Genital studies of enantiomorph taxa pairs of Alopia

Hartmut Nordsieck (III.2021)

Introduction

Alopia species from the southern Carpathians, Romania, are left-coiled (L) or right-coiled (R). In some mountains left- and right-coiled taxa, which look like mirror-images = enantiomorphic taxa, occur together. These taxa have been treated until now as species or as subspecies of one species. They are similar in shell and genital characters; in some cases it was shown that they hybridize. If more widely distributed, as in three mountains of the region (Piatra Craiului, Bucegi, Ciucaş), the ranges of the enantiomorphs (and their subspecies) are not separated, but mosaic-like meshed with that of the other enantiomorph, with occasional syntopic occurrences of both enantiomorphs (Nordsieck 2008). Therefore, to avoid imbalances within the genus and obscuration of the diversity, most enantiomorphic taxa are treated here as species (same arguments as for hybridizing species in general, see website article on hybridization).
A good example to show the problems of uniting enantiomorphic taxa to species is given by the A. livida group from the Bucegi Mountains. If one unites the species of that group (A. straminicollis, A. livida with A. l. fussi,,A. nixa), which hybridize, to one (mega)species (Koch et al. 2020), one must do this also with other enantiomorph taxa pairs of the genus. These megaspecies would then contain subspecies of different rank, the enantiomorphs and the subspecies of the enantiomorphs each. Besides, in the megaspecies A. livida group, one had to include also A. glorifica from the Piatra Craiului Mountains (and its enantiomorph A. lischkeana, both belonging to another megaspecies), because it hybridizes with A. livida in that part of the mountains where the latter species occurs (Măgura Mountains) (Nordsieck 2016).

Genital studies of enantiomorphs

In the course of my work on Alopia the genital organs of 36 species taxa have been investigated. It was of special interest to state if enantiomorphic Alopia taxa exhibit genital differences. The literature dealing with is not sufficient, because descriptions and figures of the genitalia are not exact enough. Therefore, the genitalia of ten enantiomorph taxa pairs have been examined and measured.
The enantiomorphs occur sympatrically, but not syntopically (except taxa pair VI from Bucegi Mountains, Valea Velicanului).
The taxa pairs are ordered from W to E. The names are those of the system presented in Nordsieck (2008).
The preparation numbers are given in brackets. Two specimens each, in some cases three, have been examined.

I:
A. subcosticollis occulta (L), Cheile Costeşti near Pietreni (418),
A. hildegardae fortunata (R), Cheile Bistriţa near Pietreni (417).
The enantiomorphs have a relatively short epiphallus (ratio epiphallus/penis ~ 1.1) in common.
In A. h. fortunata penis and epiphallus are shorter (in comparison ~ 0.8).

II:
A. glorifica boettgeri (L), Piatra Craiului Mts.,Valea Râului (lower part) (419),
A. lischkeana obesa (R), Piatra Craiului Mts.,Valea Râului (upper part) (420).
The enantiomorphs have a relatively long epiphallus (ratio epiphallus/penis ~ 1.4) in common.
In A. l. obesa the proximal parts of bursa copulatrix (diverticulum, bursa + proximal pedunculus) (~ 0.7) and the epiphallus (~ 0.8) are shorter.

III:
A.glorifica glorifica (L), Piatra Craiului Mts., Degetul lui Câlnic (385),
A. lischkeana lischkeana (R), Piatra Craiului Mts., Prăpăstii (386).
The genitalia of the enantiomorphs are different.
In A. l. lischkeana the vagina (~ 0.7) and the male copulatory organs, especially the distal part of epiphallus (glorifica ratio proximal/distal part of epiphallus ~ 1.0, lischkeana ~ 1.5) are shorter.

IV:
A.glorifica glorifica (L), Piatra Craiului Mts., Valea Brusturetului above Cabana Brusturet (Valea Seacă a pietrelor, 1050 m a. s. l.) (682),
A. lischkeana lischkeana (deceptans) (R), Piatra Craiului Mts., Valea Brusturetului above Cabana Brusturet (Valea Seacă a pietrelor, 1120 m a. s. l.) (683).
The enantiomorphs have a relatively long epiphallus (ratio epiphallus/penis ~ 1.8) in common.
In A. l. lischkeana the proximal parts of bursa copulatrix (diverticulum, bursa + proximal pedunculus) (~ 0.7 and 0.8, respectively) and the penis and proximal part of epiphallus (both ~ 0.8) are shorter.
Note the correspondence to the enantiomorph pair II.
This is the taxa pair, in which according to Fehér et al. (2013) the COI sequences are identical.

