Marine Annelida of India: taxonomy and status evaluation and an updated checklist

We present an updated checklist of marine annelids from the Indian subcontinent. Records of annelid species were obtained from published and grey literatures and online databases. Our review of annelid publications was restricted to the Indian continental shelf region. This paper also discusses the taxonomic status of marine annelid species recorded from this region and problems that impede its research. The updated list comprises of 727 species belonging to 334 genera and 72 families. A total of 152 species have their type locality in India including 88 species that are endemic to the region. The current checklist indicates that 25% (183 species) of the records are questionable and require further examination. Our results highlight that marine annelid richness of the Indian sub-continent is underestimated with many of the native undescribed species being most likely concealed under ‘erroneous’ or ‘cosmopolitan’ records. With a combination of factors that include a lack of experts, funding, and failure to update regional literature has resulted in an incomplete state of knowledge for the marine annelid biodiversity from this region. Therefore, there is an urgent need for extensive and intensive sampling to discover new species, conduct detailed re-examinations of doubtful records and, collaborate within the local and international institutes and organizations to improve the regional biodiversity studies.


INTRODUCTION
The Phylum Annelida is among the most diverse invertebrate groups that inhabits the marine, freshwater, brackish, and terrestrial ecosystems. Annelids exhibit exceptional morphological and ecological diversity. Evolving and radiating globally around the Cambrian period (490-500 million years ago) this group diversified into 21,000 species (Appeltans et al. 2012;Weigert et al. 2014). The evolution of numerous feeding guilds, modes of locomotion, and reproductive strategies allow them to inhabit a wide range of marine habitats, spanning from the intertidal to the deep sea (Carvalho et al. 2013), including extreme environments such as Oxygen minimum zones (OMZ), cold seeps, and hydrothermal vents. Because of their diversity and dominance in most benthic habitats, they are a significant component of the marine ecosystem, forming an important link in the food web and nutrient recycling (Hutchings 1998). In addition, they are reliable ecological indicators for marine habitat quality because they are abundant, diverse, and contain both sensitive and tolerant species (Pocklington & Wells 1992).
Introduced as an established phylum (Lamarck 1802), classification of the Annelida has been updated numerous times and, of all the major animal clades, the annelid phylogeny has always been a unique and evolving challenge (e.g., Rouse & Pleijel 2007;Weigert & Bleidron 2016). Moreover, Annelida show the highest discordance between morphology and molecularbased phylogenetic knowledge (Andrade et al. 2015). Recent studies using next-generation sequencing and phylogenomic analyses have been able to resolve the annelid phylogeny, but many questions about their phylogeny are still unresolved (Weigert et al. 2014;Andrade et al. 2015;Struck et al. 2015;Weigert & Bleidorn 2016).
Classification of polychaete into Errantia and Sedentaria was the most common and widely used during the 20 th century (e.g., Day 1967;Hartman 1968). Based on morphological cladistics analysis of Annelida and other groups, a new classification was outlined ; however this classification was challenged by molecular data (Rouse & Pleijel 2007). According to Weigert & Bleidorn (2016), Annelida are divided into two major clades, Errantia and Sedentaria, and five basal branching lineages (Sipuncula, Amphinomida, Chaetopteridae, Magelonidae, and, Oweniidae).
The mega diverse Indian subcontinent contributes to approximately 7-8% of the total species recorded on our planet and shows a high level of endemism. The varied climatic, topographic, oceanographic, and hydrodynamic conditions have resulted in a wide range of habitats accounting for this rich biodiversity. Despite being labelled as a biodiversity hotspot region; with the exception of birds, mammals, and a few plant groups, rest of this biodiversity has received little attention. Comprehensive reviews of marine biodiversity, the most recent rate of loss of marine life, along with updated taxonomic monographs and checklists are lacking for many marine invertebrates, including the Annelida. Because of this, India has failed to overcome its taxonomic impediment for most of its biodiversity groups (Dar et al. 2012).
Studies on the Annelida in India dates from the late 17 th century with the description of a new species, Amphinome rostrata (Pallas, 1766). It was only in 1921, that the first comprehensive checklist of brackish water polychaetes was published (Southern 1921). A total of 30 polychaete species was reported including three new genera and 27 new species from the Gangetic Delta and Chilika in the east, and Kochi backwaters in the southwestern coast of India. During the following years, numerous papers were published, mostly from southern India (e.g., Gravely 1927;Krishnan 1936;Panikkar & Aiyar 1937;Paul 1942). Aiyar & Alikunhi focused on the interstitial polychaetes and made a number of significant publications (Aiyar & Alikunhi 1940, 1944Alikunhi 1941Alikunhi , 1942Alikunhi , 1943Alikunhi 1946Alikunhi , 1947Alikunhi , 1948Alikunhi , 1949Alikunhi , 1951. Annandale & Kemp (1915), Prashad (1919Prashad ( , 1921Prashad ( , 1935, Prashad & Awati (1929), DattaGupta et al. (1963), DattaGupta & Menon (1966), and DattaGupta (1974) made a significant contribution to the study of the Echiura from India. Badri Prasad Haldar contributed to the study of sipuncula from India and published the first checklist of Indian sipuncula (Haldar 1991). The aquatic oligochaetes of India were compiled by Naidu (2005) in the series of taxonomic publications, "Fauna of India" by the Zoological Survey of India (ZSI).
The first monograph on Indian polychaetes "Fauna zone (EEZ) has an area of 2.015 x 106 km 2 . The width of the western continental shelf varies from 345km off Daman (north) and tapers to 60km off Kochi (south). The western continental shelf of India has an area of about 3,10,000km 2 , with sediment and organic matter varying from the inner shelf to the outer shelf (Faruque & Ramachandran 2014). The eastern continental shelf also has a variable width of 35km off Tamil Nadu (south) to 120km around Digha (north). Just like the western shelf, the eastern continental shelf is also characterized by various sediment features . The country has 14 major, 44 medium, and 162 minor rivers with a total catchment area of 3.12 x 106 km 2 , discharging 1,645km 3 of freshwater every year to the seas around the country. The Ganga-Brahmaputra is the largest river in the country and third largest freshwater outlet to the world's oceans. All these features create a diverse coastal habitat which includes rivers and estuaries endowed with extensive mangroves and mudflats (e.g., the Sunderbans, the largest mangrove ecosystem of the world), coral reefs, seagrass beds, sandy and rocky shores, largest saltwater lake in Asia (Chilika) and the largest and most intense Oxygen minimum zone (OMZ) extending from 100 to 1,000 m depth (Arabian Sea). All these diverse habitats make the Indian coast a complex region that supports a speciesrich marine fauna ).

