Metaconchoecia crassiseta

Chavtur, Vladimir Grygorjevich, 2003, Morphology and distribution of some new pelagic ostracods of genus Metaconchoecia (Halocyprida: Halocyprididae) from the North Pacific, Zootaxa 229, pp. 1-102 : 59-72

publication ID	https://doi.org/ 10.5281/zenodo.156688
DOI	https://doi.org/10.5281/zenodo.6276959
persistent identifier	https://treatment.plazi.org/id/03E51C2A-FFF8-FFAF-FEE0-FB2085D9FD5A
treatment provided by	Plazi
scientific name	Metaconchoecia crassiseta
status

Treatment

Metaconchoecia crassiseta View in CoL nov. sp.

( Figs. 3644 View FIGURE 36 View FIGURE 37 View FIGURE 38 View FIGURE 39 View FIGURE 40 View FIGURE 41 View FIGURE 42 View FIGURE 43 View FIGURE 44 )

Metaconchoecia View in CoL species 5 Chavtur, 1991: 46 (part); 1992; 49, table 2 (list)

Etymology. The specific name “ crassa ” from the Latin (=thick) and “ seta ” (=bristle), refers to the size of the “a” bristle in base on the first antenna in male.

Holotype. IBM 2811 – adult male, length 1.23 mm, appendages mounted on slide and valves in alcohol, in collection of the Museum of Institute of Marine Biology, Vladivostok, Russia (together, with paratypes).

Typelocality. RV Vityaz 45th Cruise, station 6126, lat. 55º22.5’ N and long. 134º47’ W, depth layer 200 100 m, May 22, 1969, using a Bogorov – Rass’s Net (S = 0.5 m ²).

Paratypes. IBM 2812 and 2813 – adult males (1.25 and 1.20 mm), RT Thyhookeansky, lat. 44°70’ N and long. 126°40’ W depth 500 200 m, August 1, 1978; IBM 2814 and 2815 – 2 adult females (1.17 and 1.20 mm), RV Vityaz 29th Cruise, station 4143, sample 388, lat. 49°30.7’ N and long. 128°41.7’ W, depth 215 95 m, November 21, 1958.

Additional material. RV Vityaz 29th Cruise – female, station 4179, sample 583, lat. 42°40’ N and 124°59.03’ W, depth 500 200 m, December 6, 1958; 2 females, station 4183, sample 608, lat. 40°01’ N and 127°39.03’ W, depth 500 200 m, December 6, 1958.

SRT Birokan – 2 females and one juvenile, station 6, sample 3, lat. 37°18’ N and long. 172°47.7’ W, depth 5000 m, September 1, 1964. RV Vityaz 45th Cruise – one female, station 6127, lat. 55°19.4’ N and long. 134°46.2’ W, depth 200 100 m, May 22, 1969. RT Thyhookeansky – one male, one female, station 2, sample 47, lat. 42°20’ N and long. 128°18’ W, depth 100 50 m, August 3, 1978.

MALE

Carapace ( Fig. 36 View FIGURE 36 A, B). The length of adult specimens range from 1.231.25 mm (mean 1.24 mm). Carapace is elongated. Its maximum height is 4445% 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 4849% 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 slightly 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 slightly curved, curving smoothly into posterior end. The rostrum is developed and has a pointed tip. The rostral incisure is fairly deep. In ventral view, the sides of the carapace are only gently curved. On the right carapace valve the asymmetric gland opens somewhat above 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. There is no surface ornamentation.

Frontal organ ( Fig. 36 View FIGURE 36 C, D). 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 wide and parallelsided. The surface of the capitulum is partially covered with numerous minute spines.

First antenna ( Figs.36 View FIGURE 36 CE; 37 A, B). The segmentation is fairly distinct. The aseta has very thick base and extends back parallel to the limb (except proximally where it loops down and is slightly swollen) beyond end of the limb. The bseta is slightly shorter than the dseta and bears some various sized anterior and posterior spines. The cseta is relatively thin and short, and shorter than the total combined lengths of segments the third to fifth. The dseta is armed with some closely spaced varioussized anterior spines. The most eseta is about 1.8 the length of the limb. The eseta armature comprises 10 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. 36 View FIGURE 36 E, 37 AD, 38 B). The protopodite has some dark pigment spots. The exopodite is about 60% 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 cand dsetae are relatively long. The eseta is minute. 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 curved distal section and no subterminal ridges. The sensory h, j and isetae are about 45% the length of the gseta. The gseta is about 90% to the protopodite, about 1.5 the length of the exopodite and 3.5 of the first endopodite segment. The fand gsetae are somewhat flattened distally.

Mandible ( Figs. 38 View FIGURE 38 G, 39). The coxale cutting edge has a straight anterior section followed by about 20 teeth. The distal list has onetwo large pointed posterior tooth, followed by1517 small teeth. The proximal list is armed with large pointed posterior tooth, followed by about 25 small teeth. 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; there 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 relatively developed. The exopodite is represented by slight and plumose seta. It is as long as the first endopodite segment (or barely longer). The dorsal seta on this segment is rather thick, plumose and subequal to the segment. The most seta from the three dorsal setae on the second segment is stout and somewhat longer than the main clawlike seta of this limb.

