Acanthocephalans and Nematomorphids Flashcards
outline the defining features of acanthocephala parasites
thorny headed worms
they posses a retractable proboscis at the anterior end with rows of spines for attaching to the intestinal wall of hosts due to the high turn over of cells and peristalsis movements
= the hook bands and lines can be used to identify the species of acanthocephala
outline some characteristics of acanthocephalian parasites
hooks covering the probosic which damage the intestinal lining and cause pathology to host
1100 species described
obligate intestinal parasite of verterbrates (fresh water teleost fish)
intermediate host = arthropods
definitive host= vertebrates
why is the distribution of acanthocephala unusual
few individuals will be infected within an area however the individuals which are infected have very large abundances of the parasites within them
= not evenly distributed
what is a paratenic host
a host organism which harbours the parasite without allowing it to develop further= used as a transport for the parasite with the hope that it furthers the Lifecyle through trophic relationships ect
what species of acanthocephala is most common
Bolbosoma balaenae
krill = intermediate host
definitive host = baleen whale
what are the four classes that acanthocephala are divided into
1) ARCHIacanthocephala
2)EOacanthocephala
3) PAELOacanthocephala
4)POLYacanthocephala
= Usually based on taxonomy and morphology of the hook
outline the morphology of acanthocephala parasites
= pseudocoelomate animals
= high reproductive capacity (10,000,000 eggs per female)
= size varies from 0.992mm up to 93cm
= dioecious with females being larger than males usually (more room for eggs)
= facultative anaerobes
although acanthocephala are closely related to the phyla rotifer why are they different
rotifer are a complex phyla with complex organs and systems
acanthocephalan have shown an evolutionary regression with the digestive tract no longer existing and a reduction in muscular, nervous and circulatory systems
This is because the adults have no use for the complexity= only need to reproduce
outline the morphology of the acanthocephala proboscis
everted and inverted which can retract into a sac
= the attachment organ, also used for locomotion
= alternating longitudinal rows of hooks and spines in a specific pattern
= cerebral ganglion in receptacles which control the contraction and retraction of proboscis
= uterine bell which brings eggs into uterus for selective fertilisation
outline the characteristics of the species corynosoma cetaceum from the phyla acanthocephala
Definitive host - cetaceans
unlike other species the whole body is covered in spikes/hooks
females are smaller but spikier than males allowing them to be at less risk of being dislodged
indirect data suggests females live longer than the males with sex ratios skewed towards females
why are Corynosoma cetaceum
evolved to have their whole body covered in spikes
definitive hosts include dolphins and cetaceans which eat lots of fish at once, this adaptation avoids it from being dislodged in the gut
outline the Lifecyle of an acanthocephalan parasite
1) eggs are ingested by the intermediate host (white grubs)
2)the defintive host becomes infected by the ingestion of infected intermediate host, this can also infect humans (usually ones with chaotic lifestyles such as children or mental disorders who eat raw insects)
3) eggs hatch producing larvae and develop into adults which produce eggs shed into the faeces
what is an acanthor
contained within the eggs and is a spiny shaped embryo with hooks inside which burrows into the body cavity of the intermediate host
how can adult acanthocephala cause trauma to the intestinal mucosa
the proboscis penetrates the intestinal lining with hooks and tends to release and reattach
= complete perforation of the gut can occur which is fatal to mammals
= very painful
can sometimes result in secondary bacterial infections causing haemorrhage or ulcers
why are anthelminthics less effective on acanthocephala compared to Platyhelminthes and nematodes
works by paralysing the parasite so it is passed out by natural peristaltic movements
the hooks and spikes allow acanthocephala to remain attached more effectively so less effective
= better to control exposure to definitive host than treat already infected individuals e.g. bio/chemical control to kill of grubs (intermediate host)
outline the Lifecyle of the class eoacathnocephala
e.g.Neoechinorhynchus saginatus
- eggs eaten by ostracod crustacean which is the intermediate host
= eggs hatch within 1 hr and penetrate the gut within 36hrs - by 16 days the canthella have developed into infective cystacanth
= these mature in creek chub fish when they ingest crustaceans (definitive host)
outline the lifecule of palaeacanthocephala
e.g.Leptorhynchoides thecatus
- eggs are coated in fibres making them sticky becoming entangled in algae
- amphipods ingest eggs with algae where they hatch in the intestine
- amphipods ingested by either definitive or paratenic host where adults attach to gastric cecum
outline the Lifecyle of Archiacanthocephala
- eggs eaten by white grubs which are the intermediate host
- hacth in midgut in an hour
- 5-20 days acanthcella is either firee in haemocoel or attached to intestinal lining
- 60-90 days infective cystacanth develop
- pigs (final host) eat grubs r adult metamorphized beetles
outline how some acanthocephala can change their host behaviour to increase infection rates
e.g. host amphipods
showed that phototaxic behaviour in amphipods was altered by cystacanths of acanthocephalans polymorphus paradoxus
uninfected= photophobic and moved towards gravity
infected= photoactic and moved away from gravity which increases risk of predation by definitive host
e.g. woodlice
infected= attracted to low relative humidity and open areas with no shelter, spent more time in light
why are parasitic infections in humans by acanthocephalans rare
few people eat raw beetles or cockroaches
only 7 species infect humans
= usually associated with times of famine where people eat raw insects
outline some characteristics of the phyla nematomorpha
- superficially similar to the morphology of nematodes
= two orders
1) nectonematoidea = pelagic in costal marine habitats
2) gordioidea = freshwater and semiterrestrial- 1-3mm in diameter and around 30cm in length
- non-functional digestive tract and appear to lack excretory mechanism= evolutionary regression
- adults are free living
- larvae known to alter host behaviour causing them to jump into water allowing adult to esacpe and reproduce
outline the morphology of nectonematoideas
- double row of natatory setae on each side
- dorsal and ventral longitudinal epidermal cords
- fluid filled pseudocoelom
- larvae parasitic to decapod crustaceans
what is the sexual dimorphism between male and female nematomorphids
both have a cloacal pore
females have caudal lobes depending on the species
outline reproductive methods in nematomorphids
Females remain inactive, males highly motile during breeding period
Male wraps his body around female, deposits a drop of sperm
near the cloacal pore.
Sperm can be stored by the female while the eggs mature, then the
eggs are fertilised internally.
Eggs laid in gelatinous strings
Larvae develop inside the eggs; emerges and actively seeks an
arthropod host
*probably* arthropod attempts to eat the larvae
Some cases of active penetration of host cuticle
