Contributions to Zoology, 80 (4) 213-230 (2011) Transformational homology of the tergal setae during postembryonic development in the Sinella-Coecobrya group (Collembola: Entomobryidae) Feng Zhang1, 3, Daoyuan Yu1, Guoliang Xu2 1 School of Life Science, Nanjing University, No. 22 Hankou Road, Nanjing 210093, P. R. China 2 Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510160, P. R. China 3 E-mail: [email protected] Key words: primary homology, larval chaetotaxy, primary setae, s-chaetae Abstract to develop and unify descriptive methods, particularly in setal nomenclature, which has been performed using The homology concept and its recognition criteria are intro- an evolutionary perspective (Deharveng, 2004). The duced and discussed, with the importance of transformational arrangement of setae (chaetotaxy) in larvae and (primary) homology assessment in phylogenetic analysis em- phasized. We use an ontogenetic approach to explore the setal adults is widely used in descriptive and phylogenetic transformational homology in polychaetotic entomobryid gen- studies of arthropods, for example in Collembola, as era (Collembola), where tergal chaetotaxy is usually the most well as Lepidoptera, Coleoptera, Acarina et cetera. informative character for taxonomy. The postembryonic devel- (Kitching, 1984; Miller, 1991; Archangelsky, 2004; opment of setae on terga of three species in the Sinella-Coeco- Beutel and Leschen, 2005; Solodovnikov, 2007). brya group, Sinella curviseta, Coecobrya tenebricosa and C. aokii are studied following Szeptycki’s principle. Different However, the problems of chaetotaxic homology of- chaetotaxic patterns of each tergite are homologized and classi- ten affect the reliability of species description and fied for more than 50 species of the two genera. The taxonomi- phylogenetic analysis. cal significance of chaetotaxy of abdomen V, which has been The concept of homology is the fundamental basis rarely studied, is evaluated and affirmed here. The system pre- sented here is a revised and updated from Szeptycki’s system. for comparative and evolutionary biology, as well as phylogenetic systematics. ‘Classical’ homology is a similarity due to historical continuity of information, a Contents feature shared because of descent from a common an- cestral character. Actually, studies employ different Introduction ................................................................................... 213 homology concepts in the light of their different inter- Material and methods .................................................................. 215 ests and goals (Brigandt, 2003). Describing and ex- Results ............................................................................................. 216 plaining the adaptive modification of characters in Postembryonic development of the tergal setae in comparative and evolutionary biology is referred to as S. curviseta, C. tenebricosa and C. aokii .......................... 216 Discussion ...................................................................................... 223 transformational homology. By contrast, taxic homol- Comments on existing systems ............................................ 223 ogies are features that provide evidence of phyloge- Setal homology ....................................................................... 223 netic relationships (taxic homology = synapomorphy) S-chaetotaxy ............................................................................ 224 (Patterson, 1982, 1988; Rieppel, 1994; Sluys, 1996). Chaetotaxy of Abd. IV ........................................................... 224 Recognition of homology involves both the estab- Acknowledgements ...................................................................... 224 References ...................................................................................... 224 lishment of a proposition of homology and the subse- Appendix ........................................................................................ 