Data Collection
The marine annelid species data was compiled from published and grey literature. Our review of annelid related publications was restricted to the Indian continental shelf region. As for the deep sea, most of the knowledge on marine biodiversity is a result of environmental impact assessment (EIA) studies in the Central Indian Ocean basin, and ecological studies of OMZ and Carlsberg Ridge. Although, in most of these studies, polychaetes were the dominant taxa, identification was restricted to the genus or family level (Parulekar et al. 1993;Ingole et al. 2005Ingole et al. , 2010Pavithran et al. 2007Pavithran et al. , 2009 and therefore, were not considered in this review. Data from predatory journals were also not considered due to their conflicting and controversial information. The compiled species lists were checked against the World Register of Marine Worms (WoRMS) database (WoRMS Editorial Board 2020) for the synonyms, spelling errors, and updated species names. In this paper, we followed the classification of Weigert & Bleidorn (2016). The final list is presented in Table 1 with the following information: Species author, type-locality, distribution, Waltair = Visakhapatnam.

RESULTS
The updated checklist of marine annelids is presented in Table 1 that includes the accepted names, authors, the type locality, distribution information (world and India) followed by remarks, and references. The type locality information was taken from the original descriptions; however, whenever original publications were not available, information was extracted from other publications, WoRMS, and online resources. For publications with ambiguous information, e.g., Willey (1905), did not clearly describe if the type locality of species recorded were in India or Sri Lanka, and because of this we did not consider this information in the type locality species list from India. The annelid families and species names are presented alphabetically. Some recent changes in the families or genera have been followed, and their sources have been mentioned in the reference and remarks column. In the remarks and reference column, a short remark on the questionable records and references are mentioned to encourage further studies.
The marine annelids in India comprise of 727 species belonging to 334 genera and 72 families (Table 1 and Figure 2). Errantia is the most species-rich clade with 354 species belonging to 31 families in 151 genera (Table  2), and the most species-rich families are Nereididae (72 species and 17 genera), Eunicidae (33 and 8 genera), and Polynoidae (32 species and 22 genera). Sedentaria is

