Arcuatula senhousia (Benson, 1842), the Asian date mussel in the UK.
An articulated shell of Arcuatula senhousia was found loose on sand in the intertidal mid-high shore area of a site in the Solent on 25th October 2017. The specimen was not living but was generally in good condition (Fig. 1 A–D). The shell is thin and fragile and the left valve has a small hole near the posterior edge (Fig. 1 A–B). It measures 18.7mm (length) x 9.0mm (height) x ~6.3mm (breadth). The shell has been deposited at Amgueddfa Cymru – National Museum Wales, Cardiff: NMW.Z.2018.003.00001.
The article cited above was the first published evidence for the species in the UK.
The article cited above was the first published evidence for the species in the UK.
Media coverage
The story was first published in The Times and then picked up by other news outlets.
Reuters - Thursday, January 03, 2019
Invader mussels encroach on British beaches
That's TV (Solent) - Wednesday, January 23, 2019
A non native species of mussel has been discovered in the solent
Daily Mail (online) - Wednesday, January 02, 2019
'Sinister' Chinese mussel that can smother scallops and oysters has made its way into British waters
The story was first published in The Times and then picked up by other news outlets.
Reuters - Thursday, January 03, 2019
Invader mussels encroach on British beaches
That's TV (Solent) - Wednesday, January 23, 2019
A non native species of mussel has been discovered in the solent
Daily Mail (online) - Wednesday, January 02, 2019
'Sinister' Chinese mussel that can smother scallops and oysters has made its way into British waters
The text that follows contains further thoughts and information and should be cited separately as, for example:
Barfield, P.D. (2018). Sea-nature Studies - Arcuatula senhousia (Benson, 1842), the Asian date mussel in the UK [online]. Available at: <https://www.seanature.co.uk/arcuatula_senhousia.html>. Accessed [day month year].
Barfield, P.D. (2018). Sea-nature Studies - Arcuatula senhousia (Benson, 1842), the Asian date mussel in the UK [online]. Available at: <https://www.seanature.co.uk/arcuatula_senhousia.html>. Accessed [day month year].
Many live specimens were subsequently found, and these have been sampled and are stored in ethanol for molecular analysis. After writing the article it became clear that some previously unpublished data existed. Nine Environment Agency (EA) records from 2016 were added to the National Biodiversity Network (NBN) Atlas for Southampton Water. This and other data were kindly provided by the EA who first found the species in samples from the same broad area in 2011* and then again in 2013. Natural England also had one unpublished record from 2013, again in the Solent.
At the time the original article was written it was clear that A. senhousia was living and feeding in the intertidal area sampled but it remained unclear whether or not it was part of an 'established' population. An ‘established’ population, according to the Convention on Biological Diversity, is one that is ‘successfully producing viable offspring with the likelihood of continued survival’ (COP 6, decision VI/23). Or, in other words, one that is self-sustaining without the need for repeated introduction events. It can now be said, with a degree of certainty, that the species is 'established' in the UK. I presented this finding in a poster at the 20th Anniversary of the Malacological Societies, Molluscan Forum on the 22nd of November 2018 at the Natural History Museum in London:
At the time the original article was written it was clear that A. senhousia was living and feeding in the intertidal area sampled but it remained unclear whether or not it was part of an 'established' population. An ‘established’ population, according to the Convention on Biological Diversity, is one that is ‘successfully producing viable offspring with the likelihood of continued survival’ (COP 6, decision VI/23). Or, in other words, one that is self-sustaining without the need for repeated introduction events. It can now be said, with a degree of certainty, that the species is 'established' in the UK. I presented this finding in a poster at the 20th Anniversary of the Malacological Societies, Molluscan Forum on the 22nd of November 2018 at the Natural History Museum in London:
The following video was taken on the 30th September 2018.
- The native range of A. senhousia extends from the type locality of Zhoushan, China (an island near Shanghai) north to the Kuril Islands and the Siberian coast and south to Singapore;
- The northern edge of the native distribution is at the southern end of the Kuril Islands, just north of Japan;
- The species now has a global distribution and the UK population was its most northerly extent until it was reported from the Netherlands, summer 2018 (Faasse, 2018);
- The previous closest record to the UK was from Arcachon Bay, southern Bay of Biscay (first found in 2002, Bachelet et al., 2009);
- The Solent population was likely seeded from an introduction event somewhere nearby;
- It is not clear how it arrived but shipping is suspected as the most likely vector;
- It is important to note that positive and negative effects have been reported from other locations;
- It is often predated by local native fauna and the first specimen found in the Solent had, what appeared to be a drill-hole in it’s left valve;
- If conditions support a population increase such that continuous mats form then negative impacts may be observed;
- These mats have been reported as having densities in excess of 1500m-2; and,
- It is considered prudent to monitor the UK population to track it's development and interactions with local species as it could pose a threat to coastal habitats / economies.
