The World Amphipoda Database: History and Progress

. We provide an overview of the World Amphipoda Database (WAD), a global species database that is part of the World Register of Marine Species (WoRMS). Launched in 2013, the database contains entries for over 10,500 accepted species names. Edited currently by 31 amphipod taxonomists, following WoRMS priorities, the WAD has at least one editor per major group. All accepted species are checked by the editors, as is the authorship available for all of the names. The higher classification is documented for every species and a type species is recorded for every genus name. This constitutes five of the 13 priorities for completion, set by WoRMS. In 2015, five LifeWatch grants were allocated for WAD activities. These included a general training workshop in 2016, together with data input for the superfamily Lysianassoidea and for a number of non-marine groups. Philanthropy grants in 2019 and 2021 covered more important gaps across the whole group. Further work remains to complete the linking of unaccepted names, original descriptions, and environmental information. Once these tasks are completed, the database will be considered complete for 8 of the 13 priorities, and efforts will continue to input new taxa annually and focus on the remaining priorities, particularly the input of type localities. We give an overview of the current status of the order Amphipoda, providing counts of the number of genera and species within each family belonging to the six suborders currently recognized.


Introduction
The order Amphipoda forms part of the superorder Peracarida, uniting a diverse group of small shrimp-like taxa that brood their young in a pouch, with no independent larval dis persal stage.Amphipods range in size from a millimetre in length to the supergiant amphipod, Alicella gigantea Chevreux, 1899, at 340 mm body length.Amphipods can be found in all marine habitats from beaches to the deepest ocean trenches, and have also colonized freshwaters and terrestrial habitats.Amphipods are important herbivores, detritivores, micropredators, scavengers, and ectoparasites and they form an important component of aquatic ecosystems.The World Amphipoda Database (WAD) (Horton et al., 2022; https://www.marinespecies.org/amphipoda/ ) is a global species database, providing the most up-to-date classification and catalogue of amphipod species names from all habitats, and is based on published literature.It is part of The World Register of Marine Species, a community-driven program to provide "An authoritative classification and catalogue of marine names" (WoRMS Editorial Board 2022; https://www.marinespecies.org/;(Horton et al., 2017;Vandepitte et al., 2018), which is now accepted as a global standard for marine species names (Vandepitte et al., 2018).As a global species database, WAD includes not only marine species, but also brackish, freshwater, and terrestrial amphipods.WoRMS (and WAD) is managed within the Aphia platform (Vandepitte et al., 2015) following a successful collaborative model between taxonomists and data managers (Costello et al., 2018;Kroh et al., 2018).Each taxonomic editor is responsible for the updating and curation of a taxon (or taxa).This editing process can take place online through the editor interface or, if uploads of larger amounts of data are needed, with the help of the Data Management Team (DMT).
The aim of the World Register of Marine Species is to provide an authoritative and comprehensive list of names of marine organisms, including information on synonymy and the most up-to-date higher classification.While highest priority goes to valid names, other names that have been used are included in order to serve as a guide to interpret the taxonomic literature and results in a scientifically valuable catalogue and bibliography.Each taxon page can hold a great deal of information in addition to the currently accepted taxonomic name and authority.Associated data can include, but is not limited to, the original description of the taxon (including links to the actual publication), additional references, type locality, type specimen, environment, geographic distribution and images.
In contrast to many earlier web-based checklists, WoRMS has a permanent host institution, the Flanders Marine Institute, VLIZ, in Belgium, that is a professional data centre, collaborating with the scientific community through an editorial board of around 300 peer-selected experts from all around the world and for all taxonomic groups.WoRMS is open-access and archived monthly with a Digital Object Identifier (DOI) to ensure long-term preservation of content, and is working towards full compliance with FAIR data practices (Wilkinson et al., 2016).
This collaboration between a team of expert amphipod taxonomists and the DMT support of the WoRMS database has resulted in the generation of a freely available global database of amphipod names.This is a large dataset of more than 10,600 accepted species names (as of 6 November 2023 there are 15,897 total name entries, including higher taxa and unaccepted names), which can be used for a wide range of research and non-research applications.WAD/WoRMS can be used by individuals checking on the validity of names or conducting research on the dataset, and also by institutes and other globally important scientific databases (e.g., GenBank (GenBank, 2022;Benson et al., 2008); Barcode of Life Data System (BOLD, 2022;Ratnasingham & Hebert, 2007); Catalogue of Life (CoL; Bánki et al., 2022); Global Biodiversity Information Facility (GBIF; GBIF, 2022); and Ocean Biodiversity Information System (OBIS; OBIS, 2022)), which use WoRMS as the taxonomic backbone for their own databases.Beneficiaries of the information, which is often accessed through other databases that are fed by WoRMS, include scientists, consultants, conservationists, journalists, the general public, and many others.
The WAD has facilitated several studies on the Amphipoda, including analyses of the taxonomic impediment (Coleman, 2015), species discovery (Arfianti et al., 2018), global biogeography (Arfianti & Costello, 2020), surveys of types in museum collections (Lo Brutto, 2017), and genetic barcode gap analysis (Jażdżewska et al., 2021).Amphipod taxonomists and others also make frequent use of the WAD, to provide or confirm information on the systematic and taxonomic status of entities from the species level and upwards (e.g., to provide the most up-to-date list of species in a particular genus).This is exemplified by the 328 citations of the WAD to date (via google scholar) and the number of web hits for the database (800K in 2021).

