Neoichnology of two spirobolid millipedes: improving the understanding of the burrows of soil detritivores

Abstract

In order to improve the recognition of millipede burrows and, therefore, the presence of millipede macrodetritivores in the fossil record, this study describes the burrowing behavior and resulting burrow morphologies of two species of spirobolid millipedes: Narceus americanus and Floridobolus penneri. Millipedes were placed in terraria filled with sediment of varied compositions and controlled moisture contents for 7-94 days. Open burrows were cast with plaster, excavated, and described both qualitatively and quantitatively. Both N. americanus and F. penneri produced vertical, subvertical, helical, and O-shaped burrows. Floridobolus penneri also produced J-shaped burrows. Burrow morphologies of both species were found to be similar and unaffected by sediment properties using the Bray Curtis similarity and Spearman's rank correlation tests, respectively. Burrows of two other millipede species of the Order Spirostreptida, Orthoporus ornatus, and Archispirostreptus gigas, produced in a previous study were also compared to the spirobolid burrows. While burrows of O. ornatus were similar, burrows produced by A. gigas, the largest of the four species, were the least similar even after removing size-dependent burrow properties from the analysis. Differences and similarities in burrow morphology were instead attributed to the behavioral function of the burrow: refuge or feeding. Despite some differences, all millipede burrow shafts and tunnels had a mean width-to-height ratio of 1.0-1.14. These results show that juliform millipedes produce burrows with unique morphologies that may be used to differentiate their burrows from those produced by other soil organisms.

Neoichnology of the burrowing spiders Gorgyrella inermis (Mygalomorphae: Idiopidae) and Hogna lenta(Araneomorphae: Lycosidae)

“…Two burrows with a rank of 1.0 were considered identical, ranks between 0.9 and 0.6 express high to moderate similarity, and ranks ≤ 0.5 are dissimilar 6 (cf. Hembree et al, 2012;Hembree, 2013;Bowen and Hembree, 2014;Catena and Hembree, 2014;Dzenowski and Hembree, 2014;Hembree, 2014).…”

“…It was expected that arachnid burrows would be similar as all five species share the same basic arachnid body plan. The burrows of the American giant millipede (Figure 4.4), Narceus americanus (n = 15) (Diplopoda: Spirobolida) (Bowen and Hembree, 2014), were used to determine the similarity of the spider burrows with unrelated arthropods. It was expected that the spider burrows would not be similar to the millipede burrows because the body plans and life habits of millipedes are very different than those of arachnids.…”

“…Cluster E shares only depth in common with the other clusters (Table 9.4). The similar- (Bowen and Hembree, 2014) (Appendix 13). The burrows of Narceus americanus differ from the spider burrows in seven properties (Table 6.5).…”

“…Terrestrial arthropods contribute to soil formation by burrowing through and manipulating sediment as they make shelter, find food, and create places for reproduction (Smith and Hasiotis, 2008;Counts and Hasiotis, 2009;Hembree, 2009;Halfen and Hasiotis, 2010;Melchor et al, 2010;Fairchild and Hasiotis, 2011;Getty et al, 2013;Mikuś and Uchman, 2013;Hembree, 2013;Bowen and Hembree, 2014;Hembree, 2014). Ratcliffe and Fagerstrom (1980) provided some examples of the types of continental biogenic structures produced by several extant soil arthropods and the purposes of these structures.…”

Neoichnology of tarantulas (Araneae: Theraphosidae): Criteria for recognizing spider burrows in the fossil recor

“…Similarity is ranked from 0.0 (completely dissimilar) to 1.0 (identical). Two burrows with a rank of 1.0 were considered identical, ranks between 0.9 and 0.6 express high to moderate similarity, and ranks ≤ 0.5 are dissimilar (c.f., Hembree et al, 2012;Hembree, 2013Hembree, , 2014Catena and Hembree, 2014;Dzenowski and Hembree, 2014;Bowen and Hembree, 2014). Bray Curtis similarity scores were used to construct dendrograms of similarity.…”