Trophomera megala		Contents		Rev 11/21/2025
		Classification		Hosts
		Morphology and Anatomy		Life Cycle
Return to Trophomera Menu		Economic Importance		Damage
		Distribution		Management
Return to Benthimermithidae Menu		Feeding		References
		Go to Nemaplex HomePage		Go to Dictionary of Terminology

Classification:

  Enoplea

Dorylaimia

Mermithida

            Mermithina

               Mermithoidea

                           Benthimermithidae

Trophomera megala (Petter, 1987) Miljutin, 2006

Synonyms

Benthimermis megala Petter, 1987

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Morphology and Anatomy:

• White medium size nematodes vary from 3 to 10 cm long.

• Slender nematodes up to 15 cm long with a diameter around 500 um
• Anterior end is rounded, posterior truncate and conical terminating in an axial spine
•  Cuticle thin and transparent so that trophosome and genital system are visible.
• Cuticle with very fine annnulation. numerous conical somatic setae 5 - 6 um long distributed laterally throughout the body
• Cuticle in cephalic region with very fine punctations extending from anterior end apex to almost the level of amphids
• Mouth opening is absent, but there is a central apical light spot surrounded by six minute marks that may be vestigial subsurface cephalic sensilla; also, four cephalic setae 7 - 8.5 um long
• Amphids with small transversely oval pore-like opening 8 - 9 um wide located 170 - 260 um from cephalic apex
• Esophagus vestigial without a lumen
• Midgut is a trophosome made up of large radial cells and a very thin axial internal lumen. The trophosome cells are  filled with various inclusions,
• Nerve ring  embedded in the anterior trophosome.
• No anus is present at the posterior end of the body.
• Terminal spine is prominent, 750 - 1200 um long, solid,cuticular without cells or cell processes

Female:

• Amphidelphic, germinal zone of  the ovaries T. megala extends the length of the gonad (hologonic ovary), whereas the ovaries of smaller Trophomera species are telogonic.
• Vulva at about mid-body.
• Males not seen, neither spermatheca or sperm were seen in female genital system

Ref: Miljutin and Tchesunov, 2001.

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Distribution:

Reported from bottom sediments of the deep-sea off the coast of Norway  at depths of 2668-2904 m (Miljutin and Tchesunov, 2001).

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Feeding:

Juveniles parasitic in marine invertebrates, adults apparenly not feeding. The intra-cellular inclusions and shrinkage of the trophosome, together with degradation of the reproductive organs, suggest that the trophosome functions to store nutrients that are expended during the free-living adult stage in sediments (Miljutin and Tchesunov, 2001).

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Biology and Ecology:

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Life Cycle:

Like the mermithids of fresh-water and soil environments (Order Mermithida), the larval stages of benthimermithids parasitise the body cavities and internal organs of invertebrate hosts, including polychaetes, priapulids, various crustaceans, holothuroids and free-living nematodes. Adult or late larval stages leave the host and enter a nonparasitic phase in which they reproduce but, based on their modified digestive system and lack of a mouth, apparently do not feed. So, larval stages parasitize benthic invertebrates, while non-feeding adult stages reproduce in benthic sediment  (Miljutin and Tchesunov, 2001).

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Ecosystem Functions and Services:

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Management:

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References:

Platonova, T. A., & Galtsova, V. V. (1976). Nematodes and their role in the meiobenthos. Akademiya Nauk

Rubtsov, I. A., & Platonova, T. A. (1974). A new family of marine parasitic nematodes. Zoologicheskii Zhurnal, 53, 1445-1458.

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Copyright 1999 by Howard Ferris.
Revised: November 21, 2025.