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Melica V, Thornton SJ. Killer whale fecal samples: How to get the most out of a single extraction. Gen Comp Endocrinol 2024; 354:114544. [PMID: 38705419 DOI: 10.1016/j.ygcen.2024.114544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 04/19/2024] [Accepted: 04/30/2024] [Indexed: 05/07/2024]
Abstract
Fecal samples are a non-invasive and relatively accessible matrix for investigating physiological processes in resident killer whale (Orcinus orca) populations. The high lipid content of the diet (primarily salmonids) leads to lower density fecal material and slower dispersion, facilitating sample collection. As fecal discharge is relatively infrequent and the volume of sample is variable, maximizing analytical options is an important consideration. Here we present an extraction methodology to measure hormones and lipid content from the same fecal aliquot. Lipid extractions are commonly conducted using chloroform and methanol from Folch or Bligh and Dyer (B&D), while alcohol is the primary solvent for hormone extraction. We evaluated the possibility of using the methanol layer from lipid extractions to assess fecal steroid hormone levels. Folch and B&D methanol residues were assayed form metabolites of progesterone (PMs) and corticosterone (GCs), and results were compared to aliquots extracted in 70 % ethanol. Hormone concentrations measured in the methanol layer from Folch and B&D extractions were 55 % to 79 % lower than concentrations in 70 % ethanol. We developed mathematical corrections, using linear regression models fitted to Folch or B&D methanol vs 70 % ethanol hormone concentrations (p < 0.01). Fecal concentrations of PMs and GCs from methanol extractions were biologically validated and are significantly higher in confirmed pregnant females compared to non-pregnant individuals (p < 0.05). This study demonstrates that lipid extraction protocols may be used for the analysis of multiple biomarkers, maximizing the use of small-volume samples.
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Affiliation(s)
- V Melica
- Marine Mammal Conservation Physiology Program, Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC, Canada
| | - S J Thornton
- Marine Mammal Conservation Physiology Program, Fisheries and Oceans Canada, 4160 Marine Drive, West Vancouver, BC, Canada.
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Renaud LA, Bordeleau X, Kellar NM, Pigeon G, Michaud R, Morin Y, Lair S, Therien A, Lesage V. Estimating pregnancy rate from blubber progesterone levels of a blindly biopsied beluga population poses methodological, analytical and statistical challenges. CONSERVATION PHYSIOLOGY 2023; 11:coad075. [PMID: 37771677 PMCID: PMC10533324 DOI: 10.1093/conphys/coad075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 07/13/2023] [Accepted: 09/06/2023] [Indexed: 09/30/2023]
Abstract
Beluga (Delphinapterus leucas) from the St. Lawrence Estuary, Canada, have been declining since the early 2000s, suggesting recruitment issues as a result of low fecundity, abnormal abortion rates or poor calf or juvenile survival. Pregnancy is difficult to observe in cetaceans, making the ground truthing of pregnancy estimates in wild individuals challenging. Blubber progesterone concentrations were contrasted among 62 SLE beluga with a known reproductive state (i.e. pregnant, resting, parturient and lactating females), that were found dead in 1997 to 2019. The suitability of a threshold obtained from decaying carcasses to assess reproductive state and pregnancy rate of freshly-dead or free-ranging and blindly-sampled beluga was examined using three statistical approaches and two data sets (135 freshly harvested carcasses in Nunavik, and 65 biopsy-sampled SLE beluga). Progesterone concentrations in decaying carcasses were considerably higher in known-pregnant (mean ± sd: 365 ± 244 ng g-1 of tissue) than resting (3.1 ± 4.5 ng g-1 of tissue) or lactating (38.4 ± 100 ng g-1 of tissue) females. An approach based on statistical mixtures of distributions and a logistic regression were compared to the commonly-used, fixed threshold approach (here, 100 ng g-1) for discriminating pregnant from non-pregnant females. The error rate for classifying individuals of known reproductive status was the lowest for the fixed threshold and logistic regression approaches, but the mixture approach required limited a priori knowledge for clustering individuals of unknown pregnancy status. Mismatches in assignations occurred at lipid content < 10% of sample weight. Our results emphasize the importance of reporting lipid contents and progesterone concentrations in both units (ng g-1 of tissue and ng g-1 of lipid) when sample mass is low. By highlighting ways to circumvent potential biases in field sampling associated with capturability of different segments of a population, this study also enhances the usefulness of the technique for estimating pregnancy rate of free-ranging population.
