Occurrence of Life Cycle Dependent Monophasic and Biphasic Molting in a Parasitic Isopod, Mothocya renardi

Abstract

This paper reports the occurrence of life cycle dependent monophasic and biphasic molting in Mothocya renardi (Bleeker, 1857), a protandrous hermaphroditic cymothoid parasitizing the banded needle fish, Strongylura leiura. Although the molting in manca I is monophasic, the infective manca II, juvenile and adult stages including male, transitional, and female opt biphasic molting in which the posterior half of the body molts first, followed by the anterior half. The molt cycle (monophasic and biphasic) in M. renardi is broadly divided in to four sequential stages, premolt, molt, postmolt and intermolt. Five distinct premolt stages (D₀-D₄) were also identified through the microscopic observation of characteristic changes reflected in different appendages of manca stages and adult infective stages. Pleotelson, uropod rami and dactylus of the first pereopod and antennae were used for the identification of stages of monophasic molt cycle. By undergoing monophasic molting, the manca I was transformed into the manca II which then undergoes biphasic molt. The characteristic changes related to biphasic molting were well reflected in the maxillule. When the maxillule showed characters of the premolt stage D₂, the posterior half of the body had already exuviated. Molting of the anterior half ensued within 2–3 days after posterior half ecdysis. Occurrence of a series of biphasic molts resulted in the transformation of manca II into the successive stages in the order juvenile, male, transitional and female.