Thorne B L
Department of Biology, Northeastern University, Boston, Massachusetts 02115.
Proc Biol Sci. 1990 Jul 23;241(1300):37-41. doi: 10.1098/rspb.1990.0062.
Living species of the cockroach family Cryptocercidae have intestinal symbionts that are congeneric with some of the gut protozoa found in Isoptera. Presence of such closely related symbionts in cryptocercids and in termites has been frequently interpreted as a uniquely derived homologous character shared between the two xylophagous groups. This may not be the most parsimonious interpretation. Cryptocercus nymphs placed into Zootermopsis (dampwood termite) colonies were killed and eaten by the termites. Termites placed into a Cryptocercus nest box were also fully consumed. Modern Cryptocercus punctulatus and Zootermopsis are often found in the same decaying logs in the Pacific Northwest of the U.S.A., and it is likely that their ancestors also cohabited in at least a portion of their ranges. By occasionally killing and consuming an intruder from the other group, gut protozoa could have been acquired and exchanged between termites and Cryptocercus or their ancestors, under natural conditions and before the life histories of the protozoa became specialized within the host orders. Implications for assessing the phylogeny of the two dictyopteroid groups are also discussed.
隐尾蠊科的现存物种具有肠道共生体，这些共生体与等翅目昆虫体内发现的一些肠道原生动物同属。在隐尾蠊和白蚁中存在如此密切相关的共生体，这一现象常被解释为这两个食木类群共有的一种独特衍生同源特征。但这可能并非最简洁的解释。放入动白蚁属（湿木白蚁）蚁群中的隐尾蠊若虫会被白蚁杀死并吃掉。放入隐尾蠊巢箱中的白蚁也会被全部吃光。现代的点刻隐尾蠊和动白蚁属昆虫在美国太平洋西北部的同一腐朽原木中常常被发现，而且它们的祖先很可能在至少部分分布范围内也是共同生活的。在自然条件下，以及在原生动物的生活史在宿主目内变得特化之前，通过偶尔杀死并吃掉来自另一类群的入侵者，肠道原生动物可能在白蚁和隐尾蠊或它们的祖先之间被获取并交换。本文还讨论了对评估这两个蜚蠊类群系统发育的影响。
