Helanthium zombiense is related to Echinodorus tenellus from which it differs in particular by its longer submerged leaves (10–35cm versus 4–7cm), longer inflorescences (15–40cm versus 5–15cm) and various other palynological characters, cytogenetic and chemical properties which have been demonstrated following comparative studies carried out for these two species.
Individuals belonging to these two species, cultured in the same aquarium for six years, show very clear differences in leaf morphology. Echinodorus zombiensis develops very long (up to 80cm) banded and linear leaves, 5–7 mm wide, floating on the surface of the water and showing very small marginal teeth, while the leaves of H. tenellus are lanceolate, do not exceed 20cm in length, are wider (8–12 mm) and have no marginal teeth. These characters are specific to the culture conditions and have not been observed on the individuals examined in the wild and on the herbarium specimens.
Note that the species name of Helanthium zombiense, has nothing to do with voodoo. According to taxonomic rules, the suffix "ensis" or "ense" indicates a geographical location. Helanthium zombiense comes from Guadeloupe, in Basse-Terre, northeast of Trois-Rivières, in the Zombi pond at about 420 m altitude.
The sole habitat, lake Zombi in Guadalupe, has water that is very low in minerals (conductivity between 30 and 70 μS/cm). The Zombi pond is located in the heart of the dense forest, on the slopes of the Soufrière massif, on the edge of the Guadeloupe National Park. Unlike other lakes located nearby (Grand Étang, Étang As de Pique, Étang Madeère, Étang Roche), it is not yet easily accessible (lack of trails) and therefore has not been object of intensive surveys, which explains why this new species has not been observed before.
Ref: Aquaportal
