Embryonic and larval development of green panchax (Aplocheilus blockii): insights into the reproductive strategy of native killifish with biocontrol potential

The green panchax, Aplocheilus blockii, is valued for aesthetic appeal as an ornamental fish and for their biocontrol competencies.Developing suitable captive propagation methods helps reduce the risk of mosquito-borne disease and the undue use of harmful chemicals.They exhibit sexual dimorphism, with males having vivid colours and females having curved anal fins rather than the long, pointed fins seen in males.The green panchax is a batch spawner, producing 3686 ± 303 eggs per year, and it had a consecutive pattern of 75 ± 4.9 days of continued breeding followed by 31.7 ± 3 days of discontinued breeding and abstained from breeding for 44.1 ± 3.9 days.The eggs were round, demersal, and adhesive with an average diameter of 1.3 ± 0.05 mm.This killifish has a fertilisation and hatching percentage of 86.3 ± 9.7% and 72.2 ± 26.8% respectively with an incubation period of 8.3 ± 0.4 days at 28 ± 3°C.The newly hatched larvae have a total length of 4.5 ± 0.1 mm with an ovoid yolk sac.Larvae exhibited cannibalism during their developmental phase and attained metamorphosis by the 48th day post-hatch.The first sexual maturity was attained at 2.9 ± 0.1 cm and 3.1 ± 0.1 cm, at an average age of 60.4 ± 3.2 days and 66.6 ± 3 days respectively for females and males.The present study provides comprehensive documentation of the developmental process of A. blockii, accompanied by a detailed description of embryonic and larval development.The study highlights the importance of morphological characteristics for precise identification of A. blockii, even in the absence of distinctive features during early developmental stages.