Animal Diversity Web

Ge­o­graphic Range

Anisakis sim­plex has a wide range of hosts through­out its life cycle and an equally large ge­o­graphic range. This par­a­sitic worm can be found in crus­taceans, squid, fish, and ma­rine mam­mals in oceans and seas from the trop­ics to the arc­tic and antarc­tic re­gions. (Bullini, 1997; Oliva, 1999)

• Biogeographic Regions
• nearctic
• palearctic
• neotropical
• oceanic islands
• arctic ocean
• atlantic ocean
• pacific ocean

Habi­tat

The im­me­di­ate habi­tat of Anisakis sim­plex is in­side the he­mo­coel of its crus­tacean in­ter­me­di­ate host where the par­a­site de­vel­ops into its third stage ju­ve­nile. Gen­er­ally it is in­side the gut of its paratenic and de­fin­i­tive hosts as a third stage ju­ve­nile and adult re­spec­tively. Sec­ond stage ju­ve­niles are able to live freely in sea water until be­com­ing in­gested by a crus­tacean.

The more in­di­rect habi­tat of A. sim­plex is the ma­rine en­vi­ron­ment where its hosts live. (Kara­sev, 1993)

• Habitat Regions
• saltwater or marine

• Aquatic Biomes
• pelagic
• benthic
• reef
• coastal
• brackish water

• Other Habitat Features
• estuarine
• intertidal or littoral

Phys­i­cal De­scrip­tion

Mem­bers of the Phy­lum Ne­ma­toda are worm­like, have a pseudo­coel and com­plete di­ges­tive sys­tem. Their bod­ies are cov­ered with a non-cel­lu­lar cu­ti­cle com­posed of col­la­gen and other com­pounds which is se­creted by the epi­der­mis. The cu­ti­cle has three main lay­ers and is shed four times through­out their life cycle. The ne­ma­tode psue­do­coel, filled with fluid, func­tions as a hy­dro­sta­tic skele­ton. So­matic mus­cu­la­ture, com­posed of lon­gi­tu­di­nal mus­cles, acts against the stretch­ing and com­pres­sion of the cu­ti­cle to pro­duce move­ment. Con­nected to the main body of mus­cles are dor­sal and ven­tral lon­gi­tu­di­nal nerve cords.

Like most other as­cari­did ne­ma­todes, A. sim­plex pos­sesses three pro­trud­ing lips around its mouth open­ing. These lips are poorly de­vel­oped in ju­ve­nile stages, but con­tain inner labial papil­lae, which may func­tion as com­bined chemo­mechanosen­sory re­cep­tors in adults. Male as­cari­dids pos­sess sim­ple spicules used to hold the fe­male gen­i­tal pore open against hy­dro­sta­tic pres­sure dur­ing cop­u­la­tion.

Anisakis sim­plex ju­ve­niles range in size from less than 5 mm as sec­ond stage ju­ve­niles to more than 30 mm in their fourth stage. (Barnes, 1987; Br­usca and Br­usca, 2003; Roberts and Janovy, 2000; Smith, 1983)

• Other Physical Features
• ectothermic
• heterothermic

• Sexual Dimorphism
• female larger
• sexes shaped differently

• Range length

  5 to 30 mm

  0.20 to 1.18 in

De­vel­op­ment

The life cycle of A. sim­plex be­gins when eggs are passed through the feces of its de­fin­i­tive host. The de­fin­i­tive hosts of this species in­clude many ma­rine mam­mals such as whales, por­poises, and seals. Once the eggs are passed, they hatch into sec­ond stage ju­ve­niles. The ju­ve­niles must be con­sumed by an in­ter­me­di­ate host, usu­ally a eu­phausiid crus­tacean, for the life cycle to con­tinue. Phys­i­cal changes to the en­vi­ron­ment that are spe­cific to the he­mo­coel of the crus­tacean prob­a­bly sig­nals the worms to de­velop into a third stage ju­ve­nile. Preda­tors of crus­taceans, usu­ally fish or squid, be­come in­fected by A. sim­plex after eat­ing an in­fected crus­tacean. Be­cause A. sim­plex does not un­dergo any de­vel­op­ment in­side the gut of the fish or squid, these preda­tors are con­sid­ered paratenic hosts of the ne­ma­tode. The life cycle is com­pleted after the paratenic host is in­gested by a de­fin­i­tive host. In­side its final mam­malian host, the worm de­vel­ops into a sex­u­ally ma­ture adult. Be­cause A. sim­plex eggs are shed from the host through­out the year, they may de­velop and hatch at any time, thus ac­qui­si­tion of in­fec­tion by hosts is non-sea­sonal.

