Metabolic energy demand and food utilization of the hydrothermal vent crab Xenograpsus testudinatus (Crustacea: Brachyura)

Abstract

The hydrothermal vent crab Xenograpsus testudinatus (Crustacea: Brachyura) is endemic near Kueishan Island, Taiwan, where it lives in shallow waters close to the hydrothermal vents located in this area. X. testudinatus is adapted to a sulfur-rich and thus potentially toxic environment. It has established a specialized feeding strategy focusing on dead zooplankton organisms killed by the toxic discharges from the vents. During slack water, when there is little or no current, the crabs leave their crevices to feed on this 'marine snow'. In the present study, we investigated the physiological aspects of nutritional adaptations of X. testudinatus. The crabs showed high digestive capacities of major digestive enzymes and particularly high activities for proteolytic enzymes. This feature can be regarded as an adaptation to irregular food availability. Furthermore, enzymes were stable at elevated temperatures, in a wide pH range, and in the presence of inorganic inhibitors like Cu . These enzyme properties can be considered essential to functioning in a vent habitat over long exposure times. Moreover, X. testudinatus is able to store significant amounts of lipid (50 to 60% of dry mass in the midgut gland), which may help to overcome periods of food scarcity. Fatty acid profiles revealed high amounts of saturated and monounsaturated components (mainly 16:0, 16:1(n-7), 18:1(n-9), and 18:1(n-7)). These findings reflect physiological adaptations and energetic strategies that enable this crab to exist in this extreme hydrothermal vent habitat.

Invasive versus native brachyuran crabs in a European rocky intertidal: respiratory performance and energy expenditures

“…We assessed the energetic impact of the C. maenas and H. sanguineus populations onto their rocky intertidal habitat around the island of Helgoland via their food uptake, similar to a procedure used by Hu et al (2012). Population respiration and energy expenditures were calculated based on the respiration models developed in this study, as well as the abundance and biomass data of both species from the four main intertidal sites in August 2014 (Table 1).…”

Foraging strategies under extreme events: Contrasting adaptations by benthic macrofauna to drastic biogeochemical disturbance

“…Vent crabs have until now only been found at three shallow hydrothermal vents with high sulfide concentration (38). Hence, vent crabs are considered endemic to these habitats because they are physiologically adapted to tolerate the high concentration of toxic sulfur fluids and are able to ingest sulfur bacteria (12,22). Our results show that vent crabs have an obligate nutritional relationship with chemosynthetic bacteria despite their otherwise opportunistic foraging behavior.…”

“…body length 0.5-50mm) to inhabit the hostile YV environment is the endemic vent crab Xenograpsus testudinatus. Its successful existence in the YV has been attributed to its physiological adaptation to highly acidic and toxic hydrothermal fluids (19,22,23). Although vent crabs are closely associated with toxic sulfur vent habitats, it is unclear whether they are obligate feeders of sulfur bacteria because vent crabs also rely on substantial contributions from photosynthetic derived sources by feeding on dead zooplankton, detritus and biofilms on vent rocks (11)(12)(13)(14).…”

“…The large endemic faunal diversity in deep-sea hydrothermal habitats can undoubtedly be linked to their relatively stable and static environmental conditions. In the much more unstable and dynamic shallow vents, the vent crabs can survive prolonged periods of food scarcity by storing nutrients and exploiting a range of nonsulfur bacterial derived resources(22). Nevertheless, the sparse geographical distribution of vent crabs and their population decline following the decrease in YV activities at the KST shows that they are obligate sulfur vent species and that they are much more vulnerable to vent shutdown than the non-endemic mollusks.…”

Distribution and sexual dimorphism of the crab Xenograpsus testudinatus from the hydrothermal vent field of Kueishan Island, northeastern Taiwan

“…Specimens of this crab were firstly discovered from fishery bycatches [14]. Later there were several related research reports on it, such as on its detoxification mechanism [17], bioaccumulation of trace metals [22], metabolic energy demands, and food utilization [23], feeding [24][25], selective behavior [26], role in the trophic structure [27][28], and reproduction [28]. However, although this species has been exploited during two decades, the in situ distribution pattern and many aspects of biology of this crab in the hydrothermal vent area has not been understood.…”