Biogeography and phylogeny of the scavenging amphipod genus Valettietta (Amphipoda: Alicelloidea), with descriptions of two new species from the abyssal Pacific Ocean
Author
Stewart, Eva C. D.
School of Ocean and Earth Sciences, University of Southampton, Southampton, SO 14 3 ZH, United Kingdom & Life Sciences Department, Natural History Museum, London, Cromwell Road, South Kensington, SW 7 5 BD, United Kingdom
Author
Bribiesca-Contreras, Guadalupe
Life Sciences Department, Natural History Museum, London, Cromwell Road, South Kensington, SW 7 5 BD, United Kingdom
Author
Weston, Johanna N. J.
Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
Author
Glover, Adrian G.
Life Sciences Department, Natural History Museum, London, Cromwell Road, South Kensington, SW 7 5 BD, United Kingdom
Author
Horton, Tammy
National Oceanography Centre, Southampton, SO 14 3 ZH, United Kingdom
text
Zoological Journal of the Linnean Society
2024
2024-08-19
201
4
1
23
http://dx.doi.org/10.1093/zoolinnean/zlae102
journal article
303373
10.1093/zoolinnean/zlae102
8b8d46f3-fbd6-409b-bd15-0bad95f4c76b
0024-4082
13786330
64C1409-DD34-4196-ACDB-B72DCE516D4A
Valettietta synchlys
sp. nov.
Figs 4–7
Valettietta
cf.
anacantha
CCZ
_056C—
Bribiesca-Contreras
et al
. 2021: 1–15
, figs 1, 4–6, table 1.
Valettietta
cf.
anacantha
—
Mohrbeck
et al
., 2021: 1–12
, figs 3, 5, 7, tables 2, 3.
ZooBank registration:
http://zoobank.org/
F787152D-237B-4C45-A6DA-C7A366D9D62A
Holotype
:
Immature, 16.1 mm, carcass and 22 slides,
ECDS
_
AMP33
,
NHMUK 2024.63
, Clarion-Clipperton Zone, Pacific Ocean (
17.321 N
,
122.833 W
),
expedition JC120, Station 039, depth 4230 m, genseq-1
COI
(
PP841420
), genseq-
1 16S
(
PP849019
), genseq-1
H3
(
PP855322
), genseq-
1 28S
(
PP848491
).
Paratypes
:
Immature,
9.23 mm
, carcass, NHM_10315,
NHMUK 2024.75
,
Clarion-Clipperton Zone, Pacific Ocean (10.33 N, 117.17 W), expedition C7B, Station AT-03, depth
4292 m
, genseq-2
COI
(
PP841434
), genseq-2 16S (
PP849032
), genseq-2
H3
(
PP855323
), genseq-2 28S (
PP848494
). Mature male,
15.44 mm
, carcass and 13 slides,
ECDS-AMP32
,
NHMUK 2024.62
,
Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth
4230 m
, genseq-2
COI
(
PP841419
), genseq-2 16S (
PP849018
), genseq-2
H3
(
PP855321
), genseq-2 28S (
PP848490
). Immature,
11.33 mm
, carcass,
ECDS-AMP35
,
NHMUK 2024.65
,
Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth
4230 m
, genseq-2
COI
(
PP841422
), genseq-2 16S (
PP849021
).Mature male,
14.35 mm
, carcass,
ECDS-AMP38
,
NHMUK 2024.68
,
Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth
4230 m
, genseq-2
COI
(
PP841424
), genseq-2 16S (
PP849024
). Immature,
10.96 mm
, carcass,
ECDS-AMP16
,
NHMUK 2024.38
,
Clarion-Clipperton Zone, Pacific Ocean (16.891 N, 123.004 W), expedition JC120, Station 008, depth
4313 m
, genseq-2
COI
(
PP841404
), genseq-2 16S (
PP849005
)
.
Type locality:
The Clarion-Clipperton Zone
,
central Pacific Ocean
(
17.321 N
,
122.833 W
), expedition JC120, Station 039, depth
4230 m
.
Table 3.
Estimates of K2P divergence values within and between species of
Valettietta
, estimated from
COI
sequence data. Sequence data from this study,
Bribiesca-Contreras
et al
. (2021)
,
Weston
et al
. (2021b)
, and
Mohrbeck
et al
. (2021)
|
Intraspecific
|
Interspecific
|
|
Species
|
Min
|
Max
|
Mean
|
Min
|
Max
|
Mean
|
|
Valettietta gracilis
|
0.0000 |
0.0068 |
0.0045 |
0.0804 |
0.1048 |
0.0914 |
|
Valettietta synchlys
|
0.0000 |
0.0049 |
0.0016 |
0.0804 |
0.1048 |
0.0949 |
|
Valettietta trottarum
|
0.0000 |
0.0018 |
0.0001 |
0.0901 |
0.1002 |
0.0952 |
Figure 4.
