关键词: 半叶马尾藻中国变种, 有性生殖, 生长, 形态特征

Abstract:

Sargassum hemiphyllum var. chinense J. Agardh is an economic seaweed widely distributed along the coast of the South China Sea. To investigate the sexual reproductive characteristics and the feasibility of artificial seedling propagation of this brown macroalga, this study employed optical microscopy to examine the morphological features of the thallus, male and female receptacles, and the early developmental stages of fertilized eggs in S. hemiphyllum var. chinense from Naozhou Island. The results revealed that the mature thallus of this Chinese variant exhibited a yellow-brown hue with a height of 0.8 to 1 m. It exhibited dioecious traits and possessed discoid holdfasts composed of repetitive bifurcations. The female receptacles were yellow-brown and cylindrical, adorned with numerous surface spines, measuring (0.46 ± 0.05) mm in diameter and (2.50 ± 0.67) mm in length. Conversely, the male receptacles were lighter in color, adopting a rod-like morphology, with a diameter of (1.01 ± 0.18) mm and a length of (9.21 ± 2.36) mm. Eggs released from the female structures exhibited an eight-nucleate one-egg configuration, either ellipsoidal or oval, with an outside diameter of (76.32 ± 10.11) μm. Following ovulation, these eggs adhered to the female structures awaiting fertilization. Sperms released from the male structures were pear-shaped, measuring (27.52 ± 5.43) μm in length and equipped with flagella. At the post-fertilization stage, the majority of fertilized eggs detached from the receptacles, affixing to substrates and undergoing early developmental processes. Within six hours, these fertilized eggs underwent their initial transverse division, subsequently progressing through multiple transverse and longitudinal divisions, and ultimately culminating in the development of landmine-shaped sporophytes within 24 hours, with primary fronds emerging after 28 days. Additionally, this study investigated the indoor use of suitable artificial substrates for the germination of sporophytes and the effect of temperature on the S. hemiphyllum var. chinense growth. Results indicated that, after seven days of culture, the mesh curtain yielded a germination rate of (7.25 ± 3.64) sporophytes per cm², measuring (1.38 ± 0.35) mm in sporophytes’ length. Additional indoor suspension culture experiments revealed a 90% survival rate of sporophytes at the optimal temperature of 25℃, with a thallus growth rate of 90.1 μm·d⁻¹, significantly outperforming other temperatures. These findings provide valuable preliminary data on which to base further studies of the early development and large-scale artificial seedling propagation of S. hemiphyllum var. chinense, thereby facilitating the rapid establishment of natural Sargassum habitats in coastal regions and contributing to the swift rehabilitation of China’s nearshore marine ecosystems.

Key words: Sargassum hemiphyllum var.chinense J. Agardh, sexual reproduction, growth, morphological characteristics