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  • Author: Yang Yang x
  • Life Sciences, other x
  • Microbiology, Virology and Infection Epidemiology x
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Seasonal population dynamics of the monogeneans Pseudorhabdosynochus coioidesis and P. serrani on wild versus cultured groupers in Daya Bay, South China Sea

Abstract

In this paper, seasonal samples of wild versus cultured groupers, Epinephelus spp., from Daya Bay, South China Sea were examined to survey the seasonality of two important species, Pseudorhabdosynochus coioidesis and P. serrani (Monogenea: Diplectanidae), and to analyze the interspecific relationships between these two parasites. Between April 2008 and January 2009, P. coioidesis and P. serrani were found to be parasitic only on E. coioides Hamilton during summer and winter in the natural waters of Daya Bay, exhibiting a high degree of host specificity, whereas they co-occurred and persisted on several species of hosts, such as E. coioides, E. bruneus Block and E. awoara Temminck & Schlegel, in an experimental polyculture pond during several seasons. E. coioides is the main host for both of these two monogenean species. The overall prevalences and mean intensities of these two parasites on polycultured Epinephelus spp. showed the same pattern of seasonal fluctuations, with the maximum values during autumn, except for the overall prevalence of P. serrani, which reached its maximum values during summer and winter and the minimum values during spring and autumn. Prevalence and mean intensity were found to be related to host size. In the wild, medium-sized fishes harboured higher infections, whereas under cultured conditions the small-sized and large-sized fishes were more heavily infected. Simultaneous infections of P. coioidesis and P. serrani were common, and there was a significant positive interspecific correlation between these two parasites.

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Morphological and molecular characterization of two isolates of Paratrichodorus porosus from Shenzhen, China

Abstract

Studies were conducted to characterize morphological and molecular profiles of two isolates of Paratrichodorus porosus (SZ1 and SZ2) which were recovered from Acacia mangium in Tianxinshan and Gleichenia linearis in Yangmeikeng environmental monitoring sites in Shenzhen, China, respectively. Analysis of morphometric, morphological and molecular characters revealed these two Shenzhen isolates are identical to P. porosus. Measurements of both study isolates lie within the ranges for P. porosus. It is typologically characterized by possessing a clearly swollen body cuticle after fixation, an onchiostyle ventrally curved, 46–58 μm long, a pharyngeal bulb usually with a well developed anterior-dorsal intestinal overlap, a secretoryexcretory pore opening between the nerve ring and anterior end of pharyngeal bulb, 90–110 μm from the anterior end, a reproductive system with didelphic, amphidelphic, without spermathecae, a pore-like vulva in ventral view and occupying 52.0 %–59.5 % of total body length from anterior end, a short and barrel-shaped vagina with small sclerotizations, a pair of ventromedian advulvar body pores located prevulvar and postvulvar, a rounded tail and a subterminal anus in females. The sequence analysis based on partial rDNA 18S gene and 28S D2/D3 expansion segment confirm its identity as P. porosus. This is the first report of P. porosus associated with A. mangium and G. linearis.

Open access