What is the purpose of modification of the general body shape
Modification of the general body shape to facilitate movement on the host and to enable them to hide in tight spaces when off the host
Why does some parasites have dorsoventral or lateral flattening
dorsoventral or lateral flattening of the body usually involve in parasitic lineages that exhibit long-term, close association with host animals. This feature allows them to move more freely on hosts and hide in tight spaces when off of hosts.
Examples of parasites that have dorsoventral or lateral flattening of the body
- Dorsoventral flattening examples: bed bugs, bat bugs, lice, beaver beetles (Leiodidae, genus Platypsyllus), parasitic dermapterans (genus Hemimerus), louse flies & keds, and ticks
- Lateral flattening example: fleas
Why are wings indispensable features of many parasitic insects?
Wings are indispensable features of many parasitic insects, because they would not be able to reach their hosts without them
Compare and contrast the mouthparts of Class Insecta and Class Arachnida
Class Insecta
* Parasites that feed on host body fluids have mouthparts that pierce host skin. Parasites that feed on solids externally mostly retain chewing-type mouthparts.
- Telmophages first lacerate host skin before feeding on blood at the site.
- Solenophages have styletiform mouthparts that allows for specialised piercing-sucking. This allows them to pierce and feed on individual capillaries and leave no evidence of any bites.
Class Arachnida
* They feed on host blood during each of their developmental stages (i.e. larvae, nymphs and adults)
- Similarly to Insecta, their mouthparts are modified for piercing host tissue. However they also anchor to the host, and drawing blood into alimentary tract
Compare and contrast the legs of Class Insect and Class Arachnida
Class Insecta
* The tarsus can be divided into subsegments or tarsomeres, providing flexibility.
- Claws are mainly found on the apical tarsomere. In many ectoparasitic insects, the legs are modified to facilitate host attachment and dispersal to new hosts.
Examples:
* Adult fleas have hind legs to enable them to jump remarkable distances or to evade removal by host grooming.
Other modifications include an enlarged, muscular femur and an elastic protein in the integument called resilin (helps to store energy and significantly increase the efficiency of the hind legs in jumping abilities of fleas).
- Lice are noted for their ability to cling tenaciously to their hosts. The legs of sucking lice are particularly well adapted for grasping host hair. The claws are formed by modifications of the tibia and tarsus.
*The legs of hippoboscids (e.g. keds or deer flies) are therefore stout and usually spinose, with enlarged tarsal claws. These features enable hippoboscids to hold onto their host and to move about quickly and efficient amid host pelage.
Class Arachnida
* In parasitic mites, various modifications of the legs enable elongate apoteles with terminal suckers. These structures allow the mites to move about quickly on the surface of the skin and to hold tightly to the epidermis.
- Certain feather mites (e.g. Analgidae) have sucker empodia and large spurs on their legs for securing themselves to their avian hosts
What is the function of parasitic arthropods having various of sensory structures
Various sensory structures of parasitic arthropods function to detect motion, vibrations, temperature, moisture, carbon dioxide, and a plethora of chemical substances produced by potential hosts
Explain the sensory structures of Class Insecta
Class Insecta
* The antennae of blood-feeding insects, particularly hematophagous dipterans, have receptors that detect chemicals emanating from the skin and present in the exhaled breath of potential hosts
Explain the sensory structures of mosquitoes
Mosquitoes
* Sensory receptors in the basal segment of the antenna are highly developed to form the Johnston’s organ, which is specialized for detecting airborne vibrations
- Host-seeking female mosquitoes may cue in on vibrations produced by host movements and even vocalizations by hosts such as birds and frogs.
What are the Host substance that are known to attract mosquitoes
Host substances known to attract mosquitoes include carbon dioxide, lactic acid, octenol, estrogen, fatty acids, and amino acids
Explain the sensory structures of fleas
Fleas
* the antenna is short, flattened, and fits into a protective groove on the side of the head. This allows the antennae to be retracted to not be damaged or impede movement as the flea maneuvers within host hair or feathers
- In fleas, the dorsal portions of the terminal abdominal segments are modified as a sensory organ, called the sensilium. It specialized for detecting host- associated cues such as vibrations and temperature gradients.
Explain the modification of sensory structure due to vision in some parasitic arthropods.
- In fleas and lice, the eyes are generally reduced in size or may be altogether absent to prevent damage to the sense organs and to reflect the relative unimportance of vision in the life of the parasite.
- In many other insects, such as mosquitoes, biting midges, and horse flies, the eyes are greatly enlarged to reflect the more significant role that light perception and vision play in locating, or orienting toward, potential host animals.
What are the sensory structures found in mouthparts
- In many solenophages (e.g. mosquitoes and bed bugs respectively), these receptors are concentrated near the tip of the proboscis or rostrum to detect the precise location of capillaries beneath the surface of the skin)
- In biting midges, sensory receptors for detecting environmental and host cues are concentrated in a specialized pit, in the form of a sensory organ on the enlarged third segment of the maxillary palp
Explain the sensory structures of Class Arachnida (Mites and Ticks)
Mites
* In mites, chemical and tactile cues are perceived by sensory structures on the pedipalps, legs, and various other parts of the body
- Specialized sensory setae with an associated socket-like base, called trichobothria, are common in many groups of mites and other arachnids for detecting airborne and substrate vibrations and other tactile cues
- In certain group of mites, the first pair of legs may be unusually long and slender, with numerous receptors, serving as a sensory organ, much like the antennae of insects
Ticks
* In ticks, a complex sensory structure, called Haller’s organ, is located on the dorsal aspect of the tarsus of the first pair of legs and functions in detection of temperature, air movements, host odors, and other host and environmental cues
Chemicals serve a number of functions, including
- Communication (inter and intra species)
- Sex attraction and mating
- Aggregation
- Predation
- Defense
- Alert
- Trail
What is toxin and venom
Toxin (hydrophobic) = any specific chemical compound or molecule that causes harm to an organism on contact or when INGESTED
Venom (hydrophilic) = a toxin or, more typically a mixture of two or more toxins and other chemicals, involving specialised morphological structures for injecting, spraying, or otherwise directing them to a target
The injection of venom by such specialized structures is called
envenomation
Effects of Arthropods Toxins and Venom
- Variety of venom proteins are known enzymes (such as phospholipases, hyaluronidases, phosphatase, esterases, and proteases), in addition to specific enzymes acting as neurotoxins. Responsible for much of the damage and sometimes lethality.
- Venom peptides include hemolysins, such as melittin, that destroy blood cells; kinins, which cause pain and cardiovascular effects
- Venoms also can contain cocktails of biogenic amines, including histamine, serotonin, acetylcholine, and epinephrine. These components can cause swelling and other reactions, sometimes the pain at sting sites.
- victims can succumb to lethal envenomation by various biting and stinging arthrpods such as honey bees, Asian hornets, scorpions and spiders
Benefits of Arthropods Toxins and Venom
- Melittin from honey bees: inhibit bacteria, including the Lyme disease agent Borrelia burgdorferi
- Solenopsin from fire ants: insecticidal, antibacterial, antifungal and antiviral activity
- Many antimicrobial peptides from scorpions and spiders
- Peptides in the venom of many arthropods, particularly scorpions and spiders: analgesics or painkillers
- Cantharidin from blister beetles: aphrodisiac, a topical compound to remove warts and treatment for other skin conditions such as molluscum contagiosum
- Pederin and its derivatives from staphylinid beetles: inhibit protein and DNA synthesis and slowing the division of cancer cells
Morphological Adaptations for Toxins and Venoms
- The modified female reproductive organs and associated muscles and glands forming the sting apparatus in bees, wasps, and ants
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