Conchoecia skogsbergi Chavtur, 2003, species nov.
Creators: name: Chavtur, Vladimir Grygorjevich
Publisher: name: Zenodo
Year: 2003
Subjects: Biodiversity
Taxonomy

description: Key to species of “ skogsbergi ” complex
Only for male
1. Copulatory appendage is very curved .......................................................... M. australis
­ Copulatory appendage is straight or almost straight ..................................................... 2
2. Left asymmetrical gland is placed more than17% length of carapace behind tip of rostrum .................................................................................................................... M. discovery
­ Left asymmetrical gland is placed less or about 15% of carapace behind tip of rostrum ....................................................................................................................................... 3
3. Length is about or more than 1.7 mm, dorsal margin is broadly V­shaped with apex just posterior to insertation of protopodite of 2nd antenna, length of seta­g is about 2.5 length of 1st endopodite segment of 2nd antenna ................................ M. ampla nov. sp.
­ Length is less 1.7 mm, dorsal margin is straight, length of seta­g is 3 times as long as length of 1st endopodite segment of 2nd antenna........................................................... 4
4. Length is more than 1.3 mm .......................................................................................... 5
­ Length is less 1.3 mm (except in M.fowleri Form A) ................................................... 7
5. Right asymmetrical gland opens near posterior dorsal corner ..................................... 6.
­ Right asymmetrical gland is placed somewhat below posterior dorsal corner (about 10% length of posterior margin) ................................................. M. skogsbergi nov.sp.
6. Carapace is short and round in lateral view (height more than 50% of length), seta­c of 1st antenna is thick, shorter than total combined length of segments 3 to 5, seta­e of 2nd antenna is large, stout and claw­like ...................................................... M. alta nov. sp.
­ Carapace is more cylindrical (height usually less than 50% of length), seta­c of 1st antenna is thin and subequal to total combined length of segments 3 to 5, seta­e of 2nd antenna is tiny, thin, and peg­like .................................................. M.longiseta nov. sp.
7. Seta­c of 1st antenna is subequal to total combined length of segments 3 to 5, seta­e is twice as long as this limb ................................................................................ Mwolferi
­ Seta­c of 1st antenna is shorter than total combined length of segments 3 to 5, seta­e is less than length of this limb .......................................................................................... 8
8. Seta­a of 1st antenna is proximally noticeable swollen and extends beyond proximal end of limb ................................................................................... M. crassiseta nov. sp.
­ Seta­a of 1st antenna is either usual, or proximally slightly swollen and barely reaches or does not reaches of proximal limb............................................................................ 9
9. Carapace is unusually broad in ventral view (more than 50% of length) ................... 10
­ Carapace is less broad in ventral view (less than 50% of length), except in M. acuta (48.6+ 2.6%)................................................................................................................ 11
10. Capitulum of frontal organ is broad, seta­c of 1st antenna is short; seta­e of 2nd antenna is developed, its proximal spines are short .......................................... M. inflata inflata
­ Capitulum of frontal organ is narrow, seta­c of 1st antenna is short; setae of 2nd antenna is minute, its proximal spines are long ...................................... M. inflata lata nov. spp.
