Woollacott Robert M
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138.
J Morphol. 1993 Dec;218(3):301-321. doi: 10.1002/jmor.1052180306.
Early developmental stages of Haliclona tubifera are retained by the parent and larvae are released on illumination of dark-adapted colonies. Larvae are parenchymellae without provision for feeding on particulate matter and without identifiable sensory and neuronal elements. Larvae, however, are strongly photonegative on release and remain so throughout the duration of larval existence. The anterior and lateral epidermal fields are composed predominantly of elongate flagellate cells which form a pseudostratified columnar epithelium. Interspersed among elongate cells are globular flagellate cells which, based on ultrastructural criteria, are thought to be secretory in function. The posterior surface is not flagellated and is composed of a cuboidal epithelium. A 5-7 cells wide ring of epidermal cells with flagella 50 μm in length forms a prominent flagellar band separating the posterior from lateral fields. Measurements of swimming speeds in the horizontal plane indicate that H. tubifera larvae swim at speeds intermediate between Halichondria melanadocia, which have a posterior tuft of 25 μm flagella and Haliclona sp, with a posterior ring 75 μm flagella. Morphometric analysis of larval length, larval diameter, and flagellar band diameter shows significant correlations in all pair-wise tests. Band diameter varies less than larval length or width suggesting that it is a conserved trait. A negative allometry exists between band diameter and larval length. As larval length increases elongate flagellar cells of the lateral and anterior surfaces become relatively more important for locomotion. A prominent cup-like sheath of subepidermal cells separates the epidermis from the central region of the larval interior. These cells are not associated with collagen as are cells similar in appearance and location in several other haplosclerid larvae. Their function remains unknown. Spicules occur in the posterior region. As in the adult, these spicules are hastate oxeas, but they are significantly different in length, width, and length/width from those of the adult. Their function is unknown, but several obvious potential functions in both larval and postlarval life exist and await further study. Archeocytes are the dominant cell type of the central region. Bacteria are found inter- and intracellularly. Based on morphological data, they appear to be of a single type, pleomorphic rods without thick walls, but further study utilizing isolates in culture is needed to establish their diversity and identity. Intracellular bacteria are associated with a cell type provisionally designated a bacteriocyte. Three stages of bacteriocytes are described based on anatomical criteria, presence/absence of bacteria, and what appear to be stages in degradation of bacteria. The significance of this association and of the bacteriocyte cell type remain to be explored. © 1993 Wiley-Liss, Inc.
管栖扁海绵（Haliclona tubifera）的早期发育阶段由亲体保留，在适应黑暗的群体受到光照时释放幼虫。幼虫为实质胚，没有摄取颗粒物质的结构，也没有可识别的感觉和神经元件。然而，幼虫在释放时对光具有强烈的负反应，并且在幼虫期一直保持这种状态。前部和侧面的表皮区域主要由细长的鞭毛细胞组成，形成假复层柱状上皮。在细长细胞之间散布着球形鞭毛细胞，根据超微结构标准，这些细胞被认为具有分泌功能。后部表面没有鞭毛，由立方上皮组成。一圈宽5 - 7个细胞、鞭毛长50μm的表皮细胞形成一条明显的鞭毛带，将后部与侧面区域分开。在水平面内对游泳速度的测量表明，管栖扁海绵幼虫的游泳速度介于具有25μm后束鞭毛的黑扁海绵（Halichondria melanadocia）和具有75μm后环鞭毛的扁海绵属（Haliclona sp）之间。对幼虫长度、幼虫直径和鞭毛带直径的形态测量分析表明，在所有成对测试中都存在显著相关性。鞭毛带直径的变化小于幼虫长度或宽度，这表明它是一个保守的特征。鞭毛带直径与幼虫长度之间存在负异速生长关系。随着幼虫长度增加，侧面和前部表面的细长鞭毛细胞对运动变得相对更为重要。一层突出的杯状表皮下细胞鞘将表皮与幼虫内部的中央区域分隔开。这些细胞不像其他几种单沟型幼虫中外观和位置相似的细胞那样与胶原蛋白相关。它们的功能仍然未知。骨针出现在后部区域。与成体一样，这些骨针是戟状单尖骨针，但它们在长度、宽度和长/宽方面与成体的骨针有显著差异。它们的功能未知，但在幼虫期和幼体后期生活中存在几种明显的潜在功能，有待进一步研究。原细胞是中央区域的主要细胞类型。细胞内和细胞间都发现有细菌。根据形态学数据，它们似乎是单一类型，为无厚壁的多形杆菌，但需要利用培养分离物进行进一步研究以确定它们的多样性和身份。细胞内细菌与一种暂定为细菌细胞的细胞类型相关。根据解剖学标准、细菌的有无以及细菌降解的明显阶段，描述了细菌细胞的三个阶段。这种关联以及细菌细胞类型的意义仍有待探索。© 1993威利 - 利斯公司。
