Prevalence, Seasonality, Host Preferences and Life Cycle of Fish Parasitic Isopod, Norileca indica (Milne Edwards 1840) in Andaman Waters

• M. Nashad ^[1] ; Bhavya Kachiprath ^[1] ; K. K. Bineesh ^[2] ; A. A. Mohamed Hatha ^[1]
  1. [1] Cochin University of Science and Technology

     Cochin University of Science and Technology

     India

     
  2. [2] Zoological Survey of India
• Localización: Thalassas: An international journal of marine sciences, ISSN 0212-5919, Vol. 41, Nº. 4, 2025
• Idioma: inglés
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• Resumen

  • The gill-infecting isopod Norileca indica is the most recurrent parasitic isopod in Indian waters, with a wide host specificity. The prevalence, intensity, abundance, and seasonality of N. indica on Indian mackerel (Rastrelliger kanagurta) and bigeye scad (Selar crumenophthalmus) showed monthly variations in both hosts. The highest prevalence of N. indica on S. crumenophthalmus was recorded in September (44.74%), followed by a decline in the subsequent months, with values ranging from 37.95% to 44.51%. Meanwhile, prevalence of N. indica on R. kanagurta peaked during the pre-monsoon period, with the highest prevalence in April (48.08%), followed by March (45.27%) and February (40.83%). A pair of male and female N. indica co-existed in the gill chamber of both host species, with a sex ratio of 1:1. There was a positive correlation between the size of the parasite and host (correlation coefficient, r = 0.69 for R. kanagurta; r = 0.81 for S. crumenophthalmus). The fecundity of N. indica varied between 110–750 eggs in R. kanagurta and 180–640 eggs in S. crumenophthalmus, respectively, with a positive correlation between the size of the female parasite and its fecundity (r = 0.82 for R. kanagurta; r = 0.83 for S. crumenophthalmus). N. indica exhibits protandrous hermaphroditism, where the eggs are well-protected inside the brood pouch of female, undergoing substantial development as they progress through various stages, viz., embryonic stage I, II, and III, and manca stage I and II (larval stages). The free-swimming manca stages are released into the sea, where they infest and settle on new hosts