Trioecy, a unique breeding strategy in the sea anemone Aiptasia diaphana and its association with sex steroids.
Reproductive development of anthozoans reveals wide range of breeding strategies. Here, we report the occurrence of trioecy in the sea anemone Aiptasia diaphana (co-occurrence of males, females, and hermaphrodites), which so far was well documented only in plants. Age-homogeneous populations were obtained from pedal lacerates (asexual propagules) and cultured under control conditions. Careful documentation of growth, gamete morphology, and vertebrate-like steroid (i.e., progesterone, testosterone, and estradiol) levels were carried out over a 9-wk period between 4 and 12 wk postlaceration (wpl). First phenotypic signs of gametes development were observed in 6-wk-old anemones, pointing to the differentiation of males and hermaphrodites. While the males exhibited cellular progression of spermatogenesis, the hermaphrodites underwent a process of sex allocation, giving rise to male, female, and hermaphrodite phenotypes. Testosterone levels were relatively high prior to gamete appearance (4 wpl) and later on during gamete maturation (10 wpl). Conversely, estradiol levels steadily increased from 6 to 10 wpl, reaching their peak concomitant with oocyte maturation. Interestingly, increased oocyte atresia incidences were recorded during 9-12 wpl, coinciding with declining levels of steroid hormones. These results point to a strong similarity between the activity of sex steroids in vertebrates and that of vertebrate-like sex steroids on critical stages of A. diaphana's sexual differentiation and gametogenic cycle. The reproductive characteristics of A. diaphana make this anthozoan an important model species for the study of evolutionary drivers and processes underlying sexual development.
National Center for Mariculture, Israel Oceanographic and Limnological Research, Eilat, Israel Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel The H. Steinitz Marine Biology Laboratory, the Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel rachelarmoza@gmail.com.
Rachel
R
Armoza-Zvuloni
Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel.
Esti
E
Kramarsky-Winter
Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel.
Yossi
Y
Loya
The H. Steinitz Marine Biology Laboratory, the Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel.
Ami
A
Schlesinger
Department of Zoology, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel.
Hanna
H
Rosenfeld
D000818:Animals; D004958:Estradiol / Q000378:metabolism; D005260:Female; D005854:Germ Cells / Q000502:physiology*; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D057850:Hermaphroditic Organisms / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D012098:Reproduction / Q000502:physiology*; D012615:Sea Anemones / Q000502:physiology*; D012727:Sex Characteristics; D012733:Sex Differentiation / Q000502:physiology*; D013045:Species Specificity; D018709:Statistics, Nonparametric; D013739:Testosterone / Q000378:metabolism
D012739:Gonadal Steroid Hormones; D013739:Testosterone; D004958:Estradiol
Aiptasia diaphana; Cnidaria; gametogenesis; sex differentiation; steroid hormones; trioecy