V:
A. glorifica galbina (L), Piatra Craiului Mts., Măgura Mare (southern slope below summit, ~ 1250 m a. s. l.) (700),
A. livida deaniana (R), Piatra Craiului Mts., Măgura Mare (northern slope between summit and eastern depression, ~ 1250 m a. s. l.) (701).
The genitalia of the enantiomorphs are different.
In A. l. deaniana the diverticulum is longer (~ 1.5), the penial caecum shorter (~ 0.65) and the distal part of epiphallus longer (~ 1.4).

VI:
A. straminicollis straminicollis (L), Bucegi Mts., Valea Velicanului (upper part, ~ 1700 m a. s. l.) (698),
A. livida hypula (R), Bucegi Mts., Valea Velicanului (upper part, ~ 1700 m a. s. l.) (699).
The genitalia of the enantiomorphs, which in contrast to the other pairs occur syntopically, are largely corresponding, but especially one character of A. l. hypula, the length of the proximal part of epiphallus, is like that of A. l. bipalatalis occurring nearby (668, 679) (see table). This is a further indication of the origin of A. l. hypula from A. l. bipalatalis by hybridization with A. s. straminicollis (see Nordsieck 2016).

In the following table the length ratios of A. straminicollis and A. livida from different localities of Bucegi Mountains are given (two specimens each measured).

VII:
A. straminicollis monacha (L), Bucegi Mts., Cheile Peşterii (~ 1550 m a. s. l.) (430),
A. livida nubila (R), Bucegi Mts., Cheile Coteanu (1490 m a. s. l.) (654).
The genitalia of the enantiomorphs are different (see table).
In A. s. monacha vagina (~ 1.9), epiphallus (~ 1.6) and its proximal part (~ 1.8) are longer than in A.l. nubila.

VIII:
A. nixa (L), Bucegi Mts., Valea Obârşia Ialomiţei (~ 2000 m a. s. l.) (425),
A.livida fussi (R), Bucegi Mts., Valea Doamnelor (~ 1850 m a. s. l.) (424).
The enantiomorphs have the genital characters male copulatory organs lengthened, penial caecum reduced in common.
In A. l. fussi the penis is hardly longer than in A. nixa. Its penial caecum is reduced like in that species (in the literature, however, it is given as absent).
Note that despite of their shell similarity the male copulatory organs of A. l. fussi are much different from those of other subspecies of A. livida. Like in A. nixa they are similar to those of A. pomatias.

IX:
A. mauritii (L), Ciucaş Mts., Munţele Roşu (mountain) (426),
A. nefasta (R), Ciucaş Mts., Munţele Roşu (above Valea Berii) (457).
The enantiomorphs have a relatively long epiphallus (mauritii ratio epiphallus/penis ~ 1.8, nefasta ~ 1.5) in common.
In A. nefasta vagina (~ 1.8) and male copulatory organs (penis ~ 1.6, epiphallus ~ 1.4) are longer.

X:
A. helenae zagani (L), Ciucaş Mts., Gropşoare (SW, ~ 1300 m a. s. l.) (454),
A. helenae helenae (R), Ciucaş Mts., Gropşoare (SW, ~ 1350 m a. s. l.) (453).
The enantiomorphs have a relatively long epiphallus (zagani ratio epiphallus/penis ~ 2.0, helenae ~ 2.2) in common.
In A. h. helenae the proximal parts of bursa copulatrix(diverticulum, bursa + proximal pedunculus) are somewhat longer (~ 1.2).

It results that the genitalia of most enantiomorphs are largely, but not fully corresponding. The differences are comparable with those of the species taxa of Alopia in general. This concurs with the shell morphology.
The enantiomorphic taxa are found in the same groups of the COI tree of Fehér et al. (2013), except of taxa pairs III, V, VI and VII.
The given measurements are those of few specimens. Therefore, measuring must be expanded to check the stated genital differences of the enantiomorphs.

References

Fehér, Z., Németh, L., Nicoară, A. & Szekeres, M. (2013): Molecular phylogeny of the land snail genus Alopia (Gastropoda: Clausiliidae) reveals multiple inversions of chirality. – Zoological Journal of the Linnean Society, 167: 259-272.

Koch, E. L., Neiber, M. T., Walther, F. & Hausdorf, B. (2020): Patterns and processes in a non-adaptive radiation: Alopia (Gastropoda, Clausiliidae) in the Bucegi Mountains. – Zoologica Scripta, 49 (3): 280-294.

Nordsieck, H. (2008): The system of the genus Alopia H. & A. Adams 1855 (Gastropoda: Stylommatophora: Clausiliidae). – Mitteilungen der deutschen malakozoologischen Gesellschaft, 79/80: 7-18.

Nordsieck, H. (2016): Interspecies hybridization in the genus Alopia (Gastropoda, Stylommatophora, Clausiliidae) from southern Carpathians, Romania, demonstrated by shell examination.– Conchylia, 46 (1-4): 3-15, 3 pls.