Howardula aptini

Howardula aptini	Contents	Rev: 11/01/2022
	Classification	Biology and Ecology
	Morphology and Anatomy	Life Cycle
Return to Howardula Menu	Economic Importance	Ecosystem Functions and Services
	Distribution	Management
Return to Allantonematidae Menu	Feeding	References
	Go to Nemaplex Main Menu	Go to Dictionary of Terminology

Classification:


Howardula aptini (Sharga, 1932) Wachek, 1955

    Synonyms:

Tylenchus aptini Sharga, 1932

Anguillulina aptini (Sharga, 1932) Lysaght, 1936

Morphology and Anatomy:

Adult parasitic female:

body enlarged but shorter than free-living female.
Body surface mostly smooth.
Anterior end conoid ; stylet not retracted into inner body,
Tail end narrows quickly, resembling free-living female tail.
Esophagus and intestine degenerate. Anus not apparent.
Oviparous; gonad fills body cavity and usually has two flexures; ovary with numerous hexagonal oogonia arranged about a central rachis;
Spermatheca highly specialized, in pouch-like structure in wall of oviduct that contains individual sperm received from male during free-living stage. V
Vulva1 lips slightly protruded.

Free-living female:

Body slender'
Stylet robust, with large lumen; basal knobs well developed.
Esophagus allantonematoid, strongly swollen at level of subventral gland orifices, glands extend far posteriorly, filled with coarse globules, dorsal gland not as well developed as subventrals.
Gonad monodelphic, prodelphic; ovary with few cells; no eggs produced in this stage; small postuterine sac-like area present; v
Vulva small, round; vulva1 lips not protruded.
Anus difficult to see.
Tail wedge-shaped, rounded at the end.

Free-living male :

Smaller than female.
Stylet absent, stoma weakly cuticularized.
Esophagus weakly developed.
Gonad outstretched, reaching into esophageal region; vas deferens containing individual sperms.
Tail rounded at tip, enveloped by narrow, peloderan caudal alae.
Spicules slightly curved, distally acuminated, tylenchoid.
Gubernaculum appearing as a shepherd's crook in lateral view.

Howardula aptini: A. Male anterior; B. entire parasitic female; C: free-living female, posterior. D: free-living female: anterior. E: Male posterior

from Nickle and Wood, 1964

Males:

Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

Distribution:

Reported as a parasite of thrips in Europe and Canada.

Economic Importance:

Potential as a biological control agent for thrips.

Biology and Ecology:

Thrips feed on the unfolding leaves and cause a leaf gall to form.
Thrips lay eggs in the gall and the next generation of thrips mature before leaving the gall to overwinter in the soil and complete their life cycles.
Galls often contain both adult and immature stages of the thrips at the same time.
Numerous nematode eggs and larvae in all stages of development are found in the haemocoel, normally only one or two parasitic females are found in the body cavity of a parasitized thrip.
The nematodes mature in the host thrips and leave it as fully developed, free-living forms.
The free-living male and female nematodes probably mate within the confines of the gall and the fertilized female nematode must then enter the thrips larvae or pupae that are in the leaf gall.
The high humidity of the gall favors parasite transfer to the host.
Ovaries of the parasitized thrips are greatly reduced and do not appear capable of producing eggs.

Interestingly, another sphaerolaimoid nematode, Fergusobia tumifaciens (Neotylenchidae), which parasitizes both the adult and immature stages of agromyzid flies, Fergusonina spp., also has its free-living stages in galls formed by its host. In that case the galls are on the flowers of eucalyptus. This association was originally reported by Currie, 1937 as a mutualistic symbiosis; however,Nickle and Davis (1964) considered it more probably a true parasitic relationship. More recent authors (Giblin-Davis et al., 2004; Nelson et al., 2014) regard the associations between Fergusobia nematodes (Neotylenchidae) and Fergusonina flies (Fergusoninidae) represent a putative example of nematode- and arthropod-associated mutualism. The nematode appears to induce the bud or leaf gall that both organisms use while the fly provides gall maintenance, dispersion, and sustenance for the nematode. The family Agromyzidae, which has no known nematode associates, is the putative sister group to the Fergusoninidae. Giblin-Davis et al (2004) speculate that Fergusobia could have evolved from parasitic nematodes similar to present day Howardula that parasitised the cyclorrhaphan stem ancestor of Fergusonina flies and so developed a plant-parasitic association that provided a mutual benefit to fly host and nematode. Alternatively, Fergusobia could be related to present day nematodes of the family Anguinidae that produce above-ground galls and may have developed an association with an agromyzid ancestor. In either case, the evolution of the host-parasite interaction requires that host fly resistance and nematode virulence be moderated in female flies because they are always associated with nematodes.

