Feeding in the megalopae of the mud crab (Scylla paramamosain): mechanisms, plasticity, role of chelipeds and effect of prey density

Abstract

Feeding in the megalopae of the mud crab (Scylla paramamosain): mechanisms, plasticity, role of chelipeds and effect of prey densityWe used microscopic video records to analyse the behaviour of mud crab megalopae (Scylla paramamosain) fed on rotifers (Brachiomus spp.), Artemia sp. or copepods (Schmackeria dubin). The megalopae were able to capture prey whose sizes ranged from no larger than Artemia nauplii to no smaller than adult Artemia. The megalopae employed three feeding modes: (1) Ambush-Prey mode, (2) Swim-Suspension-Feed mode and (3) Sit-Sweep mode. These involved raptorial feeding, suspension feeding and an in-between raptorial-suspension feeding mode, depending on the size of the prey and their density in the surrounding water. The chelipeds played an important role in feeding. Megalopae used the chelipeds to grip or sweep prey items and their movement generated eddies that can increase feeding efficiency. To verify the contribution of the chelipeds to feeding efficiency, we observed and compared the animals under three cheliped treatment regimes: (1) Autotomized -chelipeds removed by induced autotomy; (2) Glued -chelipeds glued at the dactylus-propodus joint to eliminate their ability to grip; and (3) Control -normal chelipeds. The feeding rates of the autotomized and glued treatments were lower than those of the controls, demonstrating that the chelipeds assist in feeding but that the megalopae can still feed without them. The density of prey also affected feeding efficiency. Feeding rate and prey density were positively correlated. When prey density was high, megalopae were able to feed in excess of their nutritional requirements. The study shows that mud crab megalopae respond flexibly to variations in feeding conditions, such as damaged chelipeds, as well as prey size and density. We postulate that this plasticity evolved in response to the dilute and patchy prey conditions of the estuarine environment. All the analysed behaviours are illustrated with video sequences.

Scorpion Sheds ‘Tail’ to Escape: Consequences and Implications of Autotomy in Scorpions (Buthidae: Ananteris)

“…Loss of the telson, which bears the venom gland and aculeus (sting), negatively affects the scorpion’s ability to catch larger prey or to sting potential predators, and considerably reduces its defense capabilities, but post-autotomy scorpions can still capture and feed successfully on smaller prey. A similar observation has been reported in crabs with autotomy of the chelipedes [ 32 ].…”

Feeding rates and prey selectivity of planktonic decapod larvae in the Western English Channel

“…In this study, we saw no evidence of increased clearance rates of motile 1 3 cells relative to diatoms. The fact that decapod larvae in this study were ingesting a broad range of cell sizes is more consistent with suspension feeding than the raptorial or ambush feeding that has been found in later megalopae stages (Chen et al 2013). While suspension feeding is likely a requirement to capture the pico-and nanoplankton cells perhaps too small and numerous for individual handling (Price and Paffenhöfer 1983), we cannot discount the possibility that other feeding modes are employed on food items that were too large and rare for enumeration in our experiments, thereby increasing their daily ration (Wirtz 2012).…”

mRNA profile provides novel insights into stress adaptation in mud crab megalopa, Scylla paramamosain after salinity stress

“…Mud crab spends most of its life in brackish, saltwater estuaries or mangrove forests, while mature females move to offshore for spawning and hatching larvae [40]. When the larvae grow up to megalopa, they migrate back to estuaries and coasts in virtue of the flood tide, settle and recruit adult habitats and metamorphose into the crablet stage [12]. Megalopa is considered as one of the most crucial stages along the life of the mud crab due to its long habitats shifting and extensive habitats change, and the survival rate of megalopa stage significantly affects population dynamics [12].…”