Males armed with big weapons win fights at limited cost in ant-mimicking jumping spiders.

A core assumption of sexual selection theory is that sexually selected weapons, specialized morphological structures used directly in male contests, can improve an individual's reproductive success but only if the bearer can overcome associated costs, the negative effects on the bearer's fitness components. However, recent studies have shown that producing and wielding exaggerated weapons may not necessarily be costly. Rather, some traits can be selected for supporting, or compensating for, the expense of producing and wielding such exaggerated weapons. In the ant-mimicking jumping spider Myrmarachne gisti, exaggerated chelicerae are borne only by adult males and not females, showing sexual dimorphism and steep positive allometry with body size. Here, we determine the potential benefits of bearing exaggerated chelicerae during male contests and explore the potential for costs in terms of prey-capture efficiency and compensation between chelicera size and neighboring trait size. While males with longer chelicerae won most of their male-male contests, we found no significant differences in prey-capture efficiency between males and females regardless of whether prey was winged or flightless. Males' elongated chelicerae thus do not impede their efficiency at capturing prey. Furthermore, we found that the sizes of all neighboring traits are positively correlated with chelicera size, suggesting that these traits may be under correlational selection. Taken together, our findings suggest that M. gisti males armed with the exaggerated chelicerae that function as weapons win more fights at limited cost for performance in prey capture and compensate for neighboring structures.

Transcriptomic analysis of intermuscular bone development in barbel steed (Hemibarbus labeo).

Intermuscular bones (IBs), which are little, bony spicules in muscle, are embedded in lower teleosts' myosepta. Despite the importance of studying IB development in freshwater aquaculture species, the genes associated with IB development need to be further explored. In the present study, we identified four stages of IB development in barbel steed (Hemibarbus labeo), namely stage 1: IBs have not emerged, stage 2: a few small IBs have emerged in the tail, stage 3: longer IBs gradually emerged in the tail and stage 4: all of the IBs in the tail are mature and long, via Alizarin red staining. Subsequently, we used the HiseqXTen platform to sequence and de novo assemble the transcriptome of epaxial muscle (between 35th and 40th myomere) of barbel steed at 29 days (stage 1) and 42 days (stage 3) after hatching. A total of 190,814 unigenes were obtained with an average length and N50 of 648 bp and 1027 bp, respectively. We found 2174 differentially expressed genes (DEGs) between stages 1 and 3, of which 378 and 1796 were up- and down-regulated, respectively. Functional enrichment analysis showed that several DEGs functioned in ossification, positive regulation of osteoblast differentiation, osteoblast differentiation, and BMP signaling pathway, and were further enriched in signal pathway, including osteoclast differentiation, TGF-ß signaling pathway, cytokine-cytokine receptor interaction, Jak-STAT signaling pathway, and other KEEG pathways. In conclusion, we identified genes that may be related to IB development, such as kazal type serine peptidase inhibitor domain 1 (KAZALD1), extracellular matrix protein 1 (ECM1), tetranectin, bone morphogenetic protein 1 (bmp1), acid phosphatase 5 (ACP5), collagen type XI alpha 1 chain (COL11A1), matrix metallopeptidase 9 (MMP9), pannexin-3 (PANX3), sp7 transcription factor (Sp7), and c-x-c motif chemokine ligand 8 (CXCL8), by comparing the transcriptomes of epaxial muscle before and after IB ossification. This study provided a theoretical basis for identifying the molecular mechanisms underlying IB development in fish.

Fully automated leg tracking of Drosophila neurodegeneration models reveals distinct conserved movement signatures.

Some neurodegenerative diseases, like Parkinsons Disease (PD) and Spinocerebellar ataxia 3 (SCA3), are associated with distinct, altered gait and tremor movements that are reflective of the underlying disease etiology. Drosophila melanogaster models of neurodegeneration have illuminated our understanding of the molecular mechanisms of disease. However, it is unknown whether specific gait and tremor dysfunctions also occur in fly disease mutants. To answer this question, we developed a machine-learning image-analysis program, Feature Learning-based LImb segmentation and Tracking (FLLIT), that automatically tracks leg claw positions of freely moving flies recorded on high-speed video, producing a series of gait measurements. Notably, unlike other machine-learning methods, FLLIT generates its own training sets and does not require user-annotated images for learning. Using FLLIT, we carried out high-throughput and high-resolution analysis of gait and tremor features in Drosophila neurodegeneration mutants for the first time. We found that fly models of PD and SCA3 exhibited markedly different walking gait and tremor signatures, which recapitulated characteristics of the respective human diseases. Selective expression of mutant SCA3 in dopaminergic neurons led to a gait signature that more closely resembled those of PD flies. This suggests that the behavioral phenotype depends on the neurons affected rather than the specific nature of the mutation. Different mutations produced tremors in distinct leg pairs, indicating that different motor circuits were affected. Using this approach, fly models can be used to dissect the neurogenetic mechanisms that underlie movement disorders.