Impact of sand bund removal on seagrass ecosystems: A study of macrobenthic community structure and correlation with macrophytes cover and sediments.

This study investigated the impacts of the removal of sand bund on the macrobenthos community structure, seagrass cover, and sediment particle size in Merambong Shoal, Malaysia. The reclamation project deposited sand bund in the middle of Merambong seagrass shoal, resulting in its division into northern (NS) and southern (SS) halves. Ecosystem changes were monitored over a 31-month period using the transect lines method. Bi-monthly samples were collected for assessment. The results revealed a substantial decline in macrobenthos densities compared to previous studies. However, after the removal of the sand bund, there was a significant increase in macrobenthos density, specifically Polychaeta and Malacostraca, at NS. Seagrass cover at NS was initially lower than SS but showed an increase after the complete removal of the sand blockage. Sediment particle analysis reported a higher silt percentage at NS, indicating greater sedimentation at NS, which was partially sheltered from wave actions.

Phylogenomic resolution of the root of Panpulmonata, a hyperdiverse radiation of gastropods: new insight into the evolution of air breathing.

Transitions to terrestriality have been associated with major animal radiations including land snails and slugs in Stylommatophora (>20 000 described species), the most successful lineage of 'pulmonates' (a non-monophyletic assemblage of air-breathing gastropods). However, phylogenomic studies have failed to robustly resolve relationships among traditional pulmonates and affiliated marine lineages that comprise clade Panpulmonata (Mollusca, Gastropoda), especially two key taxa: Sacoglossa, a group including photosynthetic sea slugs, and Siphonarioidea, intertidal limpet-like snails with a non-contractile pneumostome (narrow opening to a vascularized pallial cavity). To clarify the evolutionary history of the panpulmonate radiation, we performed phylogenomic analyses on datasets of up to 1160 nuclear protein-coding genes for 110 gastropods, including 40 new transcriptomes for Sacoglossa and Siphonarioidea. All 18 analyses recovered Sacoglossa as the sister group to a clade we named Pneumopulmonata, within which Siphonarioidea was sister to the remaining lineages in most analyses. Comparative modelling indicated shifts to marginal habitat (estuarine, mangrove and intertidal zones) preceded and accelerated the evolution of a pneumostome, present in the pneumopulmonate ancestor along with a one-sided plicate gill. These findings highlight key intermediate stages in the evolution of air-breathing snails, supporting the hypothesis that adaptation to marginal zones played an important role in major sea-to-land transitions.