The Pycnogonids (Arthropoda, Pycnogonida) of Torrevaldaliga (Tyrrhenian Sea), Italy, with data on Endeis biseriata, new record for the Mediterranean Sea

Abstract

New data about the Mediterranean pycnogonids are given. For this contribution, we analysed 315 samples that until now had remained unidentified, collected in 1979–1980 in the Tyrrhenian Sea close to Torrevaldaliga, Italy. We found six species: Ammothella appendiculata, Anoplodactylus californicus, Endeis biseriata, Endeis spinosa, Nymphon gracile and Tanystylum conirostre. Two of them are the subject of taxonomical and faunal remarks: morphological features of Anoplodactylus californicus specimens are reported and discussed, and the first record of Endeis biseriata for the Mediterranean Sea is reported.

Keywords:

• Pantopoda
• power station
• fouling
• marine fauna
• Italy

Introduction

Pycnogonids are exclusive marine Arthropoda: Chelicerata whose morphology earned them the common name of “sea spiders”. In the basin of Mediterranean Sea about 56 species are known to date (Lehmann et al. 2014), 44 of which have been recorded in the Italian seas (Bartolino & Chimenz 2010). Very few studies about Pycnogonida have been performed in the Tyrrhenian Sea. Among these, Chimenz et al. (1979) studied the fauna of Civitavecchia harbour, finding 15 species, and used those data to outline some faunal and zoogeographical considerations (Chimenz Gusso & Lattanzi 2003). In addition, Arnaud studied samples from the same area in 1978 and confirmed the presence of some species cited by Chimenz (Arnaud 1987). In this paper we examine an old and ignored collection from the nearby locality of Torrevaldaliga with the aim to enrich our knowledge of the pycnogonid fauna in the North Tyrrhenian Sea, updating the species list for this area.

Materials and methods

Study area

The samples analysed come from the Torrevaldaliga Power Station (one group of 200 MW and three of 320 MW). This is situated in the homonymous town along the coast (near Civitavecchia, 80 km North to Rome) in the Tyrrhenian Sea; a map of the area is provided in Figure 1. Here, four main conduits pump the water from the sea, and two outfall zones discharge the water into the sea 10°C warmer than that entering the intakes (Relini et al. 1980). Between 1978 and 1979 a study of the fouling communities in different areas of this station was carried out (Relini & Bianchi 1979a; Morri 1980; Relini et al. 1980). In particular, it appears (from the available data) that pycnogonids were collected in adduction channels, with low brightness and considerable water current, and in calm tanks, characterised by exposure to light and low water speed. Only four samples were collected in the outlet channel, characterised by high water turbulence, the presence of light and warm water (Relini & Bianchi 1979b; Relini et al. 1980).

Figure 1. Localisation (red spot on the top left map) and plan of Torrevaldaliga Power Station (from Relini et al. 1980, mod.)

Collection and identification of specimens

Asbestos cement plates (200 × 300 × 3 mm) immersed in the different areas of the power station at a depth of 2 m were used to collect fouling. These panels were replaced at varying frequencies (every month, every 3 months and then after 6, 9 and 12 months) (Relini et al. 1980). Fouled panels were fixed in 10% buffered formalin in sea water. The fixing means was then inspected under a stereomicroscope and specimens were collected and preserved in pure ethanol.

The original study was focused on the presence and biodiversity of major fouling fauna, to determine dominant communities and their development (Relini et al. 1980). Pycnogonids were considered secondary organisms (Relini & Bianchi 1979a), and this is probably the reason why some samples (for a total of 40 individuals), although from the same collection, lack environmental data.

Identification of specimens was made under a stereomicroscope, based mainly on the monograph of the Iberian fauna by Munilla and Soler-Membrives (2014); the analysis of some details and diagnostic measurements were performed by means of an interference contrast microscope (Leica DM LB2), a Leica DFC 295 camera and Leica Application Suite (v. 3.8). Three specimens of Anoplodactylus californicus (two males and one female) and three specimens (two males and one female) of Endeis biseriata were dehydrated in a graded ethanol series and then were transferred onto stubs, sputter coated with gold and observed under a scanning electron microscope (SEM: Vega3_TESCAN Microscope type LMU).

All the studied material is preserved in the museum collection (Zoology section) of the Department of Earth, Environment and Life Sciences (DISTAV) of Genoa University (MU-DISTAV-UGE-Zool–Pycno: 958–1245; 1496–1510; 1514–1515; 1517; 1565–1573). The nomenclature and the systematic order proposed by World Register of Marine Species (WoRMS) (WoRMS Editorial Board, 2020) is adopted.