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Affiliation(s)
- L -A Renaud
- Department of Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, 850 Route de la Mer, Mont-Joli, Québec, G5H 3Z4, Canada
| | - X Bordeleau
- Department of Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, 850 Route de la Mer, Mont-Joli, Québec, G5H 3Z4, Canada
| | - N M Kellar
- Southwest Fisheries Science Center, National Marine Fisheries Service, P.O. Box 271, La Jolla, California 92038, USA
| | - G Pigeon
- Institut de recherche sur les forêts, Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec, J9X 5E4, Canada
| | - R Michaud
- Groupe de recherche et d’éducation sur les mammifères marins (GREMM), 108 de la Cale-Sèche, Tadoussac, Québec, G0T 2A0, Canada
| | - Y Morin
- Department of Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, 850 Route de la Mer, Mont-Joli, Québec, G5H 3Z4, Canada
| | - S Lair
- Faculté de médecine vétérinaire, Université de Montréal, P.O. Box 5000, 3200 Rue Sicotte, St-Hyacinthe, Québec, J2S 7C6, Canada
| | - A Therien
- Department of Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, 850 Route de la Mer, Mont-Joli, Québec, G5H 3Z4, Canada
| | - V Lesage
- Department of Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, 850 Route de la Mer, Mont-Joli, Québec, G5H 3Z4, Canada
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Atkinson S, Branch TA, Pack AA, Straley JM, Moran JR, Gabriele C, Mashburn KL, Cates K, Yin S. Pregnancy rate and reproductive hormones in humpback whale blubber: Dominant form of progesterone differs during pregnancy. Gen Comp Endocrinol 2023; 330:114151. [PMID: 36341970 DOI: 10.1016/j.ygcen.2022.114151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 10/19/2022] [Accepted: 10/25/2022] [Indexed: 11/04/2022]
Abstract
To better understand reproductive physiology of humpback whales Megaptera novaeangliae that reside in Hawai'i and Alaska, enzyme immunoassays were validated for both progesterone and testosterone in free-ranging and stranded animals (n = 185 biopsies). Concentrations were analyzed between different depths of large segments of blubber taken from skin to muscle layers of stranded female (n = 2, 1 pregnant, 1 non-pregnant) and male (n = 1) whales. Additionally, progesterone metabolites were identified between pregnant (n = 1) and non-pregnant (n = 3) females using high pressure liquid chromatography (HPLC). Progesterone concentrations were compared between juvenile (i.e., sexually immature), lactating, and pregnant females, and male whales, and pregnancy rates of sexually mature females were calculated. Based on replicate samples from ship struck animals collected at 7 depth locations, blubber containing the highest concentration of progesterone was located 1 cm below the skin for females, and the highest concentration of testosterone was in the skin layer of one male whale. HPLC of blubber samples of pregnant and non-pregnant females contain different immunoreactive progesterone metabolites, with the non-pregnant female eluate comprised of a more polar, and possibly conjugated, form of progesterone than the pregnant female. In females, concentrations of progesterone were highest in the blubber of pregnant (n = 28, 28.6 ± 6.9 ng/g), followed by lactating (n = 16, 0.9 ± 0.1 ng/g), and female juvenile (n = 5, 1.0 ± 0.2 ng/g) whales. Progesterone concentrations in male (n = 24, 0.6 ng/g ± 0.1 ng/g) tissues were the lowest all groups, and not different from lactating or juvenile females. Estimated summer season pregnancy rate among sexually mature females from the Hawai'i stock of humpback whales was 0.562 (95 % confidence interval 0.528-0.605). For lactating females, the year-round pregnancy rate was 0.243 (0.09-0.59), and varies depending on the threshold of progesterone assumed for pregnancy in the range between 3.1 and 28.5 ng/g. Our results demonstrate the synergistic value added when combining immunoreactive assays, HPLC, and long-term sighting histories to further knowledge of humpback whale reproductive physiology.
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Affiliation(s)
- S Atkinson
- University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, 17101 Point Lena Loop Road, Juneau, AK 99801, USA.
| | - T A Branch
- University of Washington, School of Aquatic and Fishery Sciences, Box 355020, Washington 98105, USA.
| | - A A Pack
- Departments of Psychology and Biology, University of Hawai'i at Hilo, 200 West Kawili Street, Hilo, HI 96720, USA; The Dolphin Institute, P.O. Box 6279, Hilo, HI 96720, USA.
| | - J M Straley
- University of Alaska Southeast, 1332 Seward Avenue, Sitka, AK 99835, USA.
| | - J R Moran
- National Marine Fisheries Service, Alaska Fisheries Science Center, Ted Stevens Marine Research Institute, 17109 Pt. Lena Loop Road, Juneau, AK 99801, USA.
| | - C Gabriele
- Hawai'i Marine Mammal Consortium, P.O. Box 6107, Kamuela, HI 96743, USA; Glacier Bay National Park & Preserve, P.O. Box 140, Gustavus, AK 99826, USA.
| | - K L Mashburn
- University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, 17101 Point Lena Loop Road, Juneau, AK 99801, USA.
| | - K Cates
- University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, 17101 Point Lena Loop Road, Juneau, AK 99801, USA.
| | - S Yin
- Hawai'i Marine Mammal Consortium, P.O. Box 6107, Kamuela, HI 96743, USA.