Photographs of
Valettietta synchlys
: top, holotype, immature, NHMUK 2024.63, preserved specimen; bottom, paratype, immature, NHMUK 2024.75, fresh specimen showing ocular patch. Scale bar = 2mm.
Material examined:
See Supporting information,
Table S2
.
Etymology: Synchlys
, Greek, meaning mixed or ‘washed together by the waves’, alluding to the morphological characters of this species resembling a mixture of both
Valettietta anacantha
and
Valettietta gracilis
. Used as a noun in apposition.
Diagnosis:
Coxa 1 not shorter or slightly shorter than coxa 2 and not strongly tapered distally. Gnathopods 1 and 2 weakly subchelate or simple, tapering distally, palms weakly defined or lacking. Gnathopod 1 propodus slender, tapering distally, carpus and propodus subequal. Gnathopod 2 propodus slender, length less than 5 × width. Basis of pereopod 7 with distinct posterodistal lobe. Maxilliped inner plate reaching halfway along palp article 1, with two short nodular robust setae on sub-apical medial margin. Inner ramus of uropod 1, 2, and 3 shorter than outer.
Telson
with four lateral spine groups, apices with a single subapical large robust seta and one small setae towards lateral margins.
Description (
Figs 4–7
) Based on
holotype
, immature,
16.1 mm
length, NHMUK 2024.63
Head:
Head large, rostrum absent. Pale yellow eyes present upon collection but faded in ethanol (
Fig. 4
). Lateral lobe triangular, apically rounded.
Antennae 1
(
Fig. 5
) elongate, 0.37 × as long as body length, flagellum 33-articulate, sparsely setose; accessory flagellum 6-articulate, reaching beyond end of basal conjoint article of flagellum; conjoint article subequal to length of peduncle article 1.
Antennae 2
(
Fig. 5
) 0.78 × the length of Antennae 1, 0.28 × as long as body, flagellum 31-articulate, proximal flagellar articles with slender setae.
Mouthparts: Upper lip
asymmetrically rounded with small apical notch, distal surface minutely setose (not illustrated).
Mandible
(
Fig. 6
) left incisor 8-dentate and closely applied to 8-dentate lacinia mobilis, spine row with 12 large spines interspersed with long plumose setae, left molar damaged (not illustrated), palp robust, article 1 small, article 2 elongate, broadened medially/ centrally, 14 A2 setae present, D2 setae present along distal half, B2 setae present proximally on medial margin. Article 3 oval, tapering distally; three A3 setae, two B3 setae, and five plumose E3 setae present, 19 plumose D3 setae on the posterodistal two-thirds of the margin. Right incisor 9-dentate, closely applied to 5-dentate lacinia, spine row with seven large spines interspersed with long plumose setae, molar strongly triturative; palp robust, article 1 small, article 2 elongate, broadened laterally/centrally, 21 A2 setae present, D2 setae present along distal half, B2 setae present proximally on lateral margin. Article 3 oval, tapering distally; two A3 setae, one central and two lateral B3 setae, and six plumose E3 setae present, 18 plumose D3 setae on the posterodistal two-thirds of the margin.
Maxilla 1
(
Fig. 6
) inner plate with 20 marginal plumose setae, outer plate with 6/5 setal-tooth crown arrangement; palp large, article 2 lateral margin with two long slender setae, distal margin with 12 robust setae and row of 11 long submarginal setae.
Maxilla 2
(
Fig. 6
) inner and outer plates subequal, distally setose, inner plate also with oblique row of 17 plumose facial setae.
Maxilliped
(
Fig. 6
) inner plate reaching halfway along palp article 1, with two short nodular robust setae at sub-apical medial margin; outer plate reaching halfway along palp article 2, inner margin with row of 19 short nodular robust setae grading to seven elongate and plumose setae distally; palp 4-articulate, article 4 with three robust setae distally, dactylus well-developed.
Figure 5.
Valettietta synchlys
holotype, immature, NHMUK 2024.63, 16.1 mm, Clarion-Clipperton Zone, 4230 m. A = Antenna; GN = Gnathopod. Unfilled circles indicate setal bases.
Figure 6.