While the above men­tioned life cycle is ac­cepted by many sci­en­tists, there is con­sid­er­able ev­i­dence that two molts ac­tu­ally occur dur­ing de­vel­op­ment in the egg of A. sim­plex and that it is the third stage ju­ve­nile which hatches from the egg. (Koie, 1995; Podol­ska, 1995; Roberts and Janovy, 2000; Smith, 1983)

Re­pro­duc­tion

In­side its final mam­malian host, the worm de­vel­ops into a sex­u­ally ma­ture adult. Fe­males may pro­duce a pheromone to at­tract males. The male coils around a fe­male with his curved area over the fe­male gen­i­tal pore. The gu­ber­nac­u­lum, made of cu­ti­cle tis­sue, guides spicules which ex­tend through the cloaca and anus. Males use spicules to hold the fe­males dur­ing cop­u­la­tion. Ne­ma­tode sperm are amoe­boid-like and lack fla­gella. (Barnes, 1987; Br­usca and Br­usca, 2003; Roberts and Janovy, 2000; Smith, 1983)

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • internal
• oviparous

• Parental Investment
• pre-fertilization
  • provisioning

Be­hav­ior

Ne­ma­todes such as Anisakis sim­plex swim in­ter­mit­tently. The worms are usu­ally only able to move ef­fec­tively when the pseudo­coel is filled with fluid and hy­per­tonic to the sur­round­ing media. (Barnes, 1987; Br­usca and Br­usca, 2003)

• Key Behaviors
• parasite
• motile
• sedentary

Com­mu­ni­ca­tion and Per­cep­tion

Ne­ma­todes within the Se­cer­nen­tea have phas­mids, which are uni­cel­lu­lar glands. Phas­mids likely func­tion as chemore­cep­tors. Fe­males may pro­duce pheromones to at­tract males.

Ne­ma­todes in gen­eral have papil­lae, setae and am­phids as the main sense or­gans. Setae de­tect mo­tion (mechanore­cep­tors), while am­phids de­tect chem­i­cals (chemore­cep­tors). (Barnes, 1987; Br­usca and Br­usca, 2003)

• Communication Channels
• tactile
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• tactile
• chemical

Food Habits

Like other as­cari­did ne­ma­todes, Anisakis sim­plex feeds on the gut con­tents of its de­fin­i­tive host as an adult. Pha­ryn­geal glands and in­testi­nal ep­ithe­lium pro­duce di­ges­tive en­zymes. Ex­tra­cel­lu­lar di­ges­tion be­gins within the lumen and is fin­ished in­tra­cel­lu­larly. (Barnes, 1987; Br­usca and Br­usca, 2003; Roberts and Janovy, 2000)

• Primary Diet
• carnivore
  • eats body fluids

• Animal Foods
• body fluids

Pre­da­tion

These par­a­sites are usu­ally not preyed on di­rectly, but are in­gested from host to host. Lar­val mor­tal­ity is high due to its in­abil­ity to reach a suit­able host. (Barnes, 1987; Br­usca and Br­usca, 2003)

Ecosys­tem Roles

This par­a­sitic worm can be found in crus­taceans, squid, fish, and ma­rine mam­mals in oceans and seas from the trop­ics to the arc­tic and antarc­tic re­gions.

• Ecosystem Impact
• parasite

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

Anisakis sim­plex is of much med­ical im­por­tance be­cause of the se­vere al­ler­gic re­ac­tions and gas­troin­testi­nal symp­toms it causes in hu­mans after eat­ing or han­dling in­fected fish or crus­taceans. These re­ac­tions in­clude chronic uti­caria (skin rashes), gas­tric ul­cers, and ana­phy­laxis (a hy­per-im­mune re­sponse). These symp­toms are termed anisaki­a­sis and are es­pe­cially preva­lent in coun­tries where it is com­mon to eat raw or un­der­cooked fish. Pop­u­la­tions of fish­er­men are also at risk of de­vel­op­ing anisaki­a­sis as well as de­vel­op­ing oc­cu­pa­tional asthma caused by the in­hala­tion of anti­gens from A. sim­plex. How­ever, even peo­ple who take spe­cial pre­cau­tions when han­dling and prepar­ing their fish are at risk of de­vel­op­ing anisaki­a­sis. It has been re­ported that A. sim­plex can sur­vive at tem­per­a­tures of over 65 de­grees Cel­sius in­side a mi­crowave oven. (Adams, et al., 1999; Ar­men­tia, 1998; Moreno-An­cillo, et al., 1997; Purello-D'Am­bro­sio, et al., 2000)

• Negative Impacts
• injures humans
  • causes disease in humans

Con­trib­u­tors

Renee Sher­man Mul­crone (ed­i­tor).

