Effect of temperature on development and hatching of Radix natalensis eggs

Description

The resulted data was from laboratory experiment for assessing the association of changing in temperature, with the egg development rate, hatching rate, egg mortality. In this study we assessed the effects of temperature on the development and hatching of Radix natalensis eggs. A controlled laboratory experiment was conducted at five different temperatures (15, 20, 25, 30, and 35℃), plus control at 20.8℃, to establish the effects of temperature on the development rate, hatching time and hatching rates, and morphological abnormalities of R. natalensis. We observed that egg development slows at low temperatures while hatching rates increase, leading to a long hatching duration at 15℃ compared to other studied temperatures. A strong negative correlation (-0.947) was observed between hatching days and temperature, suggesting that the duration of hatching significantly decreased as temperature increased temperatures accelerate egg development, shorten hatching durations, and diminish eclosion rates relative to temperatures ranging from 15-25℃. Temperatures ranging from 25 to 30℃ reduced hatching durations. Radix natalensis eggs could not hatch or develop at 35℃, signifying that this temperature is lethal. Snails that hatched at 25 and 30℃ exhibited high death rates. An increased temperature of 35℃ correlated with a reduced number of eclosions. Low temperatures down to 15℃ slowed egg development, increased the hatching rate, and extended both the hatching and development periods compared to temperatures ranging from 25 to 35℃. A very strong positive correlation (0.972) between hatching days and hatching percentage indicates that longer hatching times are associated with increased hatchability. The findings can be used for predicting future distribution of Radix natalensis and shifts in fascioliasis transmission patterns caused by climate changes.

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Materials and Methods Collection of egg masses Egg masses were obtained from first-generation (F1) Radix natalensis snails cultured from snails collected from from Kwafik'suthe dam (-29.672, 29.876) in Impendle municipality and from the Plains farm (-29.149; 30.008) in Mpofana municipality in Mgungundlovu district in KwaZulu-Natal, South Africa. Egg masses were deposited into Petri dishes containing fresh dechlorinated water. Experimental Design The experiment was carried out at at the Biomedical Resource Unit (BRU) laboratory, University of KwaZulu-Natal Westville Campus, South Africa. Six (6) aquariums, each with a volume of 60 litres, were assigned to five (5) temperature treatments (15°C, 20°C, 25°C, 30°C, and 35°C) in addition to control at room at average ambient temperature of 20.8°C. Each treatment was replicated three times, with each replicate comprising four egg masses making a total of 12 egg masses for each temperature treatment. Egg masses were placed in Petri dishes with 50-100 ml of dechlorinated water and incubated in their respective temperature treatment aquariums. To avoid desiccation, the water in each Petri dish was refreshed daily. Eggs were examined daily under a stereomicroscope to assess embryonic development, hatching duration, and eclosion. The number of eggs per egg mass ranged from 20 to 30. The average number of eggs per egg mass was 25.

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