Valettietta synchlys
holotype, immature, NHMUK 2024.63, 16.1 mm, Clarion-Clipperton Zone, 4230 m. MX = Maxilla;
Md = Mandible; MXP = Maxilliped; LL = Lower lip; l = left; r = right. Unfilled circles indicate setal bases.
Figure 7.
Valettietta synchlys
holotype, immature, NHMUK 2024.63, 16.1 mm, Clarion-Clipperton Zone, 4230 m. P = Pleopod; U = Uropod; T =
Telson
.
Pereon: Gnathopod 1
(
Fig. 5
) subchelate; coxa 1 shorter than coxa 2, slightly tapering distally, proximal and distal margins sub-rectangular, setose; carpus and propodus subequal, propodus not strongly elongate or tapering distally, palm acute, palmar margin straight and dentate, delimited by three bifid robust setae, dactylus overlapping palm, inner margin toothed with a few fine setules.
Gnathopod 2
(
Fig. 5
) subchelate; anterodistal corner of coxa sub-rectangular, distal margin setose, basis curved, ischium extremely elongate (sub-equal to basis); carpus slightly shorter than propodus (1:0.85), both slender, propodus length 5 × width; palm acute, palmar margin straight and dentate, dactylus shorter than palm, not reaching single palmar defining robust seta, inner margin toothed with a few fine setules.
Pereopod 3
(
Fig.7
) coxa rectangular, distal margin setose; basis curved; merus and propodus longer than carpus; all articles with long slender marginal setae.
Pereopod 4
(
Fig. 7
) coxa very broad with large posteroventral lobe, posterodistal margin broadly rounded and setose; merus and propodus subequal in length and longer than carpus.
Pereopods 5–7
(
Fig. 7
) coxa 5 broadly expanded and bilobate with posterodistal lobe largest, coxa 6 smaller than coxa 5 with posterior margin weakly lobate; coxa 7 smaller than coxa 6, not bilobate; basis broadly expanded distally, increasing from P5 to P7.
Pleon and urosome: Epimeron
(
Fig. 5
) 1 broadly rounded, 2 subquadrate, 3 produced to a subacute tooth.
Urosomite 1
with low rounded boss on dorsal margin.
Uropods
(
Fig. 7
) biramous, lanceolate.
Uropod 1
inner ramus shorter than outer (1:0.8), with both margins lined by short robust setae, adjacent margins minutely serrate, apex of both rami with inset small setule; peduncle with one apicolateral robust seta, 11 dorsolateral setae, nine dorsomedial setae, and 10 longer ventrolateral setae.
Uropod 2
inner ramus shorter than outer (1:0.75), both margins of outer ramus lined by short robust setae, inner margin of inner ramus lined by short robust setae, with one seta present on outer margin, adjacent margins minutely serrate, apex of both rami with inset small setule; peduncle with fewer setae than peduncle of uropod 1, one large robust seta present on peduncle at base of inner and outer ramus.
Uropod 3
inner ramus shorter than outer (1:0.9), distal article of outer ramus approximately two-thirds length of proximal article, apex of proximal article with robust setae, inner margin minutely serrate; proximal inner margin of inner rami with four plumose setae, distal inner margin of inner rami minutely serrate; peduncle with long fine setae on inner margin, and three groups of two short setae on outer margin.
Telson
(
Fig. 7
) triangular, 75% cleft, apices with a single subapical large robust seta and one small setae towards lateral margins; lobes with four lateral robust setae.
Habitat and ecology:
Valettietta synchlys
is a benthopelagic scavenger species, currently known only from the central Pacific Ocean in the Clarion-Clipperton Zone, at abyssal depths of
4230–4313 m
.
Remarks:
Valettietta synchlys
most closely resembles
V. anacantha
in the shape of coxa 1, gnathopods 1 and 2, and uropod 3, and has been recorded as
V.
cf.
anacantha
in recent literature (
Bribiesca-Contreras
et al
. 2021
,
Mohrbeck
et al
. 2021
).
Valettietta synchlys
can be distinguished by characters of gnathopod 1, which more closely resembles that of
V. gracilis
, with propodus longer and more strongly tapering distally (shorter and broader, weakly tapering distally in
V. anacantha
), and a longer carpus (shorter in
V. anacantha
). It can be further distinguished by the angle of the anterodistal corner of coxa 2 which is sub-rectangular in
V. synchlys
(rounded in
V. anacantha
). The basis of pereopod 7 is narrower with a distinct posterodistal lobe (in
V. anacantha
this is significantly more broadly rounded with a shallow, rounded posterodistal lobe). Body size ranged from
9.23–16.10 mm
between examined specimens.