Results

List of pycnogonid species

A total of 315 pycnogonids were collected in 1979–1980: only three specimens were identified at the genus level only (one juvenile of Achelia sp. and two juveniles of Ammothella sp.); the others were classified to the species level and assigned to the following six species: Ammothella appendiculata (Dohrn, 1881), Anoplodactylus californicus Hall, 1912, Endeis biseriata Stock, 1968, Endeis spinosa (Montagu, 1808), Nymphon gracile Leach, 1814 and Tanystylum conirostre (Dohrn, 1881). Anoplodactylus californicus and Tanystylum conirostre were the dominant species, with 178 and 101 individuals, respectively. Integrating our data with those available from Bartolino and Chimenz (2010) and Lehmann et al. (2014), an updated checklist of Central Tyrrhenian pycnogonids is given (Table I), considering the biogeographical area from the coastline of Sardinia and from Piombino to the entire Gulf of Gaeta, belonging to the northern section of the central-western area of the Mediterranean Sea (Area 2, based on Bianchi 2004). In addition, when possible, some information about historical records of species in the entire Tyrrhenian area are reported.

Table I. Checklist of pycnogonid species in the Tyrrhenian Sea, with some indications of their distribution. Legend: CT, Central Tyrrhenian Sea; GN, Gulf of Naples; NT, North Tyrrhenian Sea; SAR, Sardinia; ST, South Tyrrhenian Sea. Bibliographic references to the distribution are reported; geographical indications for which no bibliographic reference is given are reported by Bartolino and Chimenz (2010) without further references in the literature

Family	Species	CT	GN	NT	SAR	ST	Reference(s)
Ammotheidae	Achelia echinata Hodge, 1864	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Arnaud 1987; Chimenz Gusso & Lattanzi 2003)
	A. langi (Dohrn, 1881)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	A. vulgaris (Costa, 1861)		X				Gulf of Naples (Dohrn 1881)
	Ammothella appendiculata (Dohrn, 1881)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Arnaud 1987; Chimenz Gusso & Lattanzi 2003)
	A. biunguiculata (Dohrn, 1881)	X	X				Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
	A. longioculata (Faraggiana, 1940)	X		X		X	Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
	A. longipes (Hodge, 1864)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	A. uniunguiculata (Dohrn, 1881)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	Neotrygaeus communis (Dohrn, 1881)	X	X		X	X	Central Tyrrhenian Sea (Chimenz et al. 1979; Arnaud 1987; Chimenz Gusso & Lattanzi 2003); Sardinia (Bouvier 1923)
	Paranymphon spinosum Caullery, 1896	X	X	X			Gulf of Naples (Chimenz & Cottarelli 1986)
	Tanystylum conirostre (Dohrn, 1881)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Arnaud 1987; Chimenz Gusso and Lattanzi 2003)
	T. orbiculare Wilson, 1878	X		X			Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
Ascorhynchidae	Ascorhynchus arenicola (Dohrn, 1881)	X	X	X		X	South Tyrrhenian Sea (Chimenz & Cottarelli 1986; Arnaud 1987)
	A. castelli (Dohrn, 1881)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	A. pudicus Stock, 1970	X					Bartolino and Chimenz (2010)
	A. simile Fage, 1942	X					Bartolino and Chimenz (2010)
Callipallenidae	Callipallene acribica Krapp, 1975	X					Bartolino and Chimenz (2010)
	C. emaciata (Dohrn, 1881)	X	X	X			Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
	C. phantoma (Dohrn, 1881)	X	X	X			Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
	C. producta (Sars, 1888)	X					Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
	C. spectrum (Dohrn, 1881)	X	X	X			Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
	C. tiberi (Dohrn, 1881)	X	X				Central Tyrrhenian Sea (Lehmann et al. 2014)
Endeidae	Endeis biseriata Stock, 1968	X					Torrevaldaliga present paper
	E. charybdaea (Dohrn, 1881)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	E. spinosa (Montagu, 1808)	X	X	X			Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
Nymphonidae	Nymphon gracile Leach, 1814	X	X	X			Gulf of Naples (Bouvier 1923); Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
Phoxichilidiidae	Anoplodactylus angulatus (Dohrn, 1881)	X	X			X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	A. californicus Hall, 1912	X				X	Central Tyrrhenian Sea (Chimenz et al. 1979); South Tyrrhenian Sea Arnaud 1987)
	A. massiliensis Bouvier, 1916	X					Bartolino and Chimenz (2010)
	A. petiolatus (Krøyer, 1844)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003); Gulf of Naples (Dohrn 1881; Chimenz & Cottarelli 1986)
	A. pygmaeus (Hodge, 1864)	X	X	X		X	Central Tyrrhenian Sea (Chimenz et al. 1979; Chimenz Gusso & Lattanzi 2003)
	A. virescens (Hodge, 1864)	X	X			X	Gulf of Naples (Arnaud 1987)
Pycnogonidae	Pycnogonum nodulosum Dohrn, 1881	X	X		X		Gulf of Naples (Chimenz 1978); Sardinia (Lehmann et al. 2014)
	P. plumipes Stock, 1960	X					Bartolino and Chimenz (2010)
	P. pusillum Dohrn, 1881	X	X	X			Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)
Rhynchothoracidae	Rhynchothorax alcicornis Krapp, 1973	X	X				Gulf of Naples (Arnaud 1987)
	R. mediterraneus Costa, 1861	X	X				Gulf of Naples (Dohrn 1881); Central Tyrrhenian Sea (Chimenz Gusso & Lattanzi 2003)