History of the World Amphipoda Database
The World Amphipoda Database, in its current format, arose from a merger in 2010 of the World Amphipoda List, compiled over many years by Jim Lowry, with the European Register of Marine Species (ERMS) amphipod list, compiled by Mark Costello, Denise Bellan-Santini and Jean-Claude Dauvin, and edited up until 2013 with significant additions from the Register of Antarctic Marine Species (RAMS) Amphipoda list (De Broyer et al., 2007) and from other regional editors.
Jim Lowry had, for many years, compiled an unpublished list for his own use and to share with other taxonomists.This comprehensive catalogue extended over four Microsoft Word documents in alphabetical order by amphipod family, and was submitted by Jim Lowry to the Data Management Team at VLIZ for incorporation into the APHIA database in 2009.In 2010, the information was added to WoRMS, after which Jim Lowry became Chief Editor of the World Amphipoda Database.

A new editorial team and launch of the World Amphipoda Database (WAD)
In 2012, following efforts to improve the list of deep-sea Amphipoda in the World Register of Deep-Sea Species (WoRDSS; Glover et al., 2022), it was recognized that although Jim Lowry's catalogue had been incorporated into WoRMS in 2010, the database had not been comprehensively edited or updated since that time, and an entry page with an introduction to the database was lacking.The chief taxonomic editors, Tammy Horton, Claude de Broyer, and Jim Lowry, therefore enlisted 30 amphipod taxonomists to each take on responsibility for particular taxa in the database.
With almost 10,000 species to manage, it was recognized that more experts were needed to share the task of keeping the database up-to-date and to enter more information about each taxon (e.g., original descriptions, environments, type localities, life-history traits etc.).Particular expertise was required to cover the non-marine amphipod taxa.An independent account and enumeration of all freshwater amphipod taxa had been made in connection with the global Freshwater Animal Diversity Assessment project, FADA (Väinölä et al., 2008;Balian et al., 2008).The list from that project was integrated with the WoRMS database when the WAD was established.The > 2100 amphipod species and subspecies recorded from fresh or inland waters account for ca.20 % of the total known amphipod diversity (Väinölä et al., 2008;Horton et al., 2022).
In July 2013 the World Amphipoda Database http:// www.marinespecies.org/amphipodawas launched and it was first presented at the 15th International Colloquium on Amphipoda, in Szczawnica, Poland, in September 2013.A front page was created with a logo (Fig. 1), a comprehensive introduction to the database, and a menu allowing users to access additional information, including the back catalogue of Amphipod Newsletters, which was first produced in 1972 and is still produced annually (https://www.marinespecies.org/amphipoda/newsletter.php).By the time it was launched, the order Amphipoda contained 9329 species divided into four suborders; there were just over 200 unchecked names and 30 quarantined taxa.The first job was to deal with these, and then to add all the new taxa that had been described since Jim Lowry's catalogue had been incorporated.This was managed with the help of the Data Management Team at VLIZ and involved the addition of data from around 200 publications.Once the database was more up-to-date, focus was turned to improving other aspects (see below) and continuing to add new taxa annually.

