Tomocerus nabanensis, Yu, Yang and Liu, 2018

Yu, Daoyuan, Zhang, Yating, Wang, Ziqiang, Hu, Feng & Liu, Manqiang, 2024, Unravelling the obscure homology: postembryonic development of chaetotaxic traits in a basal hexapod taxon (Collembola: Tomoceridae), Zoological Journal of the Linnean Society 202 (3), pp. 1-20 : 9-12

Tomocerus nabanensis

Specimens examined. 17BN1TJ (1–8), vii.2017, leg. Shengjie Liu.

Head: First instar ( Fig. 5A ). The pattern is identical to that of T. tropicus .

Second instar ( Fig. 5B ). The chaetal transformation is identical to that of T. tropicus . The neochaetosis is also similar, with the exception that the secondary chaeta An1a appears instead of An1a0 and A2a0.

Third instar ( Fig. 5C ). Macrochaetae Pm1, Pp1, and Pe2 become mesochaetae. Pp3 becomes distinctly smaller. Secondary chaetae An1p, An3a2, An3i, A2a0, and Pe3i appear.

Fourth instar ( Fig. 5D ). Pm1, Pp1, Pp3, and Pe2 become microchaetae. Additional micro- and mesochaetae appear only in row An and along the postoccipital collar.

Adult macrochaetotaxy ( Fig. 10B ). The pattern is very similar to that of T. tropicus , but Pp3 is a microchaeta.

Th. II: First instar ( Fig. 6A ). The patterns of ordinary chaetae, s-microchaetae, and pseudopores are identical to that of T. tropicus . About 10–13 normal s-chaetae are present.

Second instar ( Fig. 6B ). Primary chaetae m1, m2, and p3 become macrochaetae; m6 becomes a bothriotrichum; ap5 becomes a mesochaeta; m4, am5, and p1 become microchaetae. Chaetal movement and neochaetosis of macro- and mesochaetae are similar to those of T. tropicus , but a4 is devoid of associated secondary chaetae at this stage. About 10 microchaetae appear in a scattered manner. The number of s-chaetae remains unchanged.

Third instar ( Fig. 7A ). The changes are very similar to those in T. tropicus , except that about five additional microchaetae appear.

Fourth instar ( Fig. 7B ). The changes are very similar to those in T. tropicus , including the transformation of a6 into a bothriotrichum.

Adult macrochaetotaxy ( Fig. 11B ). Collar and aa’ series of macrochaetae are well developed. Chaetae a2–5, m1–3, and p2–4 are macrochaetae; a6 and m6 are bothriotricha.

Th. III, Abd. I, and II: The first instar ( Fig. 6A ), postembryonic development ( Figs 6B , 7 ), and adult macrochaetotaxy are almost identical to those of T. tropicus , except for minor differences in the transformation and addition of microchaetae.

Abd. III: First instar ( Fig. 6A ). The pattern is almost identical to that of T. tropicus , with minor difference in some chaetal positions.

Postembryonic development ( Figs 6B , 7 ). The changes are very similar to those in T. tropicus , except that the transformation of p6 and addition of microchaetae occur later.

Adult macrochaetotaxy. The pattern is identical to that of T. tropicus .

Abd. IV: First instar ( Fig. 6A ). The patterns of ordinary chaetae, bothriotricha, and pseudopores are identical to those of T. tropicus . A total of 21–25 normal and 12–13 long s-chaetae are present. The five most posterior long s-chaetae are the longest (subequal to the length of Abd. V), and are each associated with a mesochaeta in row p (p1–5). The other long s-chaetae are subequal in length.

Postembryonic development ( Figs 6B , 7 ). The changes are very similar to those in T. tropicus , except for minor and apparently random differences in microchaetae and lateral mesochaetae.

Adult macrochaetotaxy. The pattern is identical to that of T. tropicus .

Abd. V: First instar ( Fig. 6A ). The pattern of ordinary chaetae is almost identical to that of T. tropicus , except that in one case p4 is absent. Six normal s-chaetae are present, with two in front of row a, two between row a and m, one posterior to p6, and one beside el. Occasionally, the s-chaeta posterior to a3 is absent and an extra s-chaeta is present posterior to p6.

Postembryonic development ( Figs 6B , 7 ). The changes are almost identical to those in T. tropicus , except that some mesochaetae become microchaetae in different instars.

Adult macrochaetotaxy. The pattern is identical to that of T. tropicus .

Abd. VI: The chaetotaxy at the first two instars ( Fig. 6 ) is identical to that of T. tropicus .

Status in the later instars and adult is not observed.

S-chaetotaxy from Th. II to Abd. V

Normal s-chaetae: 10–13/6/5/5/5/21–25 * 12–13 (long)/6

S-microchaetae: 1/1/0/0/1/0/0.

Figures

Figure 5. Cephalic chaetotaxy of Tomocerus nabanensis. A, First instar; (B) second instar; (C) third instar; (D) fourth instar.

Figure 6. ºergal chaetotaxy of Tomocerus nabanensis. A, First instar; (B) second instar.

Figure 7. ºergal chaetotaxy of Tomocerus nabanensis. A, Ŋird instar; (B) fourth instar.

Figure 10. Cephalic chaetotaxy of the adults. A, Tomocerus tropicus; (B) Tomocerus nabanensis; (C) Tomocerus nan.

Figure 11. ºergal macrochaetotaxy of the adults. A, Tomocerus tropicus; (B) Tomocerus nabanensis; (C) Tomocerus nan. Only Ŋ. II is shown for T.nabanensis and T.nan since other segments are identical to those of T. tropicus.