Taxonomic accounts

Class Pycnogonida Latreille, 1810

Order Pantopoda Gerstäcker, 1863

Family Ammotheidae Dohrn, 1881

Genus Ammothella Verill, 1900

Ammothella appendiculata (Dohrn, 1881)

Syn: Ammothea appendiculata Dohrn, 1881

Material examined

2 ovigerous ♂♂, 1♀, August 1979, calm tank; 1♂, October 1980, adduction channel.

Remarks

The only female specimen collected displays small tubercles on each lateral process; because of these details it can be confused with A. longioculata (Faraggiana, 1940) or A. longipes (Hodge, 1864), but the abdomen’s morphology and the complete segmentation of the body allowed us to identify this individual as A. appendiculata (Munilla & Soler-Membrives 2014). Although in this collection A. appendiculata is represented by only four specimens, it is well known that this species is common in fouling communities, especially in the Mediterranean area (Arnaud & Bamber 1987).

Distribution

Species distributed worldwide but absent in polar environment (Munilla & Soler-Membrives 2014).

Depth range

Infralittoral species, registered at depths between 0 and 65 m (Munilla & Soler-Membrives 2014).

Family Endeidae Norman, 1908

Genus Endeis Philippi, 1843

Endeis biseriata Stock, 1968(Figure 2)

Figure 2. Endeis biseriata Stock, 1968 (scanning electron microscope images). (a) dorsal view of an ovigerous male; (b) detail of the oviger where it is visible a bulge on the 6^th article; (c) detail of propodus and claws; (d) detail of the femur’s distal spur with a long seta (the insertion of the lateral one is also visible); (e) detail of femur on which two lines of cement gland pores are visible; (f) detail of cement gland pores. Scale bars: a = 500 μm, b–e = 200 μm, f = 100 μm

Material examined

1 ovigerous ♂, April 1979; 2 ovigerous ♂♂, 1♂, 2♀♀, August 1979, calm tank; 1♀, 2 juvenile ♂♂, November 1979; 1♂, September–November 1980; 1♂, 1♀, August 1980; 1 ovigerous ♂, 3♂♂, 4♀♀, October 1980, adduction channel.

Diagnosis

Trunk slender, with complete segmentation; lateral processes separated by a distance equal to or greater than their own diameters, with a variable number of small dorso-distal tubercles. Four eyes evident at the base of a conical ocular tubercle. Proboscis a little narrower at the base (with collar), with an enlargement at about 1/3^rd of its length and parallel to the tip. Abdomen erect, much longer than the 4^th lateral processes. The 7–segmented ovigers show a bulge on the 6^th article with recurved spines and no denticulate ones. Very long legs, femora with a long distal spur, two smaller lateral spurs and a number of variable cement gland pores, from 32 to 48. Propodus is curved, with four heel spines followed by fewer than 10 smaller spines; auxiliary claws are at least 1/3^rd the size of the main claw.

Remarks

The genus Endeis is very homogeneous, and single species are recognisable using characters that usually do not have a main role in the diagnosis of most other pycnogonid genera (Fry & Hedgpeth 1969).

