File:American malacological bulletin (1987) (17533842954).jpg

Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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Fig. 5. (A) A median section of Pisidium amnicum collected from Siilaisenpuro on 5 March 1985. High concentrations of glycogen in the subepithelial tissue of the foot is shown by black color. Allochrome HFW = 5.5 mm. (B) Ventral surface the foot of P amnicum show- ing a epithelial cilia and subepithelial cells filled with glycogen granules. Allochrome HFW = 0.05 mm. Survival times of up to 55 days at 10°C have been reported for marine molluscs (Theede ef a/., 1969; Hammen, 1976). Zs.-Nagy (1973) gives 7-10 days as the anoxia tolerance period for Anodonta cygnea (L.) at 15°C; Ligumia subrostrata (Say), another freshwater species, survived more than 15 days at 25°C(Dietz, 1974). These are, however, short times when compared to aerial survival of one year or more of some tropical unionids at very high temperatures (Dance, 1958). I also held a juvenile Anodonta piscinalis Nilsson (= A. cygnea) (30 mm, caught in March from Lake Paajarvi), 66 days in anoxic water at 3°C. When transferred to aerobic water, the foot was soon introduced but started to withdraw upon touching only after 1 day. Indications of the survival of Pisidiidae during anoxia in natural lakes range from 2-3 months (Juday, 1908; Holo- painen and Jonasson, 1983) to 5-7 months (Eggleton, 1931). In addition, some experimental data are given by Juday (1908), Jatzenko (1928) and Eggleton (1931). My data on Sphaerium corneum closely agree with the 46-day survival
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Fig. 6. A median section of Sphaerium corneum collected from Lake Varaslampi on 5 March 1985. Glycogen is seen as prominent black areas in both the foot tip and mantle with some reaction in the gill, also. Allochrome (A) HFW = 7 mm and (B) HFW = 0.7 mm. time at 14-16°C reported by Jatzenko (1928) (see Fig. 3). Besides temperature, survival times in anoxia probably depend on season, animal size and physiological state, as well as the possible existence of poisonous compounds (like H2S) in the water. In my experiments the existence of H2S was often suggested by black coloration on the shells and the odor emitted when the vials were opened. Zhadin (1952) reports Sphaerium corneum to be resistant to H2S and to sur- vive 14 days at 30mg// of H2S. Theede ef al. (1969) and Shum- way ef al. (1983) have shown the deleterious effect of this compound on survival times of marine invertebrates. Since only adults were used in most experiments, the effect of size could be examined only in case of Pisidium casertanum and P. subtruncatum from Lake Esrom. In both species juveniles appeared to die first. However, survival times of these species were long considering that at the time of sampling (September) they had already survived several weeks of anoxia in Lake Esrom (Holopainen and Jonasson, 1983). The effects of temperature on survival times are pro- minent and appear linear on semi-log scale (Fig. 3). The average 50% survival time of Pisidium amnicum, which is

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