Search

Mandibular reconstruction for large bone defects is performed with consideration of patients' specific morphology and sufficient strength. Metal additive manufacturing techniques have been used to develop biomaterials for mandibular reconstruction. Titanium artificial mandibles with a lattice structure have been proposed, and the optimal conditions for their strength to withstand mechanical stress around the mandible have been reported. This study investigated the biocompatibility of a titanium artificial bone with a lattice structure fabricated under optimal conditions. The samples were fabricated using metal additive manufacturing. Body diagonals with nodes (BDN) were selected as suitable lattice structures. Dode medium (DM) was selected for comparison. The samples were implanted into rabbit tibial defects and resected with the surrounding bone at two and four weeks. Specimens were evaluated radiographically, histologically, and histomorphometrically. Radiopacity in each lattice structure was observed at two and four weeks. Histological evaluation showed trabecular bone-like tissue inside the BDN compared to the DM at four weeks. No significant differences were noted in the bone volume inside the structures. This study demonstrated the in vivo compatibility of artificial metallic bones with a BDN structure under mechanical stress conditions. [ABSTRACT FROM AUTHOR]

Mandibular reconstructive surgery is necessary for large bone defects. Although various reconstruction methods have been performed clinically, there is no mandibular reconstruction method that meets both sufficient strength criteria and the patient's specific morphology. In this study, the material strength of the cylindrical lattice structures formed by electron-beam melting additive manufacturing using titanium alloy powder was investigated for mandibular reconstruction. The virtual strengths of 28 lattice structures were compared using numerical material tests with finite element method software. Subsequently, to compare the material properties of the selected structures from the preliminary tests, compression test, static bending test and fatigue test were conducted. The results showed that there were correlations with relative density and significant differences among the various structures when comparing internal stress with deformation, although there was a possibility of localized stress concentration and non-uniform stress distribution based on the lattice structure characteristics. These results suggest that the lattice structure of body diagonals with nodes and a cell size of 3.0 mm is a potential candidate for metallic artificial mandibles in mandibular reconstruction surgery. [ABSTRACT FROM AUTHOR]

Freshwater crayfishes are among the most successful freshwater animals and are quite important for society economically, ecologically, and culturally. Since crayfishes are almost exclusively restricted to freshwater, their dispersion potential is much lower than that of marine crustaceans. Their biogeographic distribution is thus the result of a still poorly known long and complex evolutionary history. Most of the efforts made to untangle this history have worked from the distribution of extant crayfishes and their phylogenetic relationships, seldom using the fossil record. We here review the state of our current published knowledge on the fossil record of crayfishes, from their fossilized bodies and burrows. We review the Late Triassic Enoploclytia porteri Miller & Ash, 1988 , one of the oldest crayfish body fossils, and show it is most likely a freshwater crayfish and assigned mistakenly to a marine genus. We also discuss burrows from Argentina, suggesting they are actually insect burrows, and burrows and an isolated claw from Libya, which we herein interpret as most likely from brachyuran crabs. We list a total of 65 occurrences or groups of occurrences from across the world and from the Late Devonian to Pleistocene fossils. This long history strengthens the current hypothesis that crayfishes inhabited Pangea and diversified partly via vicariance due to Pangea's breakup during the Mesozoic and into the Cenozoic. Our review also highlights the importance of fossil burrows and body fossils to understand modern faunas and the importance of taxonomic revision of fossil taxa. [ABSTRACT FROM AUTHOR]

The introduction and spread of non-native species pose major threats to biodiversity and ecosystem stability. We conducted a study to assess the spread, growth rate, and interactions of the exotic crayfish Procambarus clarkii (Girard, 1852) throughout South Korea. A total of 343 individuals (223 from reservoirs, 120 from streams) were studied in four provinces. This species has expanded its distribution to 24 regions in South Korea. The length-weight relationship indicated positive allometric growth, expressed as W = 2.855L3.0073. The highest number of adult P. clarkii individuals eradicated was 11,438 in 2022. Using the MaxEnt model and environmental variables related to the climate, a highly accurate forecast was generated for the potential distribution of P. clarkii in South Korea. The factors influencing the current distribution probability were identified as the highest temperature of the warmest month, mean temperature of the wettest quarter, and mean temperature of the warmest quarter, which contributed the most to the present distribution probability. The predicted distribution indicated a rapid increase in P. clarkii density in the southwestern region, extending towards the southeastern and central regions, including the brackish zone. Non-metric multidimensional scaling analysis (stress = 0.07) was conducted based on benthic macroinvertebrates, revealing distinct variations among the four sampling sites. The distribution of benthic macroinvertebrates was significantly influenced by the proportion of sand in the substrate (R = 0.39, P < 0.05) and water quality as estimated by the electrical conductivity (R = 0.51, P < 0.05). [ABSTRACT FROM AUTHOR]

