Chemical Ecology of Cave-Dwelling Millipedes: Defensive Secretions of the Typhloiulini (Diplopoda, Julida, Julidae).

Cave animals live under highly constant ecological conditions and in permanent darkness, and many evolutionary adaptations of cave-dwellers have been triggered by their specific environment. A similar "cave effect" leading to pronounced chemical interactions under such conditions may be assumed, but the chemoecology of troglobionts is mostly unknown. We investigated the defensive chemistry of a largely cave-dwelling julid group, the controversial tribe "Typhloiulini", and we included some cave-dwelling and some endogean representatives. While chemical defense in juliform diplopods is known to be highly uniform, and mainly based on methyl- and methoxy-substituted benzoquinones, the defensive secretions of typhloiulines contained ethyl-benzoquinones and related compounds. Interestingly, ethyl-benzoquinones were found in some, but not all cave-dwelling typhloiulines, and some non-cave dwellers also contained these compounds. On the other hand, ethyl-benzoquinones were not detected in troglobiont nor in endogean typhloiuline outgroups. In order to explain the taxonomic pattern of ethyl-benzoquinone occurrence, and to unravel whether a cave-effect triggered ethyl-benzoquinone evolution, we classed the "Typhloiulini" investigated here within a phylogenetic framework of julid taxa, and traced the evolutionary history of ethyl-benzoquinones in typhloiulines in relation to cave-dwelling. The results indicated a cave-independent evolution of ethyl-substituted benzoquinones, indicating the absence of a "cave effect" on the secretions of troglobiont Typhloiulini. Ethyl-benzoquinones probably evolved early in an epi- or endogean ancestor of a clade including several, but not all Typhloiulus (basically comprising a taxonomic entity known as "Typhloiulus sensu stricto") and Serboiulus. Ethyl-benzoquinones are proposed as novel and valuable chemical characters for julid systematics.

Harvestmen (Arachnida: Opiliones) in Eocene Rovno amber (Ukraine).

Six species of harvestman (Arachnida: Opiliones) are documented from the Eocene Rovno amber in Ukraine. From the suborder Eupnoi we record Caddo dentipalpus (C. L. Koch Berendt, 1854) (Caddidae), Amilenus deltshevi Dunlop Mitov, 2009 (Phalangiidae) and Dicranopalpus ramiger (C. L. Koch Berendt, 1854) (family incertae sedis). To these we add a new phalangiid, Metaphalangium martensi sp. n., which is the oldest representative of the Recent genus Metaphalangium Roewer, 1911 and new genus for the amber fauna. From Dyspnoi we record Sabacon claviger (Menge, 1854) (Sabaconidae) and propose Parahistricostoma gen. n. (Nemastomatidae), to accommodate Nemastoma tuberculatum C. L. Koch Berendt, 1854, yielding Parahistricostoma tuberculatum (C. L. Koch Berendt, 1854) comb. n. The Rovno harvestman fauna is briefly compared to both Baltic and Bitterfeld amber. The fossil species, C. dentipalpus, A. deltshevi, D. ramiger and P. tuberculatum occur in all three ambers, and S. claviger is found in Baltic and Rovno amber. The only genus and species unique to Rovno amber is thus our new taxon M. martensi. The composition of the Rovno opilionid fauna is discussed in the context of late Eocene palaeoenvironment and ecological preferences and the fossils are compared to the distribution of extant harvestman taxa. The oribatid mite Platyliodes ensigerus Sellnick, 1919 (Acari: Neoliodidae) is reported from Rovno amber for the first time.

Hysteretic pinching of human secondary osteons subjected to torsion.

The mechanical behavior of bone tissue's ultra- and micro- structure is fundamental to assessment of macroscopic bone mechanics. This paper explores the ultra-structural characteristics of human femoral tissue responsible for energy absorption of secondary osteons under mechanical loading. A novel mathematical interpretation of single osteon mechanics elucidates the behavior of the collagen-apatite interface. Fully calcified single osteon specimens were mechanically tested quasi-statically under cyclic torsional loading about their longitudinal axis. On each hysteretic diagram, all cycles after the initial monotonic cycle appear pinched and share two points. Stiffness degradation and pinching degradation were investigated on the torque versus deflection-angle-per-unit-length diagrams as the number of cycles increases, in relation to the appearance of osteons in cross-section under circularly polarized light microscopy. Material science's Bauschinger effect, originally defined for metals and later extended to structures reinforced with metal bars, is adapted to describe pinching. Material science's prying effect, defined as amplification of eccentric tensile load through lever action, is employed to explain pinching. The presence of the two points shared by all complete cycles is analyzed in terms of the mathematical fixed point theorem. The results allow formulation of the following conjectures: (1) the prying of carbonated apatite crystallites at the interface with the 40 nm long bands of non-calcified collagen fibrils causes pinching; (2) the prying effect increases with the increasing percentage of collagen-apatite elements that form a larger angle with the osteon axis; and (3) micro-cracks increase more in number than in length as the number of cycles increases.