Strigamia Gray, 1843 is a genus of soil-dwelling centipedes widely distributed in both the Old and the New World and comprises over 70 species (Bonato et al., 2011) of which at least 32 are considered valid (sensu Bonato et al., 2012). In Europe 12 species are known although only half of these are proved to be valid (sensu Bonato & Minelli, 2014): Strigamia acuminata (Leach, 1816), Strigamia cottiana (Verhoeff, 1935), Strigamia crassipes (C.L. Koch, 1835), Strigamia maritima (Leach, 1817), Strigamia pusilla (Sseliwanoff, 1884) and Strigamia transsilvanica (Verhoeff, 1928). In Spain only two species were known until the present record: S. acuminata and S. crassipes, both apparently distributed in northern peripheral areas (Attems, 1952; Matic et al., 1967; Salinas, 1990; Gregory & Lewis, 2015), although distribution of these species in Spain is poorly known. A third Strigamia species is now added to the Spanish catalogue of centipedes, S. maritima. The main goal of this work is to document this discovery by providing morphological and ecological data and updated keys of identification for the genus Strigamia in Spain.

Strigamia can be distinguished from other Spanish geophilomorph genera by several characters as the dark brown or reddish colour of the trunk, number of leg pairs, anterior part of the body slightly narrowed and distally thickened throughout its length, a prominent basal denticle in the forcipular tarsungulum, pore-fields constricted mid-longitudinally in the posterior part of metasternites and many scattered ventral pores in the ultimate coxopleura. Strigamia maritima is readily differentiated from S. acuminata and S. crassipes by having sutural sulci separating pretergite and intercalary pleurites in the ultimate leg bearing segment (Bonato et al., 2012; Iorio & Labroche, 2015). Strigamia maritima may also differ in habitat segregation because it is a halobiont species frequently found under stones in intertidal coastal areas or in rock crevices on cliffs (Leach, 1817; Barber, 2009; Racine & Iorio, 2017; Cherpitel et al., 2019) since it can endure immersion in sea water for many hours (Lewis, 1961; Binyon & Lewis, 1963). The species is known from other coastal areas of Europe, specifically Belgium, Denmark, France, Germany, Great Britain, Ireland, Netherlands, Norway, Poland and Sweden (Bonato et al., 2012, 2016) (Fig. 1A). Strigamia maritima is one of the best known chilopod species with numerous biogeographical, development and genomic studies, especially in the past two decades (Kettle & Arthur, 2000; Chipman et al., 2004, 2014; Arthur & Chipman, 2005; Horneland & Meidell, 2009; Simaiakis et al., 2010; Brena & Akam, 2012, 2013; Robertson et al., 2015; Green et al., 2016, inter alia).

Sampling was carried out on 15^th August 2019 in a location near the village of Salías (29T 660344 4821020), in the council of Castropol in the province of Asturias (northern Spain, near the border with Galicia) (Fig. 1B). The specimen was found under pebbles in the Eo estuary (Fig. 1C) at low tide at a distance of a few metres from the estuary shore. It was hand collected and then fixed in ethanol 70% to be later identified using a binocular stereo microscope model NOVEX AP-2 (10-60x). Maps of distribution were generated with QGIS Desktop 3.4.4 with GRASS 7.4.4. Habitus in vivo was photographed with a Panasonic Lumix DMC-FZ200 camera equipped with a Raynox DCR-250 macro lens. The habitat picture was provided by G. Sánchez Jardón and photographs of the morphology of specimens were taken by A. J. Narro Martín with a Nikon D810 camera equipped with a Cnscope 4X Achromatic Microscope Objective Lens with extension tube.

A female specimen with 51 leg pairs could be determined as belonging to the Strigamia genus but the specimen did not fit any of the morphological descriptions of the species reported in Spain. Several characters as the presence of sutural sulci dividing the pleuropretergite in the ultimate leg bearing segment and the medial sub-circular fossae with adjacent comma-shaped depressions in anterior trunk metasternites were definitive to determine its species, S. maritima.

Strigamia maritima (Leach, 1817)

Material examined. 1♀, Spain: Eo [Ribadeo] estuary, [village of] Salías, [council of] Castropol, [Principality of] Asturias, 29T 660344 4821020, 15/08/2019, 0 m, D. Cabanillas leg. & É. Iorio det. 2019. In the author’s collection.

Short description. Body size 29 mm and 51 leg pairs, a dark brown trunk and a reddish brown cephalic plate (in vivo) (Fig. 2A). Forcipular tergite not distinctly narrowing forwards throughout its length, forcipular tarsungulum not clearly flattened and with a well-marked basal denticle (Fig. 2B). Anterior trunk metasternites with medial sub-circular fossae with adjacent comma-shaped depressions (Fig. 2C). Trunk metasternites with paired pore-fields in the anterior part, a transverse pore-field constricted mid-longitudinally in the posterior part and without sclerotized longitudinal stripe. Ultimate leg bearing segment with sutural sulci between pretergite and intercalary pleurites (Fig. 2D), no dorsal pores in the ultimate leg bearing coxopleura but 10/11 scattered pores in the ventral side (Fig. 2E).

Ecological remarks. Halobiont species frequent in coastal areas. The specimen was found under pebbles near the estuary shore but outside the intertidal area.

Identification key. Based on previous European keys provided by Bonato et al. (2014) and Iorio & Labroche (2015), an illustrated dichotomous key for the Strigamia species of the Iberian Peninsula is presented (see Appendix 1 for key in Spanish).

Geophilomorpha is a well-known chilopod order but there is a lack of studies focused on its morphology and ecology in Spain. Only a few authors studied the morphological variations of the Spanish populations and made comparisons with other European specimens (Serra, 1978; García-Ruiz, 1997; Vadell & Pons, 2008, 2009; Gregory & Lewis, 2015). Species corology is generally poorly studied and currently it is difficult to predict the Spanish distribution of many species and what kind of habitats they are capable to exploit. It is assumed that sampling centipedes in Spanish coastal habitats is usually dismissed since it is expected to obtain low diversity values, thus overlooking the presence of halophilous or halobiont species as is the case of Strigamia maritima. This species is supposed to exclusively inhabit in European coastal areas of the Atlantic Ocean, from northern to southwestern countries (Bonato et al., 2012, 2016). The nearest record of S. maritima from mainland Spain was reported in Saint-Jean-de-Luz in the French Atlantic Pyrenees (Cherpitel et al., 2019), suggesting this species potentially occurs along the Cantabrian Sea coasts of the Iberian Peninsula. Hence the importance of sampling the Spanish coastal areas. So further studies should be focused on characterising the chilopod fauna of estuaries, beaches, cliffs and intertidal areas of northern Spain.