Parasitology and Invertebrate Zoology: Vectors, Helminths, Crustaceans, and Arachnids

Comprehensive practice vocabulary flashcards covering the morphology, life cycles, pathology, and ecology of parasitic annelids, insects, nematodes, acanthocephalans, arachnids, and crustaceans.

Landscape of Disgust

An ecological framework describing how animals perceive and behaviorally avoid areas or conspecifics associated with high infection risk (such as feces, carcasses, or sick individuals), directly paralleling the predator-induced "landscape of fear."

Class Hirudinea

A class of annelids characterized by dorsoventrally flattened bodies with fixed segment numbers, anterior and posterior suckers, and 3 chitinous toothed jaws; approximately 75% of the ~700 species are hematophagous ectoparasites that can ingest blood meals up to $10\times$ their body weight.

Invertebrate DNA (iDNA) Screening

A biodiversity survey method that extracts vertebrate host DNA preserved inside the digestive tracts of hematophagous leeches (such as Haemadipsa spp.), where mammalian mitochondrial DNA can remain amplifiable by PCR for at least 4 months after feeding.

Order Branchiobdellida

A clade of tiny (1–10 mm) clitellate annelids that live as ectocommensals or ectoparasites exclusively on the carapace, walking legs, or branchial chambers of freshwater crayfish and crabs.

Order Phthiraptera

An order of wingless, dorsoventrally flattened, hemimetabolous insects (lice) that are obligate ectoparasites of birds and mammals, possessing reduced eyes, short antennae, and legs modified with strong claws for grasping hair or feathers.

Chewing Lice

A paraphyletic assemblage within Phthiraptera (>4,000 species) that feed primarily on feathers, hair, skin secretions, and sloughed epidermis of birds and some mammals using biting mandibles.

Sucking Lice

A monophyletic group of ~500 Phthirapteran species found exclusively on mammals that possess piercing-sucking mouthparts to feed directly on blood from subcutaneous vessels.

Pediculosis

The medical condition of an active ectoparasitic infestation by lice, notably Pediculus humanus capitis (head lice), Pediculus humanus corporis (body lice), or Phthirus pubis (pubic lice).

AirAllé (LouseBuster)

An FDA-cleared nonchemical medical device that delivers heated air at controlled airflow and temperature to eradicate head lice, killing 99.2% of eggs and 80% of hatched lice via rapid desiccation.

Order Siphonaptera

An order of approximately 2,500 species of wingless, laterally compressed, holometabolous insects (fleas) with backward-pointing bristles and saltatorial hind legs, whose adults are obligate hematophagous ectoparasites.

Percolation Threshold (Sylvatic Plague)

The density threshold of an alternate rodent host, the grasshopper mouse (Onychomys leucogaster), required to connect otherwise isolated black-tailed prairie dog (Cynomys ludovicianus) coteries and trigger rapid epidemic spread of Yersinia pestis.

Tunga penetrans

The chigoe flea or sand flea, a small siphonapteran whose impregnated females burrow permanently into host skin (typically beneath toenails), causing intense inflammation, swelling, and lesions known as tungiasis.

Family Cimicidae

A family of wingless, dorsoventrally flattened true bugs (Hemiptera), including the common bedbug Cimex lectularius; they hide off-host in crevices and mattress seams, consume host blood at night, and can release up to $40\,mg$ of histamine per 1,000 bugs weekly.

Parasite Tolerance (Cliff Swallows)

The evolutionary process wherein cliff swallows (Petrochelidon pyrrhonota) nesting on bridges and artificial structures adapted over 35 years to sustain high infestations of haematophagous swallow bugs (Cimex vicarius) with reduced mortality and nestling body mass penalties.

Order Diptera

An order of ~160,000 insect species possessing a single pair of functional membranous forewings and reduced, sensory hindwings modified into club-like balancing halteres; larvae are apodous, vermiform maggots.

Myiasis

The parasitic infestation of living vertebrate tissues, organs, or body cavities by the dipteran larvae (maggots) of flies such as bot flies (family Oestridae) and blow flies (family Calliphoridae).

