Tree-climbing behaviour of Cerithidea decollata, a western Indian Ocean mangrove gastropod (Mollusca: Potamididae)

Abstract

The behaviour of Cerithidea decollata, a common western Indian Ocean mangrove tree climbing gastropod, was studied in Mida Creek, Kenya. At the study site, this snail mainly lived in Avicennia marina dominated areas, i.e. in the mangrove belt between high water spring tide and high water neap tide levels. Not a single individual was found on the less common mangrove tree Lumnitzera racemosa, living just above the A. marina level (together with terrestrial grass), and was very rarely recorded on the common Rhizophora mucronata, bordering the seaward side of the A. marina belt. No significant gradient of C. decollata density was found within the whole 150–200 m wide belt. The majority of C. decollata rested on tree trunks during high tide, creeping on the mud flat below the tree for part of low tide, and returning on the trunks well before being reached by the water. This migratory pattern was more evident at spring than at neap tide, at day than at night time and it was strongly influenced by the shore level of the mangrove zone in which animals resided. While C. decollata from lower shore levels neatly massively migrated twice a day, individuals from upper levels showed a more continuous and irregular activity, sometimes crawling on the mud even at high water of spring tide, when they experience just a few centimetres of water for no more than one to two hours.

Effects of urban wastewater on crab and mollusc assemblages in equatorial and subtropical mangroves of East Africa

“…(a) Molluscs: mainly represented by the gastropods Terebralia palustris (Fratini et al, 2004) and Cerithidea decollata (Vannini et al, 2006), and the oyster Saccostrea cucullata attached to the aerial roots of mangrove trees. Specimens were counted in the sampling quadrat.…”

Lack of inter-individual information exchange among migratingCerithidea decollata(Mollusca Potamididae)

“…In East Africa, it is commonly found within the A. marina belt (MACNAE 1963;COCKCROFT & FORBES 1981;VANNINI et al 2006), i.e. in the landward mangrove areas, between the average levels of HW during ST and NT.…”

Could Ambient Vibrations Be Related to <i>Cerithidea decollate</i> Migration?

“…It has been recently questioned whether a regular 12.4 h clock can actually cope with the variable pattern of water level due the several tide irregularities within the synodic month [6]. In East Africa, where a research has been conducted since a few years on an excellent model for such studies [6] [7], the above irregularities are mainly due to: 1) two adjacent tidal oscillations are usually of different intensity ("diurnal disparity"); 2) tidal oscillations are getting wider from Neap Tide (NT)…”

“…In East Africa it is commonly found within the Avicennia marina belt [7] [10] [11]. It is confined in the upper part of the mangrove belt, where A. marina grows, above the average height levels of High Water [10] [11], and already proved to be an excellent model suitable for intertidal migrations [7] [9]. It is known to feed on the ground and climb the trees settling on the trunk to avoid submersion [7].…”

“…It is confined in the upper part of the mangrove belt, where A. marina grows, above the average height levels of High Water [10] [11], and already proved to be an excellent model suitable for intertidal migrations [7] [9]. It is known to feed on the ground and climb the trees settling on the trunk to avoid submersion [7]. Before the water arrival, tenths of snails can be seen climbing, and clustering about 40 cm above the level that water will reach only 2 -3 hours later [9] [12].…”