Priorities for improvement and aims for completion
The main priority of WoRMS, and therefore WAD, is to ensure that all valid species names are entered into the database, enabling users to find information on which names are currently accepted, which are unaccepted and which are uncertain (or temporary names) (Horton et al., 2017).Every newly input species requires data in addition to the species name and authority, and there is a priority list for entering further information on older taxa into the database.
The WoRMS Steering Committee (SC) has provided priority aims for completing the database over the next ten years.These are: 1 To have at least one active editor per taxonomic group 2 To mark (accepted) species as "checked by editor" 3 To document the basionym (original name) 4 To complete missing authorships 5 To document the original description of each species 6 To complete the environment flags 7 To document higher classification 8 To document type localities 9 To document type species 10 To document all published name combinations 11 To make available at least one image per species 12 To document (the general) distribution for each species 13 To document relevant species traits Italicized priorities have been completed already for the WAD.These extra pieces of information are critical to the usability of the dataset.The authority and date of publication must be included, and the original description is linked to the original name as a reference, but preferably also made available as a PDF.This is particularly important when adding older taxa, as some older literature is hard to find.Unaccepted names including synonyms and older name combinations are also added to the database and linked to the currently accepted name.This allows users to find the valid name even if their taxon list is old and changes have taken place (as often happens in taxonomy!).Literature references that record changes in taxonomic status are linked to the taxon page so that the user can access this information.All information entered into the World Amphipoda Database reflects what is already published.
When the database was launched in 2013, many of the priority aims were far from completion, but targeted work through small grants since then has greatly improved the quality of the information in the database.

LifeWatch Data Grants 2015
The E-Science European LifeWatch Infrastructure for Biodiversity and Ecosystem Research targets different aspects of biodiversity research, and the Taxonomic Backbone of LifeWatch aims at bringing together taxonomic and species-related data and filling gaps in our knowledge, expanding the content and enhancing the quality of taxonomic databases.In 2015, five Lifewatch grants were awarded to support amphipod editors to facilitate improvements to the taxonomic quality of WoRMS and the World Amphipoda Database (WAD) through editorship of particular taxa.These included an editor training workshop for all Amphipoda editors, and four small data grants for the non-marine Gammaroidea (excluding Baikalian taxa), other non-marine amphipod families, the superfamily Lysianassoidea and the family Niphargidae.

Amphipod editor workshop
Since the original launch of the WAD, bringing together the editorial team, there had not been a meeting of the editors and it became evident that the editing team would benefit from meeting physically together and having the opportunity to organize their editorial responsibilities.A further meeting was therefore planned that would provide training on how the editing should take place in a consistent manner, illustrate the methods and requirements of editing, work on particular projects and propose new analyses for the future.The workshop took place in 2015 at the Flanders Marine Institute (VLIZ), the host institute of WoRMS (Fig. 2).By the time of the workshop, the database held 9,915 valid species names.Priority editing tasks that needed to be completed were tackled to ensure that the database was an accurate reflection of the published literature, that it was up-to-date with newly published species, and that it remained the authoritative global list of amphipod species.

Non-marine Gammaroidea (excluding Baikalian taxa)
Taxon data (including original name, authority, environment, fossil status) were edited for 319 taxa on-line in Aphia, and updates for a further 105 taxa (Echinogammarus Stebbing, 1899, andChaetogammarus Martynov, 1924) were provided to the data management team for upload.Missing genera (Boeckia G. O. Sars, 1894, Fontogammarus S. Karaman, 1931, Rivulogammarus S. Karaman, 1931, Trichogammarus Hou & Sket, 2016) were added with their respective constituent (child) taxa.Type localities and holotype specimen information were added when this information was available in the literature.Distribution and habitat information was added with appropriate reference sources linked for each taxon.Original description references as well as additional sources (re-descriptions, identification keys) were linked and in many cases supplemented by pdf files (Mamos & Grabowski, 2015).

Selected non-marine Amphipod families
Data were revised and added for all taxa within the families Bogidiellidae, Artesiidae, Hadziidae, and Metacrangonyctidae, partly for the Crangonyctidae, and for a number of very small families.These comprised about 250 valid non-marine species, 45 additional marine species from the same families, and about 560 names in total, including original names, synonyms, and genus-group names (ca.100).The progress corresponded to about 40% of the unattended groups that need to be covered for the non-marine Amphipoda (Väinölä et al., 2015).

Superfamily Lysianassoidea
The Lysianassoidea is a large superfamily that, at the time of the grant, contained 22 families, 173 genera, and just over 1000 accepted species in the WAD list (1,447 total accepted and unaccepted names).Targeted work resulted in the addition of 115 taxon names to the Lysianassoidea (54 accepted names, 21 of which were described in 2014-2016; 47 unaccepted, with the remainder being temporary names etc.).The 29 taxa (unaccepted) without authority were checked and the authority added; 316 original names and 271 original descriptions were linked.An additional 353 edits were made to existing taxon names in the database (Horton & Thurston, 2015).

