Factors affecting the hatching ofStreptocephalus macrourus Daday (Crustacea; Eubranchiopoda) eggs

Abstract

A major drawback to the use in aquaculture of members of the Eubranchiopoda from temporary pool environments is that their eggs do not hatch readily. An investigation of the factors influencing the hatching of eggs of the fairy shrimp Streptocephalus macrourus, showed that light was the only factor of those investigated that was obligatory for hatching. It was found that eggs which had not been desiccated hatched successfully in the presence or absence of adults, while those which had been desiccated showed a block in hatching initially, although this block deteriorated with time and after approximately two months the eggs which had been desiccated showed a similar hatching success to that of the nondesiccated eggs. Exposure of eggs to extremes of heat or cold before incubation did not influence the hatching success of the eggs significantly, but the temperature at which incubation took place was important. The optimal range lay between 14 C and 20 C. Eggs hatched and nauplii survived at dissolved oxygen tensions of below 0.5 mg 1-'

Observations on the biology of the rare Branchipus visnyai Kertesz 1956 (Crustacea, Anostraca) from Monti Reatini (Latim, central Italy)

“…As to hatching, the events in the pool and in the pond showed that the species responds not to a single but to combined stimuli, as suspected in other species (Brown & Carpelan, 1971) . Moreover, dessiccation is not a pre-requisite for development, in line with previous results (Lowndes, 1993 ;Castle, 1938 ;Avery, 1939 ;Dexter & Ferguson, 1943 ;Hall, 1953Hall, , 1961Prophet, 1963 ;Broch, 1965 ;Mitchell, 1990) . Both assumptions receive further support from the hatching pattern in the pond : nauplii predictably appear after thawing, as soon as temperature reaches suitable values, and in autumn after dilution by the first summer rains .…”

Comparison of the hatching process of the tadpole shrimps Triops cancriformis and Lepidurus apus lubbocki (Notostraca) and its relation to their distribution in rain-pools in Israel

“…This is particularly apparent in the case of the rare T cancriformis, which has markedly declined since the 1950's . In the present study, as in others (Minkoffet al ., 1983 ;Mitchell, 1990 ;Murugan & Dumont, 1995 ;Seaman et al ., 1991 ;Takahashi, 1977), light was shown to be a key factor in inducing hatching in branchiopods including Notostraca .…”

“…Hatching success in darkness was about one order of magnitude lower than under light (Figure 4) . It is possible that the short exposures to light during the daily microscopic examination, of the eggs induced hatching of some of the dark-treated eggs, since according to Mitchell (1990), a 10 minute exposure to light may induce hatching of some eggs in anostracan branchiopods. All other hatching experiments were carried out under continuous light .…”

Anostracans (Branchiopoda) of Botswana: Morphology, Distribution, Diversity, and Endemicity

“…The optimal hatching temperature range ( 14-20°C) for S. macrourus from Bloemfontein (Orange Free State, South Africa), measured by Mitchell (1990) does not correspond with the mean daily temperatures in the Botswana sites during the wet season (24-26°C). This discrepancy cautions us in using laboratory results of temperature requirements for hatching to explain actual species distributions, since thermal requirements may merely reflect local adaptation and not necessarily the amplitude of thermal conditions under which all members of the species may exist.…”