不同pH值水溶液对现生介形类壳体保存的影响

PRELIMINARY STUDIES ON EFFECTS OF DIFFERENT pH VALUES ON CARAPACES OF LIVING OSTRACODS

本文报道了在人工控制水体的酸碱度(pH5.2—pH8.3)条件下,实验室饲养介形类?Cypri-notus sp.1,C.sp.2,C.sp.3的生活状态及其死亡后壳体的保存情况。实验结果表明:当水体的pH值在5.2时,经过48小时介形类壳体中的碳酸钙成份几乎全部被溶解,但壳体的表皮层及其附肢却保存完好。同时报道了它们在不同pH值水溶液中的存活时间及壳体的保存状态。最后,对有关问题进行了讨论。

Three living species,? Cyprinotus sp.1,C. sp. 2 and C. sp. 3 collectedfrom 3 localities (an unnamed marsh in Tibet, Caohai Lake in Guizhou andEast Lake in Hubei)were subjected under laboratory conditions, to water solu-tions with the following pH values: 5.2, 5.8, 6.4, 7.0, 7.7 and 8.3. At pH 5.2,the calcified endocuticle (as defined by Bate, 1.972) of each species was com-pletely dissolved after 48 hours, but the non-calcified epicuticle, its setae and nor-mal pore canal openings remained intact. The ostracods in solutions at pH 5.8,6.4, 7.0, 7.7 and 8.3 respectively all died daring the period from 2 to 70 min-utes but their shape and ornament still appeared unaffected after 48 hours. Aweakly acidic microenvironment may result from a variety of factors (decay oforganic material, CO_2 accumulation, etc.) and it is emphasized that ostracodsinhabiting such a microenvironment in the past probably would not be preservedin the fossil record.