Parasites could outnumber fish by ten to one

1c835920-42b8-443e-8b6f-756a63cdb5bc

Editor's Picks
Features Post
The brightest pupils
04 October 2021
Features Post
Dealing with egg ‘fungus’
04 October 2021
Features Post
Rathbun’s tetra in the wild
13 September 2021
Fishkeeping News Post
Report: 2021 BKKS National Koi Show results
13 September 2021
Features Post
The World's forgotten fishes
16 August 2021


Parasites on reef fishes could outnumber fishes by ten to one, according to the results of a new study which has revealed the presence of 12 species of fluke on the gills of a single species, eight of which were previously unknown to science.

According to the results of the study, which is due to be published shortly in the journal Systematic Parasitology, an analysis of the parasites of the grouper Epinephelus maculatus has shown the presence of more than a dozen species, indicating that parasite biodiversity may be considerably greater than fish biodiversity in the reef environment.

Jean-Lou Justine of Institut de Recherche pour le Developpement in New Caledonia studied more than 800 monogean flatworms, or flukes, found on Epinephelus maculatus, and identified 10 members of the monogenean family Diplectanidae and two from the family Ancyrocephalidae.

The parasites discovered have not previously been recorded from other groupers in the area and Justine believes that they are probably specific to this fish species.

Besides the monogeans, which were the focus of Justine's research, the analysis also found three species of copepod and an isopod species, taking the total number of parasite species found on the fishes' gills to 16. "...parasite biodiversity could be more than ten times greater than the number of fish species..."Says Justine: "Diplectanids include Laticola dae Journo and Justine, 2006, which is the most abundant species representing about 50% of the specimens, and nine species which are rare, each representing 2-7% of the specimens: Diplectanum uitoe n. sp. and eight species of Pseudorhabdosynochus Yamaguti, 1958. D. uitoe, provisionally attributed to Diplectanum Diesing, 1858, is characterised by a small conical penis with internal walls.

"Pseudorhabdosynochus auitoe n. sp., P. buitoe n. sp., P. cuitoe n. sp., P. duitoe n. sp., P. euitoe n. sp. and P. fuitoe n. sp. are differentiated on the basis of the morphology of the sclerotised vagina, but are very similar in other characteristics; P. guitoe n. sp. is characterised by a quadriloculate organ with very thick walls and a very small sclerotised vagina; and P. huitoe n. sp. is characterised by its sclerotised vagina and by very long ventral and dorsal haptoral bars.

"Two rare (2-3% of specimens) ancyrocephalids, Haliotrema epinepheli Young, 1969 and Haliotrema sp., are briefly described in relation to the male copulatory organs and haptoral bars; H. epinepheli is apparently a generalist species found in various epinephelines and other fish species."

Justine claims that although coral reefs are known for their high level of biodiversity, the number of parasites present has not been evaluated. He believes that parasite biodiversity could be more than ten times greater than the number of fish species, and consequently, that the extinction of fish could result in the co-extinction of at least ten times as many parasite species.

For more information see the paper: JL Justine (2006) - Parasite biodiversity in a coral reef fish: twelve species of monogeneans on the gills of the grouper Epinephelus maculatus (Perciformes: Serranidae) off New Caledonia, with a description of eight new species of Pseudorhabdosynochus (Monogenea: Diplectanidae). Systematic Parasitology, 2006. (In Press)