11. Seta­e of 1st antenna is with short spines ......................................................... M. obtusa
­ Seta­e of 1st antenna is with long spines...................................................................... 12
12 Length is more than 0.9 mm ........................................................................................ 13
­ Length is less than 0.9 mm ......................................................................... M.rotundata
13. Seta­c of 1st antenna is about half of total combined length of segments 3 to 5, and seta­a reaches proximal end of limb............................................................................ 14
­ Seta­c of 1st antenna is barely shorter than total combined length of segments 3 to 5, and seta­a does not reach proximal end of limb ......................................... M. subinflata
14. Length is 1.1 mm or over, seta­e of 2nd antenna is armed with 12­15 pairs of spines..... ....................................................................................................................... M. fowleri
­ Length is less than 1,0 mm, seta­e of 2nd antenna is armed with 10­12 pairs of spines .. ............................................................................................................................ M.acuta
Only for female
1. Left asymmetrical gland is situated more than or about 17% length of carapace behind tip of rostrum............................................................................................ M. discoveryi
­ Left asymmetrical gland is situated less than or about 15% length of carapace behind tip of rostrum ................................................................................................................ 2
2. Exopodite of 2nd antenna is about 80% length of protopodite ...................................... 3
­ Exopodite of 2nd antenna is less than or about 70% length of protopodite ................... 4
3. Length is less than 1.3 mm, height is more than 50% of length, terminal setae on endopodite of 2nd antenna is half as long as exopodite .............. M. inflata lata nov.ssp.
­ Length is more than 1.6 mm, height is less than 50% of length, terminal seta on endopodite of 2nd antenna is about 80% of exopodite ......................... M. ampla nov.sp.
4. Terminal setae on endopodite of 2nd antenna is about 40% and 60% length of proto­ podite and exopodite ......................................................................................... M.acuta
­ Terminal setae on endopodite of 2nd antenna is more than or about 50% length of pro­ topodite and more than 60% length of exopodite ......................................................... 5
5. Length is less than 0.9 mm ......................................................................... M. rotundata
­ Length is more than 0.9 mm .......................................................................................... 6
6 Length is about or more than 1.3 mm ........................................................................... 7
­ Length is less than 1.3 mm (except M. fowleri Form A) .............................................. 9
7. Right asymmetrical gland open near posterior dorsal corner........................................ 8
­ Right asymmetrical gland open somewhat below posterior dorsal corner (about 10% length of posterior margin) ........................................................................ M.skogsbergi
8. Length is about 1.3 mm, 2nd segment of 1st antenna is without seta. M. aff. skogsbergi
­ Length is more than 1.4 mm, 2nd segment of 1st antenna is armed with minute seta .. 15
9. Seta­e on 1st antenna is about or more than 2.5 length of limb, terminal seta of 2nd antenna is about or more than 80% length of exopodite ............................................. 10
­ Seta­e on 1st antenna is less or about twice as long as limb, terminal setae of 2nd antenna is less than 80% length of exopodite ............................................................. 11
10 Length is about or 1.1 mm or over ................................................................. M. fowleri
­ Length is about or less than 1.0 mm ................................................................ M. obtusa
11. Exopodite of 2nd antenna is about 80% length of protopodite ...... M. iflata lata nov. sp.
­ Exopodite of 2nd antenna is about or less than 70% length of protopodite ................. 12
12. Seta­e of 1st antenna is twice as long as limb or sensory setae.................................... 13
­ Seta­e of 1st antenna is less than twice length of limb or sensory setae .......................... ...................................................................................................... M. crassiseta nov. sp.
13. Height and breadth of carapace are more than 50 and 40% of its length, respectively .. ...................................................................................................................... M. australis
­ Height and breadth of carapace are about or less than 50 and 40% of its length, respec­
tively .................................................................................................................... 14 14. Carapace is prolonged, capitulum of frontal organ is straight and with rounded tip ...... ........................................................................................................................ M. wolferi
­ Carapace is high, capitulum of frontal organ is curved and with pointed tip ................ .................................................................................................................... M. subinflata
15. Capitulum of frontal organ is fused to shaft or separated by indistinct suture, 1st segment of 1st antenna is bare, length of 1st endopodite segment on maxilla is about 1.5 of its height ................................................................................................. M. alta nov. sp.
­ Capitulum of frontal organ is separate from shaft by distinct suture, 1st segment of 1st antenna is armed with dorsodistal spines, length of 1st endopodite segment on maxilla is subequal to height ....................................................................... M. longiseta nov. sp.
