Helix straminea Briganti, 1825

Korábek, Ondřej, Juřičková, Lucie & Petrusek, Adam, 2014, Resurrecting Helix straminea, a forgotten escargot with trans-Adriatic distribution: first insights into the genetic variation within the genus Helix (Gastropoda: Pulmonata), Zoological Journal of the Linnean Society 171 (1), pp. 72-91 : 80-84

Helix straminea Briganti, 1825 ( Figs 1B , 4A–F )

Type locality: Distribution of the species was originally described as ‘ in Principatu Citeriori, Aprutio, aliisque nostri Regni locis ’ [in the (then) Principato Citra, Abruzzo, and other places in our Kingdom (the Kingdom of the two Sicilies)]. Nevertheless, ‘Muro in Basilicata’ (Muro Lucano, the locality cited by some later authors: Tiberi, 1869; Kobelt, 1906a) has been referred to as an original place of discovery (‘ Primum hanc speciem inveni in denso nemore Muri Pricipatus Citerioris oppidi, et in finitimis locis ’ [I have found species first in dense forest of the town of Muro, and on adjacent places]). The only known specimens that are the likely syntypes, discussed below, come from ‘Roccamuria’, an unidentified locality in Abruzzo.

Type material: Presumed syntypes MHNG 18135 , 18136 .

The two lots (of one specimen each) in the collection of J. R. Bourguignat in Geneva seem to correspond to the original figures in V. Briganti’s original description ( Briganti, 1825). One of them ( MHNG 18135; Fig. 1B ) is more conspicuously ribbed than usual and has barely visible bands, and probably represents original pl. II, figs 3, 4 in Briganti (1825). The lot is accompanied by Bourguignat’s handwritten label stating that the specimen was given to him by Briganti and was depicted in Bourguignat (1860: pl. 20 fig. 3). The specimen actually shown in that figure is nevertheless clearly MHNG 18136, and probably corresponds to pl. II. figs 1, 2 in Briganti (1825). Both specimens bear the label ‘Roccamuria, Abruzzes’; material from that locality was apparently donated by Briganti’s son in 1858 ( Bourguignat, 1883). However, it is not clear whether three other shells labelled as being from Roccamuria ( MHNG 18145) are also syntypes. The individual in Bourguignat’s collection from Muro Lucano ( MHNG 18129), the locality specifically mentioned in the original description, cannot be unambiguously referred to Briganti and thus has no type status. The presumed syntypes fully conform to the sense in which the name H. straminea was used by Kobelt (1906a).

Helix straminea Briganti, 1825: 172 , pl. II, figs 1–4.

Helix straminea var. elongata Bourguignat, 1860: 155 , pl. 4, fig. 4. Unavailable name, non Helix elongata Röding, 1798 .

Type locality: Italy: Abruzzo: ‘Roccamuria’. Syntype: MHNG 18145 (shell with ‘4’ written in the aperture).

Helix straminiformis Bourguignat, 1876: 53 .

Type locality: Italy: Abruzzo, Monte Amaro in Majella. Syntype: MHNG 18064 .

Helix yleobia Bourguignat, 1883: 265 . Type locality:

Italy: Basilicata: Tricarico Matera . Syntype: MHNG 18139 .

Helix lucorum var. candida Mascarini, 1892: 251 .

Type locality: Italy: Abruzzo: Settecerri. Syntypes: SMF 74529.

Helix lucorum var. annosa Mascarini, 1892: 251 .

Type locality: Italy: Abruzzo: Agelli near Rocca Fluvione. Syntype: SMF 74530.

Material examined: All type specimens and other individuals from type series listed above. Additional material examined from Albania, Italy, and Macedonia is listed in Supporting Information ( Table S1).

Revised diagnosis: Medium to large Helix species possessing a broadly conical shell with broad first whorls, no umbilicus, and rounded aperture that is small relative to the shell size. The shell usually has four longitudinal bands and its aperture is usually brown coloured.

