No common name

Tetraonchus monenteron

ORDER

Monopisthocotylea

FAMILY

Tetraonchidae

TAXONOMY

Tetraonchus monenteron Wagener, 1857; Diesing, 1858.

OTHER COMMON NAMES

None known.

PHYSICAL CHARACTERISTICS

Body elongated, about 0.04 in (1 mm) in length. Haptor with four similar hamuli, arranged in lateral pairs, each pair comprising one dorsally orientated and one ventrally orientated hamulus. Transverse supporting bar between hamulus pairs. Sixteen hooklets present; one pair central on ventral surface, two pairs dorsally orientated. Haptor glands present. Head region with four eyespots and three pairs of adhesive sacs that can be turned inside out. Male copulatory organ is a hardened tube with associated accessory sclerite. Single testis.

DISTRIBUTION

Recorded in Europe, North America and Russia on its specific host, the freshwater pike, Esox lucius. Not systematically mapped.

HABITAT

Abundant on gills of Esox lucius. Haptor lodges between two secondary gill lamellae.

BEHAVIOR

The parasite secures itself to the host by counter-rotating its ventral and dorsal hamuli until they push through the sec ondary gill lamellae. Each laterally situated pair of hamuli is operated by a single muscle. This muscle gives rise to a long tendon, which is threaded through loops attached to the hamuli. The arrangement resembles a pulley system and is likely to confer mechanical advantage. The hamuli are assisted by hooklets and possibly by glands. Sticky eversible sacs on head permit leech-like movement along the gill.

FEEDING ECOLOGY AND DIET

Feeds on gill epithelium; may take blood when the secondary gill lamella is ruptured.

REPRODUCTIVE BIOLOGY

Mating not recorded. Ovoid eggs presumably leave the gill chamber and settle to the bottom. Ciliated oncomiracidium hatches after 3-4 days. Immature parasites have been found on host skin.

CONSERVATION STATUS

Not threatened.

SIGNIFICANCE TO HUMANS None known. ♦

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