Photoperiodic manipulation modulates the innate and cell mediated immune functions in the fresh water snake, Natrix piscator

Abstract

Objectives of the current work were to investigate the role of photoperiod and melatonin in the alteration of immune responses in a reptilian species. Animals were kept on a regimen of short or long days. Blood was obtained and leucocytes were isolated to study various innate immune responses. Lymphocytes were separated from blood by density gradient centrifugation and were used to study proliferation. Respiratory burst activity was measured through nitrobluetetrazolium reduction assay while nitric oxide production by leucocytes was assayed by nitrite assay. Lymphocytes were isolated and used to study proliferation with and without B and T cell mitogens. Photoperiodic manipulation acted differentially on leucocyte counts. Nitrite release was increased while superoxide production was decreased in cultures obtained from the snakes kept on the short day regimen. Significant enhancement of mitogen induced lymphocyte proliferation was observed in cultures from the animals kept in either long or short days compared to cultures from the animals kept in natural ambient day length. Use of in vitro melatonin showed that lymphocytes from the animals, kept in long days, were more reactive. Photoperiod induces changes in immune status which may permit adaptive functional responses in order to maintain seasonal energetic budgets of the animals. Physiological responses (like elevated immune status) are energetically expensive, therefore, animals have evolved a strategy to reduce immune functions at times when energy is invested in reproductive activities. Natrix piscator breeds from September to December and elevated pineal hormone in winter suppresses reproduction while immunity is stimulated.

Annual rhythm in immune functions of blood leucocytes in an ophidian, Natrix piscator

“…In the present study, the number of leucocytes was elevated during winter. In contrast, we previously found that short photoperiod suppresses leucocyte number in N. piscator 16 . The disparity in the results may be attributed to the differential effect of photoperiodic modulation in this species.…”

“…So far non-mammals are concerned, a few studies on the modulation of immune surveillance by blood cells have been performed in fish where significant annual rhythm has been reported in many immune parameters 14 , 15 . In an earlier study, we found circadian and seasonal alterations in nine immune parameters of splenic macrophages in N. piscator 16 . Reptiles are crucial heterotherms because of their significant phylogenic position and N. piscator is a potent contender for studies regarding vertebrate seasonality.…”

“…It has been postulated that in the non-mammals, the respiratory burst activity of leucocytes is compromised in winter due to cold stress 42 – 45 . When N. piscator was treated with different photoperiodic regimens for 30 days, the superoxide production did not vary significantly 16 . However, in the present work, we have found a significant annual rhythm in superoxide production by leucocytes being highest during winter.…”

Circadian rhythms of hosts and their gut microbiomes: Implications for animal physiology and ecology

“…However, the entrainment of peripheral circadian rhythms in immunity and metabolism may be microbiota‐independent in species where metabolic requirements are not circadian, as well as in species where metabolic requirements and pathogen exposure are uncoupled. For example, ectotherms exhibit circadian rhythms in body temperature and activity (Bartell et al, 2004; Oishi et al, 2004; Tawa et al, 2014), and have some level of circadian cycles in metabolism (Roe et al, 2004) and immunity (Singh et al, 2020; Tripathi et al, 2015), but feeding patterns are often not circadian (e.g. for large reptiles such as snakes and crocodiles that are infrequent feeders).…”

Melatonin as a Possible Natural Anti-Viral Compound in Plant Biocontrol

“…Melatonin ( N -acetyl-5-methoxytryptamine) is an indoleamine derived from tryptophan and produced by several organisms such as animals [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ], bacteria [ 8 , 9 , 10 , 11 ], fungi [ 7 , 12 ] and plants [ 7 , 10 , 13 ]. In mammals, it was discovered in 1958 in the pineal gland where it is synthesized [ 14 ].…”