Description: Height: 35–60 mm. Diameter: 35–55 mm. Shell within the genus medium-sized to very large with variable conicity ( Figs 1B , 4 ), slightly depressed to rather conical, with blunt apex and smooth, broad protoconch (diameter of first 1.5 whorls c. 5.0– 6.5 mm).; 5–5.5 whorls regularly increasing in width. Coarse surface, irregularly grooved, with nodules along the suture; usually covered by an easily flakingoff periostracum of yellowish or straw-like colour, which, together with fine darker transverse striation, gives it a wood-like appearance. If this layer is not present, the shell is whitish. No spiral sculpture. Usually four chestnut brown longitudinal bands (the second resulting from merger of second and third of the five bands present in numerous Helix species ); these may fade or merge occasionally ( Fig. 4 ). Uppermost band very thin, second and third wide, the fourth narrower, but almost always developed and separated from the third one. Rarely, the bands may be missing altogether or merge into two broad bands, but in general the colouration pattern is very stable. Last whorl descending slightly towards the aperture, with insertion of the outer aperture margin placed variously from the middle of the median light stripe to the lower margin of the third dark stripe. Aperture regularly semicircular, slightly higher than wide, rather small relative to the shell and frequently positioned somewhat under it. Outer aperture margin thin, not reflected, light to dark brown, often reddish or brown, rarely almost white. A thin brown palatal callus is developed in some populations. Slightly broadened columella with a lip, oblique, slightly curved. Completely covered umbilicus, only very rarely open; a shallow vertical groove frequently present on the umbilical cover. The foot and mantle variable in colour, from dark grey-brown to light yellowish grey.

Distribution and habitat: Helix straminea is found in the Apennines from the Basilicata and Apulia ( Briganti, 1825; Tiberi, 1869) through Molise, Abruzzo and Lazio ( Giusti, 1971) to Marche, Umbria and Toscana regions ( Fig. 5 ). Its exact limits in the northern Apennines are not known. The species is absent in Calabria ( Cesari, 1978) and in the Gargano Peninsula ( Holdhaus, 1912; A. Petrusek, pers. observ.).

On the opposite side of the Adriatic Sea, H. straminea is known scarcely from Albania ( Dhora & Welter-Schultes, 1996) and in western Macedonia ( Knipper, 1939). The northern limits of its distribution are not known due to possible confusion with H. vladika (see Fig. 5 ).

Most records of H. straminea originate from highlands and mountainous areas; however, the altitudinal extent of its distribution is not sufficiently known. Giusti (1971) has reported it (as H. lucorum ) from Monti Reatini at 1600 m a.s.l., and from Siena at 330 m. It is a species of woodlands and shrubs, and can be found in broadleaved forests and their margins, under shrubs and in orchards.

Differential diagnosis: Helix straminea is characterized by combination of characters (large size, large apex, broadly conical shell, half-rounded brown aperture, four brown bands on brownish background) which, although the whole set is not always present, make it easily distinguishable from most Helix species in the study area with the exception of H. vladika and H. pelagonesica , which are apparently close relatives or conspecifics of H. straminea .

Helix vladika typically has brown-coloured shells with inconspicuous or missing bands, often with a high spire. However, specimens with a low spire (e.g. the lectotype of H. vladika ), which in shape closely match some Italian H. straminea individuals, may be found. Similarly, bands are developed in some H. vladica , but reduced in H. straminea . We have found no character that could reliably distinguish between these two taxa.

Helix pelagonesica is in general slightly smaller (c. 35–45 mm in diameter). It sometimes ( H. vardarica , H. pelagonesica s.s.) has a very dark aperture and usually the third band is narrower than the second (this can also be found among Italian H. straminea ). The sequenced Macedonian population of H. straminea differs conchologically only in size from some individuals assigned to H. volensis . Helix pelagonesica pelagonesica , however, differs slightly from H. straminea : it has a more diffuse coloration, the shell is flatter, the aperture has a different shape (not rounded as in H. straminea ) and faces more downward, and the columella is considerably thickened.