Julie Rit­ter (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Barry OCon­nor (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Adams, A., K. Miller, M. Wekell, F. Dong. 1999. Sur­vival of Anisakis sim­plex in mi­crowave-processed ar­row­tooth floun­der (Ather­es­thes sto­mias). Jour­nal of Food Pro­tec­tion, 62 (4): 403-409.

Ar­men­tia, A. 1998. Oc­cu­pa­tional asthma by Anisakis sim­plex. Jour­nal of Al­lergy & Clin­i­cal Im­munol­ogy, 102 (5): 831-834.

Barnes, R. 1987. In­ver­te­brate Zo­ol­ogy. Or­lando, Florida: Dry­den Press.

Br­usca, R., G. Br­usca. 2003. In­ver­te­brates. Sun­der­land, Mass­a­chu­setts: Sin­auer As­so­ci­ates, Inc..

Bullini, L. 1997. Antarc­tic Com­mu­ni­ties: Species, Struc­ture, and Sur­vival. UK: Cam­bridge Uni­ver­sity Press.

Cen­ter for Food Safety & Ap­plied Nu­tri­tion, 2003. "Anisakis sim­plex and re­lated worms" (On-line). Bad Bug Book. Ac­cessed Sep­tem­ber 14, 2004 at http://​vm.​cfsan.​fda.​gov/​~mow/chap25.​html.

Kara­sev, A. 1993. Par­a­sito­log­i­cal Stud­ies of North­ern Basin Fish. Rus­sia: Pinro, Mur­mansk.

Koie, M. 1995. De­vel­op­ment to third stage lar­vae oc­curs in the eggs of Anisakis sim­plex and Pseudoter­ra­nova de­cip­i­ens. Can­dian Jour­nal of Fish­eries and Aquatic Sci­ences, 52: 134-139.

Moreno-An­cillo, A., M. Ca­ballero, R. Ca­banas, J. Con­tr­eras, J. Mar­tin-Bar­roso. 1997. Al­ler­gic re­ac­tions to Anisakis sim­plex par­a­sitiz­ing seafood. An­nals of Al­lergy, Asthma, & Im­munol­ogy, 79 (3): 246-250.

Ohio State Uni­ver­sity, 2001?. "Anistakis spp." (On-line). Par­a­sites and Par­a­sito­log­i­cal Re­sources. Ac­cessed Sep­tem­ber 15, 2004 at http://​www.​biosci.​ohio-state.​edu/​~par­a­site/anisakis.​html.

Oliva, M. 1999. Meta­zoan par­a­sites of the jack mack­erel Tra­chu­rus mur­phyi in a lat­i­tu­di­nal gra­di­ent from South Amer­ica (Chile and Peru). Par­a­site, 6 (3): 223-230.

Podol­ska, M. 1995. The role of cod (Gadus morhua) in the life-cy­cle of Anisakis sim­plex in the south­ern Baltic Sea. Sci­en­tific Pa­pers Pre­sented at the Pol­ish-Swedish Sym­po­sium on Baltic Cod, No. 327: 115-122.

Purello-D'Am­bro­sio, F., E. Pa­s­torello, S. Gangemi, G. Lom­bardo, L. Ric­cia­rdi. 2000. In­ci­dence of sen­si­tiv­ity to Anisakis sim­plex in a risk pop­u­la­tion of fish­er­men/fish­er­mon­gers. An­nals of Al­lergy, Asthma, & Im­munol­ogy, 84 (4): 439-444.

Roberts, L., J. Janovy. 2000. Foun­da­tions of Par­a­sitol­ogy: Sixth Edi­tion. Boston: Mc­Graw-Hill Higher Ed­u­ca­tion.

Smith, J. 1983. Anisakis sim­plex: Mor­phol­ogy and mor­phom­e­try of lar­vae from eu­phausi­ids and fish, and a re­view of the life-his­tory and ecol­ogy. Jour­nal of Helminthol­ogy, 57 (3): 205-224.