Coptodon guineensis, (Gunther, 1862) (Gunther, 1862)

Louizi, Halima, Hill-Spanik, Kristina M., Qninba, Abdeljebbar, Connors, Vincent A., Belafhaili, Amine, Agnèse, Jean-Francois, Pariselle, Antoine & Buron, Isaure de, 2022, Parasites of Moroccan desert Coptodon guineensis (Pisces, Cichlidae): transition and resilience in a simplified hypersaline ecosystem, Parasite (Paris, France) 29 (64), pp. 1-18 : 11

Population dynamics of parasites in C. guineensis

Overall, 68.8% (221/322) of fish were infected by A. (A.) cf. tilapiae (mean intensity 4.6 ± 0.29), 74.15% (194/264) by metacercariae of P. genata , and 21.5% (50/232) by the unidentified metacercariae. For all three parasites, fish as small as 20 mm in TL were infected. Infection results are reported in Table 5 .

The acanthocephalan was present throughout the four sampling periods, and there was no seasonal pattern of transmission with respect to prevalence (Χ 2 = 7.035, df = 3; P = 0.071) ( Fig. 6 ). Mean intensity was significantly lower in April when ovigerous females were in highest proportion compared to the rest of the year (Kruskal– Wallis: H = 25.16; df = 3, N = 221, P <0.01; Figs. 7 and 8 ). Gravid females were found throughout the year and in highest proportion in December and July ( Fig. 8 ). Analysis of female acanthocephalans indicated a significant overall effect of season relative to female worm length (Welch’ s ANOVA, P <0.001; Fig. 9 ). Significantly longer (more mature) female worms were found during the summer (2820.5 ± 133.7) compared to the spring (2141.3 ± 89.4; P = 0.038) and in the winter (2460.2 ± 88.7) as compared to the fall (2013.4 ± 191.8; P <0.001; Fig. 9 ). Sex-ratio was ~ 1 male: 2 females at each collection time (male to female ratios were 125:246, 31:69, 95:175, 78:137 for winter, spring, summer, and fall, respectively). There was no effect of fish sex on intensity of infection (Kruskal– Wallis: H = 3.66, df = 1, N = 152, P = 0.06 for males vs. females, and H = 3.82, df = 2; n = 210, P = 0.148 with inclusion of a group for undetermined sex). Fish size had no effect on prevalence of infection, but abundance (Spearman’ s Rho: r s = 0.263, P <0.001, Fig. 10 ) and intensity (Spearman’ s Rho: r s = 1, P <0.001) of infection increased with fish total length.

There was a significant seasonal pattern of transmission as prevalence of metacercariae of P. genata was significantly lower in April (56.2%) and highest in October (94.3%) (Χ 2 = 10.93, df = 3; P = 0.012) ( Fig. 6 ). The unidentified metacercariae were encountered only in July and October when, overall, 85.7% of the 60 fish examined were infected (Χ 2 = 180.95, df = 3; P <0.0001). Fish size had no effect on prevalence of infection of either metacercariae.

Figures

Figure 6. Prevalence of infection (%) of Coptodon guineensis at Sebkha Imlili. Blue bars = acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae (December 2018: n = 93; April 2019: n = 80; July 2019: n = 92; October 2019: n = 57); Orange bars = metacercariae of Pygidiopsis genata (Dec 2018: n = 92; April 2019: n = 80; July 2019: n = 39; October 2019: n = 53); Grey bars = unidentified metacercariae (December 2018: n = 92; April 2019: n = 80; July 2019: n = 25; October 2019: n = 35).

Figure 7. Mean intensity of infection of Coptodon guineensis at Sebkha Imlili by acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae (December 2018: n = 69; April 2019: n = 41; July 2019: n = 66; October 2019: n = 45). Mean intensity was significantly lowest in April.

Figure 8. Proportions of females of acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae in Coptodon guineensis at Sebkha Imlili according to stage of maturity. Solid bars = immature females (no genitalia visible); dotted bars = ovigerous females (ovarian balls visible); striped bars = gravid females (December 2018: n = 41; April 2019: n = 42; July 2019: n = 47; October 2019: n = 50). Gravid females were present throughout the year but significantly more abundant proportionally in December and July, which may indicate a short life span of the worms and quick turnover in the fish.

Figure 9. Mean trunk length of females of acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae in Coptodon guineensis at Sebkha Imlili (December 2018: n = 41; April 2019: n = 42; July 2019: n = 47; October 2019: n = 50). Worms were significantly smaller in April and October compared to December and July.

Figure 10. Abundance of infection of Coptodon guineensis at Sebkha Imlili by acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae according to fish total length. Infection occurred in fish as small as 20 mm. Larger fish were more often infected than smaller fish.