Other species: Helix lucorum is very variable in shape and colour, and may be similar to H. straminea . However, H. straminea can be distinguished by its large protoconch, which is small in H. lucorum (3.5– 4.7 mm when only European populations are considered). The surface of H. lucorum is smoother and its periostracum does not form a conspicuous layer. All other differences apply in general, but can be suppressed in individual cases. Helix straminea is usually larger than specimens of H. lucorum from adjacent areas. It has, due to its large apex, more regularly increasing whorls; the aperture is less downward facing. Helix lucorum differs by its more contrasting coloration, which is frequently very variable within a single population. All upper and both lower bands usually almost completely merge on the last whorl. Bands are darker, and the median light band is very prominent and whitish. Bands tend to be interrupted by irregular transverse dark bands that develop by pigment deposition near the aperture during periods of suppressed growth. These are much more conspicuous and pronounced than in any other species of the genus, so they are sometimes more evident than the longitudinal bands, which may even be missing. The umbilicus is sometimes open, the aperture margins tend to be darker with violaceous tones, and the columella often forms a plate. Within H. lucorum , European populations differ conspicuously from those found in most of Asia Minor, and the intraspecific variability of H. lucorum needs a thorough revision.

Helix pomatia has more globose shells than H. straminea . The latter has a lower and narrower last whorl and thus a denser coiling, and the aperture, relatively smaller than the shell, is moved somewhat under the shell, whereas the last whorl in H. pomatia is quite prominent. The umbilicus is rarely fully covered in H. pomatia .

In comparison with H. cincta and H. borealis , the shells of H. straminea are usually broader relative to height and always more robust in appearance than either of the two species. Whorls of H. straminea are more ventricose, and the protoconch is much larger. It has an aperture that is smaller proportionally to the shell. They also differ in colour; both H. cincta and H. borealis sometimes have all three upper bands separated and clearly visible on older whorls; the upper bands may also fuse together and form a uniformly darker upper half of the shell on the last whorl. Lower bands are frequently weak or missing, but in some populations of H. cincta they fuse. Some H. cincta populations from southern Turkey and Syria may resemble H. straminea in shell shape, but they always have a different banding pattern and a small protoconch.

Helix secernenda can reach the size of H. straminea , but it also has a different coloration with white background and violaceous bands that do not exhibit the four-band pattern of H. straminea . Most of its populations also have a very large aperture. The shell of H. schlaeflii is characteristically globular with a large aperture with reddish-brown margins; the shell coloration is uneven with whitish blurs.

Of the other species whose ranges overlap with that of H. straminea , the H. ligata complex (i.e. including H. delpretiana and H. mileti ), H. philibinensis , and H. figulina have smaller globular shells. Helix figulina usually has three upper bands that are merged and the two lower are narrow; the shell surface is regularly finely ribbed; the apex is minute and the aperture is almost circular and large relative to the shell, with vertical rounded columella. Helix philibinensis and H. ligata resemble each other in shell shape, which is more globular than in H straminea , H. vladika and H. pelagonesica due to the relatively higher last whorl; both are smaller and less robust than H. straminea . They have an apex of size comparable to that of H. lucorum . The H. ligata complex is usually characterized by a white aperture margin; H. dormitoris is very similar to the H. ligata complex.

Distribution of conchologically similar taxa: Helix vladika (as defined above) is known from northeastern part of Montenegro ( Wohlberedt, 1907; Knipper, 1939) and Serbia south of the Sava and Danube (Pavlovic´, 1912). The species is not recorded from Bulgaria (Irikov & Ero˝ss, 2008), although its presence in the country cannot be excluded; it may have been confused with H. pomatia . The species is probably distributed widely in eastern Bosnia and Herzegovina along the borders of Serbia and Montenegro ( Fehér, 2011), but its extent has not have been verified as gastropod material from this country is generally scarce.

