Cubozoa jellyfish species exhibit either internal or external fertilization, and reproductive behavior involving spermcasting or complex copulatory sexual behavior, but male gonad morphology has not been investigated broadly in cubozoans. In this study, a histological comparison was conducted of the testes of four cubozoan species in two orders: Carybdea marsupialis (Carybdeidae), Morbakka virulenta (Carukiidae), and Tamoya cf. haplonema (Tamoyidae) in Carybdeida and Chiropsalmus quadrumanus (Chiropsalmidae) in Chirodropida. Our results show spermatic follicles present in all species, with spermatogenesis occurring in two layers, the gastrodermis and the gonadal mesoglea. Specimens were either immature males or unspawned males, except in the case of Tamoya cf. haplonema which displayed rupture sites in the wall of the follicles, indicating prior release of sperm. Interspecific comparative histological study revealed that spermatogenesis generally occurs in a polarized manner towards the lumen of the spermatic follicle, with mature spermatozoa in the center awaiting gonadal rupture and release for either internal or external fertilization. Furthermore, we provide a synopsis of the histological findings to date on cubozoan testes, emphasizing incidences of conserved male gonad morphology regardless of mode of fertilization, in addition to separate novelties that have arisen in two internally fertilizing lineages, each exhibiting unique reproductive behavior. Further taxon-sampling of additional species at different development stages may reveal a broader diversity in testes morphology across Cubozoa and serve as a basis for a deeper investigation into the emergence of novel modes of sexual reproduction in non-bilaterian animals.

中文翻译：

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箱形水母（刺胞动物；立方体）睾丸的组织形态学比较：形态是否因繁殖和受精方式而异？

Cubozoa 水母物种表现出内部或外部受精，以及涉及精子铸造或复杂交配性行为的生殖行为，但尚未在 cubozoans 中广泛研究雄性性腺形态。在这项研究中，对四种长绒动物的睾丸进行了组织学比较，分为两个顺序：有袋动物 Carybdea marsupialis (Carybdeidae)、Morbakka virulenta (Carukiidae) 和 Tamoya cf。Carybdeida 中的 haplonema (Tamoyidae) 和 Chirodropida 中的 Chiropsalmus quadrumanus (Chiropsalmidae)。我们的结果显示所有物种中都存在精卵泡，精子发生在两层，即胃真皮和性腺中胶层。标本要么是未成熟的雄性，要么是未产卵的雄性，但 Tamoya 的情况除外。单倍体在毛囊壁显示破裂部位，表示先释放精子。种间比较组织学研究表明，精子发生通常以两极分化的方式发生在精索卵泡的内腔，成熟的精子在中心等待性腺破裂和释放以进行内部或外部受精。此外，我们提供了迄今为止对立方动物睾丸的组织学发现的概要，强调了无论受精模式如何，保守的雄性性腺形态的发生率，以及在两个内部受精谱系中出现的单独新奇，每个谱系都表现出独特的生殖行为。