Journal of Tropical Oceanography >
Distinct structures of gonads and germ cell development of lined seahorse, Hippocampus erectus
Copy editor: LIN Qiang
Received date: 2020-02-02
Request revised date: 2020-03-11
Online published: 2020-03-11
Supported by
the National Key Research and Development Program(2016YFC1403003)
Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)(GML2019ZD0407)
Natural Science Foundation of Guangdong Province(2017A030313249)
Copyright
Seahorses (Genus Hippocampus) have not only peculiar reproductive strategy of male pregnancy but also unique ovarian and testis structures. Developmental characteristics of the ovary and testis as well as the germ cells of the lined seahorse (Hippocampus erectus) were clarified in the present study. Based on the histological structure and morphological features, we described six stages of gonadal development of lined seahorse. Seahorses have an asynchronous ovarian developmental characteristic. The stageⅠovary contained only oogonia and early meiotic oocytes (d<20 μm). In the stage Ⅱ ovary, phase Ⅱ oocytes (d=20-140 μm) began to appear. In the stage Ⅲ ovary, the number and volume of the phase Ⅲ oocytes (d=140-260 μm) were increased remarkably. The vitellogenic oocytes (d=260-1100 μm), in which transitional yolk sphere was accumulated, could be observed in the stage Ⅳ ovary. Phase Ⅴ maturational oocytes (d=1100-2000 μm), which were characterized by highly compact vitelline envelope and fluid yolk mass, were observed in the stage Ⅴ ovary. The ovary shortly after ovulation with decrement of the number of oocytes was stage Ⅵ ovary. The testis of the lined seahorse is of the unrestricted lobular type. Stage Ⅰ testis mainly contained spermatogonia with large nuclear and one or more nucleolus. In the stage Ⅱ testis, the spermatocyst began to appear, inside of which were the primary spermatocytes with smaller nuclear. The secondary spermatocytes were first present in the stage Ⅲ testis. In the stage Ⅳ testis, the volume of testis was increased significantly and the matured spermatids appeared. Large scale of mature spermatozoa was restricted into the testicular lumen and ready to be released in the stage Ⅴ testis. The stage Ⅵ testis was vascularized with few spermatozoa or spermatocytes in the lumen. Further histochemical analysis showed that the amino acid and fat were positive in the cytoplasm and yolk mass of oocytes, and accumulated with the oocytes development. Generally, our results provide basic evidence for further understanding of male pregnancy strategies of seahorses.
Key words: Hippocampus erectus; gonad development; histological structure; ovary; testis
CHEN Lingzhen , QIN Geng , WANG Xin , LIU Yali , XIAO Wanghong , LIN Qiang . Distinct structures of gonads and germ cell development of lined seahorse, Hippocampus erectus[J]. Journal of Tropical Oceanography, 2020 , 39(6) : 93 -102 . DOI: 10.11978/2020014
表1 线纹海马不同生长时期性腺形态学特征Tab. 1 Morphological characteristics of gonads at different development stages of lined seahorse H.erectus |
生长时期/d | 体重/g | 体长/cm | 卵巢 | 精巢 |
---|---|---|---|---|
14 | 0.03±0.01 | 2.20±0.13 | 性腺不可见 | 性腺不可见 |
21 | 0.04±0.01 | 2.59±0.10 | 肉眼可见 | 肉眼不可见 |
30 | 0.15±0.02 | 3.37±0.74 | 肉眼可见 | 肉眼可见 |
40 | 0.33±0.14 | 4.52±0.70 | 性腺细丝状, 透明, 组织切片可辨 | 性腺细丝状, 透明, 组织切片可辨 |
55 | 0.41±0.07 | 5.11±0.41 | 肉粉色, 性腺增粗, 细丝状, 肉眼可辨 | 透明, 性腺增长, 细丝状, 肉眼可辨 |
70 | 0.55±0.08 | 5.55±0.20 | 肉粉色至浅黄色, 性腺带状, 较精巢略短 | 透明, 性腺增长, 带状 |
90 | 2.14±0.73 | 8.36±0.93 | 淡橘色, 性腺增粗, 圆柱状, 较短, 含少量卵黄颗粒 | 乳白色, 性腺增粗增长, 管状, 结缔组织增多 |
120 | 4.42±0.80 | 9.75±1.93 | 橘色, 性腺增大, 蛹状, 卵黄颗粒增多, 但不能分离 | 乳白色, 性腺进一步增长、增粗, 管状, 结缔组织增厚 |
150 | 5.08±1.74 | 10.01±0.77 | 深橘色, 性腺体积进一步增大, 蛹状, 卵黄颗粒增多, 饱满 | 乳白色, 性腺依然在增粗、增长, 长管状, 结缔组织增厚, 肉眼可见血管 |
180 | 9.67±1.28 | 13.58±0.65 | 橘红色, 性腺体积进一步增大, 蛹状, 卵粒饱满, 卵子可从卵巢中挤出 | 乳白色, 性腺圆管状, 较粗, 精液可从精巢中挤出, 肉眼可见血管 |
250 | 10.30±0.19 | 13.80±0.22 | 深橘红色, 性腺体积变小, 松弛, 含皱缩空泡, 含卵黄颗粒, 但不能分离 | 乳白色, 性腺圆管状, 较粗, 肉眼可见血管 |
图1 线纹海马不同发育时期卵巢的组织学结构CA: 皮质小泡; DF: 退化的滤泡细胞; FC: 滤泡细胞; FM: 滤泡膜; L: 脂滴; N: 细胞核; NU: 核仁; O: 卵原细胞; PO: 初级卵母细胞; VO: 含卵黄颗粒卵母细胞; YM: 卵黄囊; YS: 卵黄球. Fig. 1 Histological structures of different stages of H. erectus ovaries. CA: cortical alveoli; DF: degenerated follicle cell; FC: follicle cell; FM: follicle membrane; L: lipid droplet; N: nuclear; Nu: nucleolus; O: oogonia; PO: primary oocyte; VO: vitellogenic oocyte; YM : yolk mass; YS: yolk sphere. |
图2 线纹海马不同发育时相卵母细胞的组织学及组织化学特征a—e: HE染色; f—j: 氨基酸染色; k—o: 脂肪染色; BL: 基膜; CA: 皮质小泡; FC: 滤泡细胞; L: 脂滴; N: 细胞核; Nu: 核仁; O: 卵原细胞; VE; 卵黄膜; YM: 卵黄囊; 小三角形代表氨基酸和脂肪阳性信号 Fig. 2 Histological and biochemical analysis of different stages of oocytes in H. erectus. (a-e) hematoxylin and eosin staining; (f-j) staining of amino acid; (k-o) staining of fat. BL: basal lamina; CA: cortical alveoli; FC: follicle cell; L: lipid droplet; N: nuclear; Nu: nucleolus; O: oogonia; VE: vitellogenic envelope; YM: yolk mass. Small triangles represent signals of amino acid and fat |
图3 线纹海马不同发育时期精巢的组织学结构GE: 生殖上皮; L: 精腔; MF: 肌肉纤维; PSC: 初级精母细胞; SC: 支持细胞; SG: 精原细胞; SSC: 次级精母细胞; ST: 精子细胞; SZ: 精子; W: 精巢膜 Fig. 3 Histological structures of different stages of H.erectus testis. GE: germinal epithelium; L: lumen; MF: muscle fibres; PSC: primary spermatocyte; SC: sertoli cell; SG: spermatogonia; SSC: secondary spermatocyte; ST: spermatid; SZ: spermatozoa; W: wall |
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