Philonema oncorhynchi

Philonema oncorhynchi	Contents	Rev 11/18/2024
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Philonema oncorhynchi Kuitunen-Ekbaum, 1933

Type species of the genus.

Juveniles:

Long filiform tail which tapers into a sharp point.
Oral opening is surrounded by papillae and a triangular denticle is situated dorsally.
Esophagus homogeneous andcontains numerous refractile particles; nerve ring was halfway along the esophagus.
Intestine of 18-30 cells with prominent nuclei and was not joined to the proctodeum.
Genital primordia of four cells with nuclei with large clumps of chromatin. Rectum was a thin-walled tube, and the anus was clearly demarcated on the body wall.


Philonema oncorhynchi 1. First stage juvenile; 2: Second stage juvenile anterior; 3: Third stage juvenile, anterior and posterior; 4: Caudal region, subadult male; 5: Subadult male, en face Drawings from Platzer and Adams, 1967
Males: Subadult males 18 mm long, Spicules, anal papillae, tridentate telamon, and a reproductive tract with regional differentiation and motile sperm. Oral and tail papillae are obscure in adult P. oncorhynchi	Female: Subadult females were 42 mm longwith large uteri, ovaries, and open vulva. Ref: Platzer and Adams, .1967
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

Parasites of the body cavity of salmon

Female nematodes are fully grown and gravid with fully developed first-stage larvae when the salmon spawn in freshwater.
The nematodes are probably passed out with the fish eggs into the redd (a depression in the river or lake bottom gravel created by the upstroke of the female salmon's body and tail).
After about 1 minute in the river or lake water, the female nematodes burst, liberating many thousands of larvae. The larvae tend to remain in suspension which makes them readily available as food for copepods, Cyclops bicuspidatus, their intermediate host, in which they become infective.
The copepods are the main food supply for young salmon which hatched from the eggs deposited in the redd.
Infection of the youg salmon occurs mainly in January and February in Canada, and the young salmon have accumulated a substantial nematode burden by April when they migrate to the sea.
The nematode larvae infect the swim bladder of the fish (Platzer and Adams, 1967)..