Redescription of Euconchoecia chierchiae Müller, 1890 and Euconchoecia aculeata (Scott, 1894) (Halocyprididae: Ostracoda) from the Atlantic, and descriptions of two novel species of Euconchoecia Müller 1890, from the Gulf of Oman
Author
Graves, Carol
text
Journal of Natural History
2011
2011-08-31
45
31 - 32
1937
1981
http://dx.doi.org/10.1080/00222933.2011.573100
journal article
10.1080/00222933.2011.573100
1464-5262
5204078
Euconchoecia chierchiae
Müller, 1890
(
Figures 1–6
,
21A,B
)
Euconchoecia chierchiae
Müller, 1890: 277
, Pl. XXVIII, fig. 1–10.
Brady, 1902: 190
, Pl. XXIV, fig. 9–15.
Vavra, 1906: 29
, Pl. 1, fig. 1–6.
Skogsberg, 1920: 740
, fig. CXLVIII– CLI.
Deevey, 1968: 116
, fig. 62.
Poulsen, 1969: 38
, fig. 12, 13.
Tseng, 1969: 2
, fig. 1.
George, 1977
: fig. 1, 2.
Paraconchoecia oblonga
Cleve, 1900: 40
.
Material
The material is not “
type
” material, but material collected from
Discovery station
8281 (see above).
Permanent
preparations of dissected specimens used to prepare the illustrations in this paper have been deposited at the
Natural History Museum
,
London
: registration number
BMNH 2009.316
for the female and
BMNH 2009.317
for the
male. Registration numbers
BMNH 2009.318
–
327
are for the
32 females
and
9 males
retained in 80% ethyl alcohol
.
Description
A full redescription is merited because this is the
type
species for the genus.
The
meristic characters of the carapaces of both sexes, the frontal organs, first and second antennae, mouthparts and limbs are listed in
Tables 2–9
, together with comparative data for the other species examined:
E. aculeata
Scott 1894
, and the two new species from the
Gulf
of
Oman
.
Female
Carapace
(
Figure 1A, B
). Mean length 1.24 ±
0.05 mm
(
n
= 32). Carapace of exemplar specimen (
Table 2
) with length
1.28 mm
, height
0.56 mm
and breadth
0.50 mm
. Height: length ratio 43.8%, breadth: length ratio 39.1%. Carapace unsculptured. In lateral view slightly elongate: maximum height just posterior to mid-length. Ventral margin curves smoothly into posterior margin. Posterior dorsal corner of both valves furnished with a small spine. Spine slightly smaller on left valve. Dorsal margin arcs anteriorly up towards dorsal end of hinge between carapace valves. Both rostra curve ventrally, the left rostrum is the longer and more pointed. The “asymmetrical” glands open at a similar height on posterior margin of each valve just below spine at posterior dorsal corner.
Frontal organ
(
Table 2
;
Figure 1C
). Frontal organ fused into a single slender structure with rounded end that is just shorter than A1 and 18.9% CL.
First antenna
(
Table 3
Figure 1C
). With five segments, but suture between fourth and fifth segments ill-defined. Limb length ∼ 31% CL. Fourth segment with ∼ 24 thin walled bundle setae all 17% CL. Fifth segment with four more unequal setae; a-seta quite short 5.1% CL; b-seta 9.4% CL; c-seta 17.2% CL; d-seta 13.9% CL.
Second antenna
(
Table 3
;
Figure 1D
). Protopodite 27.7% CL. Length of first exopodite segment ∼ half protopodite. Most swimming setae similar in length to protopodite, all but the shortest terminal seta have long hairs distally. Endopodite (
Figure 1E
) with short, pointed, bare a- and b-setae. There are no c-, d- or e-setae. The f- and g-setae, respectively, 26.6% CL and 44.9% CL. The i-seta 13.3% CL, but h- and j-setae are absent.
