Protozoan Parasites of Iranian Freshwater Fishes: Review, Composition, Classification, and Modeling Distribution

Abstract

This article investigates the occurrence and distribution of parasitic protozoa of Iranian freshwater fishes (both farmed and wild). Our search shows 26 known parasitic protozoan species were recorded from 52 freshwater fish species across different ecoregions of Iran. Most of these fish are edible. While none of the identified protozoan parasites are of zoonotic importance, our study does not exclude presence of zoonotic species in Iranian fishes. Present data suggest the northern and western regions of the country are the main macrohabitat of protozoa (35 parasitic records reported), with the greatest concentration of parasitic protozoa occurring in the Urmia basin in Iran's northwest. The clustered distribution pattern of protozoa among freshwater fish was also more evident in the northern and western parts of the country. The gills and skin were the most infected microhabitats for parasitic protozoa. The highest number of parasites was observed in the fish family Cyprinidae with nine species found in the native fish, Capoeta capoeta. The most diverse host range was observed in the holotrich ciliate, Ichthyophthirius multifiliis isolated from 46 cyprinid species in 39 different locations. However, due to the great richness of fish and extreme habitat diversity, parts of the parasite fauna of Iranian freshwater fish are still poorly understood. Furthermore, current and future changes in climate and environmental parameters, and anthropogenic interventions are likely to affect fish hosts and their parasites.

Keywords: Iran; checklist; freshwater fish; geographical distribution; protozoan parasites.

Figure 1

Flowchart of review process.

Figure 2

Flowchart of methodological and analytical processes of MaxEnt modelling to project potential distribution of future climatically suitable habitats for freshwater fish protozoa under different global change scenarios.

Figure 3

(a): Phyla of protozoan parasites found in Iranian freshwater fishes; (b): Order of Iranian freshwater fish infected with protozoan parasites.

Figure 4

Map of Iran showing main drainage basins and spatial distribution of localities where protozoan species of freshwater fishes have been reported. (* Tonekabon River is considered the Cheshme Kilah River. ** Zangmar River is also known as the Zangbar River).

Figure 5

The results for Average Nearest Neighbor.

Figure 6

Hotspot mapping of individual protozoan species (a); and the protozoan occurrence points relative to the DM aridity index (DMAI) map of Iran, based on the past two years’ average (2020–2022) (b). In the top figure red clusters illustrate the higher number of protozoan species, and the lighter-toned cluster zones (light blue) indicate a lower number of species. In the bottom figure red-colored cluster zones indicate a higher DMAI value, while the lighter-toned cluster zones show a lower DMAI value.

Figure 7

The relative importance of different predictor variables based on the results of jackknife tests in MaxEnt. Graphs represent the contribution of the variables in regularized training test gain (a); test gain (b).

Figure 8

Potential distribution of protozoan parasites of freshwater fishes in Iran; current (A) and future distribution; the 2050s (2041–2070) from IPSL-CM6A-LR according to the different climate scenarios (RCPs); RCP2.6 (B); RCP 7.0 (C); and RCP 8.5 (D); and the 2080s (2071–2100) from IPSL-CM6A-LR according to the different climate scenarios (RCPs); RCP2.6 (E); RCP 7.0 (F); and RCP 8.5 (G). Colors display the habitat suitability for fish hosts (green = high suitability).