The fishing behaviour of Metopograpsus messor (Decapoda: Grapsidae) and the use of pneumatophore-borne vibrations for prey-localizing in an arid mangrove setting

Abstract

This study presents the first documented observations of a brachyuran crab's proactive fishing behaviour in conjunction with mangrove pneumatophores which are employed as prey-localization devices. All ecological data were recorded in situ using simple behavioural observations, visual census and field experiments. Field experiments were based on stimulus-response and ecological surveys on random displacement. Assemblages of Metopograpsus messor were observed daily performing a foraging/predatory tide-related cyclic behaviour pattern in an arid mangrove ecosystem which experiences challenging environmental conditions. Prey-localizing behaviour was observed during the flood tide when pneumatophore-borne vibrations were used to identify potential prey. The prey simulation field experiment (where a single pneumatophore was stimulated by knocking) showed that in >93% of instances a crab approached the exact pneumatophore being stimulated. As water levels increased during the tidal cycle M. messor was observed climbing pneumatophores. The crabs anchored themselves to the pneumatophore just above the water level with their pereiopods. The chelipeds were positioned in a pincher-like trap, and remained in a ‘capture-position’ waiting for prey to move within striking range. This characteristic fishing behaviour was performed daily by a population of M. messor. Ecological observations suggest that both these predatory behaviours are associated with the fish Aphanius dispar dispar in a direct prey–predator relation. Evidence suggests that these fishing behaviours evolved due to characteristics within the M. messor phylogeny (foraging in intertidal zones; daily displacement following tidal levels; high sensitivity to vibrations; and an opportunist diet) and its associated environment (presence of pneumatophores and high availability of a fish resource).

Functional responses of mangrove fauna to forest degradation

“…Many mangrove macrofauna do exhibit trait variations to promote opportunistic feeding behaviours (see Fratini et al 2000;Poon et al 2009). In mangroves, omnivorous crabs foraging in open-canopy forests exhibit enhanced functional plasticity across trophic traits to counter otherwise challenging environmental conditions (Giraldes et al 2019). On the flip side, species of the normally litter-dependent species (Sesarmidae) alter their diets with season, climate and food availability (Poon et al 2009).…”

Two new sponge species (Demospongiae: Chalinidae and Suberitidae) isolated from hyperarid mangroves of Qatar with notes on their potential antibacterial bioactivity

“…Recent studies on the biodiversity of bioturbating crabs [61], based in the same arid mangrove setting, support the theory that the southwest coast of PAG is an isolated marine province. A mangrove setting in an isolated marine province that houses an abundant endemic shrimp Palaemon khori De Grave & Al-Maslamani, 2006 [7,15] that occurs only in this mangrove setting in Qatar and remains absent in the entire Arabian Gulf [62] (BWG pers. Observ.).…”

“…and 75 ppt [4][5][6][7], levels much higher than the East coast of the Gulf [1][2][3][7][8][9][10][11]. The southwestern coast forms an isolated marine province with a high rate of marine endemism and lower species richness than the eastern coast of PAG, the latter receives an influx of waters from the Indian Ocean which results in a higher diversity of species [1,[12][13][14][15].…”

The tale of an endemic shrimp’s exceptional osmoregulation and the ancient Athalassic mangrove oasis

“…The shrimp P. khori was described in 2006 16 and has not been documented in any other hyperarid mangroves within the Gulf or Red Sea 17 , 20 – 23 . This species exhibits high abundance, forming dense populations within the riparian zones of channels in the hyperarid mangrove located in the southwestern regions of the Gulf 8 , 16 . It coexists as a permanent resident in the riparian zone with only a few other species, including the endemic fish Aphaniops dispar (Rüppell, 1829) 8 .…”

“…This species exhibits high abundance, forming dense populations within the riparian zones of channels in the hyperarid mangrove located in the southwestern regions of the Gulf 8 , 16 . It coexists as a permanent resident in the riparian zone with only a few other species, including the endemic fish Aphaniops dispar (Rüppell, 1829) 8 . The endemic P. khori has been observed across all tidal zones within this mangrove setting, including tidal pools in the high intertidal levels during summer when salinity and temperature levels are elevated.…”