Yellow grub diseases on two seasonal killifish (Cyprinodontiformes, Rivulidae): a histopathological study

Area of Science:

• Ichthyology
• Parasitology
• Ecology

Background:

• Yellow grub disease is a parasitic infection caused by Clinostomum spp. metacercariae.
• Seasonal killifish in the Neotropics are vulnerable vertebrates with short lifespans and limited breeding periods.

Purpose of the Study:

• To analyze the injury and inflammatory reactions caused by Clinostomum spp. in seasonal killifish.
• To investigate the impact of this parasitic infection on fish reproductive capacity and species perpetuation.

Main Methods:

• Histopathological examination of testes, ovaries, liver, intestine, and mesentery in Trigonectes aplocheiloides and Titanolebias monstrosus.
• Identification of inflammatory responses and cellular infiltration in affected organs.

Main Results:

• Clinostomum spp. metacercariae caused significant inflammation, including vascular congestion and inflammatory cell infiltration, across multiple organs.
• The pancreas, ovaries, and testes were most severely affected, showing pancreatitis, reduced ovarian follicles, and impaired spermatogenesis.
• Parasitic migration via the circulatory system was suggested by the presence of a cercaria in a hepatic sinusoid.

Conclusions:

• Yellow grub disease significantly impairs the reproductive capacity of seasonal killifish, potentially causing infertility or sterility.
• This parasitism poses a considerable threat to the perpetuation of these vulnerable species due to their short breeding windows.