

reproducible information is often used

Growth of Discipline

Introductory books and increased output of research articles fuel growing interest