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

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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.

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SK gratefully acknowledges University Grant Commission, New Delhi [F.No:38-218/2009(SR) dated 24/12/2009], Kerala State Council for Science Technology and Environment, Government of Kerala [No. (T) 093/SRS/2011/CSTE dated 25/06/2011& KSCSTE/5224/2017-SRSLS dated 28/08/2018] and Department of Science and Technology, Government of India (DST-SERB:EMR/2016/001163 dated 28.08.2017) for financial support to carry out this work and the preparation of the manuscript.

Funding Information

This study was funded by University Grant Commission, New Delhi (F.No:38–218/2009(SR); dated: 24/12/2009), Kerala State Council for Science Technology and Environment, Government of Kerala (No. (T) 093/SRS/2011/CSTE; dated: 25/06/2011) and Department of Science and Technology, Govt. of India DST-SERB (EMR/2016/001163 dated 28.08.2017).

Author information

APT worked on the topic and prepared the first draft of the manuscript. SK drew out the concept, supervised the work, interpreted the results, corrected and finalized the manuscript. All authors read and approved the final manuscript.

Correspondence to Sudha Kappalli.

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The authors declare that they have no conflict of interest.

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This article does not contain any studies with animals which require ethical approval.

Sampling and Field Studies

Permission from the competent authority is not required as the specimens (parasitic isopods and the host fish) sampled for the present study were not in the scheduled list of protected animals.

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Panakkool-Thamban, A., Kappalli, S. Occurrence of Life Cycle Dependent Monophasic and Biphasic Molting in a Parasitic Isopod, Mothocya renardi. Thalassas (2020) doi:10.1007/s41208-019-00188-6

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  • Cymothoid
  • Mothocya renardi
  • Molt cycle
  • Monophasic molt
  • Biphasic molt