Maxilla ( Fig. 40 View FIGURE 40 B). The basale has no seta. The length of the first endopodite segment is about 1.5 times the width. At about the middle of the anterior side there are three shorthaired setae. The posterior side bears four shorthaired setae. The distomedial seta does not extends beyond (barely reaches) tip of the limb. On the ventral surface of this segment there are some short spines. The terminal segment is comparatively short and wide. The anterior claw is 1.61.8 times the length of the posterior claw. The structure of the precoxal and coxal endites is obscure.

Fifth limb ( Fig. 40 View FIGURE 40 CF). The first endite of the protopodite bears one long plumose seta and one short shorthaired seta, and the second endite carries one long plumose and two short, shorthaired setae. On the endopodite there are eight setae, two of which are clawlike, threelong and plumose, and remainder are short with shorthairs. The first exopodite segment bears five ventral setae, one dorsal seta and one lateral seta. All these are 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. 41 View FIGURE 41 AC).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 not (?) covered with some short spines. The longer seta on the endopodite is plumose. On the first exopodite segment there are three short ventral and one plumose long lateral setae. The second segment has a short ventral seta, and the third segment is with a short ventral seta and barely longer dorsal seta lying parallel to the limb. The terminal setae of the limb and the exopodite are subequal.

A – upper lip, B – 2nd antenna, C – distal part of endopodite of 2nd antenna, D – right clasper of 2nd antenna, E and F left clasper of 2nd antenna, G – mandible.

A – tooth edge of basal endite of mandible, B – tooth rows of coxa of mandible, C – proximal tooth row of coxa of mandible, D and E – tooth rows and masticatory pad of coxa of mandible.

A – endopodite of mandible, B – lateral seta of 1st endopodite segment of maxilla, CF – 5th limb.

AC – copulatory appendage, D and E – distal part of copulatory appendage, F – lateral view of left valve of shell, G – ventral view of shell, H – upper lip, I – capitulum of frontal organ.

A – frontal organ and 1st antenna, B and C – 2nd antenna, D – distal part of 1st endopodite segment of 2nd antenna, E and F – maxilla.

Seventh limb ( Fig. 41 View FIGURE 41 D). The limb is thin, long and bare. The terminal segment bears two setae, one about 3.5 times the length of the other.

Caudal furca ( Fig. 42 View FIGURE 42 AE). There are eight pairs of clawsetae and an unpaired seta dorsal to the smallest clawseta. The inner surface is covered with fine hairs.

Copulatory appendage ( Fig. 42 View FIGURE 42 AE). The limb is straight, relatively narrow and 29 32% the length of the carapace. Its end is obliquely truncated. The anterior side is distinct concave near the end. There are threefive oblique muscle bands.

Upper lip ( Fig. 38 View FIGURE 38 A). The posterior ventral edge is interrupted by a deep Vshaped notch. On each side of the notch there are some very short spinelike processes.

FEMALE

Carapace ( Fig. 42 View FIGURE 42 F, G). The lengths of adult females range from 1.17 to 1.35 mm (mean 1.20 mm). The maximum height of the shell is 5051% of the carapace length (CL), and the posterior part is considerably larger than the anterior part. Its maximum width (38 39% 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. 42 View FIGURE 42 I, 43 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 fused to shaft. 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 ( Fig. 43 View FIGURE 43 A) The boundary between second and third segments is indistinct. There is no minute dorsal seta on the second segment. The a, b, c, and dsetae are about a half the length of the eseta and are subequal or slightly shorter in length than the limb. The eseta is about twice as long as the limb and bears short posterior spines placed along its distal sections. It tapers to a pointed tip, which is unflattened.

Second antenna ( Figs. 43 View FIGURE 43 BD; 44 A). The protopodite contains some dark pigment spots. The exopodite is short and about 70% 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 a one third the 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 70% 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 (40 A). The limb is similar to that of the male, but differs in following respects: the dorsal seta on the endopodite segment is slight and short, and the shortest seta of the three distodorsal setae on the second segment is longer.

Maxilla (43 EF). Similar to the male’s.

Fifth limb ( Fig. 44 View FIGURE 44 B, C). Similar to that of the male except there are 89 setae on the endopodite and 67 setae on the first exopodite segment.

Sixth limb ( Fig. 44 View FIGURE 44 D). The limb is same as in the male, but differs in following respects: the first exopodite segment has five ventral (all plumose) setae and one dorsal, plumose seta. The setae on the second and third segments are relatively long. The main terminal seta is somewhat longer than the epipodial plate of this limb.

Seventh limb, Caudal furca and Upper lip ( Fig. 42 View FIGURE 42 H) are all similar to those of males.

Remarks. This species is closely related to M.. subinflata ( Gooday, 1981) . Some distinguishing characteristics between the two species are listed in the Table 11 View TABLE 11 .

Distribution. This is known from the area of the NorthEastern Pacific between 37° and 55° at the depth range 10007140 m.