Mandible
(
Table 4
;
Figure 2A,B
). Coxale toothed edge of pars incisiva has two large and 10 small smooth teeth. Distal tooth list slightly narrower with two large tusklike teeth and 10 small smooth teeth. The proximal tooth list very narrow, with two large and five small teeth. Outer margin of toothed edge of basal endite with a large dagger-shaped tooth, a slightly smaller, rounded, tubular tooth and six subserrate teeth. Two spinose setae are inserted laterally on basal endite. Exopodite represented by moderately long plumose seta inserted on outer margin of basis. First endopodite segment with one short, bare, subterminal, dorsal seta and three finely spinose ventral setae. Second segment with one ventral and two dorsal setae, all finely spinose. Third segment with seven spinose terminal setae; one very long and robust.
Figure 1.
Euconchoecia chierchiae
female: (A) lateral view, (B) carapace dissected and viewed dorsally – arrows indicate gland openings, (C) first antenna and frontal organ, (D) second antenna viewed from inside, (E) endopodite viewed from inside.
Table 2. Female
Euconchoecia
species
differences.
| Female |
E. chierchiae
|
E. aculeata
|
E. omanensis
E. hormuzensis
|
| Carapace |
| length |
1.28 mm |
1.28 mm |
1.42 mm |
1.00 mm |
| height |
0.56 mm |
0.64 mm |
0.46 mm |
0.42 mm |
| breadth |
0.50 mm |
0.42 mm |
0.40 mm |
0.40 mm |
| height: length % |
43.8% |
50.0% |
32.4% |
42.0% |
| breadth: length % |
39.1% |
32.8% |
28.2% |
40.0% |
| PDC, left tip to posterior |
6.3% |
6.6% |
13.0% |
11.0% |
| hinge (% CL) |
| PDC, right tip to posterior |
7.0% |
9.8% |
15.8% |
11.5% |
| hinge (% CL) |
| Rostrum, left tip to anterior |
14.5% |
15.6% |
15.1% |
12.0% |
| hinge (% CL) |
| Rostrum, right tip to anterior |
13.3% |
12.1% |
11.6% |
12.0% |
| hinge (% CL) |
| Incisure, left rostrum tip to |
12.5% |
14.5% |
14.1% |
10.0% |
| inner edge (% CL) |
| Incisure, right rostrum tip to |
9.4% |
10.5% |
11.3% |
9.5% |
| inner edge (% CL) |
| Frontal organ |
| stem and capitulum length |
18.9% |
22.3% |
18.7% |
20.3% |
| (% CL) |
| length relative to antenna 1 |
slightly |
marginally |
significantly |
slightly longer |
| shorter |
longer |
longer |
Notes:
n
= 1 for each species
% CL, % of carapace length; PDC, posterior dorsal corner.
Maxilla
(
Table 4
;
Figure 2C
). Basal segment with five anterior, one lateral and four posterior setae. Distal segment comparatively short and wide with six terminal claw setae, the posteriormost is longest, anterior claw with secondary spines.
Fifth limb
(
Table 5
;
Figure 2D
). Ventrally basale with five (2+1+2) setae all with secondary spines; laterally two plumose setae, dorsally a single long spinose seta – the remnant of the exopodite. First segment with two ventral setae and one dorsal seta, all spinose. Second segment with three unequal, curved terminal claw setae; middle claw the longest 5.7% CL.
Sixth limb
(
Table 5
;
Figure 2E
). Basale with one proximal, two medial ventral spinose setae and a distal plumose seta, laterally a plumose seta and dorsally a terminal spinose seta. First endopodite segment with two ventral setae. Second segment with a single spinose seta both ventrally and dorsally. Third segment with three unequal spinose, terminal claw setae; longest middle claw 10.4% CL.
