ORCID Profile
0000-0002-8797-4451
Current Organisations
Marine Megafauna Foundation
,
Murdoch University
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Publisher: Frontiers Media SA
Date: 18-09-2018
Publisher: Spandidos Publications
Date: 12-2006
Publisher: Springer Science and Business Media LLC
Date: 26-09-2021
DOI: 10.1186/S43591-021-00017-9
Abstract: Marine plastic abundance has increased over the past 60 years and microplastics ( 5 mm) constitute a primary component of such litter. Filter-feeding megafauna, such as the whale shark, might be particularly affected by microplastic pollution as their feeding mode requires filtration of up to thousands of cubic meters of water. In addition, the habitat range of whale sharks intersects with several recognized microplastic pollution hotspots, among which is the Coral Triangle. Direct evidence for microplastic ingestion in whale sharks however, has not yet been presented. Here we show that whale shark scat collected in the Philippines from 2012 to 2019 contained a mean of 2.8 microplastics g − 1 . Contrary to our expectations, the microplastic concentration in the scat remained consistent from 2012 to 2019. Water s les from the study site in 2019 indicated that the local microplastic pollution (5.83 particles m − 3 ) was higher than in surface waters in other whale shark habitats, but well below other pollution hot-spots found in Southeast Asia and China (range: 100–4100 particles m − 3 ). With the predicted growth in plastic use, leading to increased plastic marine pollution, whale sharks are expected to become more exposed to this form of pollution. To what extent microplastic ingestion impacts the overall health status of this endangered species remains an open question.
Publisher: The American Association of Immunologists
Date: 11-2009
Abstract: Invariant NKT (iNKT) cells can induce potent antitumor responses in vivo. However, the mechanisms that regulate the effects of iNKT cells are unclear. The chemokine receptor CXCR6, and its ligand CXCL16, have been shown to play critical roles in iNKT cell homeostasis and activation. Thus we investigated the role of CXCR6 in protection against experimental metastasis of B16-F10 melanoma (B16) and Lewis lung carcinoma (LLC) cells to the liver and lungs. Wild-type and CXCR6−/− mice exhibited no differences in tumor cell metastasis to the lungs. However, metastasis of LLC and B16 tumor cells to the liver was enhanced in CXCR6−/− mice. Liver metastasis was also increased in wild-type mice treated with a CXCL16 neutralizing Ab. As Ab treatments did not alter iNKT cell numbers, this implicates a direct role for CXCR6/CXCL16 in regulating antitumor immunity. Cytokine induction was significantly attenuated in CXCR6−/− mice upon systemic iNKT cell activation with the glycolipid Ags α-galactosylceramide (α-GalCer), α-C-GalCer (a Th1 polarizing derivative), or OCH (a Th2 polarizing derivative). Despite differences in the levels of cytokine production, liver and lung metastasis were inhibited significantly in both wild-type and CXCR6−/− mice treated with glycolipids. Single doses of α-GalCer, α-C-GalCer, or OCH were sufficient to prevent liver metastasis and subsequent doses failed to elicit optimal cytokine responses. Our findings implicate a role for CXCR6 in natural immunosurveillance against liver metastasis. However, CXCR6 deficiency could be overcome by systemic iNKT cell activation, demonstrating that even suboptimal iNKT cell activation can protect against metastasis.
Publisher: Frontiers Media SA
Date: 19-11-2019
Publisher: Frontiers Media SA
Date: 05-2019
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.TREE.2018.01.005
Abstract: Microplastic pollution can impact filter-feeding marine megafauna, namely mobulid rays, filter-feeding sharks, and baleen whales. Emerging research on these flagship species highlights potential exposure to microplastic contamination and plastic-associated toxins. Research and its wide communication are needed to understand the magnitude of the issue and improve marine stewardship.