Endeis biseriata shows a massive body (Figure 2(a)) compared to other species, but the main diagnostic character for its identification consists in the different number of cement gland pores and their arrangement on the male femora (Stock 1968). With the use of SEM, we verified the presence of two sinuous lines of pores on male femora, variable in number from 40 to 48 (Figure 2(e,f)). This character combined with all morphological features cited previously (some reported in Figure 2) made it possible to distinguish this species from others having two rows of cement glands. Endeis flaccida Calman, 1923 shows a large number of pores on the femora (about 57; Calman 1923), and Endeis nodosa Hilton, 1942 can be identified from its ventral femoral projection (Stock 1968; Müller 1992). Endeis holthuisi Stock, 1961 differs from the others by its very robust legs and straight propoda (Stock 1968). Finally, there are very slight differences between E. straughani (Clark, 1970) and E. biseriata (Staples 1982) – for example, the length of the auxiliary claws (half the length of the main claw in E. straughani and shorter in E. biseriata) and the distance between lateral processes (wider in E. biseriata) (Clark 1970; Staples 1982). In spite of this, the main diagnostic feature to distinguish these species is the number and configuration of cement gland pores: E. straughami possesses 25–30 cement gland openings in a main row and eight openings in a second irregular row (Staples 1982), while in E. biseriata the two rows are comparable.

Chimenz et al. (1979) and Arnaud (1987) did not find Endeis biseriata in their studies of pycnodonids from the nearby locality of Civitavecchia. This species was not even mentioned by Arnaud in his list of Torrevaldaliga’s fauna (see Final remarks). Despite this, based on the presence of ovigerous males and juveniles, the population of Endeis biseriata can be considered steady and reproductive in the studied site. For this reason, and due to the long amount of time that has passed since the collection of the specimens we studied, we can suppose the current presence of this species also in other areas of the Tyrrhenian Sea.

This is the first record of the species for the Mediterranean Sea. Although it has not been reported elsewhere, we cannot exclude the invasiveness of this species. The presence of E. biseriata in the Indo-Pacific waters and the Red Sea (Lucena et al. 2018) and its absence from the Eastern Atlantic coasts (Lucena et al. 2018) could suggest a Lessepsian migration, but an anthropochorous dispersal (fouling) seems more probable.

Distribution

Species widespread in Pacific, Indian and West Atlantic oceans; Arabian and Red seas (Stock 1970; Lucena et al. 2018). New record for the Mediterranean Sea.

Depth range

Endeis biseriata is a shallow-water species, found in a bathymetric range from 0 to 46 m (Stock 1992; Müller 1993; Lucena et al. 2018).

Endeis spinosa (Montagu, 1808)

Syn: Phallangium spinosum Montagu, 1808

Material examined

5♂♂, August 1979, calm tanks; 2♂♂, September–November 1980; 1 juvenile ♂, October 1980.

Remarks

In the Mediterranean Sea only two species of the genus Endeis Philippi, 1843 (Bartolino & Chimenz 2010) were recorded to date: E. charybdaea (Dohrn, 1881) and E. spinosa. The first is recognisable by its larger body than E. spinosa and by the higher number of cement gland pores (Stock 1968). There are some other characters which are easier to see but not as reliable, because of their frequent variability: in E. charybdaea the auxiliary claws are often longer than half the length of the main claw (Krapp 1975; King 1986; Munilla & Soler-Membrives 2014) and the mouth is often surrounded by numerous spines, more than in E. spinosa (King 1986). Another diagnostic feature is the distance between the lateral processes: in E. charybdaea they are separated by 3 times their diameter, while in E. spinosa they are separated by only 2 times their diameter (Munilla & Soler-Membrives 2014).

Endeis spinosa and E. biseriata differ in the general aspect of the body (more robust in E. biseriata), in the proboscis morphology (in E. spinosa the distal part is narrower than the proximal one) and in the length of auxiliary claws (about 1/3^rd the length of the main claw in E. biseriata vs. half the length of the main claw in E. spinosa) (Munilla & Soler-Membrives 2014). Another character useful to distinguish these species is the number of cement gland pores: E. spinosa possesses up to 20 pores in a single row (Stock 1968).

Distribution

Species widespread in the Atlantic Ocean and the Mediterranean Sea (Munilla & Soler-Membrives 2014).

Depth range

0–537 m, on Posidonia and algae (Müller 1993; Munilla & Soler-Membrives 2014).

Family Nymphonidae Wilson, 1878

Genus Nymphon Fabricius, 1794

Nymphon gracile Leach, 1814

Syn: Nymphon gallicum Hoek, 1881

Material examined

1♂, 10 September 1979, 1 m depth.

