Zoological Institute and Museum, Department of Cytology and Evolutionary Biology, University of Greifswald, Soldmannstr, 23, 17487, Greifswald, Germany.
Front Zool. 2012 Nov 14;9(1):31. doi: 10.1186/1742-9994-9-31.
We describe the tagmatization pattern of the anterior region of the extant stomatopod Erugosquilla massavensis. For documentation we used the autofluorescence capacities of the specimens, resulting in a significant contrast between sclerotized and membranous areas.
The anterior body region of E. massavensis can be grouped into three tagmata. Tagma I, the sensorial unit, comprises the segments of the eyes, antennules and antennae. This unit is set-off anteriorly from the posterior head region. Ventrally this unit surrounds a large medial sclerite, interpreted as the anterior part of the hypostome. Dorsally the antennular and antennal segments each bear a well-developed tergite. The dorsal shield is part of tagma II, most of the ventral part of which is occupied in the midline by the large, partly sclerotized posterior part of a complex combining hypostome and labrum. Tagma II includes three more segments behind the labrum, the mandibular, maxillulary and maxillary segments. Tagma III includes the maxillipedal segments, bearing five pairs of sub-chelate appendages. The dorsal sclerite of the first of these tagma-III segments, the segment of the first maxillipeds, is not included in the shield, so this segment is not part of tagma II as generally thought. The second and third segments of tagma III form a unit dorsally and ventrally. The tergites of the segments of tagma III become progressively larger from the anterior to the posterior, possibly resulting from a paedomorphic effect during evolution, which caused this reversed enlargement.
The described pattern of tagmosis differs from current textbook knowledge. Therefore, our re-description of the anterior body area of stomatopods is of considerable impact for understanding the head evolution of Stomatopoda. Likewise, it has a bearing upon any comparisons with fossil stomatopods, as mainly sclerotized areas are fossilized, and, on a wider scale, upon larger-scale comparisons with other malacostracans and eucrustaceans in general.
我们描述了现存的口足目动物 Erugosquilla massavensis 前区的体节模式。为了记录，我们使用了标本的自发荧光能力，使得硬骨和膜质区域之间形成了显著的对比。
E. massavensis 的前体区可分为三个体节。体节 I 是感觉单元，由眼节、触角和触角的节组成。这个单元从前头部区域向前突出。腹面，这个单元包围着一个大的中央硬骨片，被解释为口前板的前部。背面，触角和触角节各自带有一个发育良好的背板。背甲是体节 II 的一部分，其大部分腹面中线被复杂的口前板和上唇的大的部分硬化的后部占据。体节 II 后面还有三个节，分别是上唇节、颚足节和颚节。体节 III 包括五对亚螯肢的步足节。这些步足节的第一节，即第一对颚足的节，其背甲不包括在背甲中，因此，这个节不是通常认为的体节 II 的一部分。体节 III 的第二和第三节在背面和腹面形成一个单元。体节 III 的节的背板从前端到后端逐渐变大，可能是进化过程中幼态持续的结果，导致了这种反向放大。
所描述的体节模式与当前教科书上的知识不同。因此，我们对口足目前体区的重新描述对口足目头部进化的理解具有重要影响。同样，它对与化石口足目动物的任何比较都有影响，因为主要是硬骨化的区域被化石化，更广泛地说，对与其他软甲类和真软甲类的更大规模比较都有影响。
