New species of Alvinellidae (Polychaeta) from the North Fiji back-arc basin hydrothermal vents (southwestern Pacific)

12 Pages·1993·6.3 MB·

by  D Desbruyeres

PROC. BIOL. SOC. WASH.
106(2), 1993, pp. 225-236
NEW SPECIES OF ALVINELLIDAE (POLYCHAETA)
FROM THE NORTH BACK-ARC BASIN
FIJI
HYDROTHERMAL VENTS (SOUTHWESTERN PACinC)
Daniel Desbruyeres and Lucien Laubier
Abstract. —The polychaete family Alvinellidae Desbruyeres & Laubier, 1986
comprises two genera, Alvinella and Paralvinella, and ten species or subspecies.
All species are strictly associated with hydrothermal vents in the Pacific Ocean.
The genus Paralvinella includes eight species or sub-species, plus one additional
new species presently being described from North East Pacific hydrothermal
fields. In 1989, the French research submersible Nautilehad 12 successful dives
in the North Fiji back-arc Basin and explored two active hydrothermal vents.
Numerous specimens of two additional new species of the genus Paralvinella
were collected using the manipulator ofthe submersible. Paralvinella uniden-
tata, new species, exhibits several features that lead us to erect three different
subgenera, Paralvinella s. s., Miralvinella, new subgenus andNautalvinella, new
subgenus, within the genus Paralvinella. This species lives within the anhydrite
mass, very close to hot fluid openings. The second new species, P. fijiensis,
found in the anhydrite mass, but also on basaltic rocks, is closely related to P.
grasslei, the type species, and to P. palmiformis.
While the first discovery ofhydrothermal built up by anhydrite, with hydrothermal
phenomena occurring at the axes ofoceanic fluid temperature up to 285°C; the fluid is
ridges goes back to 1976 (Lonsdale 1977), translucent, relatively depleted ofmetal due
the exploration ofhydrothermal systems in to subsurface phase separation and shows a
back-arc basins is rather recent (Both et al. low content ofhydrogen sulfide. The site is
m
1986, in Manus Basin, Hessler et al. 1988, located at a depth of2000 at 16°59'S and
in Marianas back-arc Basin, Fouquet et al. 173°55'E. Another hydrothermal field
1990, 1991, in Lau Basin, Ohta 1990, in named Mussel Valley consists of Bathy-
Okinawa back-arc Basin) (Auzende et al. modiolus spp. beds developing on the ba-
1989, Jollivet et al. 1989). During the early salt; there is no chimney and the hydro-
summer of 1989, a French-Japanese bio- thermal fluid diffuses from cracks between
STARMER
logical cruise, 2 (30 June 1989 basaltic rocks; the ffuid temperature does
to 19 July 1989) was devoted to the study not exceed 8.5°C. This site is located at a
m
of biological communities associated with depth of 2700 at 18°49'S and 173°29'E.
A
deep-sea hydrothermal vents in the South- large collection of polychaetes including
western Pacific, in the North Fiji back-arc representatives of the family Alvinellidae
Basin (Desbruyeres et al. 1991). The French were collected from the submersible.
research submersible Nautile, operated from Since our last publication on Alvinellidae
R/V Le Nadir, had 12 successful dives in (Desbruyeres & Laubier 1991), the total
these areas. Two different active sites were number of known Paralvinella species in-
explored. White Lady vent has one large cludes eight species or subspecies (Detinova
diffuser plus several small cylindrical chim- 1988). At least one additional new species
neys; the edifice is a few meters high and is from North East Pacific hydrothermal fields
1
PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
226
is presently being described and additional the peculiar unidentate uncini. The lack of
material tentatively identified as Paralvi- a secondary tooth on the uncini is unique
nella hessleri has recently been collected within the family Alvinellidae.
from Okinawa vent fields (Miura & Ohta Description. —Holotype 1 1 mm long and
mm
1991). 1.1 wide with 81 setigerous segments.
