Effect of boron deprivation on reproductive parameters in Xenopus laevis

Low boron (−B), boric acid supplemented (+B), or traditional beef liver and lung (BLL) diets were administered to adult male and female Xenopus laevis for either 28 d or 120 d to evaluate reproductive status. The boron content was the only difference between the −B and +B diets. To evaluate further the potential impact of boron deprivation on adult reproduction, a detailed evaluation of ovary and testis morphology and weight, oocyte fecundity and maturation, and sperm count and dysmorphology was conducted. Adult females were depleted of boron for 120 d and subsequently superovulated to flush mature eggs from the ovaries. Following an additional 45‐d oocyte maturation period in which the frogs were maintained on their respective diets, the ovaries were removed and oocytes evaluated. Adults administered the −B diet had distinctly atrophied ovaries and testes when compared to adults administered either the +B or BLL diet. Females administered the −B diet had a much greater proportion of immature oocytes in stages 1 and 2 (ca. −B = 87% vs. +B = 23% following the 120‐d regimen) than females fed the +B diet, which had a greater proportion of mature oocytes in stages 5 and 6 (mature) (ca. −B = 3% vs. +B = 45% following the 120‐d regimen). Co‐culture of progesterone with normal stage 1 and 2 oocytes to stages 5 and 6 oocytes in vitro allowed for the successful maturation of stages 1 and 2 oocytes from the +B or BLL diet‐fed females, but not from the −B females, which did not respond to hormone treatment. The adverse effects of low dietary boron in the female Xenopus were noted following both depletion periods; however, the effects were more dramatic following 120 d of boron depletion. Reductions in sperm counts and increases in sperm dysmorphology rates were noted in males fed the −B diet when compared to males fed either the BLL or the +B diet. These results on reproduction, development, and maturation further indicate the nutritional essentiality of boron in Xenopus. J. Trace Elem. Exp. Med. 12:187–204, 1999. © 1999 Wiley‐Liss, Inc.