Morphological and molecular description of a new species of Myxobolus (Myxosporea: Myxobolidae) infecting Planiliza macrolepis (Smith, 1846) from India

Abstract

The present paper describes a novel species of Myxobolus parasitizing the gill laments of the largescale mullet, Planiliza macrolepis from Cochin backwaters, Kerala, India. The parasite develops in the gill laments; plasmodia elongated, milky white, measured 1.37 -2.18 (1.78 ± 0.35) mm x 0.07-0.12 (0.10 ± 0.02) mm in size. Mature myxospores ovoid in valvular view, biconvex in sutural view with smooth shell valves and measured 6.24 -7.02 (6.63 ± 0.23) × 5.01 -6.18 (5.68 ± 0.25) μm in size. Polar capsules equal, oval with pointed anterior ends, 3.07 -3.58 (3.33 ± 0.12) × 1.68 -2.42 (2.09 ± 0.18) μm in size. Polar laments with 4 coils, measured 29.61 ± 4.75 μm in length when extruded. Sporoplasm binucleate with a rudimentary nucleus and a vacuole. A comparison with related Myxobolus species revealed signi cant morphological & morphometric differences. In BLASTN and genetic distance analysis, the present parasite showed high divergence with other myxosporean sequences, indicating its molecular uniqueness. In Maximum Likelihood and Bayesian Interference analysis, the present species stands out with M. ramadus as sister branch within the Myxobolus clade. In infected gill laments, the plasmodia caused swelling/deformation, compression of lamellae and reduction in respiratory surface area. Three of 222 P. macrolepis screened were infected, indicating a prevalence of 1.3%. Considering the morphological, morphometric, molecular and phylogenetic differences with the previously described species of myxosporeans, along with the dissimilarities in host and geographical locations, the present parasite is treated as a new species and the name Myxobolus cochinensis n. sp. is proposed.

Dynamic Distribution of Mesanophrys sp. and Tissue Enzyme Activities in Experimentally Infected Mud Crab Scylla paramamosain

“…Histopathology revealed that the gill filament of the infected S. paramamosain appeared slightly swollen, accompanied by a detached cuticle. These alterations in the gill surface architecture can reduce the gaseous exchange capacity of the gills [24]. It has been reported that some ciliates such as Synophrya sp.…”

“…The culture medium contained sterilized sea water (salinity = 25 psu), 10% (v/v) heat-inactivated fetal bovine serum (FBS, Gibco, Billings, MT, USA) and 5% crab soup (100 g crab muscle and 1000 mL water, boiled to 100 mL). The temperature was maintained at 12-14 • C. In order to observe its growth curve, the number of ciliates contained in 10 µL of the culture medium was counted three times at 0, 6,12,18,24,30,36,42,48,54,60,66,72,78, 84 and 90 h using light microscopy (Nikon Eclipse Ni-U) as described by Parama [19].…”