Cepaea hortensis & nemoralis genetics

Cepaea hortensis

 

Cepaea nemoralis

 

Fundort / Location

Ladenburg Apiary 25.05.2024

 

Here is the banded colour form. The light coloured form is thought to dominate in dry, warm urban zones related to climate specifics. The Apiary at Ladenburg contains some xerophile Carabid species in dicating that the habitat indeed a warm spot over average years.

 

Wikipedia:

Diagnostics

Die Mündung ist bei der Garten-Bänderschnecke hell, während die Hain-Bänderschnecke eine dunkle Mündung besitzt. Weitere Unterschiede sind vier oder mehr Drüsenanhänge am Genitalapparat bei C. hortensis (bei C. nemoralis sind es drei oder weniger) und gegabelte Klingen des Liebespfeils. /

 

 

Identification

Cepaea nemoralis is closely related to Cepaea hortensis. They share much the same habitat and exhibit a similar range of shell colours and banding patterns. Cepaea nemoralis tends to grow larger, but usually the species can most easily be recognised by the colour of the lip of adult shells. In a high proportion of regions, C. nemoralis consistently has a dark-brown lip to its shell, whilst C. hortensis has a white lip.[10]

 

Love darts of Cepaea, cross sections on left[11]

sketch of dart

C. nemoralis

sketch of dart

C. hortensis

In areas where lip colour is variable, dissection is necessary. A cross-section of the love dart of C. nemoralis shows a cross with simple blades, whereas that of C. hortensis has bifurcated blades. The mucus gland has 3 or fewer branches in C. nemoralis, but 4 or more in C. hortensis.[12]

 

Two superficially similar species Caucasotachea vindobonensis and Macularia sylvatica both have a lip that is brown near the columella becoming pale towards the suture, and they have fine growth ridges on the shell whereas in both Cepaea species it is smooth. Also, M. sylvatica is distinct in having a small blunt tooth in its aperture, whilst the lowest brown band on the shell of C. vindobonensis lies noticeably closer to the columella than in Cepaea.

 

Reference

1. Kerstes, N. A., T. Breeschoten, V. J. Kalkman, and M. Schilthuizen. 2019. Snail shell colour evolution in urban heat islands detected via citizen science. Communications Biology 2:264.

2. Koene, J. M., and H. Schulenburg. 2005. Shooting darts: co-evolution and counter-adaptation in hermaphroditic snails. BMC Evolutionary Biology 5:1-13.

3.Neiber, M. T., and B. Hausdorf. 2015. Molecular phylogeny reveals the polyphyly of the snail genus Cepaea (Gastropoda: Helicidae). Molecular phylogenetics and evolution 93:143-149.

4.Davison, A., S. Chiba, N. H. Barton, and B. Clarke. 2005. Speciation and gene flow between snails of opposite chirality. PLoS Biology 3:e282.

5.Saenko, S. V., D. S. Groenenberg, A. Davison, and M. Schilthuizen. 2021. The draft genome sequence of the grove snail Cepaea nemoralis. G3 11:jkaa071.

6.Johansen, M., S. Saenko, and M. Schilthuizen. 2023. Fine mapping of the Cepaea nemoralis shell colour and mid-banded loci using a high-density linkage map. Heredity 131:327-337.

7. Köhler, H.-R., C. Schultz, A. E. Scheil, R. Triebskorn, M. Seifan, and M. A. Di Lellis. 2013. Historic data analysis reveals ambient temperature as a source of phenotypic variation in populations of the land snail Theba pisana. Biological Journal of the Linnean Society 109:241-256.

8. Ożgo, M., and M. Schilthuizen. 2012. Evolutionary change in Cepaea nemoralis shell colour over 43 years. Global Change Biology 18:74-81.

 

Photo Dirk Lankenau

Done