Amino acid and related compound composition in two symbiotic mytilid species from hydrothermal vents

Abstract

ABSTRACT-Two species of deep-sea mussels belonging to the genus Bathymodiolus were collected from 5 vent fields distributed over 2 basins of a hydrothermal system in the South Pacific. Free and bound primary amino compounds were analysed in gills and mantles using OPA-HPLC. The method allowed the detection of 32 amino acids and related compounds (AARCs). An undetermined free chemical was found at hlgh levels (up to 30% of the total free AARCs) In vent mussel tlssues This amino compound is presumed to be an end-product from specific metabolism occurnng in vent n~ussels. Except for this unknown compound, comparlson of the biochemical composition between vent and littoral mussels revealed that the general nitrogenous requirement as well as the endogenous metabolic pathways of the main amino acids seem to be similar for the 2 mussel types. Ultrastructural observations indicated that these deep mussels harbour bacteria in their gills. Indices of high metabolic rates found in these organs appear to be related to the presence of endobacterial. It seems that symbionts could provide a preponderant fraction of essential amino acids to their host. In particular, free thiotaurine displayed high concentrations (up to 13% of the total free AARCs). This sulphur-containing compound could be involved in a specific metabolism related to toxic forms of sulphur. Variations of the AARC composition between the 2 vent mussel species do not appear to be species related but appear to be due to environmental constraints. As shown by stress indices, deterioration of the physiological condition in these mussels is directly hnked to the quantity and/or the quality of the hydrothermal vent emissions.

Ultrastructure and stable carbon isotope composition of the hydrothermal vent mussels Bathymodiolus brevior and B. sp. affinis brevior from the North Fiji Basin, western Pacific

“…In the case of B. brevior, the low abundances of symbionts appear to be characteristic for this association, as similarly low numbers of symbionts were observed in B. brevior specimens collected several years earlier from a different hydrothermal vent site in the North Fiji Basin (see Fig. 2 in Pranal et al 1995). This conclusion is further supported by the fact that B. sp.…”

“…Further indications for the presence of sulfur-oxidizing symbionts are high concentrations of the amino acid thiotaurine and (n-?) monounsaturated phospholipid fatty acids in the gills of B. brevior (Pranal et al 1995(Pranal et al , 1997.…”

“…Beyond general descriptions of hydrothermal vent communities in the southwestern Pacific (Desbruyeres et al 1994) and some stable isotope data on unidentified mytilid species of the Mariana Trough (Van Dover & Fry 1989) and Okinawa Trough (Kim & Sakai 1991), only a few stud-ies have examined the symbioses of western Pacific Bathymodiolus species in more detail (Pranal et al 1995(Pranal et al , 1997. Until recently, investigations were hampered by a lack of information on the taxonomy of hydrothermal vent mytilids from the western Pacific.…”

Hypotaurine and sulfhydryl-containing antioxidants reduce H2S toxicity in erythrocytes from a marine invertebrate

“…In sulfide-exposed animals that lack sulfide-oxidizing endosymbionts, the resulting ThT may be enzymatically recycled back to HT, thereby releasing sulfide at a rate that allows detoxification through other mechanisms (Rosenberg et al, 2006). In sulfide-exposed animals with sulfideoxidizing endosymbiotic bacteria, the conversion of HT to ThT may provide a mechanism to transport sulfide to the endosymbionts, which would then convert ThT back to sulfide and HT (Pranal et al, 1995;Pruski and Fiala-Medioni, 2003;Pruski et al, 1997;Pruski et al, 2001;Pruski et al, 2000b). Accordingly, Pranal and colleagues proposed that the ratio of ThT to HT in tissues represents the extent of that animal's recent sulfide exposure (Pranal et al, 1995).…”

“…In sulfide-exposed animals with sulfideoxidizing endosymbiotic bacteria, the conversion of HT to ThT may provide a mechanism to transport sulfide to the endosymbionts, which would then convert ThT back to sulfide and HT (Pranal et al, 1995;Pruski and Fiala-Medioni, 2003;Pruski et al, 1997;Pruski et al, 2001;Pruski et al, 2000b). Accordingly, Pranal and colleagues proposed that the ratio of ThT to HT in tissues represents the extent of that animal's recent sulfide exposure (Pranal et al, 1995). This was confirmed by Brand and colleagues and Rosenberg and colleagues for vent species with and without sulfide-oxidizing endosymbionts, respectively (Brand et al, 2007;Rosenberg et al, 2006).…”