The immune system of vertebrates involves both innate and acquired immune responses. The innate immunity is more generalized with robust response whereas the other has a highly specific response to infectious pathogens. Because of the lack of specialized lymphatic organs, innate immunity is an important mode of defense in fishes. The less specific innate immune system acts mainly through complement pathway which depends on pattern-based recognition of “self” and “non-self” targets by host lectins and associated proteins. This ultimately results in the clearance of target cells. Lectins are glycoproteins which possess at least one carbohydrate recognition domain (CRD) that specifically and reversibly binds to a carbohydrate which is widely distributed in bacteria, fungi and viruses, and thus activates the innate immune system. Lectins are involved in many biological functions including cell adhesion, phagocytosis, complement activation and innate immunity. Fish lectins have also an important role in fertilization, embryogenesis and morphogenesis. Based on the structure, binding specificities and calcium dependency, lectins are classified into different families like C-type lectins, F-type lectins, galectins, intelectins, rhamnose binding lectins, I-type lectins, Lily-type lectins etc. Lectins such as ficolins, galectins, calnexin, pentraxin, F-type lectins, intelectins, mannose-binding proteins (MBPs) are known to play an important role in innate immunity and disease resistance. The skin forms an important immune structure in fish and the skin mucus is reported to have lectins, as well as stomach, intestine, liver, gills, eggs, skin, serum, and plasma of different families of fish. In addition to their important role in cellular recognition as pattern recognition receptors, the interaction of lectins with carbohydrates has been explored in various fields of research where saccharide specificity is essential. These proteins are invaluable tools for the study of simple or complex carbohydrates, in solution or on cell surface, as well as for cell characterization. The action of the innate immune system in recognition of a pathogen is initiated by pathogen recognition receptors (PRRs). This can detect and respond to the pathogen-associated molecular patterns (PAMPs). PRRs also detect death-associated molecular patterns (DAMPs) which are endogenous molecules released by damaged or stressed cells. Lectins belong to the humoral component of innate immune system and are involved in recognition of PAMPs effecting in agglutination and neutralization of potential microbial pathogens or activation of complement components. Taken together, various study reports suggest that fin fish lectins plays a major role in immune recognition of microbial pathogens and facilitate their clearance by phagocytosis. The present review discusses the occurrence and biological role of lectins in finfish.

Migratory shorebirds that move across continents along their flyways are undergoing a drastic decline globally. A greater proportion of them that regularly winter along the Indian coasts within the Central Asian Flyway (CAF) are also undergoing severe declines. However, the mechanisms underlying the population trends in these areas remain little understood. This study investigated the diversity, abundance, population dynamics and distribution patterns of shorebirds along the Indian coasts based on the available literature. The west coast of India is relatively less studied than the east coast in the CAF. Further, we observed that the diversity, abundance, population dynamics and distribution pattern of the shorebirds follow different trends on the west coast compared to the east coast. These variations are in accordance with the differences in topography and biotic and abiotic factors between the coasts. Anthropogenic activities have far-reaching effects on the survival and persistence of shorebirds along the coasts. The west coast is evidently more productive than the east coast at every trophic level and thus the west coast is expected to account for more abundance and diversity of shorebirds. Paradoxically, we found that the east coast supports a greater abundance and diversity of shorebirds than the west coast. The west coast, therefore, requires further investigations to obtain a better understanding of the causes of apparent differences in abundance and diversity as well as the observed declines in shorebirds, compared to the east coast of India.

Bahrain is a cluster of islands in the mid-section of the Arabian Gulf that serves as an important wintering and stop-over ground for many migratory shorebirds in the Central Asian Flyway (CAF). However, natural and anthropogenic factors have had a significant impact on these ecosystems over the last few decades. Long-term, systematic studies based on standardized survey observations are needed to understand the population dynamics and diversity changes of shorebirds in these critical sites. We systematically surveyed the shorebird population and community in Bahrain between 2010 January to 2021 December. This is the first comprehensive study from the entire Kingdom of Bahrain, and covered 13 sites over 12 years to establish the results. A total of 39 species were encountered during the study period from all 13 sites in Bahrain, of which 27 species were common and regular migrants to all the study sites; these were selected to analyze the population trend. Five species represented 77% or more of the total wintering shorebird population. All the shorebird species assessed exhibited significant declining trends over the years, and majority of them had over 1% relative abundance. Shorebirds in Bahrain were severely threatened at these sites, indicating that their population trend in the area could be crucially affected. Further conservation efforts are needed, aided by an understanding of the mechanisms driving the decline and diversity changes of shorebirds in the most stressed coastal regions of Bahrain. Further studies organized throughout the country’s coasts may aid in establishing improved conservation measures to protect the shorebirds of the CAF in Bahrain.

Habitat fragmentation and degradation in natural wetlands has resulted in declines in the populations of shorebirds in the Indian subcontinent. Shorebirds rely on these wetlands as wintering or stop-over sites along the southern extent of the Central Asian Flyway. Shorebirds are known to utilize agroecosystems as alternate foraging habitats. The suitability of agroecosystems as foraging areas for overwintering migratory shorebirds has not been well studied in the Indian subcontinent. We conducted a comprehensive assessment of published literature and compiled field observations to investigate the importance of inland and coastal agroecosystems for shorebirds in India. We assessed the shorebird populations at natural wetlands: mudflats and mangroves of Kadalundi Vallikkunnu Community Reserve (KVCR) and Puthuvypu sand beach, as well as adjacent agroecosystems on the west coast of India, including Sanketham Wetlands, Manthalakkadavu, Vazhakkad, Elamaram, Kodinhi, and Kooriyad. On the east coast, we assessed the natural wetland habitats of Valinokkam, Point Calimere, and Pichavaram and evaluated inland agroecosystems in regions, such as Jammu and Kashmir, Punjab, Rajasthan, Gujarat, Uttar Pradesh, Tamil Nadu, and Kerala. Fifty-three shorebird species utilize diverse agroecosystems from various parts of India. While studies on the use of agroecosystems by shorebirds are limited on the east coast, evidence suggests that major wintering sites are adjacent to paddy fields, fostering substantial shorebird diversity. In Pichavaram, Point Calimere, and Gulf of Mannar regions, 22 shorebird species utilize agroecosystems, including the notable near-threatened Eurasian Curlew. Seventeen of these species are winter arrivals, highlighting the crucial role agroecosystems play as stopover areas. On the west coast, 19 shorebird species appear to utilize agroecosystems in Kooriyad, Manthalakkadavu, Vazhakkad, Sanketham Wetlands, Elamaram, and Kodinhi. Few species use agricultural fields in the north (Jammu and Kashmir). Paddy fields, that are flooded as part of the cropping cycle, support diverse prey species, such as macroinvertebrates, amphibians, and small fish, that could attract and support migratory shorebirds. Agricultural practices like fallowing, flooding, and ploughing could further increase the abundance and accessibility of prey for shorebirds, drawing them in greater numbers. It is crucial to recognize that unsustainable and unethical agricultural methods could detrimentally affect shorebird numbers. The accumulation of pesticide residues and the contamination from heavy metals could also threaten shorebirds. As a result, there is an urgent need for detailed research to better evaluate the importance of agroecosystems in supporting resident or migratory shorebirds. Systematic studies that explain the population dynamics, habitat selection trends, habitat utilization, and the over-summering behavior of the migratory birds at agroecosystems are needed. Implementing sustainable conservation strategies and adopting environmentally friendly agricultural practices are essential to support the rich biodiversity of the region.