New data on tardigrades of the genus Milnesium (Tardigrada, Eutardigrada, Milnesiidae) from the Russian Far East, obtained using the method of molecular barkoding

A study of terrestrial tardigrades of the genus Milnesium Doyère, 1840 collected in Russky Island (Primorsky kray, Vladivostok) was carried out using the methods of integrative taxonomy, including the analysis of morphological and molecular biological data. Three species are recorded from this island, of which M. inceptum Morek, Suzuki, Schill, Georgiev, Yankova, Marley et Michalczyk, 2019 is new for the fauna of Russia. New data were obtained on the distribution and genetic diversity of M. tardigradum Doyère, 1840. The third species, Milnesium sp., is similar to M. tardigradum but differs from latter in the presence of a characteristic thickened cuticle zone at the base of the claws of the fourth pair of legs and is probably a new for science species.

Lacking sensory (rather than locomotive) legs affects locomotion but not food detection in the harvestman Holmbergiana weyenberghi

The ability to release a leg when forced by predators or during agonistic interactions is widespread and frequent in arthropods. Despite immediate benefits, losing legs may affect locomotion, sensory performance, reproduction, and fitness. The costs of autospasy in arachnids have been scarcely addressed. Therefore, we tested the hypothesis that the number and type of self-amputated legs (sensory or locomotive) affect locomotion and food detection speeds in the harvestman Holmbergiana weyenberghi (Holmberg, 1876) (Sclerosomatidae). With field surveys in a subtropical forest in Uruguay we found that 35% of individuals lacked at least one leg, and sensory legs (second pair) were the most frequently lost. In an indoor setup, we found that individuals missing one sensory leg walked and climbed a trunk slower than individuals lacking a locomotive leg (first, third, or fourth pair), or compared with those with eight legs. Lacking legs did not affect the food detection speed. Additionally, larger individuals with eight legs had greater walking and climbing speeds. Therefore, losing sensory legs affects locomotion in these harvestmen and may confer costs in orientation, balance, and substrate recognition. Finally, we compared our results with the different patterns reported for the effect of autospacy in other harvestman species.

Ontogeny of the redlichiid trilobite Metaredlichia cylindrica from the lower Cambrian (Stage 3) of South China

A number of immature and mature exoskeletons allow the first detailed description of the ontogeny of the early Cambrian redlichiid trilobite Metaredlichia cylindrica, from black shale of the Shuijingtuo Formation in Hubei Province, South China. The material includes numerous complete protaspides, within which two stages can be differentiated according to the appearance of a shallow furrow that separates the protopygidial area from the protocranidium. Also, identification of the subsequent ontogenetic stages, including meraspides and holaspides, depends on isolated cranidia that display prominent morphological changes such as the contraction of frontal glabellar lobe, appearance of the fourth pair of glabellar furrows, and modification of the facial suture from proparian to opisthoparian. Incorporating the whole ontogenetic sequence allows us not only to trace the developmental trends of various structures with growth, but also to assign the protaspides to their adults correctly, particularly with the help of meraspid specimens.

Effect of Extrinsic Rearfoot Post Design on the Lateral-to-Medial Position and Velocity of the Center of Pressure

Findings from investigations of the effects of external forefoot and rearfoot posts added to foot orthoses have been inconclusive. This study was undertaken to examine the effects of rearfoot post design on the lateral-to-medial position and velocity of the center-of-pressure path. Four identical pairs of neutral-cast polypropylene orthotic shells were constructed; three pairs had a rearfoot post of specified design added. The fourth pair, the control, did not have a post added. Stance period data were broken down into four functional phases, and the statistically significant differences between the experimental conditions were calculated and analyzed. The addition of a rearfoot post to an orthotic shell affects center-of-pressure lateral-to-medial position and velocity. Although the effect of the post designs seemed to provide reasonably predictable changes in center-of-pressure position, the effect on center-of-pressure velocity was variable and inconsistent. The effect of the orthotic post was dependent on design and phase of gait. The addition of a rearfoot post and, specifically, the design of the post can probably be used to alter the center-of-pressure position and velocity. (J Am Podiatr Med Assoc 96(5): 383–392, 2006)

A new species of Temnocephala Blanchard (Platyhelminthes, Temnocephalida) ectosymbiont on Trichodactylus fluviatilis Latreille (Crustacea, Decapoda, Trichodactylidae) from southern Brazil

Temnocephala trapeziformis sp. nov., ectosymbiont on Trichodactylus fluviatilis Latreille, 1828 is described from the State of Rio Grande do Sul, southern Brazil. Sixty-eight crabs were examined, of which 61 (89.7 %) were positive for this species of the genus Temnocephala Blanchard, 1849. Eggs, as well as adult and young specimens, were found on the pleural areas of the carapace, in the orbital cavities, and, usually, on the fourth pair of pereiopods. The temnocephalans were always devoid of body pigmentation, although they kept the red eye pigment, undiluted in specimens fixed by hot (90ºC) phosphate buffered 10% formalin. The most distinctive characters of the new species are: 1) the shape and size of the cirrus and the characteristics of its introvert section; 2) the trapezoidal shape of the dorsolateral post-tentacular 'excretory' epidermal syncytial plates, with the nephridiopore in the lower inner corner of the plate; and 3) the number, size, and distribution of the rhabdite producing glands, as observed in very young specimens.

Three new genera of zerconid mites (Acari, Gamasida: Zerconidae) from the United States of America

Three new monotypic genera in the family Zerconidae (Acari: Gamasida) from the United States are described: Krantzas gen.nov. (type species K. mirificus sp.nov.), Lindquistas gen.nov. (type species. L. amyihetes sp.nov.), and Hypozercon gen.nov. (type species. H. macleani sp.nov.). Krantzas is related to genera characterized by absence both of adgenital shields and a single opening of glands gv2, and is also related to genera characterized by peritremal shields terminating truncately behind the fourth pair of coxae. In this genus the additional lateroventral shield is situated between the peritremal and ventroanal shields. Lindquistas is related to genera characterized by the peritremal shield terminating truncately behind the fourth pair of coxae and by having two short, smooth peritremal setae. Members of this genus are similar to those of Macrozercon Błaszak and Bledas Halašková. Hypozercon is related to genera characterized by having the peritremal shields extended posteriorly and having two unequal setae on the peritremal shield. Members of this genus are similar to those of Mesozercon Błaszak and Neozercon Petrova.

The Role of the ‘Walking Legs’ in Aquatic and Terrestrial Locomotion of the Crayfish Austropotamobius Pallipes (Lereboullet)

1. The hydrodynamic drag acting on the crayfish Austropotamobius pallipes is measured and it is concluded that, in the range of velocities used in walking, the drag is independent of the posture of the limbs and the direction of motion of the body. At swimming velocities the streamlining caused by promotion of the legs reduces the drag losses to half that of a crayfish moving in the forwards walking posture at the same speed. 2. The forwards walking of intact crayfish is compared with that of the same animal after amputation of one or more pairs of legs. It is concluded that the third and fourth pair of legs provide most of the propulsion under water and the second pair is not essential to locomotion under any of the conditions tried.

LINKAGE GROUP IV OF TRIBOLIUM CASTANEUM

A new recessive eye color mutant, hazel, of the flour beetle, Tribolium castaneum, has been mapped in linkage group IV near the white locus, thus establishing the existence of a fourth pair of closely linked eye color genes in this species. A revision of linkage group IV is proposed.