Corresponding author: Emilia Rota (
Academic editor: Robert Blakemore
The ocnerodrilids
The
All of the endemic ocnerodrilid genera and species are confined to South America, sub-Saharian Africa, and India but several peregrine species are currently distributed at tropical and subtropical latitudes worldwide:
The collection in the River Thames (UK) occurred during a benthic survey carried out by Emu Ltd in 2000, covering both intertidal and subtidal areas. Intertidal cores were collected using a PVC pipe sampler (12 cm ID, 50 cm long), subtidal samples were taken by means of a small grab from a vessel (Dr Steve Jarvis, in litteris). The worms were passed to me, partly in alcohol and partly sectioned on slides, by Dr Tarmo Timm (Estonia). The specimens from River Golo (Corsica) were extracted alive in Siena from moist grey sand sampled on the river bank and carried to Siena in PVC vials by Prof. Folco Giusti. All the material from Liguria, Italy, was collected by Dr Marco Bodon and colleagues during regional water quality monitoring programs using standard macroinvertebrate methods for rivers (handnet and Surber net sampling). The many occurrences in Liguria cover a variety of situations: perennial and intermittent water courses, stream beds with or without vegetation, gravelly or sandy-muddy bottoms, with slopes 0.2-3.5%, at a distance of up to 4.2 km from the river mouth (altitude 1-148 m a.s.l.), in the proximity or not of agricultural, domestic and industrial waste and sewage inputs. At the time of collection, the wet river bed at the various stations ranged between 2-40 m in width, the mean depth 10-35 cm, pH 7.9-8.4, conductivity 187-390 µS/cm, and IBE values ranged overall between 5 and 9-10. Adult specimens were sampled from April through November. The collection in Veneto, Italy, was part of an unpublished 1981-1983 survey of the earthworm fauna populating the center of the Veneto region. The finding occurred in an area of warm saline springs surrounded to the west by the Euganean Hills and to the east by a network of waterways that flow downwards to the Adriatic sea. The worms were collected manually by digging at a distance of 0.5-5.0 m from a thermal ditch.
Body size 30-70 x 1-1.8 mm. Segment number 70-130. Easily identified by the annular clitellum covering XIII-XX and marked ventrally by two longitudinal grooves connecting the prostate pores (in XVII, XIX) and male pores (in XVIII) of each side (Fig.
Body size 30-40 x 1-1.4 mm. Segment number 60-80. Easily identified by the annular clitellum covering XIII-XIX or XIII-XX marked ventrally by small paired male porophores on XVII (Fig.
In Europe
A survey of the literature suggests the ability of this species to colonize diverse habitats through multiple pathways. Records in non-native regions range from well-preserved natural water bodies to artificial wet biotopes (man-made water catchments, flooded or irrigated areas, zoological gardens) or degraded sites along streams or rivers (e.g.
River traffic and port activities have made the Thames catchment one of the most highly invaded freshwater systems in the world, particularly in the London area (
Floods and roads (i.e. human activities involving downhill and uphill transport) must play an important role in accelerating the local dispersal of this species. Both the River Golo and the majority of watercourses in Liguria are characterised by a torrential mode with short and violent floods. The former record from Italy (
The only outdoor records of
The present new records are the first from northern Italy (Veneto and Liguria). The recording site in Liguria was near an area of floral trading companies (e.g. MFI Italia Esportazione Fiori).
Increasing international trade and human-induced environmental changes are multiplying the chances, modes and pathways of dispersal of exotic earthworm species in Europe. The case of an epigeic tropical megascolecid s.l.,
I wish to thank Steve Jarvis (Marine Invertebrate Ecological Services, UK), Marco Bodon (ARPAL, Liguria Regional Environmental Protection Agency, Italy), Pietro Omodeo and Folco Giusti (University of Siena, Italy), for collecting the examined material and Tarmo Timm (Estonian University of Life Sciences) for forwarding the London sample. Marco Bodon kindly provided also environmental data for the stations sampled in Liguria.
Map of outdoor records of