Lophuroecia Chavtur, 2018

Chavtur, Vladimir G. & Bashmanov, Alexander G., 2018, Pelagic ostracods of the new subtribe Conchoeciina (Ostracoda, Crustacea) from the North Pacific, Zootaxa 4516 (1), pp. 1-127 : 57-59

Lophuroecia Chavtur , gen. nov.

1906 Conchoecia Magna-Gruppe—Müller: 98–99 (partly);

1968 Conchoecia Magna-Groupe—Deevey: 76–77 (partly);

1973 Conchoecia —Poulsen: 123–124 (partly);

1979 Conchoecia —Martens: 317 (partly);

2012 Conchoecia —Drapun & Smith: 53 (partly).

Type-species. Conchoecia lophura Müller, 1906 .

Etymology. The name is derived from the Latin specific name “lophura” and “-oecia” derived from the Greek word “oɩĸoσ” meaning house, from which the terms ecology and economy have been derived, and is the ending that has become standard for the Conchoeciinae genera.

Composition. This genus is monospecific including only Hyalocoecia lophura ( Müller, 1906) comb. nov., which was found in the analyzed material and is described below.

Diagnosis of genus. Adult male. Carapace. The length is between 2.08–3.00 mm. The carapace is subrectangular, and sometimes slightly tapered anteriorly. The locations of the asymmetrical glands are usual for the subtribe. A unique feature is that the left valve has a row of closely spaced long and narrow gland cells at the postero-ventral corner. Each carapace valve has a single lateral gland opening near the postero-ventral corner and another near the postero-dorsal corner.

Frontal organ. It is bent downwards. The end of the capitulum is rounded and slightly down-turned or not.

First antenna. Armature of seta-e consists of a comb of about 60–75 pairs of small and directed proximally spines; length of spines clearly shorter than the diameter of the seta.

Second antenna. Seta-b of the endopodite has about 6–14 long, basal, fine filaments. The right clasping organ is sub-squared or somewhat oblique proximally, unswollen, and terminally rounded and with a spine. The left clasping organ is moderately thick, not tapered to the end and right- or acute-angled, with a pointed or spine-like tip.

Mandible. The epipodite has a rudimentary seta on a verruca. The ventral margin of the first endopodite segment bears four setae (one long and three medium-length or short).

Maxilla. Anterior setae are located along the anterior margin.

Fifth limb. It is usual for the subtribe.

Sixth limb. The basale bears five ventral plumose setae and one lateral short, plumose seta.

Caudal furca. An unpaired seta is present.

Copulatory appendage. It is elongated, broader at the middle, and tapered to a rounded end.

Adult female. Carapace. The length is 2.20–3.08 mm. It is tapered anteriorly.

Frontal organ. It is slightly bent downwards. The capitulum has a pointed, slightly down-turned tip.

First antenna. The dorsal seta on the second segment is well developed. Seta-e has no proximal filaments on its anterior margin.

Second antenna. The first endopodite segment is about 25–29%, 34–40% and 42–53% the lengths of setae-g, - f and –h, respectively. Seta-b on the first endopodite segment is spinous.

Mandible, maxilla and caudal furca are similar to those of the male.

Sixth limb. The basale bears five ventral long, plumose setae and one lateral long, plumose seta.

Description of genus. Adult male. Carapace. The length is between 2.08–3.00 mm. The carapace is subrectangular, and can be slightly tapered. The height is half or somewhat more than the length, with the maximum height being at the posterior part of the carapace. The posterior margin is almost straight or slightly arched, and the ventral margin is slightly concave. As is usual in the subtribe, the right asymmetrical gland is placed near the postero-ventral corner and the left one slightly anterior to the postero-dorsal corner on the dorsal margin. There are two gland cells on the anterior edge beneath the rostral incisures. The left valve uniquely has a row of closely packed long and narrow gland cells close to the postero-ventral corner. Each valve has a single lateral gland near the postero-ventral corner and another near the postero-dorsal corner. Sculpture consists mainly of concentric lines.