Order HALOCYPRIDA Dana, 1853
Suborder HALOCYPRIDINA Dana, 1853
Superfamily HALOCYPRIDOIDEA Dana, 1853
Family HALOCYPRIDIDAE Dana, 1853
Subfamily CONCHOECIINAE Müller, 1906
Genus METACONCHOECIA Kock, 1992
Metaconchoecia longiseta nov. sp.
(Figs. 2­13)
Conchoecia skogsbergii: Chavtur, Shornikov, 1974: 286 (part).
Metaconchoecia skogsbergii: Chavtur, 1976: 105 ­106 (part); 1977a: 145­146 (part); 1977b: 30 (part); 1977c: 20 (part).
Metaconchoecia species nov. 2 Chavtur, 1991: 46 (part); 1992: 49, table 2.
Etymology. The specific name “ longiseta ”, is derived from the Latin word “ longa” meaning long and “seta” refers to the exceptionally long c­bristle on the endopodite of the second antenna.
Holotype. IBM 2792 – adult male, length 1.42 mm, appendages mounted on slide and valves in alcohol, in collection of the Museum of Institute Marine Biology, Vladivostok, Russia (together with paratypes).
Type­locality. RV Vityaz 39th Cruise, station 5617, sample 126, at 45º49’N, 153º33’E, depth 500­ 200m, August 5 1966, using a Bogorov – Rass’s Net (S = 1,0 m²).
Paratypes. IBM 2793 –adult male, IBM 2794 – adult male, IBM 2795 – adult male, IBM 2796 – adult female, IBM 2797 – adult female, IBM 2798 –adult female, IBM 2799 – adult male, same station and sample as for holotype. Paratypes IBM 2793 –2799: append­ MALE
Carapace (Figs. 2 A­F; 3 A; Table 1). The length of adult specimens ranges from 1.30­ 1.55 mm. Carapace is relatively elongated. Its maximum height is 45­51% of the carapace length (CL), and occurs posterior to the midline. Hence the posterior half of the shell is somewhat larger than the anterior half. The maximum width of the carapace is 45­51% CL and is positioned just anterior to midlength; generally the anterior region of the carapace is slightly broader than the posterior region. The shoulder vault is weakly developed and rounded. The dorsal margin is either straight or broadly V­shaped with the apex just posterior to the insertion of the protopodite of the second antenna. The posterior dorsal corner is a rounded angle with a distinct apex. The posterior margin curves evenly, and the ventral margin is almost straight or slightly curved, curving smoothly into posterior end. The rostrum is minute and has a pointed tip. The rostral incisure is fairly shallow. In ventral view, the sides of the carapace are only gently curved. On the right carapace valve the asymmetric gland opens almost at the posterodorsal corner, whereas the gland on the left valve is located at a position just posterior to the rostral incisure. Dorso­medial glands are weakly developed. The glands along the anterior margin of the shell are rather distinct. There is no surface ornamentation.
A­C ­ lateral view of left valve of carapace; D ­ lateral view of right valve of carapace; E ­ anterior of right carapace valve; F ­ posterodorsal region of carapace; G ­ distal end of frontal organ.
A ­ ventral view of carapace; B ­ upper lip; C ­ frontal organ and 1st antenna; D ­ terminal part of 1st antenna; E and F ­ second antenna; G – b­seta of endopodite of second antenna.
A­C ­ medial part of c­, d­ and e­setae of 1st antenna; D and E ­ endopodite of left second antenna; F ­ endopodite of right second antenna; G and H ­ hook appendage of endopodite of left second antenna.
Frontal organ (Figs. 2 G; 3 C). The shaft extends beyond the end of the second segment of the first antenna. The proximal half of the capitulum is expanded, with a strongly convex ventral margin, whereas the distal part is narrow, and either tapers slightly or is parallel­sided. The surface of the capitulum is densely covered with numerous minute spines.
