Biology subjects

Dabolkar, S.

Publications and source records attributed to Dabolkar, S..

4 recordsLinked to original sources

bioRxiv2017

Calcimycocavitological Studies on Seashells from Beaches of North Goa, India

Calcimycocavitology deals with the study of hollowing out of spaces in hard calcareous seashells by the fungi called calcimycocavites. Endolithic fungi in the shells were first reported and named as the trace fossils in 1889 by Bornet and Flahault. Endolithic fungi bore inside the shell by the process of bioturbation by using organic acids (oxalic acid, citrate) and enzymes (proteases, dehydrogenases and oxidoreductases). Previous reports show the presence of tunnels formed by fungal hyphae in the shells. The present work reports preliminary results of calcimycocavitological studies on the seashells from beaches of north Goa, India. The calcareous sand samples were collected from Arambol, Ashvem, Morjim, Vagator, Anjuna, Baga and Miramar beaches by pool sampling method and were separated into different fractions by using standard sieves. Each fraction of sand was subjected to stereomicroscopic studies which revealed that the sand fraction between 150-250 m included irregular shell fragments showing positive colonization by calcimycocavites. Hydrochloric acid treatment was used to dissolve the shells and release calcimycocavites biomass which was stained with Congo Red and tentatively identified as distinct microfungal forms. SEM studies of the calcareous shell fragments revealed the microtunneling behavior of the fungi. Digital analysis of SEM images using Mountain premium 7.2 software revealed the fine topography of calcimycocavites hyphae along with unidentified presumptive biomineral encrustations. The ecological, biological and biogeochemical implications of the findings are presented with respect to possible role of calcimycocavites in Calcium and Carbon cycling by breakdown of the calcareous shells and release of inorganic and organic components in the ecosystem.

microbiology↗

bioRxiv2017

Fossilized Microbial Forms in Baltic and Goan Amber - A Comparative Pioneer Study

This paper is based on surveys, exploration and standardization of techniques to recover rare amber samples from sands in Goa and identify specimens embedded with distinct microbial fossils based on studies on reference samples of imported Baltic amber. We developed techniques to locate, detect and identify amber samples in local sand. In this pioneer study, we report presumptive microbial forms such as actinobacteria and fungi in amber samples of Goa throwing light on microbial paleobiodiversity. Baltic amber (Succinate) is fossilized resin belonging to the Eocene period (44-49 million years old) derived from the Araucariaceae and Leguminoseae families of trees containing up to 8% of Succinic acid and compounds such as terpenoids and phenolic derivatives. Sooty moulds in the amber fossils have been studied (Schmidt et al., 2014). Samples of imported Baltic amber were validated, studied and used as reference for identification and characterization of amber found in sand of Goa. FTIR Spectroscopic tests diagnostic of presence of Succinate proved that both samples meet the criteria as plant derived Succinate containing products. Fossil fungi in Baltic amber were observed, and compared with similar forms in rare amber fragments of Goa. These samples were subjected to microscopic examination. Actinobacterial and fungal forms embedded in local amber were compared with similar forms found in imported Baltic amber and those published in literature. Detection of fossilized actinobacterial and fungal forms has shown us the potential for further studies for comprehensive collection and microscopic examination of such paleomicrobial forms in rare local amber samples.

evolutionary biology↗

bioRxiv2017

Subsurface Zircons With Presumptive "Biogenic" Inclusions As Potentially Useful Proxies For Studying Precambrian Bygone Biospheres In Goa

This work was inspired by recent report by Bell et al., 2015 who studied potentially biogenic carbon preserved in a 4.1 billion-year-old Zircon and need to assess the potential of Zircons found in Goa. Zircons (ZrSiO4) are naturally occurring silicate minerals which show radioactivity and high ductility and contain traces of Thorium and Uranium useful in Uranium-Thorium /Thorium -230 dating techniques. Zircons can be found in igneous, metamorphic rocks, sedimentary deposits and occurs as a detrital minerals in river and beach sands. Previous reports show that the Zircons can occur in different shapes such as round, elongated and with surface characteristics (Gartner et al.,2013). U-Pb Zircon dating methods had been used to study the continental growth in the western Dharwar craton of southern India (Jayananda et al., 2015). The present study was aimed at detection of subsurface Zircons with biogenic inclusions and assess their use as proxies for studying bygone Precambrium biospheres in Goa. Deep tubewell drilled Cores (60 and 65 m deep from surface) in island of Tiswadi at Taleigao were analyzed by light microscopy, Phase contrast microscopy and SEM to detect and classify the Zircons. In rapid preliminary sampling, total 50 Zircons were identified and 98% indicated the presence of interesting inclusions. These could be bubbles or kerogens or unidentified biological material. Zircons were classified as elongated, slightly rounded with sharp edges and showed widespread variety of surface characteristics like fracturing, cracks, scratches, striations and impact pits which may occur during transport processes. It is suggested that Zircons with presumptive biogenic inclusions can be further studied using techniques such as Raman Spectroscopy, Carbon Isotopic Measurements, X-Ray Microscopy, Trace Element Measurement consistent with Bell et al., 2015. More exhaustive studies have been undertaken to create a detail image database of Zircons from various other local samples to pinpoint those specifically useful for advanced work based on image analysis of the presumptive bioinclusions. Further attempts would be made to develop specific harvesting techniques to select potentially useful Zircons. International collaborations would be sought for applications of advanced techniques to local Zircons. Such studies would shed light on nature of bygone Precambrian biospheres in Goa and help in understanding evolution of life and the impact of plate tectonics and cataclysmic events shaping life on this planet.

evolutionary biology↗

bioRxiv2017

Novel Techniques To Study Ancient Micro Amber From Tropical Beach Sand Reveal A Treasurehouse Of Exceptionally Well Preserved Fossilized Microfungi

Simple, novel techniques developed for separation and simultaneous direct morphometric study of Amber micro fragments (AMF) from tropical beach sand are reported yielding rich information on unidentified fossilized microfungi. Sieves of different mesh sizes were used to separate AMF from tropical beach sand. Fractions below 150 m which proved rich in AMF were used for manual retrieval using stereomicroscope. A handprinted slide microarray having 4 X 12 squares used for microscopic examination of multiple AMF mounts revealed AMF having either rough or smooth surfaces and with or without microinclusions. The microinclusions could be morphologically attributed to fungi. The potential for systematic and comprehensive studies to retrieve and examine AMF at high frequency from tropical beach sand in the world and especially those which are threatened due to sea level rise due to climate change was demonstrated. The potential of retrievable AMF from tropical beach sand in microbiological, metagenomic studies and as biological proxies to reconstruct bygone biospheres has been highlighted.\n\nSummaryNovel techniques for retrieval of AMF and visualization using slide microarray are described. Sand samples from various locations from Goa were collected by pool sampling method. Microscopic study helped to reveal that fraction between 150 and below 53 m contained microscopic fragments of Amber ranging from size of within the size range of 70 m or below and with or without bio inclusions. AMF Specimens with microinclusions such as fungi were identified and studied using standard keys.

evolutionary biology↗