Doubtful species records from India
The checklist of marine Annelida from India that we have compiled is far from complete due to a number of reasons. Based on the criteria established, we identified a total of 173 species as questionable records and 10 misidentifications from the region (Tables 1 and 2). An example is the species Paraprionospio pinnata from the Spionidae family. This species has been frequently reported from ecological publications and local checklists. Yokoyama & Sukumaran (2012), however, suggested that the Paraprionospio species reported from India have been misidentified as P. pinnata. At present, Paraprionospio cordifolia (Yokoyama, 2007), P. cristata (Zhou, Yokoyama & Li, 2008), and P. patiens (Yokoyama, 2007) are the species of Paraprionospio reported from the region. Paraprionospio pinnata is considered a dominant species in the macrobenthic community having a wide distribution along the Indian coast, including the upwelling and OMZ areas Sivadas et al. 2016b). Based on type locality (Chile) and the recent publication of Yokoyama & Sukumaran (2012), there is a vital need to re-evaluate all records reported as P. pinnata. In addition to the above examples, based on the taxonomically revised publications, Capitella capitata (Fabricius, 1780), Eurythoe complanata (Pallas, 1766), Hydroides norvegica Gunnerus, 1768, Marphysa sanguinea (Montagu, 1813), Owenia fusiformis Delle Chiaje 1844, Serpula vermicularis Linnaeus, 1767, Sternaspis scutata (Ranzani, 1817), S. costata Marenzeller, 1879), and Terebellides stroemii Sars, 1835 and others are also considered as questionable records from India (Table 1).

DISCUSSION
The checklist presented in this publication represents the most updated list of marine Annelida recorded from the Indian subcontinent. The updated information based on species occurrence data recorded 727 species belonging to 72 families. We have identified 173 questionable and 10 misidentified species because all correspond to species with type localities and distributions outside the Indian Ocean region. Of the total of 183 erroneous species recorded, almost 50% of the species were reported by Fauvel (1932Fauvel ( , 1953 and five species by Hartman (1974a,b).
The use of publications from other regions (e.g., Day 1967) also resulted in the erroneous records. Fauvel and Day's monographs continue to be the most widely used references by most Indian researchers. Taxonomists like Fauvel, Day, and Hartman believed in the cosmopolitan distribution of polychaete species (Salazar-Vallejo et al. 2014;Hutchings & Kupriyanova 2018). Therefore, they recorded European species in their publications in the Indian Ocean and other regions and synonymized several species without evidence (Hutchings & Kupriyanova 2018). This resulted in the species found A. iricolor is probably a species complex and its cosmopolitan distribution is questionable (Colbath 1989;Zanol & Ruta 2015). Wehe & Fiege (2002); Glasby et al. (2016).

Family Bonneliidae
Acanthobonellia miyajimai (Ikeda, 1904) Tomari (Okinawa Island, Japan), Sea of Japan   (Sivadas et al. 2016a;Hutchings & Kupriyanova 2018). Like the polychaetes, there are no updated publications on the other marine annelid groups from this region. In the case of sipunculans, after the publication of the first checklist (Haldar 1991), there was no other publication on this group, except for a new subspecies report (Saiz et al. 2015). The aquatic oligochaetes of India were compiled by Naidu (2005) that reported 101 species and one subspecies from the region. Only three species, however, were reported from the estuarine and coastal areas. Although, oligochaetes, sipunculans, and echiurans are frequently reported in ecology papers, their identification is usually restricted to higher taxonomic level.

