BackgroundHere we provide the most comprehensive study to date on the cranial ossification sequence in Lipotyphla, the group which includes shrews, moles and hedgehogs. This unique group, which encapsulates diverse ecological modes, such as terrestrial, subterranean, and aquatic lifestyles, is used to examine the evolutionary lability of cranial osteogenesis and to investigate the modularity of development.ResultsAn acceleration of developmental timing of the vomeronasal complex has occurred in the common ancestor of moles. However, ossification of the nasal bone has shifted late in the more terrestrial shrew mole. Among the lipotyphlans, sequence heterochrony shows no significant association with modules derived from developmental origins (that is, neural crest cells vs. mesoderm derived parts) or with those derived from ossification modes (that is, dermal vs. endochondral ossification).ConclusionsThe drastic acceleration of vomeronasal development in moles is most likely coupled with the increased importance of the rostrum for digging and its use as a specialized tactile surface, both fossorial adaptations. The late development of the nasal in shrew moles, a condition also displayed by hedgehogs and shrews, is suggested to be the result of an ecological reversal to terrestrial lifestyle and reduced functional importance of the rostrum. As an overall pattern in lipotyphlans, our results reject the hypothesis that ossification sequence heterochrony occurs in modular fashion when considering the developmental patterns of the skull. We suggest that shifts in the cranial ossification sequence are not evolutionarily constrained by developmental origins or mode of ossification.

The phylogenetic relationships of major groups within the Order Eulipotyphla was once highly disputed, but the advent of molecular studies has greatly improved our understanding about the diversification history of talpids, soricids, erinaceids, and solenodontids. Their resolved phylogenetic relationships now allow us to revisit the turbinal and lamina evolution of this group. The inner structure of the nasal cavity of mammals is highly complicated and the homologies of the turbinals among mammalian species are still largely unsettled. In this regard, investigation on fetal anatomy and ontogenetic changes of the nasal capsule allows us to evaluate the homologies of the turbinals and laminae. We observed various fetuses and adults of talpids and soricids using high-resolution diffusible iodine-based contrast-enhanced computed tomography (diceCT) and reviewed previous reports on erinaceids, solenodontids, and other laurasiatherians. Although the turbinal and lamina morphology was previsouly considered to be similar among eulipotyphlans, we found phylogenetic patterns for talpids and soricids. The nasoturbinal of the common ancestor of talpids and soricids was most likely rostrocaudally elongated. The epiturbinal at the ethmoturbinal II disappeared in soricids independently. Finally, we propose two possible scenarios for the maxilloturbinal development: 1) the maxilloturbinal of talpids and soricids became small independently with a limited number of lamellae as a result of convergent evolution, or 2) the common ancestor of talpids and soricids already had a small and simple maxilloturbinal.

The additive effect of lithium tetrahydrofurfuryloxide (LiTHF) and alkyl lithium on the nucleophilic substitution reaction of anionic living polyisoprene with 4-bromobutoxy-tert-butyldimethylsilane (BBS) in heptane was investigated. When BBS was allowed to react with polyisoprenyllithium in heptane in the absence of any additives, considerable amount of dimeric polymers as well as aimed end-functionalized polymer were formed via lithium-halogen exchange followed by the homo coupling of the polymers. Degree of the dimer formation was dramatically suppressed when the reaction was carried out in the presence of LiTHF. Quantitative introduction of silyl-protected hydroxy group was achieved when the reaction was carried out in heptane at 0°C in the presence of LiTHF (5 eq to active chain end). Similar additive effect was observed for n-butyllithium whereas no such an effect was observed for sec-butyllithium. The cross-association of these lithium compounds with the active chain end of anionic living polyisoprene might have prevented the homo coupling of the polymers.