Avaliação dos padrões metabólicos induzidos por diferentes tipos de dietas em diversas ordens de vertebrados

O estudo da evolução dos processos de controle do metabolismo energético comparativo envolve o estudo e a comparação do comportamento metabólico de diferentes espécies frente a situações nutricionais específicas, e a análise, em cada espécie, dos mecanismos celulares e intercelulares de adaptação a diferentes condições de oferta de material energético. Dentre os principais estudos neste sentido, estão trabalhos envolvendo diversos vertebrados que se alimentam de diferentes tipos de dietas, principalmente os de dieta rica em carboidratos (frugívoros, nectarívoros, etc) e os de dieta rica em proteínas (carnívoros, insetívoros, etc) e suas adaptações ao jejum. Tem sido observado, através destes estudos, a formação de um padrão metabólico bem definido e distinto entre vertebrados que consomem estes dois tipos de dietas, estabelecido através de estudo em diversas classes, desde peixes até mamíferos. A resposta ao jejum também tem se mostrado bastante distinta entre estes vertebrados que consomem diferentes tipos de dieta, indicando que o tipo de dieta induziria respostas metabólicas específicas em vertebrados submetidos ao jejum. Analisados conjuntamente, os estudos referentes às diversas classes de vertebrados indicam a formação de um padrão metabólico distinto para animais com dieta rica em carboidratos e dieta rica em proteínas. A única exceção já estudada refere-se ao morcegos hematófago Desmodus rotundus (Chiroptera: Phyllostomidae), que consome dieta rica em proteínas (sangue bovino) e parece apresentar um comportamento metabólico similar aos vertebrados que consomem dieta rica em carboidrato

The spermatogenic process of the common vampire bat Desmodus rotundus under a histomorphometric view.

Among all bat species, Desmodus rotundus stands out as one of the most intriguing due to its exclusively haematophagous feeding habits. However, little is known about their spermatogenic cycle. This study aimed at describing the spermatogenic process of common vampire bats through testicular histomorphometric characterization of adult specimens, spermatogenic production indexes, description of stages of the seminiferous epithelium cycle and estimative of the spermatogenic process duration. Morphometrical and immunohistochemical analyzes for bromodeoxiuridine were conducted under light microscopy and ultrastructural analyzes were performed under transmission electron microscopy. Vampire bats showed higher investment in gonadal tissue (gonadosomatic index of 0.54%) and in seminiferous tubules (tubulesomatic index of 0.49%) when compared to larger mammals. They also showed a high tubular length per gram of testis (34.70 m). Approximately half of the intertubular compartment was found to be comprised by Leydig cells (51.20%), and an average of 23.77x106 of these cells was found per gram of testis. The germline cells showed 16.93% of mitotic index and 2.51% of meiotic index. The overall yield of spermatogenesis was 60% and the testicular spermatic reserve was 71.44x107 spermatozoa per gram of testis. With a total spermatogenesis duration estimated at 37.02 days, vampire bats showed a daily sperm production of 86.80x106 gametes per gram of testis. These findings demonstrate a high sperm production, which is commonly observed in species with promiscuous mating system

Germ cells and spermatic production indexes in <i>Desmodus rotundus</i>.

<p>Germ cells and spermatic production indexes in <i>Desmodus rotundus</i>.</p

The most advanced labelled germ cell types found after intratesticular bromodeoxiuridine injections in <i>Desmodus rotundus</i>.

<p>Leptotene to Zygotene cells in stage 3 (a) and type A spermatogonia in stage 3 to 4 (b) of the seminiferous epithelium cycle. Arrows indicate marking with bromodeoxiuridine. Bars: 20 μm.</p

Ultrastructure of the germ cells of the seminiferous epithelium in <i>Desmodus rotundus</i>.

<p>A: type A spermatogonia; PL-L: primary spermatocyte in preleptotene to leptotene; Z: primary spermatocyte in zygotene; P: primary spermatocyte in pachytene; D: primary spermatocyte in diplotene; Rs: round spermatid; Es: elongated spermatid; Tp: tunica propria; Ic: intertubular compartment; M and →: mitochondria; Cb: cytoplasmic bridge; *: Acrosomal cap.</p

Histological cross-sections of seminiferous tubules showing the eight stages of the seminiferous epithelium cycle in <i>Desmodus rotundus</i>, according to the tubular morphology method.

<p>(a) Stage 1; (b) Stage 2; (c) Stage 3; (d) Stage 4; (e) Stage 5; (f) Stage 6; (g) Stage 7; (h) Stage 8. Sc: Sertoli cell; A: type A spermatogonia; I: intermediate spermatogonia; B: type B spermatogonia; PL-L: primary spermatocyte in preleptotene to leptotene; Z: primary spermatocyte in zygotene; P: primary spermatocyte in pachytene; D: primary spermatocyte in diplotene; M: metaphase figure; Rs: round spermatid; Es: elongating/elongated spermatid; Rb: residual bodies; L: lumen of seminiferous tubule; →: myoid cell at tunica propria. Bars: 40 μm.</p

Biometric and morphometric data of testicular components in the bat <i>Desmodus rotundus</i>.

<p>Biometric and morphometric data of testicular components in the bat <i>Desmodus rotundus</i>.</p

Organization of the intertubular compartment in the testis of <i>Desmodus rotundus</i>.

<p>SE: seminiferous epithelium; BV: blood vessel; LS: lymphatic space; Black arrow: Leydig cell nuclei; *: Leydig cell nucleoli; White arrowhead: lipid droplet at Leydig cell cytoplasm. White arrow: mitochondria at Leydig cell cytoplasm. Light microscopy, scale bar 30 μm (a); Transmission electron microscopy, scale bar 2 μm (b).</p

Leydig cell morphometry in the bat <i>Desmodus rotundus</i>.

<p>Leydig cell morphometry in the bat <i>Desmodus rotundus</i>.</p