Publisher: PeerJ
Date: 16-05-2022
DOI: 10.7717/PEERJ.13302
Abstract: The reef manta ray ( Mobula alfredi ) is a globally threatened species and an iconic tourist attraction for visitors to Indonesia’s Komodo National Park (NP). In 2013, manta ray fishing was banned in Komodo NP and its surroundings, preceding the nationwide manta ray protection in 2014. Over a decade ago, a previous acoustic telemetry study demonstrated that reef manta rays had high fidelity to sites within the park, while more recent photo-identification data indicated that some in iduals move up to 450 km elsewhere. Characterization of manta ray demographics, behavior, and a focused assessment on site use of popular tourism locations within the park is vital to assist the Komodo NP Management Authority formulate appropriate manta ray conservation and management policies. This study uses a long-term library ( MantaMatcher.org ) of photo-identification data collected by researchers and citizen scientists to investigate manta ray demographics and habitat use within the park at four sites frequented by tour operators: Cauldron, Karang Makassar, Mawan, and Manta Alley. Residency and movements of manta rays were investigated with maximum likelihood analyses and Markov movement models. A total of 1,085 in idual manta rays were identified from photographs dating from 2013 to 2018. In general, in idual manta rays displayed a higher affinity to specific sites than others. The highest re-sighting probabilities came from the remote southern site, Manta Alley. Karang Makassar and Mawan are only ~5 km apart however, manta rays displayed distinct site affinities. Exchange of in iduals between Manta Alley and the two central sites (~35.5 km apart) occurred, particularly seasonally. More manta rays were recorded traveling from the south to the central area than vice versa . Female manta rays were more mobile than males. Similar demographic groups used Karang Makassar, Mawan, and Manta Alley for foraging, cleaning, cruising, or courtship activities. Conversely, a higher proportion of immature manta rays used the northern site, Cauldron, where foraging was commonly observed. Fishing gear-related injuries were noted on 56 in iduals (~5%), and predatory injuries were present on 32 in iduals (~3%). Tourism within the park increased from 2014 to 2017, with 34% more e boats per survey at Karang Makassar and Mawan. The Komodo NP contains several distinct critical habitats for manta rays that encompass all demographics and accommodate seasonal manta ray movements. While the present study has not examined population trends, it does provide foundational data for such work. Continued research into manta ray abundance, long-range movements, and identifying and protecting other critical aggregation areas within the region is integral to securing the species’ recovery. We provide management recommendations to limit undue pressure on manta rays and their critical habitats from tourism.
Publisher: The Royal Society
Date: 09-10-2019
Abstract: Intraspecific colour polymorphisms have been the focus of numerous studies, yet processes affecting melanism in the marine environment remain poorly understood. Arguably, the most prominent ex le of melanism in marine species occurs in manta rays ( Mobula birostris and Mobula alfredi ). Here, we use long-term photo identification catalogues to document the frequency variation of melanism across Indo-Pacific manta ray populations and test for evidence of selection by predation acting on colour morph variants. We use mark–recapture modelling to compare survivorship of typical and melanistic colour morphs in three M. alfredi populations and assess the relationship between frequency variation and geographical distance . While there were large differences in melanism frequencies among populations of both species (0–40.70%), apparent survival estimates revealed no difference in survivorship between colour morphs. We found a significant association between phenotypic and geographical distance in M. birostris , but not in M. alfredi . Our results suggest that melanism is not under selection by predation in the tested M. alfredi populations, and that frequency differences across populations of both species are a consequence of neutral genetic processes . As genetic colour polymorphisms are often subjected to complex selection mechanisms, our findings only begin to elucidate the underlying evolutionary processes responsible for the maintenance and frequency variation of melanism in manta ray populations.
Publisher: Public Library of Science (PLoS)
Date: 22-10-2014
Publisher: The American Association of Immunologists
Date: 07-2008
DOI: 10.4049/JIMMUNOL.181.1.81
Abstract: NK T (NKT) cells play important roles in the regulation of erse immune responses. However, little is known about the mechanisms that regulate homeostasis and activation of these cells. Thymic NKT cells up-regulated the chemokine receptor CXCR6 following positive selection and migrated toward CXCL16 in vitro. However, CXCR6 was not essential for thymic development or maturation. In contrast, liver and lung NKT cells were depleted in CXCR6+/− and CXCR6−/− mice. The reduction in liver and lung NKT cells coincided with an increase in bone marrow NKT cells, suggesting a redistribution of NKT cells in CXCR6−/− animals. In wild-type mice, CXCL16 neutralization reduced accumulation of mature NK1.1+, but not immature NK1.1− NKT cell recent thymic emigrants in the liver. Given that thymic NKT cells are preferentially exported as NK1.1− cells, this suggests an additional role for CXCR6/CXCL16 in maturation or survival of immature liver NKT cells. CXCL16 blockade did not deplete resident NK1.1+ NKT cells, indicating that CXCR6/CXCL16 are not required to retain mature NKT cells in the liver. Cytokine production by liver and spleen NKT cells was impaired in CXCR6−/− mice following in vivo stimulation with α-galactosylceramide, implicating a novel role for CXCR6 in NKT cell activation. Reduced IFN-γ production was not due to an intrinsic defect as production was normal following PMA and ionomycin stimulation. Preformed transcripts for IL-4, but not IFN-γ, were reduced in CXCR6−/− liver NKT cells. These data identify critical roles for CXCR6/CXCL16 in NKT cell activation and the regulation of NKT cell homeostasis.
No related grants have been discovered for Elitza Germanov.