First antenna (Figs. 3 C, D; 4 A­C). The segmentation is fairly distinct. The a­seta extends back parallel to the limb (except proximally where it loops down and is slightly swollen) not quite reaching its proximal boundary. The b­seta is slightly longer than the dseta and bears 9­11 closely spaced various sized anterior spines and has 5­7 short spines and followed 5­6 long closely spaced spines on its posterior margin. The c­ seta is relatively thin and long, it length being similar to the total length of the third to fifth segments of the limb. The d­seta is armed with 8­9 closely spaced various­sized anterior spines. The longest e­seta is about one and a half (or somewhat longer) the length of the limb. The eseta armature comprises 13­15 pairs of spines, which lie at an acute angle to the seta. The first segment of the limb contains some dark pigment spots.
Second antenna (Figs. 3 E, F; 4 D­H; 5 A­E; 6 A, B). The protopodite has some dark pigment spots. The exopodite is about 60% (or somewhat longer) the length of the protopodite The first endopodite segment bears three triangular ridges. The distoventral surface of this segment is covered with fine hairs. The processus mamillaris is bulbous with a beak­like extension pointing slightly forwards. The b­seta is about twice the length of the a­seta and 1.5 the length of the 2nd endopodite segment. The c­ and d­setae are relatively long. The e­seta is tiny. The hook appendage on the right limb is strongly developed with a long curved distal section and a number of subterminal ridges. On the left limb the hook appendage is smaller, with a relatively short straight distal section and no subterminal ridges, but it has terminal verruca. The sensory h­, j­ and i­setae are about 40% the length of the g­seta. The sensory h­, j­ and i­setae are about 30% the length of the g­seta. The gseta is 80­85% the length of the protopodite, about 1.2 the length of the exopodite and 4 times as long as the first endopodite segment. The f­ and g­setae are somewhat flattened distally.
A­D ­ hook appendage of endopodite of right second antenna; E ­ distoventral region of endopodite of right second antenna; F ­ mandible.
A and B ­ end of hook appendage of endopodite of right second antenna; C ­ medial region of main seta of terminal segment of mandible; D ­ basal endite of mandible; E ­ toothed edge and proximal and distal tooth rows of mandibular coax; F­H ­ masticatory pad and toothrows of coxa of mandible.
A and B ­ maxilla, endite and terminal region; C – 5th limb.
Mandible (Figs. 5 F; 6 C­H; 8 A, D). The coxale cutting edge has a straight anterior section followed by 12­15 teeth. The distal list has a large double pointed posterior tooth, followed by about 25 small teeth. The proximal list is armed with large pointed posterior tooth, 3­4 small teeth, a second large tooth followed by about 20­25 small teeth, one of which near the middle, is larger than the others; the inner surface of this list is covered with very small teeth or papillae. The masticatory pad bears four narrow rounded flaps (covered with exceedingly fine, rather short and exceedingly dense spines), four stout teeth, numerous filaments (with bifurcated tip) and hairs. The cutting edge of the basale has two tube teeth, the posterior one pointed and with spines, the anterior one rounded and bare; these are followed by six serrated teeth, of which the most posterior lacks or almost lacks secondary cusps. The anterior inner tooth is rounded and lacks serrations. The epipodite is triangular and developed. The exopodite is represented by slight and plumose seta. It is as long as the first endopodite segment. The dorsal seta on this segment is rather thin, plumose and subequal to the segment. The longest seta from the three dorsal setae on the second segment is stout and somewhat longer than the main claw­like seta of this limb.
Maxilla (Figs. 7 A, B; 8 C, D). The most anterior seta on the endite of the precoxale is relatively short and bears very thick secondary setae distally. Its main claw­like seta is pectinate. There are three posterior tube setae, two of which are armed with long spines and the third is bare. On the posterior process of the coxal endite the most anterior tooth has 2­ 6 stout spines in the middle. The basale has no seta. The first endopodite segment is very broad. Its length and width are subequal. At about the middle of the anterior side there are three short­haired setae. The posterior side bears four short­haired setae. The distomedial seta extends just beyond tip of the limb. On the ventral surface of this segment there are about 10 short spines. The terminal segment is comparatively short and wide. The anterior claw is about 1.5 times the length of the posterior claw.
