A faunal inventory of methane seeps on the Pacific margin of Costa Rica.

The methane seeps on the Pacific margin of Costa Rica support extensive animal diversity and offer insights into deep-sea biogeography. During five expeditions between 2009 and 2019, we conducted intensive faunal sampling via 63 submersible dives to 11 localities at depths of 300-3600 m. Based on these expeditions and published literature, we compiled voucher specimens, images, and 274 newly published DNA sequences to present a taxonomic inventory of macrofaunal and megafaunal diversity with a focus on invertebrates.

Tiwaripotamon keeae sp. nov. (Crustacea: Decapoda: Potamidae), a new miniature species of freshwater crab from the China-Vietnam border in Napo, Guangxi.

A new miniature species of freshwater crab from the genus Tiwaripotamon Bott, 1970 (Potamidae), is described from a montane karst area in southern Napo, at the China-Vietnam border. It is the twelfth known species of the genus, and is also the smallest known, with the largest adult specimen observed barely exceeding 20 mm in carapace width. Apart from the small size, features of the eyes, carapace and ambulatory legs further set Tiwaripotamon keeae sp.

Molecular phylogeny of deep-sea blind lobsters of the family Polychelidae (Decapoda: Polychelida), with implications for the origin and evolution of these "living fossils".

A comprehensive molecular analysis of the deep-sea blind lobsters of the family Polychelidae, often referred to as "living fossils", is conducted based on all six modern genera and 27 of the 38 extant species. Using six genetic markers from both mitochondrial and nuclear genomes, the molecular phylogenetic results differ considerably from previous morphological analyses and reveal the genera Polycheles and Pentacheles to be para- or polyphyletic. As the splitting of Polycheles has strong support from both molecular and morphological data, two new genera, Dianecheles and Neopolycheles, are erected for those species excluded from the clade containing the type species of Polycheles.

Convergent Adaptation of True Crabs (Decapoda: Brachyura) to a Gradient of Terrestrial Environments.

For much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise over 7600 species representing a striking diversity of morphology and ecology, including repeated adaptation to non-marine habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families.

Tightening the requirements for species diagnoses would help integrate DNA-based descriptions in taxonomic practice.

Modern advances in DNA sequencing hold the promise of facilitating descriptions of new organisms at ever finer precision but have come with challenges as the major Codes of bionomenclature contain poorly defined requirements for species and subspecies diagnoses (henceforth, species diagnoses), which is particularly problematic for DNA-based taxonomy. We, the commissioners of the International Commission on Zoological Nomenclature, advocate a tightening of the definition of "species diagnosis" in future editions of Codes of bionomenclature, for example, through the introduction of requirements for specific information on the character states of differentiating traits in comparison with similar species. Such new provisions would enhance taxonomic standards and ensure that all diagnoses, including DNA-based ones, contain adequate taxonomic context.

Shift in symbiotic lifestyle as the major process shaping the evolution of pea crabs (Decapoda: Brachyura: Pinnotheroidea).

The pea crabs, superfamily Pinnotheroidea, are exceptional among brachyuran crabs in their diverse symbiotic associations involving both inquilinism and protective symbiosis. While this group presents a rare opportunity for evolutionary comparative study of host switching and morphological evolution in marine macroinvertebrates, previous phylogenetic studies have been focused on systematics. Here, we reconstructed the most extensive phylogeny of Pinnotheroidea based on two mitochondrial and six nuclear markers, with the aim of elucidating the host switching pathways and the correlation between symbiotic lifestyles and selected morphological adaptations.

On the identity of Pronotonyx laevis (Miers, 1884) (Crustacea: Brachyura: Pilumnidae).

The poorly known brachyuran crab, Pronotonyx laevis Ward, 1936, from northern Australia, is redescribed based on type and other material. We document adults of both sexes and confirm the taxonomic placement of the Pronotonyx in the Pilumnidae. Pronotonyx is most similar to the Australian Pseudocryptocoeloma parvum Ward, 1936, differing in features of the carapace and pereopods.

Stomatopod Crustacea of Lord Howe Island.

Prior to the present study, five species in four genera of the mantis shrimp superfamily Gonodactyloidea were known from Lord Howe Island, Australia. The 2017 Australian Museum expedition to Lord Howe Island made a small but significant collection of stomatopods, comprising four species: Chorisquilla tweediei (Serène, 1950), Gonodactylaceus falcatus (Forskål, 1775), Pseudosquilla ciliata (Fabricius, 1787) and a new species of Acaenosquilla, representing the first record of the superfamily Lysiosquilloidea from Lord Howe Island. The new species of Acaenosquilla is formally described and a key to the stomatopods of Lord Howe Island is provided.

Hawaiian larval stomatopods: molecular and morphological diversity.

Estimating stomatopod species diversity using morphology alone has long been difficult; though over 450 species have been described, new species are still being discovered regularly despite the cryptic behaviors of adults. However, the larvae of stomatopods are more easily obtained due to their pelagic habitat, and have been the focus of recent studies of diversity. Studies of morphological diversity describe both conserved and divergent traits in larval stomatopods, but generally cannot be linked to a particular species.

