Aspects of the life cycle and morphology of Hysterothylacium aduncum (Rudolphi, 1802) (Nematoda, Ascaridoidea, Anisakidae)

Abstract

Gravid Hysterothylacium aduncum from the intestine of eelpout, Zoarces viviparus, were used as the source of eggs for study. The two first moults occurred in the egg, which does not normally hatch spontaneously. The third-stage larva within the egg was not infective to either fishes or non-crustacean invertebrates, but developed into a typical third-stage larva in Acartia tonsa, harpacticoid copepods, various amphipods, isopods, and mysids. Further development in the fish host was apparently dependent only on the length of the larva. Thus, larvae from harpacticoids (< 1 mm long) and larvae less than 1.5 – 2.0 mm long from other crustaceans did not survive in the fish; larvae between about 2 and 3 mm in length remained as third-stage larvae in the fish. Larvae longer than 3 mm moulted into fourth-stage larvae in the intestinal lumen of the fish. Thus, a two-host cycle occurs when fishes ingest crustaceans harbouring third-stage larvae longer than 3 mm, and a cycle of three (or more) hosts when fishes ingest third-stage larvae less than 3 mm long. Ctenophores, chaetognaths, polychaetes, and ophiuroids, which become infected by ingesting infected crustaceans, may act as obligate intermediate hosts or transport hosts.

In vitro development of the fish parasite Hysterothylacium aduncum from the third larval stage recovered from a host to the third larval stage hatched from the egg

“…Køie (1993), in agreement with Markowski's (1937) There is also a debate about whether L2 (second larval stage) or L3 hatch from the eggs of anisakids. While some authors report that L2 is the stage that hatches (Measures & Hong 1995), others, however, report L3 to be hatching from anisakid eggs (Berry & Cannon 1981, Køie 1993, Køie & Fagerholm 1993, Køie et al 1995. According to observations by Køie (1993) made on Hysterothylacium aduncum, the hatched larvae were of L3, and were ensheathed in the thick, striated cuticle of L2.…”

“…This L2 cuticle became widely enlarged as a result of the movements of the larva. In the egg, at least 1 larva turned around inside the cuticle, as was also observed by Køie (1993). Our observations have shown that the larvae measure 144 to 215 µm in length, and are surrounded by a 237 to 305 µm-long sheath (n = 10).…”

“…While working on parasites from large gadids (Balbuena et al 1998) and salmonids (González 1998) a general hatching of developed eggs has been reported. However, the research of Køie (1993), working on worms from eelpout (possibly Hysterothylacium auctum), Yoshinaga et al (1987), working on parasites from freshwater Japanese smelt, which experimentally developed in rainbow trout, and the present study have always shown the rate of hatching larvae to be lower than 33% in seawater and several saline solutions. Køie (1993), in agreement with Markowski's (1937) There is also a debate about whether L2 (second larval stage) or L3 hatch from the eggs of anisakids.…”

“…However, the research of Køie (1993), working on worms from eelpout (possibly Hysterothylacium auctum), Yoshinaga et al (1987), working on parasites from freshwater Japanese smelt, which experimentally developed in rainbow trout, and the present study have always shown the rate of hatching larvae to be lower than 33% in seawater and several saline solutions. Køie (1993), in agreement with Markowski's (1937) There is also a debate about whether L2 (second larval stage) or L3 hatch from the eggs of anisakids. While some authors report that L2 is the stage that hatches (Measures & Hong 1995), others, however, report L3 to be hatching from anisakid eggs (Berry & Cannon 1981, Køie 1993, Køie & Fagerholm 1993, Køie et al 1995.…”

“…However, the research of Køie (1993), working on worms from eelpout (possibly Hysterothylacium auctum), Yoshinaga et al (1987), working on parasites from freshwater Japanese smelt, which experimentally developed in rainbow trout, and the present study have always shown the rate of hatching larvae to be lower than 33% in seawater and several saline solutions. Køie (1993) Køie et al 1995). According to observations by Køie (1993) made on Hysterothylacium aduncum, the hatched larvae were of L3, and were ensheathed in the thick, striated cuticle of L2.…”