Caudal furca
(
Table 5
;
Figure 2F
). Seven pairs of claw setae diminish in size dorsally; longest claw 15.2% CL. All have secondary spines along their trailing edges. Dorsal to Notes:
n
= 1 for each species
Table 3. Female
Euconchoecia
species
differences.
| Female |
E. chierchiae
|
E. aculeata
|
E. omanensis
|
E. hormuzensis
|
| Antenna 1 |
| length segment 2 (% CL) |
7.4% |
8.2% |
6.5% |
7.0% |
| length segment 3 (% CL) |
4.3% |
7.2% |
4.4% |
3.0% |
| length segment 4 (% CL) |
1.6% |
4.5% |
3.3% |
2.4% |
| approximate total length |
31.0% |
34.0% |
35.0% |
37.0% |
| bundle setae number |
24 |
24 |
24 |
24 |
| bundle setae length (% CL) |
17.0% |
17.0% |
9.2% |
16.3% |
| a-seta (% CL) |
5.1% |
3.1% |
2.1% |
3.8% |
| b-seta (% CL) |
9.4% |
6.1% |
3.5% |
5.5% |
| c-seta (% CL) |
17.2% |
14.5% |
10.0% |
17.0% |
| d-seta (% CL) |
13.9% |
11.5% |
7.7% |
13.5% |
| Antenna 2 |
| protopodite (% CL) |
27.7% |
29.3% |
24.6% |
30.0% |
| exopodite 1 (% CL) |
14.8% |
13.7% |
10.2% |
13.0% |
| exopodite 2–9 (% exopodite 1) |
53.9% |
45.7% |
37.9% |
53.8% |
| longest swimming seta (% CL) |
27.0% |
30.9% |
24.1% |
24.5% |
| shortest swimming seta (% CL) |
3.8% |
3.1% |
2.1% |
2.0% |
| endopodite segment 1 (% CL) |
9.2% |
9.4% |
7.2% |
9.3% |
| a-seta (% CL) |
1.8% |
1.2% |
1.6% |
2.3% |
| b-seta (% CL) |
3.1% |
3.5% |
3.2% |
3.5% |
| endopodite segment 2 (% CL) |
4.1% |
2.3% |
2.3% |
2.0% |
| f-seta (% CL) |
26.6% |
25.4% |
17.8% |
24.0% |
| g-seta (% CL) |
44.9% |
35.2% |
23.2% |
43.5% |
| i-seta (% CL) |
13.3% |
23.0% |
7.2% |
11.5% |
% CL, % of carapace length.
the paired spines is a single seta with bilateral secondary spines. Between the first and second pairs of claw setae is a verruciform process.
Male
Carapace
(
Figure 3A,B
). Mean length 1.24 ±
0.06 mm
(
n
= 9). Carapace of exemplar specimen (
Table 6
) with length
1.26 mm
, height
0.70 mm
and breadth
0.60 mm
. Height: length ratio 55.6%, breadth: length ratio 47.6%. Carapace unsculptured. Maximum height just anterior to mid-length. Ventral margin curves smoothly into posterior margin. Posterior dorsal corner of both valves furnished with a small spine. On the left valve the spine is slightly smaller. Dorsal margin arcs anteriorly up towards dorsal end of hinge between carapace valves. Both rostra forward pointing and of the same length. The “asymmetrical” glands open at a similar height on the posterior margin of each valve just below the spine at the posterior dorsal corner.
Frontal organ
(
Table 6
;
Figure 3C
). Frontal organ is fused into a slender structure with a rounded end, shorter than A1 and 23.2% CL.