Remarks

Three species belonging to the genus Nymphon Fabricius, 1794 are known from the Mediterranean waters (Bartolino & Chimenz 2010): N. puellula Krapp, 1974, N. parasiticum Merton, 1906 and N. gracile. The first two species lack auxiliary claws, although there are some doubts about N. parasiticum because the original description was based on a juvenile (Merton 1906); N. gracile, on the contrary, is characterised by the presence of auxiliary claws (Munilla & Soler-Membrives 2014).

Distribution

Species widespread in the North-East Atlantic and the Mediterranean Sea (Müller 1993; Munilla & Soler-Membrives 2014).

Depth range

0–52 m (Müller 1993; Munilla & Soler-Membrives 2014).

Family Phoxichilidiidae Sars, 1891

Genus Anoplodactylus Wilson, 1878

Anoplodactylus californicus Hall, 1912(Figure 3)

Figure 3. Anoplodactylus californicus Hall, 1912 (scanning electron microscope images). (a) dorsal view of a male; (b) detail of dorso-distal tubercles on lateral processes; (c) detail of the wing-shaped structures on the ventral side of female’s proboscis; (d) drawing made from (c), for clarification; (e) detail of the oviger (last two segments are particularly hairy); (f) detail of a ventral spur on coxa II; (g) detail of propodus and claws. Scale bars: a = 500 μm, b–g = 200 μm

Syn: Anoplodactylus carvalhoi Marcus, 1940; Anoplodactylus portus Calman, 1927; Anoplodactylus projectus Hilton, 1942

Material examined

2 ovigerous ♂♂, 1♂, April 1979; 3 ovigerous ♂♂, 23♂♂, 15♀♀, 13 juvenile ♂♂, 2 juvenile ♀♀, 12 juveniles, August 1979, calm tank; 1♂, 3 juvenile ♂♂, 3 juveniles, November 1979; 1 juvenile ♂, June–November 1980; 2 ovigerous ♂♂, 3♂♂, 3♀♀, 1 juvenile ♂, September–November 1980, adduction channel; 10 ovigerous ♂♂, 12♂♂, 23♀♀, 10 juvenile ♂♂, 27 juveniles, October 1980, adduction channel; 1 ovigerous ♂, 2♀♀, 5 juveniles, December 1980.

Diagnosis

Body slender with partially segmented trunk (suture between third and fourth segments almost never visible). Each lateral process with a dorso-distal tubercle; conical ocular tubercle; abdomen orthogonal to the trunk, erect and tall as the ocular tubercle. Cheliphore fingers without teeth. Ventral spurs on coxa II on legs III and IV, or II, III and IV in males and all legs in females. Females with wing-shaped processes on the ventral side of proboscis (Figure 2(c,d)), and rudimental ovigers. Oviger with the last two segments very hairy. Two small bumps on the side of the proboscis. Propodus heel with two strong spines followed by two parallel rows of 2 or 3 smaller spines; auxiliary claws present but reduced.

Remarks

Child (1992a) pointed out that A. californicus is an easily recognisable species, even if the large number of synonyms (for example A. portus Calman, 1927) creates some difficulties in identification. This may be due to the variability of certain characters in different geographical populations (Lucena & Christoffersen 2018). Because of the plasticity of many morphological characters, the genus Anoplodactylus is characterised by some species complexes, such as the californicus-digitatus complex (Arango & Maxmen 2006).

Most papers do not mention the presence of tubercles on lateral processes (Figure 3(a,b)): these body structures are described without ornamentation, or with some setae or small buds (Hall 1912; Hilton 1942; Child 1987, 1992b; Arango & Maxmen 2006; Lucena 2013). Additionally, some individuals show a rounded ocular tubercle (Lucena 2013), not very evident eyes (Hall 1912; Hilton 1942), a completely segmented trunk (Arango & Maxmen 2006) and only one major spine on propodus heel (Child 1987).

The character of ventral spurs on coxae II (Figure 3(f)) (present on each female leg, while in males on pairs of legs II, III and IV, or only on III and IV) it is not mentioned in the original description (Hall 1912). Some authors do not find differences between females and males (Lucena & Christoffersen 2018) and others point out this feature only on males (Hilton 1942; Child 1987, 1992a).