During the dives in the North Fiji Basin, Paratypes (14 specimens from PL 16) range
numerous specimens of two different spe- from 77 to 88 setigerous segments, with the
cies ofthe genus Paralvinella were collected majority (1 1 specimens) having from 79 to
mm
using the manipulator of the submersible. 83. Length ofparatypes rangesfrom 4.8
Morphological study of these animals to 9.2 mm, with an average of 5.2 mm.
showed that they represent two new species, Color pale grey-pinkish in ethanol, with
Paralvinella unidentata andP.fijiensis. Par- capillarysetae andacicularnotopodialhooks
alvinella unidentata exhibits several fea- yellow; integuments iridescent. Body grad-
tures thatleadus to erectthree different sub- ually tapering from about setigerous seg-
A
genera within the genus Paralvinella. This ment 50 to the end of the body. medio-
specieslivesintheanhydritemass, veryclose ventral row of small shields present.
to hot fluid openings. The second new spe- Prostomium well developed, with ovi-
cies, Paralvinellafijiensis, found in the an- form shield shape, clearly separated from
hydritemassandonbasalticrocks, isclosely buccal segment by deep grooves, with an-
related to P. grasslei, the type species, and terior median incision on two thirds of
P. palmiformis. length; with small glandular notch visible
(with SEM) at base of incision. Buccal ap-
paratus, from dorsum to ventrum, with
Paralvinella unidentata, new species
many grooved tentacles in several rows on
Figs. 1, 3, 4 buccal membrane arising from dorsal side
Type locality, material examined. —Sev- of buccal cavity; length of tentacles highly
enty-eight specimens collected during Nau- variable from one individual to the next
tile dives PL 1 (3 specimens. White Lady one, possibly due to preservation. Paired
site), PL 1 1 (5 specimens. White Lady site), large ventral tentacles and ventral organ ab-
PL 16 (37 specimens. White Lady site), PL sent.
20 (32 specimens. White Lady site), PL 21 Buccal segment laterally and ventrally
(1 specimen, small hydrothermal vent lo- visible, well separatedfromprostomium and
m
cated 150 from White Lady site in the from segment IL First visible segment (II)
south-west). Extra specimens from dive PL achaetous, laterally and ventrally discern-
10 and PL 20 deep frozen for biochemical ible, clearlyseparatedfrom peristomiumand
analyses. Most specimens come from White from branchial region. First 25 to 30 setig-
Lady vent site (depth 2000 m, 16°59'50"S erous segments with notopodia only.
and 173°55'47"E). Holotype (dive PL 16, 1 Branchial region with four segments, pre-
July 1989, on White Lady site) deposited in ceded by one reduced asetigerous segment,
the collections of the Museum national visible laterally and ventrally (segment II).
d'Histoire naturelle, Laboratoire de Biolo- First branchial segment (segment III) ase-
gic des Invertebres marins et Malacologie tigerous, totally fused with two first setig-
(n°UC 350). Paratypes from same dive de- erous segments. Third setigerous segment
posited in the collections of the National well separated from others. Following three
Museum of Natural History, Smithsonian segments setigerous, with notopodia dor-
(USNM
Institution, Washington, D.C. sally elevated in laterodorsal row, with no-
157044). topodia of same size as those of following
Etymology. —The specific name refers to segments.
VOLUME NUMBER
106, 2 227
Branchiae four pairs, all similar, arranged subspecies have been described within the
&
as funnel-like structure, with strong basal genus: P. palmiformis Desbruyeres Lau-
stem bearing small secondary filaments and bier, 1986, P. pandorae pandorae Desbru-
&
thin terminal tip devoid of secondary fila- yeres Laubier, 1986, P. pandorae irlandei
&
ments as long as basal stem. Branchial stem Desbruyeres Laubier, 1986 (Desbruyeres
&
bearing one, sometimes two, bean-shaped Laubier 1986), P. dela Detinova, 1988,
&
vesicles on internal side near base. Second- P. hessleri Desbruyeres Laubier, 1989
&
ary filaments inserted along stem on two (Desbruyeres Laubier 1989) and P. bac-
&
opposite areas; each leaf-shaped, strongly tericola Desbruyeres Laubier 1991 (Des-
&
flattened, with median ciliated area, and bruyeres Laubier 1991).
