Kaufman M R, Ikeda Y, Patton C, van Dykhuizen G, Epel D
Biol Bull. 1998 Feb;194(1):36-43. doi: 10.2307/1542511.
The accessory nidamental gland (AN gland), a reproductive organ of the mature female squid Loligo opalescens, harbors a dense culture of bacteria of unknown function. A multilayered sheath surrounding the L. opalescens egg case is similarly colonized by bacteria that presumably originate in the AN gland, as evidenced by their presence in the egg case at oviposition. This study investigates how these bacteria are transmitted to juvenile squid and examines some morphological consequences of bacterial colonization of AN gland tissues. By observing the structure of the AN gland in adults and the development and bacterial colonization of the gland in juveniles raised in captivity, we determined that the AN gland was absent in newly hatched squid and did not appear until 87 days post-hatching. At 129 days posthatching, the organ displayed tubules composed of a single layer of epithelial cells and expressing numerous cilia and microvilli. These tubules were not yet fully formed and thus were open to the mantle cavity and external seawater, possibly to aid in the acquisition of microorganisms. Since the AN gland developed a considerable time after hatching, it most likely acquires its symbionts horizontally from environmental seawater and not vertically from the egg case sheath. The switch from expression of cilia to production of microvilli on the epithelial cell surface may dictate the competence of the tissue for bacterial colonization. Electron microscopic examination of juvenile and adult AN glands revealed that an analogous process occurs during the development of the related light organ of other cephalopod species that harbor symbiotic bacteria.
副缠卵腺（AN腺）是成熟雌性太平洋褶柔鱼的生殖器官，其中栖息着大量功能未知的细菌。围绕太平洋褶柔鱼卵鞘的多层鞘同样被细菌定殖，据推测这些细菌起源于AN腺，产卵时它们在卵鞘中的存在就证明了这一点。本研究调查了这些细菌如何传播给幼体鱿鱼，并研究了AN腺组织细菌定殖的一些形态学后果。通过观察成年鱿鱼的AN腺结构以及圈养幼体中该腺体的发育和细菌定殖情况，我们确定新孵化的鱿鱼没有AN腺，直到孵化后87天才出现。孵化后129天，该器官显示出由单层上皮细胞组成的小管，并表达大量纤毛和微绒毛。这些小管尚未完全形成，因此通向外套腔和外部海水，可能有助于获取微生物。由于AN腺在孵化后相当长的时间才发育，它很可能是从环境海水中水平获取共生菌，而不是从卵鞘垂直获取。上皮细胞表面从纤毛表达向微绒毛产生的转变可能决定了该组织对细菌定殖的能力。对幼体和成年AN腺的电子显微镜检查表明，在其他携带共生细菌的头足类动物相关发光器官的发育过程中也会发生类似的过程。