Fifth limb (Fig. 7 C). The epipodial plate carries four plumose setae in each of the distal, middle and proximal groups of setae respectively and is also armed with some short spines. The first endite of the protopodite bears one long plumose and one short shorthaired setae, and the second endite carries one long plumose and two short short­haired setae. On the endopodite there are nine setae, two of which are claw­like, three­long and plumose, and remainder are short with short­hairs. The first exopodite segment bears seven ventral, one lateral and one dorsal short­haired setae. The second segment has two ventral and one dorsal short­haired setae. The third segment has two fairly long claw­like setae and a shorter ventral seta.
Sixth limb (Fig. 9 A). The distal, middle and proximal groups of setae of the epipodial plate consist of five, five and six (and one additional short) long and plumose setae respectively and the plate is also covered with some short spines. The longer seta on the endopodite is plumose. On the first exopodite segment there are three short ventral, one plumose long lateral setae and distal row of hairs. The second segment has a minute ventral seta, and the third segment is with a minute ventral seta and longer dorsal seta lying parallel to the limb. The terminal setae of the limb and the exopodite are subequal.
Seventh limb (Fig. 8 E). The terminal segment bears two setae, one about four times the length of the other.
A and B ­ anterior of proximal tooth­row of mandibular –oxa; C and D ­ endites of maxilla; E – 7th limb; F ­ copulatory appendage.
A ­ sixth limb; B ­ copulatory appendage and caudal furca; C ­ distal end of copulatory appendage.
Caudal furca (Fig. 9 B). There are eight pairs of claw­setae and an unpaired seta dorsal to the smallest pair of claw­setae. The inner surface is covered with fine hairs.
Copulatory appendage (Figs. 8 F; 9 B, C; Table 1). The limb is relatively wide and of average length (Table 1). Its end is obliquely truncated. The anterior side is distinct concave near the end. There are six or seven oblique muscle bands.
Upper lip (Fig. 3 B). The posterior ventral edge is interrupted by a deep V­shaped notch. On each side of the notch there are some short flaccid spine­like processes, which decrease in stoutness medially.
FEMALE
Carapace (Fig. 10 A­F). The lengths of adult females range from 1.40 to 1.60mm (mean 1.49mm). The maximum height of the shell is 47­53% of its length, and its the posterior part is considerably larger than the anterior part. Its maximum width (39­50% CL) occurs at or just posterior to the midline. In all other respects it is similar to the carapace of the males.
Frontal organ (Figs. 10 G­J; 11 A; 13 A). The shaft extends well beyond the end of the fist antenna and is about double the combined lengths of the 1st and 2nd segments. The capitulum is separated from the shaft by distinct suture. It is rather expanded proximally and tapers to a pointed tip. Its dorsal surface is either straight or slightly concave near the middle. Its ventral surface is usually slightly concave distally. The end is usually downturned, and the surface of the capitulum is partially covered with minute spines.
First antenna (Figs. 11 A, B; 13 A). The boundary between second and third segments is indistinct. The first segment bears about 10 dorsodistal spines. There is minute dorsal seta (distally spinous) on the second segment. The a­, b­, c­, and d­setae are about half the length of the e­seta and are subequal or slightly shorter in length than the limb. The b­, c­ and d­setae have thin bases but the a­seta has a thickened base. The e­seta is about 1.7 the length of the limb and bears short anterior and long posterior spines placed along its middle and distal sections. It tapers to a pointed tip, which is unflattened.