Helix pelagonesica inhabits south-eastern Macedonia (Gradeška Planina and Dojran) and Greek regions of Central Macedonia including the Athos peninsula, Thessaly, and Central Greece south to Euboea ( Knipper, 1939; Urban´ ski, 1970). Helix pelagonesica pelagonesica was collected only on Kyra Panagia island in the northern Sporades ( Knipper, 1939) at the end of the 19 th century but was not reported from there by a survey in the 1970s ( Liebegott, 1986).

Helix lucorum occurs in Italy in Lombardy, Veneto and Emilia Romagna, but may be found elsewhere occasionally. In the south, it certainly reaches Umbria ( Cesari, 1978) and Tuscany ( Kobelt, 1906a). It is unclear whether the old as well as recent records (e.g. Bisacchi, 1933; Cianfanelli, 2009) from the Apennines in northern Marche and Umbria, or even in Emilia Romagna and Tuscany, are correct; tracing the southern limits of H. lucorum ’s distribution in Italy from published records is complicated due to its confusion with H. straminea . In the southern Balkans, H. lucorum lives in Albania up to Lake Skadar, in Macedonia, southern Serbia, Kosovo, Bulgaria, and southern Romania; it is not known from Montenegro ( Wohlberedt, 1907; Pavlovic´, 1912; Knipper, 1939) nor further to the north; in Croatia a non-native population was found only recently ( Štamol, 2010).

Helix pomatia , within its broader range, lives in Italy on the southern slopes of the Alps, Alpes- Maritimes, and in the Ligurian Apennines ( Cesari, 1978) and thus probably does not significantly overlap with the range of H. straminea . In the Balkans, it is found throughout most of the northern half of the peninsula and overlaps with H. straminea in northern Macedonia (as indicated also by our sample of H. pomatia collected near Mavrovo Lake).

There is a significant overlap in distribution between H. vladika , H. pomatia , and H. lucorum in Serbia ( Wohlberedt, 1907; Pavlovic´, 1912); all three live syntopically on some localities in south-eastern Serbia (e.g. near Knjaževac). Helix pomatia lives throughout the range of H. vladika , while H. lucorum enters its range from the south-east. The range of H. pelagonesica on the mainland largely overlaps with distribution of H. lucorum .

Ranges of H. cincta and H. borealis overlap only marginally with those of H. straminea and H. pelagonesica , respectively. Helix borealis lives in southeastern Greece and shares a small part of its range with H. pelagonesica on Euboea and in Thessaly ( Triantis, 2011). Helix cincta is found in northern Italy, but it does not enter the Apennines ( Cesari, 1978).

Figures

Figure 1. Comparison of types of (A) Helix lucorum (neotype, Zoological Museum Copenhagen) and (B) H. straminea (probable syntype, MHNG 18135).

Figure 4. Conchological variability of Helix straminea and similar taxa; only individuals not previously depicted elsewhere are included. A, H. straminea, central Italy, Ripe south of Ascoli Piceno (SMF 341626); B, H. straminea, central Albania, Lis in Dibër county (SMF 341628); C, H. straminea, north-eastern Macedonia, Žirovnica (SMF 341613); D, H. vladika, south-eastern Serbia, Trgovište near Knjaževac (SMF 341629); E, H. vladika, eastern Montenegro, Gusinje (SMF 341615); F, H. pelagonesica vardarica, south-eastern Macedonia, environs of Udovo (paratype of H. vardarica, ZMB 90338).

Figure 5. Distribution of Helix straminea and conchologically similar taxa: H. vladika, and the three H. pelagonesica subspecies; own collections and unpublished collections of ZMB, SMF, MHNG, and NMBE (triangles), online photographs (diamonds) and published records (circles) based on Wohlberedt (1907, 1909), Pavlovic´ (1912), Knipper (1939), Urban´ ski (1970), Giusti (1971), Dhora & Welter-Schultes (1996), Manganelli et al. (2005), and Welter-Schultes (2012). Red symbols indicate localities with molecular data, and the dashed line separates genetically analysed Balkan populations assigned to the straminea and vladika clades in Figure 2. Type localities of the respective species and subspecies are indicated by white circles. Exact positions of some type localities and the locality on Euboea island are not known.