Examining the species of Anoplodactylus reported in Mediterranean Sea, the identification of females of A. californicus, because of the ventral wing-shaped proboscis protuberances (Figure 3(c,d)), is easy. This structure is typical of various species belonging to the californicus-digitatus complex (Arango & Maxmen 2006). On the contrary, the identification of the males is based on less evident characters of the ovigers and cement glands (Nakamura & Child 1991; Child 1992b).

Several specimens of A. californicus (under the synonym Anoplodactylus portus Calman, 1927) have previously been found in Civitavecchia harbour near Torrevaldaliga (Chimenz et al. 1979), and their presence in this area is confirmed by the samples collected around the power station (Arnaud 1987). Anoplodactylus californicus in the Italian seas was also recorded in northern Sicily (Palermo) (Chimenz Gusso 2000). It is considered an alien species in the Italian waters (Bartolino & Chimenz 2010), probably introduced by means of shipping fouling (Occhipinti-Ambrogi et al. 2010).

Distribution

Species with pantropical and pantemperate distribution, in the Atlantic and Pacific oceans and the Mediterranean Sea. It is found in a variety of substrates and often on algal vegetation in shallow waters (Child 1992a; Müller 1993; Lucena 2013; Lucena & Christoffersen 2018).

Depth range

0 to <100 m (Child 1992a; Müller 1993; Lucena 2013; Lucena & Christoffersen 2018).

Family Ammotheidae Dohrn 1881

Genus Tanystylum Miers, 1879

Tanystylum conirostre (Dohrn, 1881)

Syn: Clotenia conirostris Dohrn, 1881

Material examined

13♂♂, 56♀♀, 2 juveniles, 15 indet., August 1979, calm tank; 1♀, 10 September 1979, 1 m depth; 1 ovigerous ♂, November 1979; 1♀, 1 juvenile, June–November 1980; 2 ovigerous ♂♂, 2 juveniles, September–November 1980; 1 juvenile August 1980; 1 ovigerous ♂, 3♀♀, 1 juvenile, October 1980, adduction channel; 1♂, December 1980.

Remarks

Two species of Tanystylum are reported for the Mediterranean Sea: T. conirostre and T. orbiculare. The first has a sloped abdomen, a truncated conical proboscis and dorsal tubercles on the tibiae, bearing some setae. In T. orbiculare the abdomen is erect, the proboscis is cylindrical and there are no tubercles on the legs (Munilla & Soler-Membrives 2014).

Distribution

Species widespread in Mediterranean Sea, with amphi-Atlantic distribution (Müller 1993; Munilla & Soler-Membrives 2014).

Depth range

0–15 m (Munilla & Soler-Membrives 2014).

Final remarks

As already mentioned, pycnogonids were not the main target of the study on macrofouling due to their low abundance (Relini & Bianchi 1979a). Even in a recent technical report (Meloni & Moruzzi 2019), Pycnogonida amount to no more than 0.08% of the total arthropods of the macrobenthic community. Despite this, Relini and colleagues sent some of the specimens to the eminent specialist Françoise Arnaud, who compiled a list of the identified species attached to the technical report for the Torrevaldaliga Power Station managers, referring to some of these species in his work about Mediterranean pycnogonids (Arnaud 1987). He recorded five taxa: A. appendiculata, E. spinosa, N. gracile, T. conirostre and Anoplodactylus sp. The authors consider these results a partial validation of their analysis of this paper’s specimens, because of some recurrent species in this area (A. appendiculata, E. spinosa, N. gracile and T. conirostre).

Conclusions

Our contribution highlights the importance of the proper and accurate preservation of labelled samples obtained from faunal and/or ecological research. This is true also for those taxa not specifically studied in the original research, in order to always be able to obtain useful information from their study.

In particular, through the examination of unstudied samples from the Torrevaldaliga Power Station collected more than 30 years ago and preserved by the marine biologist Dr M. Mori, we were able to make a contribution to the knowledge of marine biodiversity of the Tyrrhenian Sea, bringing the number of known Mediterranean pycnogonid species to 37. Moreover, we outlined some remarks on the geographical distribution of Endeis biseriata, a new record for the Mediterranean Sea. The viable population of such an alien species, despite not yet being recorded from other localities in the Mediterranean Sea, should be carefully monitored in the future to prevent its further dispersion and any impact on native species and ecosystems.

Acknowledgements

We wish to thank Carlo Nike Bianchi, Mario Mori and Carla Morri for providing us with the samples and all the necessary information used to implement this work; special thanks to Laura Negretti for her valuable help in the acquisition of SEM images. Many thanks also to the anonymous reviewers whose suggestions helped us to improve our manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.