by Piter Kehoma Boll
Gastropods show an astonishing diversity of forms, being second only to insects. One of the most diverse groups within them is that of the pulmonate (i.e., lunged) gastropods, but not all pulmonate gastropods actually have lungs. This is the case with the so-called leatherleaf slugs or simply leatherleaves, one of the most peculiar pulmonate families.
Among the leatherleaves, one of the best known species is Laevicaulis alte, often called the tropical leatherleaf in English. This species is native from tropical Africa and, as all leatherleaves, it lacks lungs and has an anus located at the posterior end of the body, different from most pulmonate gastropods, in which it is twisted forward. Adult tropical leatherleaves measure about 8 cm in length and their dorsal side is completely covered by their mantle, which has a dark, almost black tuberculated skin with a central beige line. The tentacles are small and very rarely extend beyond the limits of the mantle, so they are rarely seen from above. The foot, the ventral line with which slugs move, is very narrow, only about 4 to 5 mm wide in adults.
As most gastropods, the Tropical leatherleaf is a hermaphrodite, but it starts is sexually mature life as a male and later changes its sex to female. They are well-adapted to dry conditions, having a leathery dorsum and a narrow foot, which reduce water loss. Additionally, it can contract into a smaller, rounder shape, which also reduces water loss.
The diet of the Tropical leatherleaf in its native environment is unknown. Living in the leaf litter, it probably feeds on decaying plant matter and small herbs. However, it has been accidentally introduced in many tropical areas around the world, especially in Australia and surrounding islands in the Pacific, such as Taiwan, Hawaii, Fiji, New Caledonia and Samoa, as well as in India and Indonesia. There, it can become a serious pest for some crops, such as tomatoes, cucumbers and spinach.
More than a pest to plantations, this slug can also serve as an intermediate host for the rat lungworm, Angiostrongylus cantonensis, which can cause eosinophilic meningitis in humans and other animals. This is, therefore, one more species that used to be a harmless species in its native environment, but was turned into a villain by human actions.
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References:
Brodie, G. D., & Barker, G. M. (2012). Factsheet Laevicaulis alte (Ferussac, 1822). http://repository.usp.ac.fj/5436/1/Laevicaulis_alte-_Ferussac-1822.pdf
Wikipedia. Laevicaulis alte. Available at < https://en.wikipedia.org/wiki/Laevicaulis_alte >. Access on 24 June 2021.
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