Further notes on the Type Specimen
First off it's probably worth clarifying what is meant by the term 'Type Specimen'. The International Code of Zoological Nomenclature (ICZN) describes it as follows:
'Type specimens are the objective standard of reference for the application of zoological names. When a new species or subspecies is described, the specimen(s) on which the author based his description become the type(s) (Article 72.1). In this way names are linked to type specimens, which can be referred to later if there is doubt over the interpretation of that name.'
The Type Specimen for Arcuatula senhousia i.e. the specimen which Benson used to first describe the species in 1842 was collected by Doctor Theodore Edward Cantor a Danish physician, zoologist and botanist who worked for the Bengal Medical Service. Dr Cantor was sent to Chusan, China in 1840 as an assistant surgeon to HM 26th Regiment, the Cameronians. He was there until at least November of that year and took the opportunity to collect many zoological and botanical samples for the Museum of the Court of Directors of the East India Company. Whilst there Cantor was afflicted with a 'violent cerebral fever' and because of this he was eventually sent back to India. He passed the molluscan fauna he collected in Chusan to Benson, who had expertise in this group, for analysis.
First off it's probably worth clarifying what is meant by the term 'Type Specimen'. The International Code of Zoological Nomenclature (ICZN) describes it as follows:
'Type specimens are the objective standard of reference for the application of zoological names. When a new species or subspecies is described, the specimen(s) on which the author based his description become the type(s) (Article 72.1). In this way names are linked to type specimens, which can be referred to later if there is doubt over the interpretation of that name.'
The Type Specimen for Arcuatula senhousia i.e. the specimen which Benson used to first describe the species in 1842 was collected by Doctor Theodore Edward Cantor a Danish physician, zoologist and botanist who worked for the Bengal Medical Service. Dr Cantor was sent to Chusan, China in 1840 as an assistant surgeon to HM 26th Regiment, the Cameronians. He was there until at least November of that year and took the opportunity to collect many zoological and botanical samples for the Museum of the Court of Directors of the East India Company. Whilst there Cantor was afflicted with a 'violent cerebral fever' and because of this he was eventually sent back to India. He passed the molluscan fauna he collected in Chusan to Benson, who had expertise in this group, for analysis.
The shells in the image below were all collected on the 20th December 2018. These specimens were dead and found floating in on the flood tide that day. The specimens are large with several measuring just over 30mm in length. These are the largest examples found to date.
Multiple examples of the Asian date mussel, Arcuatula senhousia (Benson, 1842) collected from a site in the Solent, 20th December 2018.
*Update October 2020
The EA records from 2011 have now been published on by Worsefold et al., 2020:
Worsefold, T. M., Pennisi, N., & Ashelby, C. W. (2020). Theora lubrica Gould 1861 (Bivalvia: Semelidae), new to the UK, with notes on associated non-native species, and an earlier date of introduction for Arcuatula senhousia (Bivalvia: Mytildae) to the UK. Journal of Conchology, 43(6), 665–674.
The EA records from 2011 have now been published on by Worsefold et al., 2020:
Worsefold, T. M., Pennisi, N., & Ashelby, C. W. (2020). Theora lubrica Gould 1861 (Bivalvia: Semelidae), new to the UK, with notes on associated non-native species, and an earlier date of introduction for Arcuatula senhousia (Bivalvia: Mytildae) to the UK. Journal of Conchology, 43(6), 665–674.
References
Bachelet, G., Blanchet, H., Cottet, M., Dang, C., Montaudouin, X. de, Queirós, A. de M., Gouillieux, B. and Lavesque, N. (2009). A round-the-world tour almost completed: first records of the invasive mussel Musculista senhousia in the north-east Atlantic (southern Bay of Biscay). Marine Biodiversity Records, 2(e119).
Faasse, M. (2018). A record of the Asian mussel Arcuatula senhousia (Benson in Cantor, 1842) from NW Europe (the Netherlands). Spirula, 416, 14–15.
Worsefold, T. M., Pennisi, N., & Ashelby, C. W. (2020). Theora lubrica Gould 1861 (Bivalvia: Semelidae), new to the UK, with notes on associated non-native species, and an earlier date of introduction for Arcuatula senhousia (Bivalvia: Mytildae) to the UK. Journal of Conchology, 43(6), 665–674.
Bachelet, G., Blanchet, H., Cottet, M., Dang, C., Montaudouin, X. de, Queirós, A. de M., Gouillieux, B. and Lavesque, N. (2009). A round-the-world tour almost completed: first records of the invasive mussel Musculista senhousia in the north-east Atlantic (southern Bay of Biscay). Marine Biodiversity Records, 2(e119).
Faasse, M. (2018). A record of the Asian mussel Arcuatula senhousia (Benson in Cantor, 1842) from NW Europe (the Netherlands). Spirula, 416, 14–15.
Worsefold, T. M., Pennisi, N., & Ashelby, C. W. (2020). Theora lubrica Gould 1861 (Bivalvia: Semelidae), new to the UK, with notes on associated non-native species, and an earlier date of introduction for Arcuatula senhousia (Bivalvia: Mytildae) to the UK. Journal of Conchology, 43(6), 665–674.