pointedtip. These secondary filaments rem- Among these species, P. pandorae and its
iniscent of species ofAlvinella. two subspecies are clearly distinguished by
Notopodia, from setiger 1 to end ofbody the presence ofuncini from setigerous seg-
(7th setigerexcepted) each cylindrical, bear- ments 5 or 6 (depending on the subspecies),
ingtwo groups ofcapillary setae. Notopodia a unique situation within alvinellids con-
without digitiform lobes. Setiger 7 strongly sidered as a plesiomorphous character.
modified, with slightly reduced cylindrical The following morphological features can
notopodia, bearingtwotothreestraight short be used to assess the relationship between
acicular notopodial setae on each side. Se- species and groups of related species: The
tiger 8 not modified. total number of segments and its range of
Cylindrical notopodia and uncinigerous variation (primitive situation: 100 to 150
neuropodial tori on each segment from se- segments, with a large range of individual
tigerous segment 26 to 29 (with a majority variation; apomorphous situation, 60 to 80
from 28 to 29). Uncini numerous (20 to 50 segments, with a reduced range ofindivid-
pertorus), in singlerows, withteeth directed ual variation); the rank ofoccurrence ofthe
anteriorly (retrogressive arrangement). Un- anteriormost neuropodial uncinigerous to-
cini with only a single main tooth, lacking rus (first uncinigerous torus anterior to the
a secondary tooth. modified setigerous segment in plesiomor-
Pygidium rounded, with five conspicuous phous situation, first uncinigerous torus
rounded papillae, two ventral paired papil- from segment 13 to more than segment 60
lae and three smaller, dorsal ones. in apomorphous situation). The range of
Tubes unknown. variation increases with the rank of occur-
Ecology.—From observations made on rence; the buccal apparatus, with two dif-
the White Lady hydrothermal site, the al- ferent basic types: the first one bears two
vinellid worms colonize the whitish mass large paired lateral tentacles in addition to
of anhydrite, living close to high tempera- the small ciliated dorsal tentacles, and a re-
ture (285°C) translucent desalinated hydro- versible ventral globular organ; the second
thermal fluid openings. On videotapes ob- one lacks the large paired tentacles and has
CCD TV
tained by the submersible 3 an unpaired pointed organ with a longitu-
camera, the branchial fans of Paralvinella dinal slit and a reversible ventral globular
spp. are visible at the surface of the mass organ. The development ofthe large paired
of anhydrite. The worms belong to P. uni- tentacles adapted for different trophic be-
dentata and to P. fijiensis, another species haviors is considered as an apomorphic fea-
(see below), thatare notdistinguishable dur- ture. P. unidentata exhibits a unique buccal
ing the sampling procedure. structure, reduced to the numerous grooved
—
Discussion. Since the discovery of the tentacles inserted on a well developed buc-
first species oiParalvinella, P. grasslei Des- cal membrane: this structure basically dif-
bruyeres & Laubier, 1982, six species or fers from all previously described species of
228 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Fig. 1. Paralvinella unidentata, new species. Entire animal in ventro-lateral view.
Paralvinella; the shape and position of the posite or adjacent longitudinal rows. There
secondary filaments ofthe branchiae. These is no obvious reason to consider either of
can be cylindrical and slender or flattened these structures or situations more primi-
and leaf-shaped, and inserted on two op- tive than the other one. Nevertheless, con-
VOLUME NUMBER
106, 2 229
•mm
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Ss-SWfigi
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Fig. 2. Parahinellafijiensis, new species. Entire animal in ventro-lateral view.
PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
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PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
232
sidering the facts that the genus Alvinella types from same dive deposited in the col-
possesses flattened leaf-shaped secondary lections ofthe National Museum ofNatural
filaments and is clearly apomorphic to the History, Smithsonian Institution (USNM
&
genus Paralvinella (Desbruyeres Laubier 157043).
1986), the question of the systematic rank Etymology. —The species is named forits
ofP. unidentata, withidentical flattenedleaf- geographic origin.
mm
shaped secondary filaments, must be con- Description. —Holotype 24 long and
mm
sidered carefully; and the shape of the un- 5 wide with 63 setigerous segments.
cini, in all alvinellids but P. unidentata, is Paratypes (15 specimens from PL 14) range
characterized by one main tooth and one from 50 to 68 setigerous segments. Color
secondary smaller tooth, while in P. uni- pale grey-pinkish in ethanol, with capillary
dentata there is only one main tooth. Still, setae and acicular notopodial hooks yellow;
the general shape ofthe uncinus is identical integument iridescent. Body maggot-shaped
in both groups and the presence or absence in large specimens; small animals withbody
of a secondary tooth is not considered an gradually tapering posteriorly; medioven-
important phylogenetic significance. How- tral area slightly depressed. When viewed
ever, the absence of a secondary tooth can under scanning microscope, integument of
be considered plesiomorphic to the biden- intersegmental areas densely covered with
tate semiavicular uncini previously known small circularglandularareas and secretions
for all alvinellids. from same.
Within the genus Paralvinella, P. uniden- Prostomium reduced medially with two
tata can be best compared with P. pandorae anterior lobes and two nucal grooves
and its two subspecies in the structure of obliquely situated near base. Prostomium
the buccal apparatus and the funnel-like ar- laterally separated from lateral parts ofbuc-
rangement of the branchiae. However, P. cal segment. Buccal segment laterally and
unidentata can be easily distinguished by a ventrally visible, well separated from pro-
series of characters including the rank of stomium and segment IL Buccal apparatus
occurrence and shape ofneuropodial uncini comprisingmanygroovedtentaclesinserted
and the leaf-shaped secondary filaments of dorsally and two large paired grooved ten-
the branchiae. tacles inserted ventrally, ending with three
unequally developed rounded lobes. Edge
ofmain lobe provided with several rows of
Paralvinellafijiensis, new species
small rounded internal papillae.
Figs. 2, 5
Branchial region comprised of four seg-
—
Type locality, material examined. ments, preceded by one reduced asetigerous
Ninety-five specimens collected and pre- segment still visible laterally and ventrally
served during Nautile dives PL 1 1 (3 spec- (segment II). First branchial segment ase-
imens, White Lady site), PL 12 (1 specimen, tigerous, ventrally visible. Next three bran-
White Lady site), PL 14 (47 specimens; chial segments (setigerous segments 1 to 3)
White Lady site), PL 16 (10 specimens. totally fused. Notopodia of first setigerous
White Lady site), PL 20 (34 specimens, segment very reduced; notopodia of2nd se-
White Lady site). All specimens come from tigerous segment reduced; notopodia of3rd
White Lady vent site (depth 2000 m, setigerous segment similar to the following
16°59'50"S and 173°55'47"E). Holotype notopodia. Notopodia ofsetigers 1 to 3 ad-
(dive PL 14) deposited in the collections of jacent to stem ofexternal pair ofbranchiae.
the Museum national d'Histoire naturelle, Fourth setigerous segment fused ventrally
Laboratoire de Biologic des Invertebres to fourth branchial segment.
marins et Malacologie (n°UC 439). Para- Branchiae four pairs, all similar, with a
VOLUME 106, NUMBER 2 233
1mm
200um 20um
500um 50um
Fig. 5. Paralvinella fijiensis, new species. A, anterior part in lateral view. B, buccal apparatus, showing
grooved tentacles (right) and the terminal lobes ofone ofthe ventral large tentacles (left). C, left parapod from
anterior setiger, showing dorsal lobe. D, capillary seta covered with small spines and two rows of larger ones
on the edge. E, modified notopodium ofsetiger 7, with large acicular hooks. F, uncinigerous torus, right side of
body.