Impediments to taxonomy
This checklist was compiled with the aim of updating the Indian annelid species list for future references. A number of factors combine to make the current marine annelid checklist of India far from complete. One of the factors that contribute to a decline in biodiversity research is that taxonomic studies are largely neglected in favour of ecological research. There are other priorities that take over taxonomic research in this country, for e.g., global science trends, commercial or political treatise, and specific interests of some scientific lobbies and corporations. Evidence for this is substantiated from our bibliography review, wherein, only 207 publications were focused on annelid studies, and in the last few decades  only 74 papers were related to taxonomy (Figure 3). The Bombay Natural History Society (BNHS), Centre for Marine and Living Resources (CMLRE), CSIR-National Institute of Oceanography (CSIR-NIO), National Centre for Coastal Research (formerly, Integrated Coastal and Marine Area Management -Project Directorate; ICMAM PD), National Centre of Sustainable Coastal Management (NCSCM), ZSI, and a few credible Indian universities (e.g., Andhra University, Anna University, Annamalai University, Cochin University of Science and Technology, Goa University) are some of the institutions working on marine biodiversity. Marine biodiversity studies on J TT this subcontinent are mainly focused on select marine taxa, considered of economic importance, and the level of identification is often kept to genera/family level. We have also observed that biodiversity and ecology research are limited to a few locations along the Indian coast, such as, habitats near and around the host institutes and biodiversity hotspot regions like, the Gulf of Kachchh in Gujarat (northwest coast), Gulf of Mannar and Palk Bay in Tamil Nadu (southeastern coast) and, Andaman & Nicobar Island (Bay of Bengal). Therefore, a vast region of this country is still underexplored.
Further, there is limited work to update the checklist of marine invertebrates in the country (Parameswaran et al. 2017;Samuel et al. 2017). Monographic revisions allow identifying missing data, the need for new collections and additional data, and updated taxonomic status of a species (Dayrat 2011). The lack of recent monographic revisions makes Indian researchers depend on older literature and monographs or literature from temperate regions. The use of such sources is one of the primary reasons for erroneous species records found in the regional biodiversity data. A major drawback when referring to older literature is that the descriptions of many species are very brief with poor illustrations, limited or no supporting information on their location, reproduction or habitat (Hutchings & Kupriyanova 2018). Another drawback of overdependence on Fauvel and Day's monographs is that new species publications from the region, post 1953 Fauvel's publication, are not referred; as a result, those species have not been reported from any other location (e.g., Glycera embranchiata Krishnamoorthi 1962, Hesionides peculiaris Westheide & Rao, 1977, and Lycastonereis indica Nageswara-Rao, 1981.
A primary reason for the poor state of marine biodiversity knowledge is that most Indian institutes and universities lack trained taxonomists; as a result, young researchers are often 'self-taught' using outdated literature. Their complete dependence on outdated keys along with very short descriptions given in those publications ultimately results in erroneous species reporting. Currently, many institutions lack access to critical taxonomic literature, which may partly explain why researchers continue their dependence on such older literature. With these outdated works still cited in many recent publications, we feel that younger and newer researchers working on taxonomy need to make an effort to update and carry out taxonomic revisions of annelids from the Indian subcontinent. Most institutes and museums in India and other regions are digitizing their library collections, hence, many of these original publications are now easily available online for free and hopefully are being referenced by numerous researchers.
Our review of several ecological publications and EIA and monitoring reports revealed doubtful species records, misidentifications, spelling errors, and a usage of unaccepted scientific species names, a trend observed in ecological studies worldwide (Bortolus 2008;Sivadas & Madeswaran 2020). Since ecological studies form the baseline for many of the biological disciplines, it also plays an important role in spreading and magnifying the conceptual and methodological errors (Bortolus 2008). Moreover, taxon authorities and literature that were used for identification are not included in the reference sections of most publications. Although such publications were not considered in the present paper, researchers need to cite the identification literature and taxonomic authority as it will allow for future correction or verification and will also help to improve the citation quality of taxonomic papers. The alarming trend in systematic and taxonomic/bibliometric evaluation of publications is a topic that is extensively discussed (e.g., Krell 2002;Boero 2010;Steiner et al. 2015). In addition to the above reasons, predatory publications are affecting the quality of local marine research and in particular, the overall biodiversity and taxonomic studies in India (Raghavan et al. 2014). The superficial or non-existing peer review process in predatory journals does not allow fixing of scientific and taxonomic errors resulting in the propagation of the mistakes.
As mentioned earlier in this paper, ecology programs have been given a top priority over taxonomic studies in India in the last few decades. Premier institutes with access to research ships and state-of-the art facilities focus their research on ecology and other scientific disciplines. Mainly, due to the fact that acquiring funding for ecology projects are comparatively easier than for biodiversity programs. Ecological and monitoring projects are conducted on a long-term basis that can generate extremely valuable data on their distribution pattern, temporal variability, and habitat information and thus contribute to an increased knowledge of marine biodiversity of a region (Sivadas & Madeswaran 2020). This is evident from some of the recent new marine invertebrate species and checklist published from India as outcomes of ecology projects (e.g., Mandal et al. 2007Mandal et al. , 2018Yokoyama & Sukumaran 2012;Saiz et al. 2015;Parapar et al. 2016).