Redescription of Euastacus clydensis Riek, 1969 (Crustacea: Parastacidae), a valid species of spiny crayfish from southern New South Wales, Australia.

The Giant Sydney Crayfish (Euastacus spinifer (Heller, 1865)) was thought to have a wide range in New South Wales, Australia, spanning some 600 km north-south. A recent extensive molecular phylogenetic and population genomic analysis of E. spinifer across its geographical range revealed strong population structure corresponding to several major geographically correlated clades, the southernmost clade being the most genetically divergent and clearly a separate species.

Phylogenetic Appraisal of Lysiosquillidae Giesbrecht, 1910, and a New Species of Manning, 1977, from Taiwan (Crustacea: Stomatopoda: Lysiosquilloidea).

The mantis shrimp family Lysiosquillidae includes the largest known stomatopods and presently includes three genera: Dana, 1852, Manning, 1995, and Manning, 1977. Since 1995, new species assigned to all three lysiosquilloid genera have been recognised: Boyko, 2000, Ahyong & Randall, 2001, Ahyong, 2001, Ahyong, 2001, and Erdmann & Boyer, 2003, and Ahyong, 2004. , Manning, 1962 and , however, proved problematical to assign to genera owing to the possession of characters intermediate between sensu stricto and sensu stricto.

Genomic analysis reveals strong population structure in the Giant Sydney Crayfish (Euastacus spinifer (Heller, 1865)).

Australia is home to over 140 species of freshwater crayfish (Decapoda: Parastacidae), representing a centre of diversity for this group in the Southern Hemisphere. Species delimitation in freshwater crayfish is difficult because many species show significant variation in colouration and morphology. This is particularly evident in the genus Euastacus, which exhibits large variations in colour and spination throughout its putative range.

The Identity of (Miers, 1884) (Crustacea: Decapoda: Brachyura).

The brachyuran crab Miers, 1884, described on the basis of two juveniles from the Arafura Sea, is a poorly known species of uncertain systematic position. It was made the type and only species of Rathbun, 1914, and assigned to the Prionoplacinae (Goneplacidae). Subsequent revisions of the goneplacids showed Prionoplacinae to be a junior synonym of Eucratopsinae Stimpson, 1871, as a member of the Panopeidae Ortmann, 1893, but no one has re-evaluated the position of .

Depth as a driver of evolution and diversification of ancient squat lobsters (Decapoda, Galatheoidea, Phylladiorhynchus).

The exceptional hidden diversity included in the squat lobster genus Phylladiorhynchus and its wide bathymetric and geographic range make it an interesting group to thoroughly study its evolutionary history. Here we have analyzed the entire currently known species diversity of Phylladiorhynchus using an integrative approach that includes morphological and molecular characters. The aim was to establish whether depth range (bathymetry) has played a role in their morphological and molecular evolution and in their diversification pathways.

Evaluating the effectiveness of drones for quantifying invasive upside-down jellyfish (Cassiopea sp.) in Lake Macquarie, Australia.

Upside-down jellyfish (Cassiopea sp.) are mostly sedentary, benthic jellyfish that have invaded estuarine ecosystems around the world. Monitoring the spread of this invasive jellyfish must contend with high spatial and temporal variability in abundance of individuals, especially around their invasion front.

Is it time to describe new species without diagnoses?A comment on Sharkey et al. (2021).

New methods in taxonomy and systematics can influence the overall practice of formally naming and describing biodiversity. DNA barcoding has been controversial since its emergence, but now, large scale species descriptions exclusively based on barcodes have created what can be called a 'new quality of performance. Its limitations are discussed from different perspectives: nomenclature, general pragmatism, and problems of DNA-based species delimitation in the light of the central aim of achieving a robust and stable nomenclature of organisms, essential for all applications of biodiversity research.

First records of two species of reef-associated mantis shrimps (Crustacea: Stomatopoda) from India.

The coastal marine environments in the Indian Exclusive Economic Zone harbour a rich diversity of mantis shrimps. However, several regions have not been adequately surveyed for their stomatopod faunal composition. In this paper, we report the first records of two species, Gonodactylopsis drepanophora (de Man, 1902) and Cloridina malaccensis (Manning, 1968) from Indian waters.

Rare specimen identification in an un-integrated taxonomy: implications of DNA sequences from a Taiwanese (Mollusca, Philinidae).

Many species of the gastropod genus have been named from northeastern Asia but scanty descriptions based predominantly on shells make it difficult to determine which are valid. This, plus the sporadic anatomical and genetic information available for many of these species has led to what may be described as an un-integrated taxonomy. In this situation, it is generally preferable to postpone dissection of rare and unusual specimens until relevant diagnostic characters can be established in broader studies.

The second known stygomorphic freshwater crab from China, gen. nov. et sp. nov. (Crustacea, Decapoda, Potamidae), diverged at the beginning of the Late Miocene.

A new genus and new species of blind freshwater cave crab are described from Chongzuo City, Guangxi Zhuang Autonomous Region, China based on morphology and mitochondrial 16S rDNA sequences. The new genus, , is established for , which is only the second blind cave crab known from China and East Asia. The combination of a very wide carapace, overall depigmentation, reduced orbits and vestigial unpigmented eyes of immediately separates it from all known potamid genera.