Molecular Characterisation and Post-embryonic Development of the Cyclopoid Copepod Apocyclops royi: Implications for Live Feed Applications in Aquaculture
Amanulla Mehar Afshan *
Unit of Research in Ecology and Ecotechnology, P.G & Research Department of Zoology, The New College, Affiliated to University of Madras, Chennai - 600014, India.
Abdus Saboor
Unit of Research in Ecology and Ecotechnology, P.G & Research Department of Zoology, The New College, Affiliated to University of Madras, Chennai - 600014, India.
Radha Vijayaraj
Aquaculture Research Laboratory, Department of Marine Biotechnology, AMET University, Chennai - 603112, India.
Kareem Altaff
Aquaculture Research Laboratory, Department of Marine Biotechnology, AMET University, Chennai - 603112, India.
*Author to whom correspondence should be addressed.
Abstract
Aims: This study confirmed the taxonomic identity of the cyclopoid copepod Apocyclops royi and described its post-embryonic development under controlled laboratory conditions to assess its potential as a live feed organism in aquaculture.
Study Design: An experimental study involving morphological characterisation, molecular identification using 18S rRNA gene sequencing, and developmental assessment of successive naupliar and copepodid stages under controlled laboratory conditions.
Place and Duration of Study: The experimental work, including culture maintenance, species identification, and developmental observations, was carried out under laboratory conditions during the study period.
Methodology: A. royi specimens were cultured under controlled laboratory conditions (29 ± 1°C, 25 PSU salinity, pH 7.8, dissolved oxygen 5.5 mg/L, and a 12L:12D photoperiod) and identified using morphological characteristics and 18S rRNA gene sequencing. The obtained sequence was compared with sequences available in the NCBI GenBank database and deposited under accession number PP275178.1. Post-embryonic development from the naupliar (NI–NVI) and copepodid (CI–CV) stages to sexually mature adults was monitored by recording body length, body width, developmental duration, and stage-specific morphological characteristics.
Results: Morphological examination revealed diagnostic features consistent with previous descriptions of A. royi, while molecular analysis confirmed the species identity with high sequence similarity to available Apocyclops sequences. Phylogenetic analysis demonstrated a close genetic relationship with previously reported congeners. The complete developmental cycle from nauplius to the sexually mature adult stage was achieved in approximately 7 days. Body length increased progressively from 96 ± 2.3 µm in NI to 299 ± 7.1 µm in NVI, and from 391 ± 12.8 µm in CI to 864 ± 7.3 µm in adult females and 774 ± 8.8 µm in adult males. Distinct morphological transformations, including appendage differentiation, segmentation, and sexual dimorphism, were observed across developmental stages. The broad size spectrum exhibited by A. royi suggests its suitability as a continuous live feed source for fish larvae.
Conclusion: The integration of morphological, molecular, and developmental analyses authenticated A. royi and provided baseline information on its life-history characteristics. The rapid developmental cycle, broad prey-size spectrum, and ease of culture highlight the potential of A. royi as a sustainable live feed organism for aquaculture and larval-rearing applications.
Keywords: Apocyclops royi, cyclopoid copepod, 18S rRNA, molecular identification, post-embryonic development, naupliar stages, copepodid stages, live feed, finfish larviculture