Family Niphargidae
The Niphargidae is a large family of freshwater Amphipods living almost exclusively in subterranean waters of the Western Palearctic.The original lists of genera and species (nine accepted genera; 274 accepted species) in the WAD were outdated and incomplete.The data grant allowed one genus (Niphargopsis Chevreux, 1922) to be moved to Niphargus Schiödte, 1949, and two new genera (Exniphargus G. S. Karaman, 2016, Niphargobatoides G. S. Karaman, 2016) were added; 111 subspecies were raised to species rank; 34 new species were added; two species were moved into synonymy.The original names for 377 taxa (species and subspecies) were documented and missing original description sources were scanned and linked (Fišer & Horton, 2015).The authorities were completed for all taxa, and years of publication were revised where necessary.Type or neotype localities for 379 taxa were documented and information on the deposition of type, lectotype or neotype material was documented for 91 taxa.The etymology for 219 taxa was documented.The environmental requirements were revised for all species.The distribution for 379 taxa was documented at the level of country and FADA biogeographical regions (Fišer & Horton, 2015).This revision was a major improvement to the taxonomic backbone and eased all subsequent work on the group.

The "Talitraits" project
In 2018, a group targeting the inclusion of talitrids' traits ("Talitraits") in WoRMS met at the Hellenic Centre for Marine Research, Crete, for a workshop sponsored by LifeWatch Belgium, https://www.marinespecies.org/amphipoda/talitraits.php.The workshop supported the broad vision to combine taxonomy and ecology, to allow the formulation of clear, testable hypotheses with respect to the category "talitrids" in a species-environment approach.Providing a taxonomic backbone for talitrids and related traits was identified as the crucial passage to do so.A dataset in WoRMS was seen as the first step towards this timely change, and the "Talitraits" project was initiated to support this aim.
"Talitraits" thematic editors met to select a set of traits, consistent with the attributes already present in WoRMS, and sufficient to define coastal talitrids.Traits were prioritized and addressed, using the published literature.Priority traits were defined, and a set of traits common to the whole group of talitrids was identified to include: qualitative body size (2-200 mm); feeding strategy (omnivorous); and development (direct development).These traits were assigned to Talitridae shared at the family level and currently linked to https://www.marinespecies.org/traits/.
Agreement was met on the curation of coastal talitrids only (excluding the ecological category of "land-hoppers", i.e. species inhabiting moist substrates, such as grasslands, forest floors, leaf litter, stream banks) and among them specifically sand-hoppers and beach-hoppers.This restricted the focus to 195 species, rather than the approximately 364 species of Talitridae known, and to the selection of the "Country name-Exclusive Economic Zone" to be used when defining each species' distribution.The list of species and related literature from Jim's catalogue were made available on WoRMS.
The traits defined were scaled by priority, on the basis of availability in the literature of information related to the trait for most of the species considered; ecological relevance of the trait; link of the trait to other WoRMS datasets and working groups (e.g., parasites).Qualitative body size was defined as the first trait to be curated, given its availability for all species, and is now completed.A set of additional traits (such as behavioural traits), were indicated for a future focus.

VLIZ-WoRMS Philanthropy grants 2019 and 2021
More recently, two VLIZ-WoRMS Philanthropy Grants were awarded within the VLIZ Philanthropy project "Support the WoRMS editors", enabling focussed work to target particular gaps within the whole WAD.Within the Amphipoda, 1004 accepted taxa remained without original names documented (as of 24 June 2019).This gap was targeted, with an aim to complete the original name information for all accepted species within the World Amphipoda Database, and to reduce considerably the total number of amphipod species without an original name linked (a further 1198 unaccepted species) at the same time.As a result of this grant, all of the 1004 accepted species without an original name linked were completed.A total of 882 taxon names were added to the World Amphipod Database and 2785 edits were made to taxa in the database during the grant period, including linking the original name, linking the original description and correcting the environment and fossil status (Horton & Valls Domedel, 2019).Of the 1325 taxa without an environment documented, 519 remained.Additionally, 115 edits were made to the sources (including creation, addition of PDF documents to existing sources, or addition of links to journals when PDF versions of the articles were not available).
The 2021 Philanthropy grant allowed further work on the remaining gaps to be completed.All of the 167 accepted species and sub-species level taxa without an original name linked were completed, and all 2108 genera (accepted and unaccepted) in the WAD now have a type species linked (> 400 of these were edited during the grant period).1436 accepted species-level taxa had the original description source linked (more than half of the 2621 which were missing an original description at the beginning of the grant).More than 1100 edits were made to existing entries in the database including linkage to the original name, to the original description and edits of the habitat information or the fossil range (Horton & Valls Domedel, 2019).

