Endangered Biota
Diversity and ecology of Spiders (Order: Araneae) with special emphasis to the web dynamics of orb weaving spiders (Family: Araneidae) of Kolkata Metropolis
Funding Agency: University Grants Commission, Government of India
Host Institute: Jogamaya Devi College, University of Calcutta, Kolkata
Principal Investigator: Rahi Soren
Spiders have often been thought of as a mere annoyance and have been universally shunned and feared, but few deserve it. Spiders occupy nearly all terrestrial environments and can be found wherever there are other terrestrial animals to prey upon. Spiders belong to the order Araneae, under class Arachnida, which is one of the most diverse groups of arthropods. Research on spider biology, particularly the diversity of their silks, webs, and venoms, together with the associated ecology and behavior, has increased in the recent decades. However, the taxonomy and ecology of many spider groups are inadequately known and knowledge of their distribution is rather poor in the Indian context at present.
Silk production is a distinctive feature of the spiders and fossil species with cleardiscernable spinnerets are known from as early as the Devonian Period. The orb weaving spiders (Family Araneidae) specialize in predation by weaving orb webs. The primary function of orb webs is prey capture but webs can also be a valuable defense. The characteristic feature of an orb-web is that the central portion, the part lying within the supporting framework, consists of a series of radiating lines of dry and inelastic silk which support a thread of viscid and elastic silk. Different webs of this type vary greatly in structure, mainly in the length of spiral line and the position of viscid thread turns. Web size and design can vary due to prey size, food availability, developmental stage, physiological status, web site and various abiotic factors. These web variations can directly influence the number and types of prey entangled. For example, a larger web will increase the rate of prey interception. Similarly, the distance between the capture spirals (mesh height) may affect the visibility of the web and the size of prey entangled.
Physical qualities of particular microhabitats allow spiders to finely partition available
space into specific, more narrowly defined niches. This in turn has an important effect on the
species richness and abundance of spiders and although most species exhibit very narrow, patchy distributions, spiders as a whole comprise one of the most conspicuous and diverse groups of terrestrial invertebrates. Few studies have been done on spider diversity in Kolkata.
The goal of this project was to address this and explain the distribution patterns and species richness of spider species and to offer additional information which might contribute to the development of conservation policies/ strategies for these ecosystems. These studies can thus be implemented as a tool in biological pest management in regard to the agro economy as well.
Objectives:
To access the species richness, abundance and assemblage of spider fauna in different habitat types in Kolkata,
To understand the plasticity of orb weaving spiders by optimizing web characters on a phylogeny,
To estimate the level of homoplasyin orb web characters with morphological characters.
There are multiple lines of evidence that show that the ecology and behavior of spiders contribute to making these predators an important control agent of insect populations, in many cases even determining the structure and size of insect communities.
Findings:
The survey revealed 43 species under 38 genera and 12 families; with Salticids (39.1 %) and Araneids (26 %) in dominance. The overall health of such a fast-degrading urbanizing ecosystem can be well represented by the complex interaction of spider and associated fauna among the diverse vegetation and habitat forms therein.
This study explores the change in web dynamics of orb weaving spider, Argiope pulchella across urbanization gradient in Kolkata.
Assessment of Heavy metal concentrations in shark and their toxicological concern
Marine ecosystems deal with heavy metals pollution as many pollutants are discharged directly into water bodies. Once in the marine environment, these pollutants can be accumulated by marine organisms and have impacts on organisms’ health. There is an urgent need for suitable and accessible indicators of ocean health, preferably ones that allow us to detect the negative impacts caused by pollutants. Sharks play a key role in the marine food webs, and also suitable bioindicators of heavy metal contamination in the aquatic environment, but are threatened by overfishing and habitat degradation. Thus, the study would focus on the role of sharks as a suitable bioindicator of marine ecosystems.
A preliminary field survey was conducted in Digha for building a network with the fishermen community. Data was collected about elasmobranch landings in West Bengal and about shark species found in West Bengal, as well as a systematic review on “effects of heavy metals on shark species” is underway.
Objectives of the proposed work for which funding is being sought:
- To determine the biometrics (Total length, age, sex) of shark species found from the bycatch in West Bengal.
- To determine the concentrations of heavy metals from shark tissue samples (Liver, Muscle)
To determine the changing socio-economic status of the fisherman community depending on shark bycatch.
To analyse the correlation between heavy metal concentration and shark biometrics, if any, with respect to shark physiology.
- Thus, all these objectives will lead towards a better understanding of the status of shark vulnerability with respect to the changing environmental parameters. Impact on the socio-economic status of the vulnerable fishermen community will also enrich the project. Thus would ultimately determine the role of the shark as a potential bioindicator of changing marine ecosystem in Indian Sundarban though a holistic approach.
Elephant-Human Conflict Research
According to the IUCN Red list (2020) of threatened species, the Asian Elephant (Elephas maximus) is classified as endangered. The Asian elephant is also the Indian National Heritage Animal. The Asian elephant habitats all over Asia are fragmented by human developmental activities and at times with just a sliver of land without barriers to movement (called elephant corridors) connecting the fragments. The population of wild elephants in the states of West Bengal and Jhrakand according to the synchronized nationwide elephant census of 2017 are respectively 682 and 679.
Project goals
- Acquire a spatio-temporal perspective (time series maps) on the trend in Elephant Human Conflict (EHC) over 3 decades (1992-2022) in the changing landscape of Jharkhand, north and south West Bengal
- Initiate long term monitoring and spatio-temporal mapping of EHC and its environmental and socio-economical drivers
- Map elephant corridors (narrow strips of barrier free land) connecting fragmented forest patches and continuous monitoring of these corridors with remote sensing
- Help the farmers affected by economic loss due to crop and property damage by elephants. We will make the process of filing for compensation easy and efficient. Means in collaboration from respective forest departments
- Citizen Science mobile app to record date, time and location of elephant presence (direct sighting or fresh elephant dung and footprints) and map the extension of the homerange of elephants.
A pilot study was successfully completed in the Ajodhya hills which is extended as the easternmost part of the Chhota Nagpur Plateau in West Bengal and covers almost 10,000 sq.km. forest area. Elephant habitat of south West Bengal connects the Ajodhya hills with the adjoining Dalma Wildlife Sanctuary. Preliminary Survey of literature indicates that after 2008, the construction of pumped storage hydro-electric plant has a negative impact on forest cover, elephant habitat and local villagers near Baghmundi.
The major aim of the study was to identify the human-elephant conflict affected villages in this study area through elephant corridor mapping. Also, a landscape modification map from 2001 to 2021 was also prepared to fulfill the purpose of the study. Google Earth, QGIS and ERDAS IMAGINE software were used to prepare the elephant corridor map and the landscape modification map of the study area.
Results till date: The study reflects upon the effect of human-elephant conflict on the residents of identified villages. The study factors in the impact of various anthropogenic pressures such as dam construction, tourism development, deforestation, road construction, picnic spot etc. For instance, the 2.1 sq.km area is covered by built up areas such as hotels, resorts, picnic spots etc. on the elephant habitat of the study area which is shown in the landscape modification map of 2021.
Currently, the ravaged dense forest affects the residential and migrated elephants of the study area. To mitigate the problem the present is an initiative to suggest some effective management in the existing problem area.
Mahilong-Kalimati elephant corridor (Prepared in Google Earth-Pro software by the author)
Landscape Modification of Baghmundi Block, Puruliya (2001-2021)
