Confirming the status of Lancashire’s endemic freshwater Nemertean – Prostoma jenningsi

Abstract

The aim of this study was to confirm the status of Lancashire’s endemic freshwater Nemertean – Prostoma jenningsi.
Due to human induced environmental change and the degradation of habitats, a vast decline in biodiversity has been witnessed on a global scale, with losses occurring among many native UK species. P. jenningsi (known locally as the ‘Croston Worm’), is considered to be Lancashire’s only endemic species, thought to exist solely in the Clay ‘Ole, Bretherton; however, its existence at the site has not been confirmed since 1999. Endemic species are considered to be of intrinsic value to the biodiversity of the UK and P. jenningsi was designated a UK Biodiversity Action Plan (BAP) species in 2007 and a Species of Principal Importance to England through the Natural Environment and Rural Communities Act from 2008, but is currently listed in the British Red Data Book as Insufficiently Known.
Nemertea are a diverse group of free-living, benthic, simple soft-bodied acoelomate animals. An eversible proboscis, used primarily in prey capture, is a shared characteristic of the taxon. Nemertea have very few morphological characteristics that can be used for diagnosis of species, genera or even family, thus making taxonomy difficult. Therefore, doubt surrounds existing species descriptions and their relationships.
In 2011, researchers at the University of Central Lancashire (UCLAN) (including the author) initiated a project in conjunction with Natural England and the Wildlife Trust for Lancashire, Manchester and North Merseyside (LWT), to confirm the existence of the ‘Croston Worm’ at the Clay ‘Ole. The initial project was unable to locate a population of P. jenningsi; however, subsequent research revealed two populations of Prostoma spp at alternative pond locations in Lancashire. Initial DNA analysis revealed the populations to be Prostoma eilhardi, a species with known worldwide distribution. A putative, type specimen of P. jenngsi, was obtained from the Natural History Museum to allow comparisons with collected specimens; however, due to the age and preservation methods associated with the sample, it was not possible to extract DNA for analysis. Results from the study raised questions regarding the validity of the designation of P. jenningsi as a unique species.
This Masters by research project sought to build upon this preliminary (unpublished) work to confirm the current status of P. jenningsi, through the extensive re-sampling of the Clay ‘Ole site and expanding sampling to further selected locations across Lancashire.
A population of Prostoma spp was located at the Clay ‘Ole site and three additional populations recorded at locations in Lancashire. Comparisons of 18s (nuclear) gene and COI (mitochondrial) gene sequences, made with those stored on global databases (GenBank and BOLD), found recovered specimens to be identical to both P. graecense and P. eilhardi. This questioned the validity of information supplied by the online databases and confirmed the miss-identifications of P. jenningsi as a separate species made through traditional histological methods. DNA barcoding, using the COI gene, is considered to be an effective tool in resolving species identity in Nemerteans; however, in the case of Prostoma spp, a larger data set may be required to distinguish whether P. graecense and P. eilhardi are two distinct species. In addition, the limited genetic diversity displayed between samples from Lancashire and locations in both Europe and USA raised further questions related to species dispersal and mode of reproduction. Further DNA research is required in order to address these questions.
In the case of P. jenningsi, it is proposed that the current listing in the British Red Data Book and designation under the Natural Environment and Rural Communities Act are no longer valid.