Tamm Sidney L
Department of Biology, Boston University, Boston, Massachusetts, USA.
J Morphol. 2012 Sep;273(9):1050-63. doi: 10.1002/jmor.20043. Epub 2012 Jun 22.
The development of comb rows in larval and adult Mnemiopsis leidyi and adult Pleurobrachia pileus is compared to regeneration of comb plates in these ctenophores. Late gastrula embryos and recently hatched cydippid larvae of Mnemiopsis have five comb plates in subsagittal rows and six comb plates in subtentacular rows. Subsagittal rows develop a new (sixth) comb plate and both types of rows add plates at similar rates until larvae reach the transition to the lobate form at ∼5 mm size. New plate formation then accelerates in subsagittal rows that later extend on the growing oral lobes to become twice the length of subtentacular rows. Interplate ciliated grooves (ICGs) develop in an aboral-oral direction along comb rows, but ICG formation itself proceeds from oral to aboral between plates. New comb plates in Mnemiopsis larvae are added at both aboral and oral ends of rows. At aboral ends, new plates arise as during regeneration: local widening of a ciliated groove followed by formation of a short split plate that grows longer and wider and joins into a common plate. At oral ends, new plates arise as a single tuft of cilia before an ICG appears. Adult Mnemiopsis continue to make new plates at both ends of rows. The frequency of new aboral plate formation varies in the eight rows of an animal and seems unrelated to body size. In Pleurobrachia that lack ICGs, new comb plates at aboral ends arise between the first and second plates as a single small nonsplit plate, located either on the row midline or off-axis toward the subtentacular plane. As the new (now second) plate grows larger, its distance from the first and third plates increases. Size of the new second plate varies within the eight rows of the same animal, indicating asynchronous formation of plates as in Mnemiopsis. New oral plates arise as in Mnemiopsis. The different modes of comb plate formation in Mnemiopsis versus Pleurobrachia are accounted for by differences in mesogleal firmness and mechanisms of ciliary coordination. In both cases, the body of a growing ctenophore is supplied with additional comb plates centripetally from opposite ends of the comb rows.
将幼虫和成虫期的海月水母（Mnemiopsis leidyi）以及成虫期的海胡桃（Pleurobrachia pileus）栉板的发育过程与这些栉水母中栉板的再生过程进行了比较。海月水母的晚期原肠胚和刚孵化的碟状幼虫在亚矢状排有5个栉板，在触手间排有6个栉板。亚矢状排会发育出一个新的（第六个）栉板，两种排的栉板以相似的速率增加，直到幼虫长到约5毫米大小并过渡到叶状形态。然后，亚矢状排的新板形成加速，这些栉板随后在不断生长的口叶上延伸，长度变为触手间排的两倍。板间纤毛沟（ICG）沿着栉板排从反口向口的方向发育，但ICG的形成本身是从板间的口向反口进行的。海月水母幼虫的新栉板在排的反口端和口端都有添加。在反口端，新板的产生方式与再生过程相同：纤毛沟局部变宽，随后形成一个短的裂板，该裂板逐渐变长变宽并合并成一个共同的板。在口端，新板在ICG出现之前以单个纤毛簇的形式出现。成年海月水母在排的两端继续形成新板。动物的八排中反口端新板形成的频率各不相同，且似乎与体型无关。在没有ICG的海胡桃中，反口端的新栉板在第一和第二板之间以单个小的未分裂板的形式出现，位于排的中线或偏向触手间平面的轴外位置。随着新的（现在的第二个）板变大，它与第一和第三个板之间的距离增加。同一动物的八排中，新的第二个板的大小各不相同，这表明与海月水母一样，板的形成是异步的。新的口板的产生方式与海月水母相同。海月水母和海胡桃栉板形成的不同模式是由中胶层硬度和纤毛协调机制的差异所导致的。在这两种情况下，不断生长的栉水母的身体从栉板排的相对两端向心式地获得额外的栉板。