234 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON
Strongbasal stem. Secondary filaments very Ecology.—yiosX specimens were collect-
abundant, inserted on two opposite areas of ed in anhydrite samples together with P.
stem to end ofbranchia, reminiscent ofPar- unidentata; on one occasion, a tube inhab-
alvinella grasslei and P. palmiformis. ited by P. fijiensis was found on a piece of
Notopodia, from setiger 4 to the end of basalt.
body (7th setiger excepted) cylindrical, Discussion.—VsfiXhm the genus Paralvi-
bearingtwogroups ofcapillary setaeheavily nella, P.fijiensis exhibits clear relationships
coated with filamentous bacteria. Notopo- withthe stem speciesP. grassleiandits close
dia from about setiger 9 to setiger 30 bearing relative P. palmiformis. These three species
dorsal and ventral rounded lobes. Setiger 7 have in common: the structure ofthe buccal
strongly modified, with two reduced dorsal apparatus, with two large trilobate paired
and ventral lobes surrounding a very re- ventral tentacles; the general shape of the
duced notopodium bearing three to four branchiae; the rank ofoccurrence ofthe un-
curved acicular notopodial setae on each cinigerous tori, starting between setiger 12
side. Surface ofacicular setae covered with (P. fijiensis, new species) and setiger 31 {P.
minute spinelets; these are longeron convex palmiformis)', and the first setigerous seg-
side of acicular hooks when viewed under ment is very reduced, and the second setig-
SEM. This structure similar to ornamen- erous segment reduced, emphasizing the
tation ofnotopodial setaeinothersegments. importance ofthe cephalization processes.
Notopodia of setiger 8 with anterior part Within this group of three species, P.
fi-
enlarged. jiensis is characterized by the number of
Uncinigerous neuropodial tori present on setigerous segments (maximum 68 in P.
fi-
each segment from setiger 12 to 19 (13 on jiensis, compared to 1 10 in P. grasslei and
the holotype). Occurrence of first uncini- 118 in P. palmiformis), the small papillae
gerous torus appears to be inversely pro- ofthe main end ofthe trilobate paired buc-
portional to total number ofsetigerous seg- cal tentacles and the shape and relative size
ments: on a total of 23 individuals, with ofthe prostomium. Additional minor diff-
total number of setigerous segments from ences can be found in the presence ofspine-
46 to 68, first uncinigerous segment occurs lets on the acicular hooks and the enlarged
from 19th to 12th setigerous segment. Re- base ofthe 7th notopodium in P. fijiensis.
gression curve:
= -
Ro (96 N)/2.54 Conclusion
where Rq = rank of occurrence of the first All Paralvinella species except P. hessleri
uncinigerous torus and N = total number and the two new species described herein
of setigerous segments of the body, indi- are known from the East Pacific Rise and
cating that the anteriormost uncinigerous related ridge systems in the Eastern Pacific.
tori appear latest. Within this general framework, two differ-
Uncini numerous (20 to 50 per row) in ent species groups can be distinguished in
single rows, withteeth facinganteriorly (ret- the Northern and Southern parts ofthe East
rogressive arrangement). Uncini increasing Pacific ridge system. These parts have been
in number posteriorly. Each uncinus with separated by the subduction ofthe Ameri-
one main tooth surmounted by smaller sec- can plate over the oceanic crust offOregon
MY
ondary tooth, as in other species of Paral- starting 35 (TunnicHffe 1988). P. pal-
vinella (except P. unidentata, see above). miformis and P. pandoraepandorae live in
Pygidium blunt, without conspicuous pa- the Northern part, while P. grasslei and P.
pillae. pandorae irlandei live in the Southern part.