Studies on the reproductive system of the alligator. 1. The effects of prolonged injections of pituitary whole gland extract in the immature alligator

Hamlin

Botteri

et al. 2009

Journal of Morphology

We investigated ovary and testis development of Alligator mississippiensis during the first five months post-hatch. To better describe follicle assembly and seminiferous cord development, we employed histochemical techniques to detect carbohydrate-rich extracellular matrix components in one-week, one-month, three-month, and five-month-old gonads. We found profound morphological changes in both ovary and testis. During this time, oogenesis progressed up to diplotene arrest and meiotic germ cells increasingly interacted with follicular cells. Concomitant with follicles becoming invested with full complements of granulosa cells, a periodic acid Schiff’s (PAS)-positive basement membrane formed. As follicles enlarged and thecal layers were observed, basement membranes and thecal compartments gained periodic acid-methionine silver (PAMS)-reactive fibers. The ovarian medulla increased first PAS- and then PAMS-reactivity as it fragmented into wide lacunae lined with low cuboidal to squamous epithelia. During this same period, testicular germ cells found along the tubule margins were observed progressing from spermatogonia to round spermatids located within the center of tubules. Accompanying this meiotic development, interstitial Leydig cell clusters become more visible and testicular capsules thickened. During the observed testis development, the thickening tunica albuginea and widening interstitial tissues showed increasing PAS- and PAMS-reactivity. We observed putative inter-sex structures in both ovary and testis. On the coelomic aspect of testes were cell clusters with germ cell morphology and at the posterior end of ovaries, we observed “medullary rests” resembling immature testis cords. We hypothesize laboratory conditions accelerated gonad maturation due to optimum conditions, including nutrients and temperature. Laboratory alligators grew more rapidly and with increased body conditions compared to previous measured, field-caught animals. Additionally, we predict the morphological maturation observed in these gonads is concomitant with increased endocrine activities.

Section: Ovarymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Posthatching development of Alligator mississippiensis ovary and testis

Hamlin

Botteri

et al. 2009

Journal of Morphology

“…Treatment of 16-month-old female alligators with super-pharmacological doses of estrone led to pronounced oviducal hypertrophy with tall columnar epithelia surrounding enlarged lumens [14]. Further, treatment with pituitary extract hypertrophied the oviducts of 20-month-old alligators and increased convolutions and columnar epithelial height, but not oviducal size or diameter, in six-month-old animals [13]. Thus, similar to observations in other species [18], immature alligator oviducts are responsive to changes in reproductive signaling.…”

Section: Introductionmentioning

confidence: 99%

“…We examined the effects of an in vivo FSH challenge on ovarian steroidogenic enzyme mRNA expression levels, circulating sex steroid hormone concentrations, and oviducal sex steroid hormone receptors and activin-inhibin-follistatin signaling factor mRNA expression levels. In previous research, alligator oviducal responses to pituitary extract treatments has been hypothesized to be indirectly mediated via alteration of ovarian sex steroid synthesis by gonadotrophin treatment [13], thus we investigated if alligator oviducts express follicle stimulating hormone receptors (FSHR) and, therefore, could be directly responsive to a gonadotrophin challenge. We measured proliferating cell nuclear antigen (PCNA) mRNA expression levels to infer a proliferative oviducal response to treatment.…”

Section: Introductionmentioning

confidence: 99%

Gonadotropin-induced changes in oviducal mRNA expression levels of sex steroid hormone receptors and activin-related signaling factors in the alligator

General and Comparative Endocrinology

Forouhar

Kohno

et al. 2012

Oviducts respond to hormonal cues from ovaries with tissue proliferation and differentiation in preparation of transporting and fostering gametes. These responses produce oviducal microenvironments conducive to reproductive success. Here we investigated changes in circulating plasma sex steroid hormones concentrations and ovarian and oviducal mRNA expression to an in vivo gonadotropin (FSH) challenge in sexually immature, five-month-old alligators. Further, we investigated differences in these observed responses between alligators hatched from eggs collected at a heavily-polluted (Lake Apopka, FL) and minimally-polluted (Lake Woodruff, FL) site. In oviducts, we measured mRNA expression of estrogen, progesterone, and androgen receptors and also beta A and B subunits which homo- or heterodimerize to produce the transforming growth factor activin. In comparison, minimal inhibin alpha subunit mRNA expression suggests that these oviducts produce a primarily activin-dominated signaling milieu. Ovaries responded to a five-day FSH challenge with increased expression of steroidogenic enzyme mRNA which was concomitant with increased circulating sex steroid hormone concentrations. Oviducts in the FSH-challenged Lake Woodruff alligators increased mRNA expression of progesterone and androgen receptors, proliferating cell nuclear antigen, and the activin signaling antagonist follistatin. In contrast, Lake Apopka alligators displayed a diminished increase in ovarian CYP19A1 aromatase expression and no increase in oviducal AR expression, as compared to those observed in Lake Woodruff alligators. These results demonstrate that five-month-old female alligators display an endocrine-responsive ovarian-oviducal axis and environmental pollution exposure may alter these physiological responses.

“…In many reptiles, hypophysectomy leads to testicular degeneration [van Tienhoven, 1983], but exogenous gonadotropins restore spermatogenesis [Licht and Pearson, 1969]. Furthermore, gonadotropin or androgen treatments of immature male alligators induces testicular development [Forbes, 1937;Ramaswam and Jacob, 1965] and dramatic increases in plasma sex steroid hormone concentrations [Edwards et al, 2004]. We have observed that ovarian development accelerates in animals held under optimum, laboratory conditions [Moore et al, in press].…”

mentioning

confidence: 99%

Gonadal mRNA Expression Levels of TGFβ Superfamily Signaling Factors Correspond with Post-Hatching Morphological Development in American Alligators

Hamlin

Botteri

et al. 2010

Sex Dev

Paracrine factor signaling regulates many aspects of vertebrate gonadal development. We investigated key ovarian and testicular morphological markers of the American alligator (Alligator mississippiensis) during the first 5 months post-hatching and correlated gonadal development with mRNA expression levels of a suite of regulatory factors. In both sexes, we observed significant morphology changes, including ovarian follicle assembly and meiotic progression of testicular germ cells. Concomitant with these changes were sexually dimorphic and ontogenetically variable mRNA expressions. In ovaries, FOXL2, aromatase, and follistatin mRNA expression was greater than in testes at all ages. At one week after hatching, we observed ovarian medullary remodeling in association with elevated activin/inhibin βA subunit, follistatin, and aromatase mRNA expressions. Three and 5 months following hatching and concomitant with follicle assembly, ovaries showed increased mRNA expression levels of GDF9 and the mitotic factor PCNA. In testes, the activin/inhibin α and βB subunit transcript levels were greater than in ovaries at all ages. Elevated testicular expression of GDF9 mRNA levels at 5 months after hatching aligned with increased spermatogenic activity. We propose that the mRNA expression levels and concomitant morphological changes observed here affect the establishment of alligator reproductive health and later fertility.