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

摘要

ABSTRACT: Anisakids are parasitic nematodes of fish worldwide, producing economic and human health concerns. It is thus important to ascertain their in vitro life cycle in laboratory studies. Here we describe the in vitro development of third-stage larvae (L3) of Hysterothylacium aduncum isolated from blue whiting Micromesistius poutassou, to the hatching of L3 from eggs obtained from H. aduncum worms grown in GLIT medium (a modified mixture of Yaeger1s LIT [Liver Infusion Tryptose] and Grace1s media) at pH 4.0, 13°C and with 5% CO₂ in air. Under these conditions, L3 recovered from fish developed to mature adults (3.4 to 6.2 cm in length), with oviposition starting from Day 26 in culture. Fertilized eggs (mean size 64 × 52 μm) had a thick, rugose eggshell and were larger than unfertilized ones (mean size 49 × 42 μm), whose eggshells were thin and smooth. Eggs laid during the first and second week of oviposition, and maintained in 2.8% NaCl solution at 13°C, developed to L3. Under these maintenance conditions, between 20.6 and 52.5% of the eggs laid during the first week developed into larvae. Motile larvae, enclosed in a sheath, hatched from between 2 and 11% of these eggs. The larvae started to hatch 23 d after deposition. These larvae were 144 to 215 μm in length, enclosed in a 237 to 305 μm-long sheath. This GLIT culture medium may help to study the biology of this and other anisakids.