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Melica V, Atkinson S, Calambokidis J, Gendron D, Lang A, Scordino J. Naturally stressed? Glucocorticoid profiles in blubber of blue and gray whales in response to life history parameters. MARINE MAMMAL SCIENCE 2022; 38:1524-1548. [PMID: 36619002 PMCID: PMC9815209 DOI: 10.1111/mms.12954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The goal of the present study was to carry out a thorough methodological validation and describe baseline profiles for glucocorticoid hormones (cortisol and corticosterone) in blubber from blue (n = 77) and gray (n = 103) whales from the eastern North Pacific Ocean. For each species, we modelled cortisol and corticosterone concentrations in response to life history parameters (age, sex, reproductive status) and season or geographic location. In blue whales, cortisol concentrations did not vary significantly by age class, sex, or reproductive status, whereas corticosterone was significantly lower in immature than in adult females (p < .001). In gray whales, cortisol concentrations were significantly higher in lactating whales (p < .05), while corticosterone was significantly different between females and males (p = .001) and elevated in calves (p = .003). In gray whales, corticosterone concentrations were significantly lower in males sampled later in the year (August to November) compared to both sexes sampled between March and August (p = .05), but no seasonal trend occurred in blue whales. Our results indicate that glucocorticoid actions vary between species and sex in large whales. Analysis of multiple hormones improves our understanding of the physiology of maintaining metabolic homeostasis or coping with chronic stressors.
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Affiliation(s)
- Valentina Melica
- Fisheries Department, College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska
| | - Shannon Atkinson
- Fisheries Department, College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska
| | | | - Diane Gendron
- Instituto Politecnico Nacional, Centro Interdisciplinario de Ciencias Marina (IPN-CICIMAR), La Paz, Baja California Sur, Mexico
| | - Aimee Lang
- Ocean Associates Inc., on contract to NOAA Southwest Fisheries Science Center, La Jolla, California
| | - Jonathan Scordino
- Marine Mammal Program, Makah Fisheries Management, Neah Bay, Washington
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Melica V, Atkinson S, Calambokidis J, Lang A, Scordino J, Mueter F. Application of endocrine biomarkers to update information on reproductive physiology in gray whale (Eschrichtius robustus). PLoS One 2021; 16:e0255368. [PMID: 34343192 PMCID: PMC8330940 DOI: 10.1371/journal.pone.0255368] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 07/14/2021] [Indexed: 11/18/2022] Open
Abstract
Most of our knowledge on reproductive biology of gray whales dates back to scientific research conducted during commercial whaling in the late 1950s and 1960s. The goal of the present study was to provide updated insights on reproductive physiology of gray whales, using progesterone and testosterone as biomarkers. We measured hormone concentrations using enzyme immunoassay (EIA) techniques in blubber biopsies collected from 106 individual whales from March to November over a span of 12 years (2004-2016) between California and Alaska. We found testosterone concentrations in males to increase significantly with age (P = 0.03). Adult males showed significantly elevated testosterone concentrations when sampled in the fall compared to the summer (P = 0.01), likely indicating physiological preparation for mating. We measured testosterone concentrations in females of different age classes, but no statistical differences were found. We found significantly higher progesterone concentrations in pregnant females compared to non-pregnant females and adult males (P< 0.001), indicating progesterone is a valid biomarker for pregnancy in gray whales. Both female and male calves had elevated progesterone concentrations, suggesting maternal transfer via lactation. We fit a mixture of two normal distributions to progesterone data from all non-calf females to identify clusters of high and low progesterone and estimated the probability of being pregnant for whales of unknown reproductive status. With this approach we identified likely pregnant and non-pregnant animals. This study represents an important milestone on reproductive profiles in this population, that can be used to estimate more accurate and precise reproductive parameters to be used for better understanding population dynamics of gray whales.
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Affiliation(s)
- Valentina Melica
- Fisheries Department, College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, United States of America
- * E-mail:
| | - Shannon Atkinson
- Fisheries Department, College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, United States of America
| | | | - Aimée Lang
- Ocean Associates Inc., on Contract to NOAA Southwest Fisheries Science Center, La Jolla, California, United States of America
| | - Jonathan Scordino
- Marine Mammal Program, Makah Fisheries Management, Neah Bay, Washington, United States of America
| | - Franz Mueter
- Fisheries Department, College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska, United States of America
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