Benchmarking global biodiversity of decapod crustaceans (Crustacea: Decapoda)

A new assessment of the global biodiversity of decapod Crustacea (to 31 December 2022) records 17,229 species in 2,550 genera and 203 families. These figures are derived from a well-curated dataset maintained on the online platform DecaNet, a subsidiary of the World Register of Marine Species (WoRMS). Distinct phases are recognised in the discovery process (as measured by species descriptions) corresponding to major historical and geopolitical time periods, with the current rate of species descriptions being more than three times higher than in the Victorian age of global exploration. Future trends are briefly explored, and it is recognised that a large number of species remain to be discovered and described

The Magnitude of Global Marine Species Diversity

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century

Systematics and Distribution of Callianassa (Crustacea, Decapoda, Macrura) from Port Phillip Bay, Australia, with Descriptions of Two New Species

Two new species of Callianassa are described from Port Phillip Bay subtidal sediments. Their systematic position and their status within the genus are briefly discussed. The distribution of the four species known from Port Phillip Bay correlates with that of sediment type and depth. C. arenosa n. sp. was distributed on silty sand sediments and was most dense between 13-19 m depth. C.limosa n. sp. was most dense (over 1,000 individuals per m2) on silty clay sediments below 15 m. C. ceramica Fulton & Grant occurred at low densities on sandy sediments less than 10m depth and has previously been reported from intertidal muddy flats along with C. australiensis (Dana)

Two new species of Tridentella (Crustacea: Isopoda: Tridentellidae) from Namibia

Tridentella namibia n. sp. and T. benguela n.sp. (Crustacea: Isopoda: Tridentellidae) are described from the shelf and slope off the coast of Namibia, south-western Africa. A key is provided to all the 16 species in the genus and distributional information tabulated

Revision of Pleuroprion zur Strassen, 1903 (Holidoteidae) and re-evaluation of Spectrarcturus Schultz, 1981 (Arcturidae) (Crustacea, Isopoda, Valvifera)

Stransky, Bente, Svavarsson, Jörundur, Poore, Gary C.B., Kihara, Terue Cristina (2020): Revision of Pleuroprion zur Strassen, 1903 (Holidoteidae) and re-evaluation of Spectrarcturus Schultz, 1981 (Arcturidae) (Crustacea, Isopoda, Valvifera). Zootaxa 4894 (1): 1-52, DOI: https://doi.org/10.11646/zootaxa.4894.1.

Improving nomenclatural consistency: a decade of experience in the World Register of Marine Species

The World Register of Marine species (WoRMS) has been established for a decade. The early history of the database involved compilation of existing global and regional species registers. This aggregation, combined with changes to data types and the changing needs of WoRMS users, has resulted in an evolution of data-entry consistency over time. With the task of aggregating the accepted species names for all marine species approaching completion, our focus has shifted to improving the consistency and quality of data held while keeping pace with the addition of > 2000 new marine species described annually. This paper defines priorities and longer-term aims that promote standardisation within and interoperability among biodiversity databases, provides editors with further information on how to input nomenclatural data in a standardised way and clarifies for users of WoRMS how and why names are represented as they are. We 1) explain the categories of names included; 2) list standard reasons used to explain why a name is considered ‘unaccepted’ or ‘uncertain’; 3) present and explain the more difficult situations encountered; 4) describe categories of sources and notes linked to a taxon; and 5) recommend how type material, type locality and environmental information should be entered

Commonness and rarity in the marine biosphere

Explaining patterns of commonness and rarity is fundamental for understanding and managing biodiversity. Consequently, a key test of biodiversity theory has been how well ecological models reproduce empirical distributions of species abundances. However, ecological models with very different assumptions can predict similar species abundance distributions, whereas models with similar assumptions may generate very different predictions. This complicates inferring processes driving community structure from model fits to data. Here, we use an approximation that captures common features of “neutral” biodiversity models—which assume ecological equivalence of species—to test whether neutrality is consistent with patterns of commonness and rarity in the marine biosphere. We do this by analyzing 1,185 species abundance distributions from 14 marine ecosystems ranging from intertidal habitats to abyssal depths, and from the tropics to polar regions. Neutrality performs substantially worse than a classical nonneutral alternative: empirical data consistently show greater heterogeneity of species abundances than expected under neutrality. Poor performance of neutral theory is driven by its consistent inability to capture the dominance of the communities’ most-abundant species. Previous tests showing poor performance of a neutral model for a particular system often have been followed by controversy about whether an alternative formulation of neutral theory could explain the data after all. However, our approach focuses on common features of neutral models, revealing discrepancies with a broad range of empirical abundance distributions. These findings highlight the need for biodiversity theory in which ecological differences among species, such as niche differences and demographic trade-offs, play a central role

The Magnitude of Global Marine Species Diversity

Background The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century