REGENERATION AND ABNORMALITY IN BENTHIC FORAMINIFER ROSALINA LEEI: IMPLICATIONS IN RECONSTRUCTING PAST SALINITY CHANGES

A laboratory culture experiment has been conducted to assess the response of marginal marine benthic foraminifer Rosalina leei to salinity and associated pH changes. Live specimens of Rosalina leei were subjected to a range (10-35 psu) of salinity. It was observed that hyposaline condition leads to dissolution of the calcareous tests. However, if the hyposaline condition persists only for a short period, then even after considerable dissolution, specimens were able to regenerate the dissolved part of the test. Additionally, in all the specimens subjected to lower than normal salinity, the regenerated chambers were abnormal. The abnormalities included smaller or larger chambers and addition of new chambers in planes different than the normal plane of the tests. The regenerated specimens, however, attained a final size almost equal to that of control specimens that were not subjected to hyposaline conditions. The differential response of R. leei was attributed to decreased seawater pH under hyposaline condition. The findings can help understand the increased abundance of abnormal specimens under ecologically stressed environments.

EXPERIMENT TO DECIPHER THE EFFECT OF HEAVY METAL CADMIUM ON COASTAL BENTHIC FORAMINIFER PARAROTALIA NIPPONICA (ASANO)

ABSTRACT The response of benthic foraminifer Pararotalia nipponica to heavy metal cadmium is observed in laboratory experiment. The results indicate that under a given set of conditions, heavy metal cadmium is deleterious to benthic foraminifera. Gradual increase in cadmium (Cd) concentration mainly affected normal growth and caused morphological abnormalities which were consistent from 4 µg/l to 14 µg/l. The intensity of deformation was severe exhibiting a peculiar change in coiling direction with increase in cadmium concentration. The presence of >50% deformed specimens at the lowest cadmium concentration (2 µg/l) indicates that the threshold of Cd concentration which is detrimental to P. nipponica is <2 µg/l

Appraisal of laboratory culture experiments on benthic foraminifera to assess/develop paleoceanographic proxies

301-321The laboratory culture studies, carried out on benthic foraminifera, with the aim to refine paleoceanographic/paleoclimatic or environmental application of benthic foraminifera, have been reviewed. The review includes studies, which refined the understanding of factors that bring out changes in benthic foraminiferal abundance, morphology and chemical composition (of the test). Additionally, studies dealing with taxonomic aspects of benthic foraminifera have also been discussed, since such studies have significantly improved application of benthic foraminifera for stratigraphic correlation. Most of the laboratory culture studies on benthic foraminifera in the early days were carried out to monitor the complete life-cycle of selected species. Such studies revealed presence of morphologically different stages in the life-cycle of single species. Thus the forms that were earlier recognized as different species were later on clubbed as developmental or ontogenetic stages of single species. Interesting relationship between mode of reproduction and coiling direction were also observed. Later on, with the growing application of foraminiferal characteristics for past climatic and oceanographic reconstruction, benthic foraminifera were maintained under controlled physico-chemical conditions in the laboratory. Such studies helped to refine the differences in the foraminiferal characteristics from physico-chemically different environments, as observed in the field. As it was proposed that the amount and type of food material is the major factor that controls the benthic foraminiferal population, numerous studies were carried out to assess the response of benthic foraminifera to different type and amount of food and oxygen concentration. Surprisingly limited laboratory culture studies have been carried out to understand the factors that govern the chemical composition of the benthic foraminiferal tests. It probably reflects the difficulties in simulating the conditions under which physico-chemical parameters can be kept constant throughout the experiment. Towards the end of 20th century application of molecular systematic analysis techniques on foraminifera started and such studies refined the evolutionary history and taxonomic position of foraminifera as well as helped recognize cryptic species. However, despite a large number of culture studies being carried out on benthic foraminifera with their paleoceanographic/paleoclimatic application in focus, still much more efforts are needed to understand the parameters affecting the benthic foraminiferal abundance, morphology and chemical composition

Effect of oxygen manipulations on benthic foraminifera: A preliminary experiment

235-239Three sediment cores were collected at 50 m water depth on the west coast of India, off Ratnagiri, and were subjected to oxygen manipulations maintaining natural temperature and salinity. The objective was to understand foraminiferal response to changed oxygen conditions. After a fortnight, the experimental cores were sub-sectioned and analyzed for their live foraminiferal content. This data was compared with background field data obtained from the non-experimental core. The data indicate that any change in natural oxygen conditions causes lowering of foraminiferal numbers. It is clearly evident that Fursenkoina and Nonions are more adaptive to changed oxygen conditions in contrast to Bolivinids and Rotalids, which quickly die out. This study clearly demonstrates the change in foraminiferal distribution in response to oxygen changes. This experimental study further can help develop foraminifera as a proxy to decipher the past fluctuations in the OMZ in the past, including assessment of their anthropogenic origin

70 kD stress protein (Hsp70) analysis in living shallow-water benthic foraminifera

International audienceHsp70 is a phylogenetically highly conserved protein family present in all eukaryotic organisms tested so far. Its synthesis is induced by proteotoxic stress. The detection of Hsp70 in foraminifera is presented here for the first time. We introduce a standard immunoblotting protocol modified for the detection of Hsp70 in shallow-water benthic foraminifera. Additionally, we showed a temperature-dependent expression pattern of Hsp70 in Ammonia tepida.</p