Boonmak P.1, Sanoamuang L.2* 2024. The impact of temperature on hatching rates of diapause eggs and subsequent development in a tropical freshwater copepod, Mongolodiaptomus malaindosinensis (Copepoda: Calanoida) // Invert. Zool. Vol.21. No.3. P.359–368 [in English].
1 Department of Science and Technology, Faculty of Liberal Arts and Science, Roi Et Rajabhat University, Roi Et 45120, Thailand.
2 Applied Taxonomic Research Center, Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand.
* Corresponding author
Phuttaphannee Boonmak: phuttaphannee@gmail.com ORCID 0000-0003-4827-5532
Laorsri Sanoamuang: la_orsri@kku.ac.th ORCID 0000-0003-0377-1225
doi: 10.15298/invertzool.21.3.08
ABSTRACT: The diapause egg is an essential component of aquatic invertebrates and is a specialized type of egg that is highly resistant to harsh environmental conditions. The diapause eggs of a tropical freshwater copepod, Mongolodiaptomus malaindosinensis (Lai et Fernando, 1978), an endemic species of Southeast Asia, were collected from Kaeng Nam Ton Swamp in Khon Kaen province, Thailand. The eggs were isolated by the sugar flotation method and maintained in laboratory conditions at three different temperature levels (25, 30, and 35 °C in an incubator). The first copepod hatching occurred between 6 and 9 days. The average hatching rate per day and the total percentage of eggs hatched in M. malaindosinensis were significantly higher (P < 0.05) at 25 °C (9.36 ± 6.7% and 55.37 ± 3.1%) and significantly lower (P < 0.05) at 35 °C (5.28 ± 3.5% and 16.67 ± 2.9%), respectively. The post-diapause developmental characteristics of M. malaindosinensis have four stages: early development embryo, intermediate development embryo, pre-nauplius, and nauplius. The results suggest that temperature levels affected hatching success in tropical copepods. There is a possibility that the reduced hatching implies that increasing temperatures over a certain threshold may be a limiting factor for its hatching and growth.
KEY WORDS: crustacean, dormant stage, fisheries, nauplius, Southeast Asia, zooplankton.