Infestation and effect of parasitic isopod Epipenaeon ingens ingens Nobili, 1906 on commercial shrimp species in the eastern Mediterranean: a case study of the population of brown shrimp Penaeus aztecus Ives, 1891

Authors: MEHMET CENGİZ DEVAL, FATMA GONCA KOÇANCI

Abstract: Monthly samples of seven species of penaeid shrimps, namely, Penaeus aztecus (Ives, 1891), Penaus hathor (Burkenroad, 1959) Penaus japonicus (Spence Bate,1888), Penaus kerathurus (Forskal,1775), Penaus semisulcatus (De Haan,1844), Metapenaeus monoceros (Fabricus, 1798) and Metapenaeopsis aegyptia (Galil & Golani, 1990) were collected from Antalya Bay in the Eastern Mediterranean Sea from March, 2019 through March, 2020. Except for P. aztecus and P. semisulcatus, no other shrimp species were infected with the parasitic isopod Epipenaeon ingens ingens. Of the 3043 P. aztecus shrimp inspected, 541 individuals were infected (17.8%) with the bopyrid parasite E. ingens ingens. However, the annual infestation rate in recruiting year class (28 mm < CL: 5.7%) was much less than in larger and sexually mature (CL ≥ 34 mm: 36.2%) individuals. Monthly infestation rates varied from 0.86 to 84.8%, and the size of infested shrimps ranged from 20 mm to 44 mm CL. The left branchial chamber was more likely infected (43.1%) than the right one (39.8%), and 17.1% appeared to be doubly infected. The percentage of the ovigerous female E. ingens ingens fluctuated between 31.7% (August) and 90.0% (February). We report for the first time the size at first accompaniment (FAS$_{50}$) and at first maturity (FMS$_{50}$) for the female parasite E. ingens ingens, 11.0 mm TL and 13.0 mm TL, respectively. The gonad weight (0.779 ± 0.73 g) and GSI (0.223 ± 0.333) value of uninfected female P. aztecus were about eight times greater than it was for infected shrimps (0.094 ± 0.18 g and 2.006 ± 1.669, respectively).

Keywords: Bopyrid isopod, Epipenaeon ingens, brown shrimp, Penaeus aztecus, Penaeus semisulcatus, parasite

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