The red swamp crayfish Procambarus clarkii (Girard, 1852) has been responsible for negative impacts on native benthic fauna and flora in invaded freshwater ecosystems around the world, including Japan. We need to clarify the reproductive biology in the invaded habitats as basic information to effectively control the introduced populations, but the reproductive biology of P. clarkii in Japan (especially in western Japan) has not been well studied. We conducted monthly samplings of P. clarkii from November 2015 to November 2016 in a pond (which does not freeze, even in winter) in Okayama, western Japan, both by using shrimp cage traps and by hand nets to examine aspects of the reproduction, including a form alternation (i.e. Form I and II). We also reared spawning females in the laboratory and calculated the accumulated water temperature during the period to Stage-3 juveniles after spawning. The total number of individuals caught throughout the study period was 6,319 (2,601 males and 2,777 females, with eight of unknown sex and 933 juveniles). The males were all Form I with a breeding status from September to November 2016. We first found ovigerous females in July 2016 and females carrying hatchlings in October 2016, even in January 2016. The form alternation in males was confirmed not only in the cheliped length, but in the hook length. In laboratory observations, approximately 52 days with approximately 1,222 °C degree-days of the accumulated water temperature were necessary to Stage-3 juveniles after spawning. Our results indicate that P. clarkii can reproduce within approximately five months of hatching. [ABSTRACT FROM AUTHOR]

Two species of fossil crustaceans from the Czech Republic are assigned to Astacus Fabricius, 1775 , a European crayfish: A. laevissimus Fritsch & Kafka, 1887 and A. cenomanensis Fritsch & Kafka, 1887. Both come from marine sediments, making doubtful their assignment to crayfishes. Specimens assigned to Astacus laevissimus correspond in fact to propodi of etyoid brachyurans. The type material of A. cenomanensis is heterogeneous, comprising fragmentary ctenochelid (Thalassinidea) propodi and isolated cheliped fingers of etyoid crabs. None of the two species belong to crayfishes. Since the studied cheliped material is too fragmentary and poorly preserved to be attributed confidently on species or genus level, A. laevissimus and A. cenomanensis are considered nomina dubia. [ABSTRACT FROM AUTHOR]

Crayfishes are rather rare in the fossil record, limiting our understanding of their evolutionary history. We describe and discuss a fossil crayfish from the Miocene of Slovenia. This fossil, comprising only the cephalothorax, first pereiopod, and another cheliped, seems closely allied to Austropotamobius Skorikov, 1907 , but also bears an epistome and postorbital carina reminiscent of Astacus Fabricius, 1775. For these reasons, it is tentatively assigned to Austropotamobius. It differs from all other Austropotamobius species by the shapes of its epistome cephalic lobe, and postorbital carina, and resemble Austropotamobius torrentium (von Paula Schrank, 1803) most due to its ornamentation. It is therefore described as a new species, Austropotamobius plenicari sp. nov. The new species is associated with brackish water ostracods, most likely reworked from slightly older sediments, suggesting a late Miocene (Messinian) age. The origin of this species and its age show it lived long after the split between Astacus and Austropotamobius , and also probably after the split between the two Austropotamobius species (Au. pallipes and Au. torrentium), and may have been contemporary to, and lived in the area of the diversification of Au. torrentium haplotypes. [ABSTRACT FROM AUTHOR]

The red swamp crayfish Procambarus clarkii (Girard, 1852) is an alien invasive species as well as a commercially exploited animal. The sterile-male-release technique (SMRT) using infertile but sexually active males has been an effective candidate measure to control this invasive crayfish. Additionally, the limited supply of juveniles due to females' spawning seasonality hinders the further development of the P. clarkii aquaculture industry. Information on its reproductive biology, such mating strategies and factors affecting offspring production, is crucial for developing an effective SMRT and aquaculture systems for P. clarkii. We review the reproductive biology of this species in terms of 1) sexual dimorphism and reproductive status, 2) sex recognition, mating, and mate preferences, and 3) egg production, embryonic development, and hatching. Intra- and intersexual dimorphisms of chelae are evident in P. clarkii , and a reproductive morphotype (form I) with larger chelae and a non-reproductive morphotype (form II) with smaller chelae are detected in both females and males, allowing us to easily determine the reproductive status of both sexes. The crayfish exhibits mutual mate choice (i.e. preference for larger mates), and small-sized males reproductive potential is low. Female fitness (i.e. number of offspring) generally depends on their body size. Female brood care appears to promote early embryo development before the egg-nauplius stage. Further study is required to identify the maternal factors affecting early embryonic development, which may improve measures for controlling invasive populations and enhancing aquaculture productivity. [ABSTRACT FROM AUTHOR]