Table 4. Female
Euconchoecia
species
similarities.
| Female |
E. chierchiae
|
E. aculeata
|
E. omanensis
|
E. hormuzensis
|
| Mandible |
| basale |
1 plumose |
1 plumose |
1 plumose |
1 plumose |
| endopodite segment 1 dorsal setae |
1 |
1 |
1 |
1 |
| endopodite segment 1 ventral setae |
3 |
3 |
3 |
2 |
| endopodite segment 2 dorsal setae |
2 |
2 |
2 |
2 |
| endopodite segment 2 ventral setae |
1 |
1 |
1 |
1 |
| endopodite segment 3 terminal setae |
7 |
7 |
7 |
7 |
| endopodite segment 3 longest claw (% CL) |
15.8% |
16.0% |
12.9% |
16.0% |
| endopodite segment 3 longest claw (% limb) |
93.2% |
93.2% |
83.9% |
94.1% |
| teeth on basal endite |
2 + 6 |
2 + 6 |
2 + 6 |
2 + 6 |
| pars incisiva |
2 + 10 |
2 + 10 |
2 + 10 |
2 + 10 |
| distal tooth list |
2 + 10 |
2 + 10 |
2 + 10 |
2 + 10 |
| proximal list |
2 + 5 |
2 + 5 |
2 + 5 |
2 + 5 |
| setae laterally on endite |
2 +2 |
2 + 2 |
2 + 2 |
2 + 2 |
| exopodite |
1 plumose |
1 plumose |
1 plumose |
1 plumose |
| Maxilla |
| basal segment anterior setae |
5 |
5 |
5 |
5 |
| basal segment lateral setae |
1 |
1 |
1 |
1 |
| basal segment posterior setae |
4 |
4 |
4 |
4 |
| terminal spines |
fine hairs |
fine hairs |
fine hairs |
fine hairs |
| distal segment claw setae |
3 |
3 |
3 |
3 |
| distal segment normal setae |
3 |
3 |
3 |
3 |
Notes:
n
= 1 for each species.
% CL, % of carapace length.
First antenna
(
Table 7
;
Figure 3C
). With five well-defined segments. Limb length ∼ 31% CL. As in the female, fourth segment with ∼ 24 thin walled bundle setae all 17.5% CL. Fifth segment with five more unequal setae: a-seta 8.3% CL; b-seta 18.1% CL; c-seta 38.9% CL; d-seta 42.5% CL; e-seta 65.1% CL.
Second antenna
(
Table 7
;
Figure 3D
). Protopodite 38.5% CL. Length of first segment of exopodite ∼ half protopodite. Most swimming setae similar in length to protopodite, all but the shortest have long hairs distally. Endopodite with short, pointed a- and b-setae. There are no c-, d- or e-setae. The f- and g-setae respectively 22.4% CL and 79.8% CL. Right endopodite (
Figure 4B
) with elongated clasping organ in form of hook with long proximal shank and very long curved end piece 9.1% CL. The h-, i- and j-setae attached distally to basal shank, h-seta is short 3.4% CL and curves over bases of other two, i-seta longest 15.9% CL. Left endopodite (
Figure 4A
) “hook” reduced to just basal shank with three setae.
Mandible, maxilla, fifth limb
(
Tables 8
,
9
;
Figures 4C–E
,
5A
). Structure and arrangement of setae for mandible, maxilla and fifth limb are same as for female.
Sixth limb
(
Table 9
;
Figure 5B
). Basale with five spinose setae ventrally, one lateral spinose seta and one bare dorsal exopodal seta. First endopodite segment with two ventral setae. Second endopodite segment with a single seta both ventrally and dorsally. Third segment with three subequal terminal setae, very long, evenly curved ventrally with long hairs 28.6% CL.
Figure 2.
Euconchoecia chierchiae
female: (A) mandible, coxale not shown, (B) basal endite of mandible, (C) maxilla, (D) fifth limb, (E) sixth limb, (F) caudal furca.
