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Love Arrow

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Two spotted Roman snails, in the body of the right snail there is a love dart

Snails reproducing with love arrow

snails after reproduction with two love arrows

The love arrow(Gypsobelum) is formed in the genital apparatus of many land snail groups and fulfils an important role in mating. The term love arrow refers to the arrows of Eros or Cupid in ancient Greek and Roman mythology.

The love arrow is formed in the arrow sac(bursa telae) in the genital apparatus of the snail. Land snails (Stylommatophora) are hermaphrodites that have a highly developed genital apparatus with male, female and hermaphrodite parts. The arrow sac belongs to the female part of the genital apparatus, it opens into the canal of the vagina near the finger-shaped glands.

Application

The love dart sits on a papilla inside the dart sac. During the mating prelude (“love play”) of the snail, the dart sack is ejected through the genital atrium, the love dart is thus ejected and stabbed into the partner’s foot. Despite the name love dart, the love dart does not describe a trajectory, it is neither shot nor thrown, but thrust like a lance. When using the love dart, it can happen that the love dart is either not pierced properly and simply remains functionless or that injuries occur, where a snail, which is hit by the love dart in the head area, can no longer extend a feeler.

Function

Schematic of the genital apparatus of a land snail
D = love dart
S = arrow sac(bursa telae)
BC = bursa copulatrix
SP = seminal pouch
P = penis
V = vagina
SO = spermoviduct
G = genital atrium
MG = finger-shaped glands

Initially, it was only assumed that the love dart fulfilled a sexually stimulating role during snail lovemaking, since after its application, lovemaking continued with increasing intensity. Later hypotheses suggested, for example, that the love dart represented a lime gift to the recipient snail, helping, for example, in the production of the lime-containing eggshells. Since the 1980s, however, more recent research has shown that the role of the love dart is quite different. The love dart transmits a hormone-containing secretion from nearby finger-shaped glands that affects the genital apparatus of the recipient snail. The so-called bursa copulatrix is an organ of the genital apparatus that digests foreign sperm, leading to selection of the most active and healthy sperm. The secretion of the finger-shaped glands enhances the peristaltic movement of the seminiferous tubule (spermoviduct), thus assisting the movement of spermatozoa through the seminiferous tubule to the seminal pocket, where they are stored until fertilization. As a result, after using a love dart, the amount of surviving sperm can double.[1]

A love dart need not be used in every mating. Each love arrow sac (some groups of snails, e.g., the deciduous snails (Hygromiidae) and the shrub snails (Bradybaenidae) have several arrow sacs) produces only one love arrow, so that a period of time subsequently elapses before another love arrow can be used in a mating. Moreover, the first mating of a young snail must first stimulate the formation of a love arrow.[2]

Forms

SEM images of love darts of various snail species

The forms of the love arrow in land snails are very diverse. The love arrow is highly species-specific, so that even closely related species, such as the garden ribbon snail (Cepaeahortensis) and the grove ribbon snail (Cepaeanemoralis) can often only be distinguished by their love arrow. While the love arrows of some species are straight like a lance (e.g. common hair snail, Trichia hispida), there are other species with sabre-like curved love arrows (e.g. tree snail, Arianta arbustorum) and even sinuous love arrows (e.g. incarnate snail, Monachoides incarnatus). The size of the love arrow is also highly variable, ranging from 1 mm in the smallest to 30 mm in the largest snail species. The arrow of love of the Roman snail(Helix pomatia) is between 7 and 11 mm long. It has a crown at the blunt end, with which it is stuck on the papilla of the arrow sac, as well as four longitudinally running side blades, which are further reinforced in Cepaea hortensis, for example.

The love-arrow consists of lime (calcium-carbonate) with most types, with some also from chitin or from cartilage.

Individual references

  1. R. Chase, K. C. Blanchard: The snail’s love-dart delivers mucus to increase paternity. In: Proc Biol Sci. 273(1593), 2006 Jun 22, pp. 1471-1475.
  2. D. J. D. Chung: Molluscan ‘Love darts’? In: Hawaiian Shell News. 1986 May, Vol 34(5), pp. 3-4.

Web links

Commons: Love Arrows– Collection of images, videos and audio files