Determining pregnancy status of extant and ancient whales by quantifying progesterone in blubber biopsies and bone

Sheridan, Mackenzie L. (2004) Determining pregnancy status of extant and ancient whales by quantifying progesterone in blubber biopsies and bone. Masters thesis, Memorial University of Newfoundland.

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Abstract

This thesis had three major objectives: 1) to determine the most appropriate method for the short-term storage of blubber biopsy samples for hormonal analyses, 2) to determine whether or not progesterone could be quantified in blubber biopsy samples from free-ranging North Atlantic humpback (Megaptera novaeangliae) and North Atlantic right (Eubalaena glacialis) whales in order to determine pregnancy status, and 3) to determine whether or not immunoassayable progesterone could be quantified in ancient whale bone samples. In order to determine the most appropriate method for storing blubber biopsies for hormone analyses, samples were collected from a known pregnant minke whale (Balaenoptera acutostratus) post-mortem and stored frozen for 2 months under different conditions- in ethanol, 100% dimethylsulfoxide (DMSO), 20% salt-saturated DMSO, and frozen. Biopsy samples stored in ethanol yielded less than 10% of the progesterone concentrations of those in the other three storage conditions (p < 0.05). However, once extracts of both the blubber samples that were in ethanol and the ethanol liquid fractions were combined, progesterone concentrations were comparable to those of the other three storage conditions (p > 0.05). Progesterone concentrations were determined from blubber biopsy samples of free-ranging humpback (n = 32) and right (n = 17) whales in order to determine pregnancy status. We hypothesized that females pregnant at the time of sampling would have elevated blubber progesterone concentrations. Thirteen of 21 female humpbacks (62%) were resighted the year following sampling. Three females with elevated blubber progesterone concentrations and one with a moderate progesterone concentration were observed with calves. Seven mature females (two with elevated blubber progesterone concentrations and four with moderate blubber progesterone concentrations) were observed without calves, introducing the possibility of neonatal mortality, spontaneous abortion, pseudopregnancy, or possibly failure of the technique. Two females that had blubber progesterone concentrations comparable to males and immature whales were observed without calves. All adult males and immature individuals had low blubber progesterone concentrations. All right whales, with the exception of one, were resighted following sampling. One mature female with an elevated blubber progesterone concentration was observed with a calf approximately six months following sampling. One mature female with a moderate blubber progesterone concentration was observed on the calving ground numerous times four to seven months after sampling but without a calf introducing the possibility of pseudopregnancy, spontaneous abortion, or neonatal mortality. All adult males and juveniles of both sexes had relatively lower blubber progesterone concentrations. Progesterone concentrations were measured in ancient bone samples from bowhead (Balaena mysticetus) and right whales killed in the 16ᵀᴴ century Basque fishery in Labrador. Immunoassayable bone progesterone concentrations from 0.19- 13.07 ng/g. were detected. Bone progesterone concentrations of samples taken from bones that were known to have been underwater until relatively recently were significantly greater than those from bone samples collected in terrestrial deposits (p < 0.05). Reproductive status could not be determined on the basis of progesterone concentrations alone, and a preliminary analysis awaits the determination of sex for each of the samples.

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