Table 5. Female
Euconchoecia
species
similarities.
| Female |
E. chierchiae
|
E. aculeata
|
E. omanensis
|
E. hormuzensis
|
| Fifth limb |
| basale ventral setae |
2 + 2 + 1 |
2 + 2 + 1 |
2 + 2 + 1 |
2 + 2 + 1 |
| basale lateral setae |
2 |
2 |
2 |
2 plumose |
| basale dorsal setae |
1 long |
1 long |
1 long |
1 long |
| endopodite segment 1 ventral setae |
2 |
2 |
2 |
2 |
| endopodite segment 1 dorsal setae |
1 |
1 |
1 |
1 |
|
height
/
length %
|
45.2% |
56.3% |
76.0% |
57.7% |
| longest terminal seta % CL |
5.7% |
6.0% |
4.1% |
5.5%
|
|
longest seta
/
length segment 2
|
341.2% |
554.5% |
522.2% |
525.0% |
|
longest seta
/
length limb
|
55.8% |
58.7% |
58.0% |
60.9% |
| Sixth limb |
| basale ventral setae |
3 + 1 plumose |
3 + 1 plumose |
3 + 1 plumose |
3 + 1 plumose |
| basale lateral setae |
1 plumose |
1 plumose |
1 plumose |
1 plumose |
| basale dorsal setae |
1 |
1 |
1 |
1 |
| endopodite segment 1 ventral setae |
2 |
2 |
2 |
2 |
| endopodite segment 1 dorsal setae |
0 |
0 |
0 |
0 |
| endopodite segment 2 ventral setae |
1 |
1 |
1 |
1 |
| endopodite segment 2 dorsal setae |
1 |
1 |
1 |
1 |
|
segment 2 height
/
length %
|
47.4% |
55.6% |
44.1% |
35.0% |
| longest seta % CL |
10.4% |
8.1% |
7.1% |
8.5% |
| longest seta % segment 2 |
278.9% |
461.1% |
238.2% |
170.0% |
| longest seta % limb |
77.9% |
159.6% |
52.9% |
50.0% |
| Caudal furca |
| paired claws |
7 pairs |
7 pairs |
7 pairs |
7 pairs |
| longest claw % CL |
15.2% |
14.1% |
10.4% |
12.0% |
| unpaired dorsal seta |
1 seta |
1 seta |
1 seta |
1 seta |
Notes:
n
= 1 for each species.
% CL, % of carapace length.
Caudal furca
(
Table 9
;
Figure 5C
). Structure and arrangement of furcal claws similar to female. The longest claw is 18.7% CL.
Intromittent organ
(
Table 9
;
Figure 5C
). Male copulatory appendage is exceptionally long, 27.4% CL.
Remarks
The original description of
E. chierchiae
by
Müller (1890)
and subsequent redescription (
Müller 1906
)
specified a wide size range; females from
1.15 to 1.53 mm
and males from
1.15 to 1.45 mm
. Size is a significant taxonomic feature of halocyprid ostracods, so a wide range such as this often suggests that there may be more than one species present. The redescriptions of
E. chierchiae
by
Brady (1902)
and by
Vavra (1906)
were considered doubtful by
Skogsberg (1920)
, and the illustration by
Skogsberg (1920)
of a female specimen in lateral aspect differs from those of
Müller (1890
,
1906
).
Euconchoecia chierchiae
as described by
George (1977)
from the Indian Ocean appears very similar to Atlantic
E. chierchiae
as described by
Müller (1890)
.
Deevey (1968)
and later
Angel (1999)
identified and illustrated
E. chierchiae
from off
Bermuda
, and recently specimens from waters west of
Bermuda
have had the cytochrome oxidase
type
1 gene (
COI
) sequenced (Angel, personal communication). However, critical comparisons of these two authors’ descriptions and figures deviate from those of both
Müller (1906)
and
Skogsberg (1920)
, and the attributions of their specimens to this species remain open to question (
Figure 6
). There is a now a need for systematic and molecular studies to clarify the status of this species. Unfortunately, despite the remarkably high abundances of
Euconchoecia
in tropical waters especially in the Pacific, no sequencing of this genus has been undertaken, and the Gulf of
Oman
material is unsuitable for molecular sequencing because it was initially preserved in formalin.