Nycteribiidae and Streblidae

Two specialized families of obligate, hematophagous bat flies (Diptera); Nycteribiidae are completely wingless, spider-like ectoparasites, whereas Streblidae generally retain functional or reduced wings.

Phylum Nematoda

A large ecdysozoan phylum of unsegmented, round pseudocoelomates possessing a collagenous, non-cellular cuticle secreted by the hypodermis, a triradiate muscular pharynx, and growth via periodic molting (ecdysis).

Hookworms

Intestinal roundworms (Necator americanus and Ancylostoma duodenale) whose infective third-stage filariform larvae (L3) penetrate bare skin, migrate through the venous circulation into pulmonary alveoli, ascend the trachea, and mature in the small intestine to feed on mucosal blood.

Ascaris lumbricoides

The giant human intestinal roundworm; large dioecious females release 200,000 to 1,000,000 resistant eggs daily in feces, which are swallowed from contaminated food or soil, leading to an extensive heart-lung-tracheal migration cycle before returning to the gut.

Enterobius vermicularis

The cosmopolitan human pinworm; lives in the ileocecal junction, and gravid females migrate out of the anus nocturnally to deposit up to 16,000 sticky eggs on perianal folds, causing localized pruritus and direct fecal-oral autoinfection.

Wuchereria bancrofti

A mosquito-vectored filarial roundworm whose adult worms reside inside human lymphatic vessels, releasing sheathed microfilariae into peripheral blood during peak nocturnal feeding windows (10:00 p.m. to 2:00 a.m.) and causing lymphatic filariasis (elephantiasis).

Onchocerca volvulus

The filarial nematode responsible for onchocerciasis (river blindness), transmitted by Simulium black flies; adults live inside subcutaneous fibrous nodules, and microfilariae migrate through connective tissue and eyes, inducing severe inflammatory blindness and dermatitis.

Dracunculus medinensis

The Guinea worm; contracted by drinking unfiltered water containing copepods infected with L3 larvae, culminating a year later when the adult female produces a burning skin ulcer to discharge L1 larvae into water.

Trichinella spiralis

A nematode acquired by consuming undercooked meat containing encapsulated larvae; larvae develop into adults in the small intestine, and newborn larvae migrate intramuscularly to alter skeletal muscle cells into collagen-encapsulated nurse cells.

Parelaphostrongylus tenuis

The meningeal brainworm of white-tailed deer (Odocoileus virginianus) that causes severe neurological damage, ataxia, and mortality known as "moose sickness" when accidentally ingested by moose (Alces alces).

Phylum Nematomorpha

An ecdysozoan phylum of pseudocoelomates (horsehair or Gordian worms) whose adults are free-living, non-feeding aquatic worms and whose larvae develop inside terrestrial arthropods, driving infected hosts to jump into water bodies.

Phylum Acanthocephala

Thorny-headed worms; unsegmented, dioecious endoparasites with an eversible, hooked proboscis, a syncytial tegument containing nutrient-absorbing crypts, and a complete absence of an alimentary canal.

Acanthor

The spined, fully embryonated first-stage larva of an acanthocephalan that hatches from the egg upon ingestion by an arthropod intermediate host and penetrates the gut wall into the hemocoel.

Acanthella

The second developmental stage of an acanthocephalan that develops in the arthropod intermediate host hemocoel, during which the proboscis, lemnisci, and reproductive organ systems form.

Cystacanth

The encysted, infective juvenile stage of an acanthocephalan inside the intermediate or paratenic host, which excysts and attaches to the intestinal mucosa upon ingestion by the definitive vertebrate host.

Parasite-Induced Trophic Transmission (PITT)

A phenomenon wherein a parasite manipulates intermediate host morphology or behavior to increase its vulnerability to predation by the definitive host, first demonstrated by Janice Moore using Plagiorhynchus cylindraceus in terrestrial isopods preyed upon by European starlings.