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Life Cycle:

In another species, Howardula husseyi, Richardson et al. (1977). reported that:

mature females were in the adipose tissues of the body cavity of the dipteran Megasella halteratahe
The nematodes deposit up to 850 eggs during the insects pupation.
The first juvenile stage is completed in the egg, hatch from the eggs and feed in the haemocoel.
Hatched lLarvae migrate to the ovaries of the fly and continue development.
Larvae are liberated during oviposition into mshroom compost.
The nematodes grow and develop using stored reserves.
Fourth stage juvenile females s are fertilized and penetrate the host flies.
Males probably die after copulation.
The nematode life cycle is completed only in female flies; parsitizing larvae in male flies die without completeing development..

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click	If species level data are not available, click for genus level parameters

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Ecosystem Functions and Services:

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Management:

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References:

Currie, G.A. 1937. Galls on Eucalyptus trees. A new type of association between 9ies and nematodes. Proc. Linnean Soc. N. S. Wales, 62:147-174

Giblin-Davis, R.M.,Scheffer, S.J., Davies, K.A., Taylor, G.S., Curole, J., Center, T.D, Goolsby, J., Thomas, W.K. 2004. Coevolution between Fergusobia and Fergusonina mutualists: Pp 407-417 in Cook, R. and Hunt, D. (eds) Proceedings of the Fourth International Congress of Nematology, 8-13 June 2002, Tenerife, Spain

Handoo, Z.A., Iqbal, E.Y., Kazi, N., and Fayyaz, S. 2010. Two new species of Howardula Husain & Khan, 1968 (Nematoda: Sphaerulariidae) associated with wheat and a diagnostic compendium to the genus. Nematology 12:181-192.

Nelson, L., Davies, K., Scheffer, S., Taylor, G., P, M., Giblin-Davis, R., Thornhill, A., Yeates, D. D. 2014.. An emerging example of tritrophic coevolution between flies (Diptera: Fergusoninidae) and nematodes (Nematoda: Neotylenchidae) on Myrtaceae host plants. Biological Journal of the Linnean Society. 111. 10.1111/bij.12237.

Nickle, W.R., Wood, G.W. 1964. Howardula aptini (Sharga, 1922) parasitic in blueberry thrips in New Brunswick. Cn. J. Zool. 42:843-846

Poinar, Jr., G.O., Jaenike, J., Dombeck, I., 1997. Parasitylenchus nearcticus sp. n. (Tylenchida: Allantonematidae) parasitizing Drosophila (Diptera : Drosophilidae) in North America. Fundam. Appl. Nematol. 20:187-190.

Richardson, P.N., Hesling, J.J., Ridoing, I.L. 1977. Life Cycle and Description of Howardula husseyi N. Sp. (Tylenchida: Allantonematidae), a Nematode Parasite of the Mushroom Phorid Megaselia Halterata (Diptera: Phoridae). Nematologica 23:217-231.

Sharga, U.S. 1932. A new nematode,Tylenchus aptini n. sp. parasite of Thysanoptera (Insecta: Aptinothrips rufus Gmelin). Parasitology 24:268-279.

Wachek, F. 1955.. System und biologic der entoparasitischen Tylenchida. Parasitolog. Schriftenreihe. Fischer Verlag, Jena. 119 pp.