''Steinernema scapterisci'', the mole cricket nematode, is a species of

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...

in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Rhabditida Rhabditida is an order of free-living, zooparasitic, and phytoparasitic microbivorous nematodes living in soil. The Cephalobidae, Panagrolaimidae, Steinernematidae, and Strongyloididae seem to be closer to the Tylenchia, regardless of whet ...

. It is a

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of insects in the order

Orthoptera Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – grassho ...

, the grasshoppers, crickets and their allies. Native to southern South America, it was introduced into Florida in the United States in an effort to provide a biological control of pest (''Neoscapteriscus'') mole crickets. A second species of "mole cricket nematode" exists in Florida, and probably elsewhere in the eastern USA. It is now called ''Steinernema neocurtillae'' Nguyen, Smart, and is known to attack only the native mole cricket ''Neocurtilla hexadactyla''

Description

''Steinernema scapterisci'' can be distinguished from other species of its genus "by the presence of prominent cheilorhabdions, an elliptically shaped structure associated with the excretory duct, and a double-flapped epitygma in the first-generation female." It does not hybridise with '' Steinernema carpocapsae'', and it infects and kills fewer than 10% of the non-orthopteran insects with which it comes in contact. Larvae of the wax moth, which all other known species of ''Steinernema'' infect, are not parasitised by this nematode.

Distribution

''Steinernema scapterisci'' is native to South America, with its range including Argentina, Brazil and Uruguay. It is more tolerant of high temperatures and less tolerant of low temperatures than are other members of its genus.

Biology

Individual adults of ''S. scapterisci'' are either male or female and their entire life cycle takes place within the host insect. This comprises an egg stage, four larval stages, the third of which is infective, and an adult stage. Depending on the conditions and the abundance of the parasite, there is either a short life cycle or a long one. The short cycle lasts six to seven days and occurs when the population of nematodes is dense and the availability of nutrients low. In this, the eggs develop through the four larval stages to first generation adults. These mate and the developing larvae become infective in the third juvenile stage. When nutrient availability is high and the nematodes are not overcrowded, the long cycle kicks in. This at first follows a similar course to the short cycle, but the eggs from the first generation adults develop through four larval stages to second generation adults. It is the eggs from these that develop into infectious juveniles. This cycle takes about ten days. The infectious juveniles can survive in the soil for eight weeks or more. They infect any mole cricket that passes, entering its body through its mouth or

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s and moving into the

hemocoel The blood circulatory system is a organ system, system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascula ...

(body cavity) which is filled with

hemolymph Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which ...

. Here they liberate a specialist

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

, ''

Xenorhabdus innexi ''Xenorhabdus innexi'' is a bacterium from the genus of ''Xenorhabdus'' which has been isolated from the nematode ''Steinernema scapterisci'' in Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental d ...

''; this causes

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

in the host insect, eventually killing it, but not before the nematode has passed through its various life cycle stages and further infective juveniles have developed. Some fifty thousand infective juveniles may have been released into the soil by each mole cricket host by the time it dies.

Use in biological control

In Florida, mole crickets in the genus ''

Neoscapteriscus ''Neoscapteriscus'' is a genus of two-clawed mole crickets in the family Gryllotalpidae. At least 23 described species are placed in ''Neoscapteriscus''. Species * '' Neoscapteriscus abbreviatus'' (Scudder, S.H., 1869) (lesser short-winged mole c ...

'' did great damage to pastures, lawns and golf courses from the 1930s to 1990s. In 1985, ''S. scapterisci'' was released in field trials and successfully infected mole crickets. After infection, the insects remain active and mobile before dying about ten days later. In this time they may disperse by flying, and in Florida three years after being released, the nematodes were found infecting mole crickets more than from the original release site. In 1990 and 1991, further releases were made on a more widespread scale and ''S. scapterisci'' is now established in Florida and was until 2014 available for purchase commercially. By 2004, pest mole cricket populations in Florida had declined by 95% due to action of three parasites, not just ''Steinernema scapterisci''; the others are ''Ormia depleta'' (Diptera: Tachinidae) and ''Larra bicolor'' (Hymenoptera: Crabronidae).

References

{{Taxonbar, from=Q20721485 Rhabditida Parasitic nematodes of animals Parasites of insects