Order Acari

The most diverse arachnid taxon (ticks and mites), characterized by the loss of external segmentation and body tagmosis into an anterior gnathosoma (capitulum) bearing mouthparts and a fused posterior idiosoma.

Family Argasidae

Soft ticks; acarine ectoparasites characterized by a leathery, flexible cuticle lacking a dorsal scutum, a subterminally situated gnathosoma concealed beneath the anterior fold in dorsal view, and multiple nymphal stages.

Family Ixodidae

Hard ticks; acarine ectoparasites characterized by a rigid anterior dorsal shield (scutum), a prominent terminal capitulum visible dorsally, a single nymphal stage, and prolonged host attachment lasting days to weeks.

Borrelia burgdorferi

The corkscrew-shaped spirochete bacterium that causes Lyme disease, transmitted primarily to humans and rodents by the nymphal stage of Ixodes scapularis in eastern North America and Ixodes pacificus in the west.

Oak Masting and Lyme Disease Dynamics

A bottom-up ecological cascade in eastern deciduous forests where synchronous heavy acorn production leads to high white-footed mouse (Peromyscus leucopus) density the following year, which drives peak densities of infected Ixodes scapularis nymphs two years post-mast.

Sarcoptes scabiei

An astigmatid mite that burrows inside the stratum corneum of human and mammalian skin to deposit eggs and feces, causing intense hypersensitivity, pruritus, and excoriation known as scabies or sarcoptic mange.

Family Trombiculidae (Chiggers)

A family of mites whose free-living adults prey on soil invertebrates, but whose parasitic 6-legged larvae attach to vertebrates to inject proteolytic salivary enzymes, feeding on liquefied host epidermis through a feeding tube called a stylostome.

Acarapis woodi

The honeybee tracheal mite; an obligate internal parasite of Apis mellifera that enters the prothoracic spiracles of young worker bees to reproduce and feed on hemolymph inside the tracheae.

Varroa destructor

A large, red-brown ectoparasitic mite that infests honeybee colonies (Apis mellifera), feeding on the fat body of larvae, pupae, and adults, transmitting RNA viruses, and causing parasitic mite syndrome and colony collapse.

Anchor Worm (Lernaea)

A genus of parasitic cyclopoid copepods that infect freshwater fishes; after mating, the adult female loses external segmentation and embeds its branched, anchor-shaped cephalothorax deep into muscle beneath scales, leaving trailing egg sacs.

Family Sarcotacidae (Sarcotaces)

A group of poecilostomatoid copepods living encysted within the muscle or visceral cavity of marine fishes, characterized by extreme sexual dimorphism where a minute dwarf male lives inside a massive, sac-like female.

Lernaeocera branchialis

A pennellid copepod ("cod worm") that utilizes a flatfish intermediate host before the fertilized female permanently embeds into the gill arch and ventral aorta of gadoid definitive fishes to feed on blood.

Superorder Rhizocephala

An order of barnacles (Thecostraca) including Sacculina that parasitize decapod crustaceans, losing all appendages, segmentation, and sense organs to form an internal root-like nutrient-absorbing system and an external reproductive brood sac.

Kentrogon

A specialized injection stage in the rhizocephalan life cycle that metamorphoses from an attached female cyprid larva, utilizing a hollow chitinous stylet to inject the primordial parasitic cell mass directly into the crab host's hemocoel.

Externa

The external gonadal sac of a rhizocephalan barnacle that erupts beneath the abdominal flap of its crustacean host, containing the ovaries and receptacles into which dwarf male trichogon larvae inject fertilizing cells.

Family Cyamidae (Whale Lice)

A family of dorsoventrally flattened, obligate ectoparasitic amphipods that cling to the skin lesions and callosities of right whales and other cetaceans using clawed legs, feeding on sloughed epidermal tissue and algae.

Family Entoniscidae

A family of highly derived endoparasitic isopod crustaceans that reside within the hemocoel and visceral cavity of decapod crabs, acting as obligate parasitic castrators that absorb host reproductive energy.