Dozens of samples of stalked barnacles were collected from deep-sea seamounts of the tropical western Pacific by remotely operated vehicles during two expeditions in 2017 and 2018. Integrative taxonomy indicates that they represent two new species belonging to the families Scalpellidae and Poecilasmatidae, respectively. In terms of morphology, Arcoscalpellum angularum sp. nov. is distinguished from congeneric species by the angular processes on the dorsum of its soft body and the absence of a caudal appendage, whereas Glyptelasma robustum sp. nov. differs from its congeners in its robust peduncle, semicircular concaved carina, and long filamentary appendages. The validity of the two new species is supported by genetic analyses inferred from COI gene sequences and geographic distribution. To date, very few seamounts in the oceans have been investigated for scientific purposes, and records about barnacles inhabiting seamounts are chaotic. A literature search reveals about 125 barnacle species recorded in seamounts mainly in the eastern and western regions of the Pacific Ocean. Existing data are insufficient for research on species speciation and diffusion; still more credible data on the distribution of barnacles in seamounts should be collected.

Brachyura represents the focus of species diversity within Decapoda. However, this diversity increases the difficulty of species identification and obscures the natural phylogenetic relationships. Mitogenomes, with their rich phylogenetic signal and evolutionary informatics, provide critical insights into brachyuran systematics. Here, we present 12 newly sequenced mitogenomes spanning 10 families, which exhibit diverse lengths, ranging from 15,320 to 16,135 bp. All circular genomes except Conchoecetes artificiosus (lacking tRNA‐S2) encode the typical 37 mitochondrial genes. Meanwhile, we identified unique gene order of Pleistacantha cervicornis and provided preliminary speculation on its hypothetical evolutionary history, which involved four gene inversion and translocation events. Phylogenomic reconstruction revealed: (1) Goneplacidae was closely related to Xanthoidea; meanwhile, Tetraliidae and Trapeziidae show divergence, resulting in the polyphyly of Goneplacoidea and Trapezioidea; (2) freshwater crabs were intimately related to thoracotrematan, and we recommended Potamoidea and Gecarcinucoidea should be classified under Thoracotremata; (3) Extensive mitochondrial gene order (MGO) diversity across Brachyura, with lineage‐specific rearrangement patterns serving as phylogenetic markers. Our research offers new insights into the phylogenetic relationships within Brachyura from mitogenome perspective, unraveling the diversity and rearrangement trajectories of MGO in Brachyura.

Microhabitat environmental factors (e.g., temperature, oxygen concentration, nutrients, osmotic stress, and topography) are critical to the survival of intertidal organisms. Understanding how transcription responses are regulated in relation to intertidal microhabitat variation has important implications for studying adaptive evolution in these organisms. The barnacle Chthamalus challengeri, which survives in the intertidal zone and is subjected to periodic tidal changes, serves as an ideal species for detecting adaptive evolution in intertidal organisms. In this study, we designed a series of in situ tidal conditions for C. challengeri and sequenced their transcriptome collected from various microhabitats. We aimed to detect the genetic adaptation mechanisms of barnacles responding to the microhabitat changes in the intertidal zone based on comparative transcriptomics. Our results indicated that different intertidal microhabitats significantly affected the gene expression models of C. challengeri, particularly for genes related to physiological and biochemical functions. Specifically, the expression of genes such as CYP450, HSP70, CYTB, and COX1 was significantly increased under low tide (air-exposed conditions), while genes like CNGA3, AK, and CP52 showed significantly increased expression under high tide (seawater-immersed conditions). The results suggest that C. challengeri relies on cytochrome p450 enzymes to enhance oxidative capacity, counts on heat shock proteins and cell phagocytosis to resist microhabitat changes in response to different tidal conditions, and produces a hypoxic stress response to regulate energy metabolism and body temperature changes upon entering into seawater. This study provides genetic resources and clues for investigating the adaptation mechanisms of intertidal barnacles and identifies different gene expression models for C. challengeri responding to various microhabitats.

The genus Neocaridina, originating from East Asia and representing a small-size landlocked shrimp group of the family Atyidae, is an important group of ornamental shrimps and plays significant ecological roles in their natural habitats. Owing to the considerable variability of the taxonomic characters it employed, Neocaridina is constantly under revision, and the validation of several species is currently questionable. In the present study, several Neocaridina shrimps were collected from the Baiyangdian drainage area. Through morphological examination, they exhibited delicately diagnostical differences in the dactyli of the third pereiopod and the endopod of the first and second pleopod and were classified into morph A, morph B and morph C. According to the literature description, morph A and morph C were identified as N. denticulata denticulata and N. denticulata sinensis, respectively. Among them, morph B presents an intermediate state between morph A and morph C. Subsequently, we determined the mitogenomes of morph A, morph B and morph C. Based on the morphological characteristics, genetic variation and phylogenetic tree, we contend that N. davidi, N. d. denticulata, N. d. sinensis and N. heteropoda should belong to the same species, and we propose retaining the name N. denticulata. The reconstructed mitogenomic phylogeny indicated that the monophyly of several genera within Atyidae has been challenged, suggesting that the established classification of Atyidae requires substantial taxonomic revision at all taxonomic levels. Furthermore, the tree’s topologies supported Atyidae at a deeper base within Caridea. More comprehensive taxon sampling is still needed to resolve the explicit internal relationships among Caridea.

Two specimens of the genusHippolytewere examined from the caridean collections of the Marine Biological Museum, Chinese Academy of Sciences. These specimens were captured in the South China Sea in 1987. Detailed inspection revealed that their morphological features closely match the (re)descriptions ofHippolyte australiensis, especially in the presence of a long, distinct lateral carina on the rostrum, a dorsally unarmed rostral border, and four prominent terminal spines on the dactylus of the last three pereiopods.The discovery ofHippolyte australiensisin Chinese waters represents a significant expansion of its geographic distribution from the South Pacific to the North Pacific. Furthermore, an additional taxonomical report ofH. australiensisis provided since its retrieval in 2001.