Freshwater Gastropods from the El Edén Ecological Reserve, and their Bearing in the Use of Periphyton by Ancient Maya

Francisco J. Vega Vera

UNAM
Instituto de Geología
Ciudad Universitaria
Coyoacán
México D.F. 04510 México
tel: (5) 622-4288
fax: (5) 550-6644
email: vegver@servidor.unam.mx

Preliminary systematic studies of the freshwater gastropods collected at the water bodies of El Edén ecological reserve, gave as result the recognition of four genera, from which one belongs to the subclass Prosobranchia, and the other three are pulmonate snails (subclass Pulmonata).

Despite the name of the subclass of these gastropods, they are completely dependent of the water. Some are in fact air breathers, but do not need to get out from the water, and frequently show a mantle fusion called the siphon, which they extend to reach the air they breath. However, their bodies are not designed to live out of the water, as they do not have the morphologic and physiological modifications of the terrestrial gastropods, which include more mucous glands, a thick epidermis, an uricoltelic excretory system, a more complicated nervous system and sense organs, a complex hermaphroditic reproductive system, and a modified digestive tract to feed on terrestrial plants and organic debris.

Freshwater genera of gastropods recognized for the area of study, include Pomacea (Prosobranchia: Mesogastropoda), Pseudosuccinea, Stenophysa, and a still unidentified member of the family Planorbidae (Pulmonata).

From these, Pomacea is the largest gastropod, reaching as much as 5.0 cm (width of shell). Populations of this genus grow just after the rain season at the studied area, and represent a significant amount of biomass of the freshwater biota. They are grazers, and feed on the periphyton, and other algae developing in the local ponds.

Hermaphroditic individuals ovoposite on the aerial exposure of ciperaceans, in order to avoid predation on their eggs. Today, members of this genus are eaten in several states of Mexico, mainly by Indian communities. Therefore, it seems probable that ancient Maya fed on these gastropods, although no formal archaeological evidence has yet been found by this author.

This leads directly to the potential use of freshwater gastropods, as an evidence of the use of the associated periphyton as fertilizer in the high lands by ancient Maya. Although presence of pomacean gastropods in archaeological sites would be related to their use as food, existence of their other species of freshwater gastropods might be an overwhelming evidence of transportation along with the periphyton, as such species are too small to be used as food, and they are also grazers, feeding on the periphyton.

This preliminary contribution is presented in hope that possible findings of freshwater gastropod shells, related to archaeological sites in the highlands of the Maya domain might be a clue to the potential use of periphyton as fertilizer during prehispanic times.