Phylogeny and characteristics of ruminants: Ruminants are a diverse group of mammals that includes families containing well-known taxa such as deer, cows, and goats. However, their evolutionary relationships have been contentious, as have the origins of their distinctive digestive systems and headgear, including antlers and horns (see the Perspective by Ker and Yang). To understand the relationships among ruminants, L. Chen et al. sequenced 44 species representing 6 families and performed a phylogenetic analysis. From this analysis, they were able to resolve the phylogeny of many genera and document incomplete lineage sorting among major clades. Interestingly, they found evidence for large population reductions among many taxa starting at approximately 100,000 years ago, coinciding with the migration of humans out of Africa. Examining the bony appendages on the head—the so-called headgear—Wang et al. describe specific evolutionary changes in the ruminants and identify selection on cancer-related genes that may function in antler development in deer. Finally, Lin et al. take a close look at the reindeer genome and identify the genetic basis of adaptations that allow reindeer to survive in the harsh conditions of the Arctic. Science , this issue p. eaav6202 , p. eaav6335 , p. eaav6312 ; see also p. 1130

Polyploidy or whole-genome duplication (WGD) is a major event that drastically reshapes genome architecture and is often assumed to be causally associated with organismal innovations and radiations. The 2R hypothesis suggests that two WGD events (1R and 2R) occurred during early vertebrate evolution. However, the timing of the 2R event relative to the divergence of gnathostomes (jawed vertebrates) and cyclostomes (jawless hagfishes and lampreys) is unresolved and whether these WGD events underlie vertebrate phenotypic diversification remains elusive. Here we present the genome of the inshore hagfish, Eptatretus burgeri. Through comparative analysis with lamprey and gnathostome genomes, we reconstruct the early events in cyclostome genome evolution, leveraging insights into the ancestral vertebrate genome. Genome-wide synteny and phylogenetic analyses support a scenario in which 1R occurred in the vertebrate stem-lineage during the early Cambrian, and 2R occurred in the gnathostome stem-lineage, maximally in the late Cambrian–earliest Ordovician, after its divergence from cyclostomes. We find that the genome of stem-cyclostomes experienced an additional independent genome triplication. Functional genomic and morphospace analyses demonstrate that WGD events generally contribute to developmental evolution with similar changes in the regulatory genome of both vertebrate groups. However, appreciable morphological diversification occurred only in the gnathostome but not in the cyclostome lineage, calling into question the general expectation that WGDs lead to leaps of bodyplan complexity.

The swimming crab, Portunus trituberculatus, is an important commercial species in China and is widely distributed in the coastal waters of Asia-Pacific countries. Despite increasing interest in swimming crab research, a high-quality chromosome-level genome is still lacking. Here, we assembled the first chromosome-level reference genome of P. trituberculatus by combining the short reads, Nanopore long reads, and Hi-C data. The genome assembly size was 1.00 Gb with a contig N50 length of 4.12 Mb. In addition, BUSCO assessment indicated that 94.7% of core eukaryotic genes were present in the genome assembly. Approximately 54.52% of the genome was identified as repetitive sequences, with a total of 16,796 annotated protein-coding genes. In addition, we anchored contigs into chromosomes and identified 50 chromosomes with an N50 length of 21.80 Mb by Hi-C technology. We anticipate that this chromosome-level assembly of the P. trituberculatus genome will not only promote study of basic development and evolution but also provide important resources for swimming crab reproduction.

Gobiocypris rarus is sensitive to environmental pollution, especially to heavy metal and grass carp reovirus (GCRV). Hence, it has potential utility as a biological monitor. Genetic deciphering of its unique immune system will advance our understanding of its unique adaptive strategies, which provide cues for its better application. A de novo genome of rare minnow was obtained, and its sex determination mechanism is ZZ/ZW. We identified several specific mutation genes and specific lost genes of rare minnow, and these might be related to the sensitivity of rare minnow to environmental stimuli. We also analyzed the gene expression level of different organs/tissues and found that several IFIT genes may play key roles in GCRV resistance. In addition, knockout of the gene PCDH10L indicates that PCDH10L affects Pb ²⁺ -induced mortality in rare minnow. Rare minnow is ready for genetic manipulation and shows potential as an emerging experimental model.

The black widow spider has both extraordinarily neurotoxic venom and three-dimensional cobwebs composed of diverse types of silk. However, a high-quality reference genome for the black widow spider was still unavailable, which hindered deep understanding and application of the valuable biomass. We assembled the Latrodectus elegans genome, including a genome size of 1.57 Gb with contig N50 of 4.34 Mb and scaffold N50 of 114.31 Mb. Hi-C scaffolding assigned 98.08% of the genome to 14 pseudo-chromosomes, and with BUSCO, completeness analysis revealed that 98.4% of the core eukaryotic genes were completely present in this genome. Annotation of this genome identified that repetitive sequences account for 506.09 Mb (32.30%) and 20,167 protein-coding genes, and specifically, we identified 55 toxin genes and 26 spidroins and provide preliminary analysis of their composition and evolution. We present the first chromosome-level genome assembly of a black widow spider and provide substantial toxin and spidroin gene resources. These high-qualified genomic data add valuable resources from a representative spider group and contribute to deep exploration of spider genome evolution, especially in terms of the important issues on the diversification of venom and web-weaving pattern. The sequence data are also firsthand templates for further application of the spider biomass.