Role of Taxonomy in Conservation
Modification of Earth's ecosystem has altered biodiversity in many regions of the world which will be further exacerbated as consequence of human-induced climate crisis. The estimated global species extinction rate is between 100 and 1,000 times the rate during pre-human history (Lamkin & Miller 2016). Despite the biodiversity crisis, data shows that there is a decrease in the number of new species described in proportion to the number taxonomists (Costello et al. 2014). The limited knowledge of Earth's biodiversity in a rapidly changing environment will have a consequence on the conservation; mainly because, developing species conservation plans requires adequate knowledge and description of the species for that region. One of the most important criteria used for conservation plans are the indices of species diversity and endemism (e.g., Myers et al. 2000;Pimm et al. 2014;Ceauşu et al. 2015). Therefore the revelation that 25% of the recorded species from the region are doubtful records will have a major implication for biodiversity studies. As species also form the basis of variety of disciplines including ecology, biogeography, and monitoring, several modelling approaches have been developed to predict species distribution (Guisan & Thuiller 2005;Elith & Leathwick 2009). Such models, however, are often limited due to uncertainty and errors which includes deficiencies in species data (Costa et al. 2015).
Considering that most of the annelid species were first recorded during the 19 th century and subsequent records were based on older monographs (e.g., Day 1967), the identities of these historical species must be used with caution. Species that are identified incorrectly contribute to a false negative towards 'taxonomic and functional diversity estimates', leading to inaccurate results on the biodiversity data of a region (e.g., Beerkircher et al. 2009;Costa et al. 2015;Soultan & Safi 2017). This causes a domino effect resulting in poorly assessed decisions, leading policy makers to underestimate critical decisions that adversely affect our sensitive ecosystems (e.g., Morrison et al. 2009;Austen et al. 2016). As the present list of erroneous records was based on distribution data and literature, it can only be confirmed by examination of type material, or collection of fresh samples that need to be identified under expert guidance. Loss of native biodiversity due to misidentification is one of the most common examples of taxonomic errors (Bortolus 2008). Therefore, the information presented here should encourage future studies on the marine Annelida of the Indian subcontinent.

Way Forward
As a positive step towards improving our regional biodiversity studies, our paper contributes to the updated checklists of marine annelids from the Indian subcontinent. National and international collaborations with initiatives focusing on new exploration and training young researchers will be fundamental to complete annelid inventories and contribute to the worldwide effort to understand the world's biodiversity. Brazil, USA, Mexico, Spain, Russia, and the European countries are examples of how a continuous support for taxonomy results in the substantial growth of biodiversity studies and is reflected in the number of taxonomic papers published from these regions (de Carvalho et al. 2007). In fact, Brazil's 'National Zoology Program' is an example of a biodiversity program that was implemented in the 1980s at a relatively low cost. Hundreds of new taxonomists were trained, resulting in rapid increase in the reporting of new species, and the Brazilian zoological community continues to grow rapidly (Buckup et al. 2007;de Carvalho et al. 2007;Lana et al. 2017).
For improving the annelid research in India, the following initiatives are recommended: · Workshops for training and exchanging new data between Indian institutes and universities.
· Updating the current literature based on reevaluating type material and new collections under expert guidance.
· Increased collaboration between organizations working on ecology and biodiversity.
· Forming taxonomic groups or societies at the local and national levels.
· Form a standard process to track and maintain new species vouchers at private collections, institutes or at museums.
· Collaborate with international researchers and museums on new information, analysis techniques, and sample exchanges.

CONCLUSION
India, although a megadiverse region, knowledge of its marine biodiversity is yet to be acquired. Based on our assessment, this is also true for the marine annelid diversity of India and the numbers reported may indeed be an underestimation of the true diversity in India. A significant percentage of this undocumented diversity of annelid exists as 'cosmopolitan/ erroneous' species records. Accurate taxonomy will greatly benefit ecological studies and conservation programs as it will be J TT based on a relatively secure species list. We, therefore, feel it is crucial for India to know and recognize its native biota. National and regional initiatives focusing on new exploration, especially in deeper waters and training new researchers is a must for the future of annelid research in India. Given that the best technology and facilities are available in some of the national institutes, we suggest the active role of these organizations in biodiversity studies. Suitable as this may sound, we would still like to point out that no matter how efficient a given training is, it can only be beneficial if there are sufficient job opportunities in taxonomy available in that country. Just like annelids, most marine invertebrates of India are neglected and while compiling this paper, we have become even more aware of the magnitude of the work that still needs to be done in the area of marine biodiversity of the region. For this, we should be willing to accept our past mistakes in identifying species, and use this as a learning curve towards the accurate identification of native biota. Through this paper, we, therefore, hope to stimulate regional and international interest in improving the overall accuracy of India's regional taxonomy and new revisionary studies.