Abstract:
Understanding the occurrence of parasites is important in the marine food fish
trade. Acanthocephalans can perforate and damage fish tissues making them
unsuitable for trade. This study focused on the identification of gut
acanthocephalans in Frigate tuna (Auxis thazard) and Mackerel tuna
(Euthynnus affinis) with a comparative analysis of the parasite occurrence
between two fish species. Fifty specimens from each fish species were
purchased from a retail store in Kandy, Sri Lanka, from June to September
2022. The fish were dissected and inspected for gut helminths. Recovered gut
helminths were washed and microscopic morphometry of the head and other
organs of the parasites was carried out for identification. The occurrence of
parasites in the two fish species was statistically analyzed using Chi-square
test. The microscopic examinations revealed two different acanthocephalan
genera, namely Rhadinorhynchus and Neorhadinorhynchus. Juveniles of
genus Rhadinorhynchus (Frigate tuna: 205 ± 0.84, Mackerel tuna: 485 ± 1.47)
and genus Neorhadinorhynchus (Frigate tuna: 61 ± 0.91, Mackerel tuna: 28 ±
2.2) were recovered from the gut of the fish. The prevalence of
Rhadinorhynchus was 82% and 74% in mackerel tuna and frigate tuna,
respectively, whereas that of Neorhadinorhynchus was 4% and 20%,
respectively. While the prevalence of Neorhadinorhynchus was lower in
mackerel tuna compared to frigate tuna (p<0.05), the co-occurrence of both
parasitic genera in mackerel tuna was also low (p<0.05). The parasite
abundance for Rhadinorhynchus was 9.7 and 4.1 in mackerel and frigate tuna,
respectively, and it was 0.56 and 1.22 for Neorhadinorhynchus. The present
study marks the first attempt to explore acanthocephalans in Sri Lankan
marine food fish.
