Steinernema hermaphroditum		Contents		Rev 07/03/2025
		Classification		Biology and Ecology
		Morphology and Anatomy		Life Cycle
Return to Steinernema Menu				Ecosystem Functions and Services
		Distribution		Management
Return to Steinernematidae Menu		Feeding		References
		Go to Nemaplex Main Menu		Go to Dictionary of Terminology

Classification:

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Morphology and Anatomy:

Hermaphrodite:

• Body C-shaped when heat-relaxed.
• Cuticle appears smooth but fine transverse striae visible under SEM. Lateral field and phasmids inconspicuous.
• Head truncate, slightly rounded, continuous with body contour.
• Six lips united each with one labial papilla. Four cephalic papillae.
• Amphid apertures small, posterior to lateral labial papillae.
• Stoma reduced, short and wide, with inconspicuous sclerotised walls.
• Pharynx set off from intestine, procorpus cylindrical, metacorpus without valve, isthmus distinct, basal bulb pyriform with reduced valve.
•  Nerve-ring around isthmusor anterior of basal bulb; ; excretory pore at posterior third of metacorpus,
• Ovaries opposed, reflexed; spermatheca filled with spermatozoa; uterus in ventral position. Vagina short, with muscular walls.
• Vulva more or less median in position with protruding lips, anterior larger than posterior.
•  Tail digitate, mucro present most specimens.

Male:

•  Cuticle, lip region, stoma and pharyngeal region as in first generation hermaphrodite.
• Single reflexed testis,
• Spicules paired, symmetrical, curved,
• Gubernaculum boat-shaped, about 66% length of spicules.
• Genital papillae 21 (ten pairs and one single)
• Second generation males similar to first generation males with differences in body length and diameter, position of excretory pore, size of spicules and gubernaculum.

Female (second generation):

• Cuticle, lip region, stoma and pharyngeal region as in first generation hermaphrodite.
• Ovaries paired, opposed and reflexed in dorsal position; spermatheca absent;
• Vulva about median position with nonprotruding or slightly protruding vulvar lips.
• Tail round-conoid, without a mucro.

Third-stage infective juvenile:

• Body slender, taperinganteriorly and posteriorly.
• Lip region smooth; mouth closed.
• Cuticle with transverse striae; lateral field distinct with eight equidistant longitudinal ridges in mid-body region.
• Pharynx long, narrow; basal bulb valvate; cardia present.
• Anterior portion of intestine with dorsally displaced pouch containing symbiotic bacteria.
•  Tail conoid with pointed terminus.

Ref: Stock et al., 2004

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Distribution:

An entomopathogenic nematode isolated from soil samples in the Moluccan islands, Indonesia. Now used as a model organism in studies on gene expression  in developmental biology and in study of symbiotic relationships.

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Feeding:

  Upon encountering a suitable insect host, an entomopathogenic nematode invades its body and resumes development, releasing endosymbiotic pathogenic bacteria from its intestine into its host (Dziedziech et al. 2020). The nematode and its bacterial symbiote rapidly kill the insect and convert the carcass into an incubator for the nematode–bacterial pair. When the carcass is exhausted of nutrients, a subsequent generation of IJs, each carrying pathogenic bacteria, disperse to begin the process anew. The entomopathogenic nematode lifecycle offers an opportunity to study the development and behavior of parasitic nematodes and their interactions with their bacterial symbiotes and their insect prey, along with other aspects of their biology shared with or differing from those described in other nematodes.

The dauer stqge infective juvenile invades invades the body of the host insect and resumes development it releases releasing endosymbiotic pathogenic bacteria (Xanorhabdus griffiniae  in this case) from its intestine into the host. The nematode and bacterial symbiont kill the insect and convert the carcass into an incubator for the nematode-bacterial pair. When the carcass is exhausted of nutrients, a subsequent generation of IJs, each carrying pathogenic bacteria, disperse into the soil. The entomopathogenic nematode lifecycle offers an opportunity to study the development and behavior of parasitic nematodes

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Biology and Ecology:

Steinernema hermaphroditum s the first self-fertile steinernematid reported (Griffin et al., 2001). There were no progeny with attempts to cross-hybridize S. hermaphroditum with other Steinernema spp., while crosses using individuals of the same species produced viable offspring, indicating the reproductive isolation of the species (Stock et al, 2004).

The bacterial endosymbiont is Xanorhabdus griffiniae (Schwartz et al., 2024).