Current Status of the World Amphipoda Database
Despite the considerable amount of work to complete gaps for the agreed priorities, the editing of the WAD is not yet complete.Work remains to complete the linking of original names (964 unaccepted taxa remain) and linking of original descriptions (780 unaccepted taxa remain).In addition, 234 species (of which 203 are unaccepted) remain without an environment flag (marine, brackish, fresh or terrestrial).
Filling of these gaps will remain high on the priority list and will be managed on an ad-hoc basis until completed.Once these gaps are filled, the work will continue to input information on the new taxa described annually, which is currently an average of 137 per year (see Table 1), and focus will turn to completing the remaining priorities, particularly the input of type localities.Following major revisions of the higher-level systematics of the Amphipoda since 2003 (Myers & Lowry, 2003;Lowry, 2006;Lowry & Myers, 2012a, 2012b, 2013, 2016, 2017), the order Amphipoda in the WAD is now (as of 12 May 2022) comprised of six suborders: Amphilo chidea, Colomastigidea, Hyperiidea, Hyperiops idea, Pseudingolfiellidea & Senticaudata; 13 infraorders, 22 parvorders, 56 superfamilies, 242 families, 1766 genera, and 10,455 species.These revisions required the addition of previously unused ranks within the Amphipoda (parvorder and infraorder).Table 2 shows the breakdown of accepted and unaccepted taxa within the available ranks of Amphipoda in the WAD.The ingolfiellids (Ingolfiellidea) were traditionally a suborder within the Amphipoda ever since their description by Hansen in 1903.They were placed outside the Amphipoda by Lowry & Myers (2017) and raised to the rank of order Ingolfiellida.They continue to be maintained as part of the World Amphipoda Database owing to their historical placement.The ingolfiellidans are now a sister group to the amphipods and comprise 51 species (of which 19 are freshwater species), and about 100 taxon names (including species names and higher taxa).The taxonomy displayed in the WAD cannot always incorporate all the newest aspects of systematic relationships due to conflicting views, but does strive to provide information on alternative classifications and names used.An example of this is provided by the recent works on the systematics and diversity of freshwater gammaroid amphipods (Hou & Sket, 2016;Sket & Hou, 2018).
We present a list of accepted infraorders, superfamilies and families within each of the six suborders, providing counts of the number of genera and species within each family in three tables (Table 3: Amphilochidea; Table 4: Hyperiidea, Hyperiopsidea, Pseudingolfiellidea & Colomastigidea; Table 5: Senticaudata) to give an overview of this information.This provides a stable reference for the current state of amphipod systematics following the extensive higher-level revisions in recent years.The majority of taxa are in the suborders Amphilochidea (688 genera, 4196 species) and Senticaudata (974 genera, 5813 species).(Hughes et al., 2023).
The WAD is an ever-expanding database, with an average of 137 newly described taxon names entered into the database annually (Table 1), with edits to and additions of older names being made all the time.The database still contains residual errors and there are certain taxa that have received less focussed attention and will need targeted improvement in the future.Amphipoda systematics are in a state of flux, particularly due to new insights from molecular data and the fact that this information is not yet available for many of the relevant taxa (Copilaş-Ciocianu et al., 2020).
Users of the database are encouraged to point out errors to the Data Management Team using the single contact email info@marinespecies.organd queries will be passed to the relevant editor.Contributors are acknowledged annually on the WAD webpages.
Table 4. Suborders Hyperiidea, Hyperiopsidea, Pseudingolfiellidea & Colomastigidea: Alphabetical list of infraorders, superfamilies and families, providing counts of the number of genera and species within each family; data from the World Amphipoda Database (Horton et al., 2022;

Table 1 .
Numbers of accepted taxa described per year since 2000, data from World Amphipoda Database (as of 12 May 2022).

Table 2 .
Number of taxon names at each of the available taxonomic ranks in the World Amphipoda Database (as of 12 May 2022).Note that "Unaccepted" includes all types of unaccepted names.