Fig 1.
a Map of Antarctica showing the areas where samples of Osedax deceptionensis were collected: South Shetland Islands (b) and South Georgia Island, b South Shetland Islands area showing location of Deception Island, c Deception Island.
GdC, Gabriel de Castilla Spanish Antarctic Base; Sta. 1, station at Whalers Bay; Sta. 2, station at Bidones Point; Sta. 3, station in front of the GdC Spanish Antarctic Base.
Table 1.
Summary of the Antarctic and Subantarctic bones analyzed during this study.
Fig 2.
Osedax deceptionensis a Living specimen showing translucent palps (pa) with red margin due to blood vessels, b Living specimen with palps (pa) retracted into a hemispherical tube (t) attached to the bone (bo), c Living specimen with palps (pa) retracted into an elongated tube (t) attached to the bone (bo). Arrows pointing areas with concentration of embryos/larvae, d Preserved specimen (CRBA-33236) with palps (pa) retracted into a multilobulated tube (t). Tube attached to a piece of bone (bo). Arrows pointing areas with concentration of embryos/larvae, e Piece of preserved tube (t) under the light microscope showing embryos/larvae. Trochophore-like larva arrowed.
Fig 3.
Semithin section and TEM micrographs of Osedax deceptionensis transition bone-roots a Eroded bone layer (bo) and root mucous sheath (ms) containing root cells (c).
Inset with two protein droplets (pro) close to the mucous sheath, b Detail of a nucleus (n) of a root cell and the highly convoluted root mucous sheath (ms). Lipid droplets (lip) into the root cell, c Vacuolar structure engulfing protein (pro) and lipid (lip) droplets, d Detail of vacuolar structure showing lipid droplets (lip) and granular inclusions (gin). Inset showing two granular inclusions in detail.
Fig 4.
TEM micrographs of Osedax deceptionensis epidermis at the roots a Columnar cells of the epidermis at distal roots, showing two nucleus (n) with nucleolus (nu) surrounded by abundant rough endoplasmic reticulum (er) and granular inclusions (gin) intermingled.
Apical part of cells covered by a dense microvillous layer (mv), b Detail of a columnar cell, showing the nucleus (n) with two nucleolus (nu), the rough endoplasmic reticulum (er) with granular inclusions (gin), and the microvillous layer (mv) limited by a mucous sheath (ms), c Detail of microvillous layer (mv) at epidermis close to ovaria with bacteria (b) intermingled with microvilli.
Fig 5.
TEM micrographs of Osedax deceptionensis bacteriocytes and endosymbionts a Bacteriocyte (bc) at roots close to ovaria, surrounded by non-symbiotic cells (ns).
Non-symbiotic cells (ns) with abundant rough endoplasmic reticulum (er) and protein droplets (prot); notice sperm (s) occasionally seen close to bacteriocytes (bc). Bacteriocyte (bc) containing bacteria (b) and myelin bodies (my), b Detail of bacteria (b) inside the bacteriocyte showing different stages of degradation, including earlier stages of degradation (dg) and myelin bodies (my) surrounding bacteria, c Detail of bacteria (b) inside the bacteriocyte including a large myelin body (my) resulting from the degradation of several bacteria.
Fig 6.
TEM and SEM micrographs of Osedax deceptionensis oocytes, sperm, embryos, and larvae a Oocyte (oo) in the ovaria packed within a collagenous layer (cl) containing yolk with protein (pro) and lipid (lip) inclusions, and glycogen (gly).
Oocyte surrounded by a follicle (fo) with muscular fibres (mu) with sperm (s) embedded, b Non-symbiotic cells (ns) with rough endoplasmic reticulum (er) producing proteins (pro) transferred to the oocyte (oo). Oocyte (oo), limited by a membrane (om), extending interdigitated cytoplasmic extensions (arrowed), c Blood vessel (bv) with several expansions close to a sperm (s). Notice the helically spiraled nucleus (n), the flagellum (fl), and mitochondria (mi) of the sperm, d Sperm (s) in longitudinal section. Notice the nucleus (arrowed), mitochondria (mi), and flagellum (fl), e Cluster of sperm (s) in transversal section, in an area surrounded by rough endoplasmic reticulum (er) close to oocytes. Inset showing a detail of a sperm in transverse section with the nucleus (n) and mitochondria (mi), f Trochophore-like larva, inside the female’s tube, filled with protein and lipid vitellogenic content. Ciliary bands (ci) present. Notice a membrane (m) limiting the larva and nucleus (n) of larval cells. Inset showing a SEM micrograph of a developing embryo inside the female’s tube.
Fig 7.
Phylogenetic tree of Osedax based on the concatenated analyses (Gblocked dataset) of COI, 16S, 18S, 28S, and H3 from Bayesian inference analysis (BI).
Squares on nodes refer to support retrieved from 4 different analyses: upper, left gblocked alignment under BI; upper right, complete alignment under BI; bottom left, gblocked alignment under ML; bottom right, complete alignment under ML. Green squares indicate posterior probability values (PP) > 0.95; bootstrap support (BS) > 95, yellow squares indicate 0.90 > PP < 0.95; 75 > BS < 95), red squares indicate clade recovered but below thresholds) and white indicates clade not recovered. Osedax deceptionensis and O. ‘mediterranea’ are indicated in bold. The six major Osedax clades previously defined by [11] and [12] are highlighted.
Fig 8.
Phylogenetic tree of Osedax endosymbionts resulting from the 16S marker, using Bayesian inference (BI).
Nodes with posterior probability values > 0.95 marked by red dots. Endosymbionts of Osedax deceptionensis and O. ‘mediterranea’ are indicated in bold in blue and orange, respectively. Seven major Osedax endosymbiont clades or ribospecies (Rs1–Rs7) are distinguished following [32].
Fig 9.
Osedax time-calibrated phylogeny based on the Gblocked concatenated (COI, 16S, 18S, 28S, and H3) BI analysis.
Fossil calibration points indicated by red stars (see Material and Methods section for details). Bars at nodes indicate the 95% highest posterior density (HPD) interval. Nodes marked by black dots indicate posterior probability values of 1, while white dots indicate posterior probability values of 0.95–0.99.
Fig 10.
Haplotype network for Osedax deceptionensis from 20 individuals, including 18 individuals from Deception Island and 2 individuals from the vicinity of South Georgia Island.
In yellow, haplotypes from Deception Island collected in 2013; in blue, the haplotype from Deception Island collected in 2010 [12]; in purple, haplotypes from South Georgia Island collected in 2013; in red, missing inferred haplotypes. Inset, observed mismatch distribution (vertical bars) and expected frequency distribution (line), assuming population size changes.