Frontal organ. It is bent downwards. The capitulum is mid-broad, with a slightly dorsal concavity. The capitulum end is rounded and slightly sloped or not.

First antenna. Lengths of the first and the second segments are subequal. Seta-a reaches slightly or clearly beyond the suture between the first and second segments of the limb. Seta-c is quite short, but is slightly or clearly longer than the combined lengths of the third, fourth and fifth segments. Armature seta-e consists of a comb of about 60–75 pairs of small and directed proximally spines; the lengths of these spines are clearly shorter than the diameter of the seta.

Second antenna. Seta-b of the endopodite has about 6–14 long, fine, basal filaments. The right clasping organ is sub-squared or somewhat oblique proximally, unswollen, and terminally rounded and with a spine. The left clasping organ is moderately thick, untapered to the end and right- or acute-angled, with a pointed or spine-like tip.

Mandible. The epipodite has a rudimentary seta on the verruca. The ventral margin of the first endopodite segment bears four setae (one long seta and three medium-length or short setae). The lateral tooth on the basale endite is present. The masticatory pad is armed with four rounded flaps, four long flat spines and one small sclerotized tubercle (or short spine?) and about 31–42 seta-like filaments.

Maxilla. The first endopodite segment has six anterior and three posterior setae. Anterior setae are located along the anterior margin. Along the distal edge of this segment is a line of five or six long spines.

Fifth limbs. The basal segment has a proximal group of three or four setae ventrally, a medio-lateral group of two and distal group of three setae. Laterally, the basal segment has a lateral seta and dorsally a long distal seta (vestige of the exopodite), which extends to beyond the end of the limb. The first endopodite segment bears two ventral setae and one dorsal seta.

Sixth limb. The coxale has two long, plumose setae. The basale bears five ventral plumose setae and one lateral short, plumose seta. The exopodite seta is short and barely reaches beyond the proximal suture of the first endopodite segment.

Caudal furca. Each lamella has eight claws. An unpaired seta is present.

Copulatory appendage. It is elongated, broader at the middle, and tapers to a rounded end. The distal seta is thin. The appendage is large, triangular and with a rounded tip. The limb has between five and eight oblique muscle bands.

Description of adult female. Carapace. The length is between 2.20–3.08 mm. The height is about 53–57% of the length. It is tapered anteriorly. The posterior margin is noticeably arched, and the ventral margin with a visible concavity. Asymmetrical and lateral corner glands have locations as the same as in the male. Sculpture is similar to that of the male.

Frontal organ. It is slightly bent downwards. The capitulum is fused with the stem or not distinctly separated, straight, somewhat higher at the distal half, with a pointed and barely downward pointing end. The surface of the capitulum is almost totally covered with slender spines of various lengths.

First antenna. Dorsal seta on the second segment is well developed and reaches to about 1/3–1/2, or somewhat more, the length of the capitulum of the frontal organ. Setae-a–d are as long as, or more than, the shaft of the limb. Seta-e has no proximal filaments on its anterior margin, and is slightly tapered towards its pointed end.

Second antenna. The first endopodite segment is about 25–29%, 34–40% and 42–53% the length of setae-g, -f and –h, respectively. Seta-b of the first endopodite segment is armed with noticeable stiff spines.

Mandible, maxilla and caudal furca are similar to those of the male.

Sixth limb. The coxale is similar to that of the male. The basale has five ventral long, plumose setae and one lateral long, plumose seta. The exopodite noticeably extends beyond the proximal boundary of the first endopodite segment.

Comparison ( Table 2). The new genus sharply differs from the other genera in the subtribe in having a row of closely spaced long and narrow gland cells at the postero-ventral corner of the left valve, the structure of the comb on the male’s seta-e of the first antenna, and in having four setae (one long and three short setae) on the ventral margin of the first endopodite segment of the mandible.

Distribution. Since the genus Lophuroecia Chavtur , gen. nov. is represented by only one species, its distribution is the same as for L. lophura (see below).