Second antenna (Figs. 11 C, D; 12 A, B; 13 B). The protopodite contains some dark pigment spots. The exopodite is short and about 65% the length of the protopodite. The distoventral corner of the first endpodite segment has three triangular ridges and is covered with fine hairs. The a­seta is about half length of the b­seta. Neither a c­ nor a d­setae are present. The f­, g­, h­, i and j­ setae are subequal, about as long as or somewhat shorter than half the length of the protopodite, about 75% of the exopodite, and twice (or somewhat more) as long as the first endopodite segment. They are parallel­sided and have pointed tips. The processus mamillaris on each endopodite is similar to the male’s.
Mandible (Fig. 12 C). It is same as in the male, only somewhat smaller.
Maxilla. Similar to the male’s.
Fifth limb (Fig. 11 E). Similar to that of the male except there is a plumose lateral seta on the first exopodite segment. All setae are somewhat stouter than those of males.
Sixth limb (Fig. 13 C). The limb is same as in the male, but differs in following respects: the first exopodite segment has five ventral (three plumose) setae and one dorsal, plumose seta. The setae on the second and third segments are relatively long. The main terminal seta is somewhat shorter than the epipodial plate of this limb.
Seventh limb, Caudal furca (Fig. 13 D) and Upper lip are all similar to those of males.
A ­ frontal organ and 1st antenna; B ­ medial section of e­seta of 1st antenna; C and D ­ anteroventral region of 1st endopodite segment of second antenna; E – 5th limb.
A ­ second antenna; B ­ endopodite of second antenna; C ­ tooth rows and masticatory pad of coxa of mandible.
A ­ medial region of frontal organ and second segment of first antenna; B ­ anteroventral region of endopodite of second antenna; C – 6th limb; D ­ caudal furca.
Remarks. This species is closely related to M. skogsbergi (Iles, 1953). Some distinguishing characteristics between the two species are listed in the Table 2.
. .....continued on the next page Characteristic M. skogsbergi M. longiseta nov. sp. M. alta nov. sp.
Female. Frontal organ:
capitulum fused to shaft separated by distinct fused to shaft or sepasuture rated by undistinct suture
First antenna:
dorsal seta absent present present
1st segment bare with dorsodistal spines bare Distribution. This is interzonal species since it occurs both in the epi­ and mesopelagic zones. M. longiseta is widely distributed in the temperate and adjacent subtropical waters between 37º and 61ºN at the depth range 25­1500m in the North­Western Pacific and between 40º and 60ºN from 50 to depth 2500m in the North­Eastern Pacific (Fig. 1). While it has been found in the Sea of Okhotsk and the Bering Sea, it appears to be absent from the Sea of Japan.
Its vertical distribution in the North­Western Pacific has been studied in the region of the Kurile­Kamtchatka Trench (Table 3), where M. longiseta occurs predominantly in the depth range 300 to 1000 m (single specimens were caught at 100­200 and 1000­1500 m). It is most abundant and its biomass was higher at depths of 300­500 m; its abundance declined abruptly below 750 m. Its abundance as a percentage the total halocyprid population is quite small. Its maximum relative abundance of about 4% was in 300­500 and 500­ 750m depth layers, and its highest relative biomass, only ~2%, was at 500­ 750m. Males, females and juveniles were most numerous in the 300­500m layer (Table 5 A).
TABLE 3. Abundance and biomass1 of halocypridids in area of the Kurile­Kamtchatka Trench (RV Vityaz 39th Cruise, 1966; Bogorov­Rass's Net, S=1,0 m2)․
1 biomass is calculated on nomogrammes (Chislenko, 1968) and equivalent to wet weight
2 ratio of mean abundance (or biomass) between M. longiseta nov.sp. and total Halocyprididae
description: Published as part of Chavtur, Vladimir Grygorjevich, 2003, Morphology and distribution of some new pelagic ostracods of genus Metaconchoecia (Halocyprida: Halocyprididae) from the North Pacific, pp. 1-102 in Zootaxa 229 on pages 3-25, DOI: 10.5281/zenodo.156688