Seasonal gonad cycle of the climbing perch Anabas testudineus (Teleostei: Anabantidae) in a tropical wetland

Abstract

Seasonal reproduction of the climbing perch Anabas testudineus in the Candaba wetland, Philippines, is described. Monthly specimens were collected, gonads and viscera excised, and the gonads histologically examined. Low mean female gonadosomatic index [GSI (%)] from September to February (0.3–2.1 %) increased in March (8.7 %), peaked in May (10.9 %), and declined in June (3.3 %), but increased again in July and August (8.3–5.5 %). Male GSIs (at least 1 %) were low from September until May, increased in June (2.5 %), and then declined thereafter. All the six oocyte and four spermatogenic cell development stages were observed in the gonads throughout the annual cycle. The ovary was dominated by primary growth oocytes (chromatin nucleolus, perinucleolus) from August to February (77–90 %), but yolky oocytes (previtellogenic, vitellogenic) comprised 15 % to 28 % of the ovary from March to July. Mature oocytes were present for most of the year, comprising 40 % of the total oocytes in March-April, peaking in May (50 %), but declining to 30 % in June–July. Spermatozoa consistently dominated the testis throughout the annual cycle, particularly in November and March (58 %). Food intake in both sexes was generally low during the dry season (December–April) when gonad activity was also low, but started to increase at the onset of the wet season (May–November) when gonad activity began to peak. These results demonstrate that the climbing perch gonads exhibit asynchronous development, allowing a protracted breeding season with intense gonad activity timed at the onset of the wet season, concurrent with increasing food intake through the rest of the season.