226 quent affirmation through congruence (Rieppel, 1988), which are evidenced respectively by Remane’s criteria (detailed similarity in position and quality of resem- Introduction blance, see Wiley, 1981), and phylogenetic criteria (con- gruence test). Embryological, ontogenetic and paleon- Taxonomy of Collembola mostly relies on the external tological evidence are the best-known methods used morphology, although limited molecular analyses have for transformational homology assessment, which re- been attempted (D’Haese, 2002; Porco and Deharveng, mains contentious and subjective, yet ultimately cru- 2009). A series of integrated approaches have been used cial in any cladistic analysis (Pimentel and Riggins, Downloaded from Brill.com09/29/2021 07:22:16PM via free access 214 Zhang et al. – Transformational homology in the Sinella-Coecobrya group 1987; Bryant, 1989; Pogue and Mickevich, 1990; De development of Seira dowlingi (Wray, 1953), Soto- Pinna, 1991; Stevens, 1991; Smith, 1994; Pleijel, 1995; Adames (2008) made some corrections on the homol- Hawkins et al., 1997). ogy of partial setae that was originally proposed by Collembolans are epimetabolic and moult through- Szeptycki (1979). Szeptycki’s hypotheses (1979) on out their lives, where a gradual differentiation occurs setal homology were only based on a few representa- during development. Most setae present in adults are tives, not entirely representing the high diversity and secondary (additional), occurring after first instar. The variability of chaetotaxic patterns that exists in ento- recognition of setal transformational homology of mobryid adults. To expand comparisons of homology adults usually depends on empirical diagnosis, which and avoid the wrong identification of transformational often becomes problematic, because it is difficult to homology in phylogeny, it’s necessary to investigate the discriminate homology of morphologically similar setal transformational homology in more taxa using an setae that are near to each other in a small area, and accurate general method. setae whose morphology varies during postembryonic Jordana and Baquero (2005) also proposed a chaeto- development. The improper determination of transfor- taxic system for Entomobrya and its related genera. mational homology will bring severe confusion in the They studied some species of Entomobrya, Entomo- further phylogenetic analysis. An effective method for bryoides, Homidia and Drepanura, but Sinella and determining the setal transformational homologies Coecobrya were not included. Most setal names of no- needs to be applied to Collembola. Ontogenetic obser- menclature were identical to those of Szeptycki, but vation, which is able to strictly trace the transformation justification for the ‘updated’ reason and changes in and the addition of setae during the postembryonic de- setal nomenclature was not explained, not was the velopment and further establish setal transformational prospect for expanding the system to other genera. homology, could be a much better choice than tradition- The two closely related genera, Sinella and Coeco- al empirical diagnosis in adults. This method primarily brya, both having reduced number of ommatidia, records developmental changes, and indicates that the 4-segmented antennae but with scales and dental spines numbering system and homologies are just hypotheses absent, are widespread and well defined among Ento- and subject to different interpretations. mobryid genera (Deharveng, 1990). Sinella-Coe- The chaetotaxy on terga, already described for most cobrya group is the second largest group in unscaled entomobryid genera, is a powerful tool in taxonomy Entomobryinae, with more than 90 species reported. and may contribute to the solution of phylogenetic re- Chen and Christiansen (1993, 1997) reviewed the best lationships among genera of Entomobryidae (Yosii, diagnostic characters for the Sinella-Coecobrya group, 1959; Szeptycki, 1979). Setal transformational homol- designating a series of adult chaetotaxic patterns or ogy plays an important role in phylogenetic analyses, groups, which were widely applied during the past fif- and its validity therefore will directly affect the relia- teen years (Chen and Christiansen, 1997; Ma and bility of results. However, the displacement and trans- Chen, 1997; Wang and Christiansen, 2000; Wang et formation, and the secondary addition of tergal setae al., 2002; Chen et al., 2002, 2005; Qu et al., 2007, during postembryonic development results in difficul- 2010). After the examination of plenty of species ty in establishing setal homology in adults. Szeptycki (many undescribed) from East and Southeast Asia, we (1969) was the first one to observe the postembryonic find that the various patterns defined by Chen and development of Entomobryoides myrmecophila (Reu- Christiansen (1993, 1997) can’t be applied to all cases, ter, 1886) in Entomobryidae. Later, Barra (1975) ob- even the conflicts occurring between the known pat- served the same in Pseudosinella decipiens Denis, terns. Because the developmental processes of tergal 1924 and P. impediens Gisin and Da Gama, 1969. setae are quite similar in Entomobryinae particularly Szeptycki (1972, 1979) also made a fundamental con- within genera (Szeptycki, 1979), we study the postem- tribution to the tergal chaetotaxy in Entomobryoidea, bryonic development of the tergal setae of only three by providing a system of nomenclature