DOES ELASTIN CONTRIBUTE TO THE PERSISTENCE OF CORPORA ALBICANTIA IN THE OVARY OF THE COMMON DOLPHIN (DELPHINUS DELPHIS)

Abstract

The corpora albicantia (CAs) from the ovaries of 39 common dolphins (Delphinus delphis) caught in driving fisheries were used, and histologically and immunohistochemically examined. The area of each corpus albicans (CA) and the proportion of that area occupied by elastin were measured using NIH-image software. In all CAs, elastoid material (EM) was apparent although EM area varied in each CA. CAs increased in number with dolphin age. Smaller CAs contained a higher proportion of EM. EM was completely digested by elastase, but not by collagenase. Furthermore, EM was immunostained with anti-␣-elastin antibody. These results demonstrated that EM was elastin. The present study is the first to describe the presence of elastin 1 Current address: Biologging Institute, 2-31-10, Rex Yushima 301, Yushima Bunkyo-ku, Tokyo 113-0034, Japan. 819 820 MARINE MAMMAL SCIENCE, VOL. 22, NO. 4, 2006 in cetacean CAs. The higher proportion of elastin in small-sized CAs of common dolphins is suggested as the likely cause of the persistence of CA.

Assessing the effect of persistent organic pollutants on reproductive activity in common dolphins and harbour porpoises

“…This was based on the following observations: CA number did not increase signifi cantly with age; pregnant D. delphis had ca 40% fewer scars than non-pregnant animals; and since all pregnant individuals were sampled between January and March, prior to the estimated calving period for the population. In contrast, studies undertaken on other populations of D. delphis, by Danil and Chivers (2007) in the eastern tropical Pacifi c, Westgate and Read (2007) in the western North Atlantic and Takahashi et al (2006) in waters off Japan have all reported a signifi cant increase in corpora number with age.…”

“…They were unable to differentiate CAs from pregnancy with those from ovulation, and it was assumed that smaller CAs, containing <15% elastin, were derived from infertile ovulations. With a reproductive period of ca 19 years reported for the ENA D. delphis population (Murphy et al, 2009b), results from Takahashi et al (2006) study suggest that CAs, of pregnancy at least, do persist throughout the lifetime of a female common dolphin.…”

“…Results from genetic analysis on the Pleubian group reported a lack of evidence for a matriarchal system, with genetic variability within the mass-stranded group similar to variability observed in single strandings i.e. common dolphins were not necessarily genetically related (Viricel et al, 2008). Therefore, the existence of non-reproductive females (based on high contaminant loads and high numbers of ovulations) within this social group is even more remarkable; though it should be noted that the whole mass-stranded group was not sampled for genetic analysis, as 50 other individuals were released alive offshore.…”

“…Takahashi et al (2006) reported that collagenous fi brous tissue in regressing corpora lutea from D. delphis off Japan was replaced by elastin tissue, a material which has a reported half life of 40-70 years. They were unable to differentiate CAs from pregnancy with those from ovulation, and it was assumed that smaller CAs, containing <15% elastin, were derived from infertile ovulations.…”

“…In all cases, data collection protocols followed European Cetacean Society guidelines for gross postmortem examination and tissue sampling (Kuiken and Garcia Hartmann, 1991 Pierce et al (2008) for further information and distribution maps), and ranged in decomposition states from fresh (CC2) to moderately decomposed (CC3) (Kuiken and Garcia Hartmann, 1991 Viricel et al, 2008), and reproductive data from 49 females were available for the current study. In a previous paper, Dabin et al (2008) assessed the use of ovarian scars to reconstruct individual reproductive histories.…”