Parvidentoecia 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 : 70-72

Parvidentoecia Chavtur , gen. nov.

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

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

1970 Conchoecia— Deevey: 815–818.

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

1979 Conchoecia —Martens: 317 (partly);

Type-species. Conchoecia parvidentata Müller,1906 .

Etymology. The name is derived from the Latin specific name “ parvidentata ” 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 Conchoeciinae genera.

Composition. This genus is monospecific including only Parvidentoecia parvidentata ( Müller, 1906) comb. nov. This species was not found in our material.

Diagnosis genus (based on literature: Müller 1906; Poulsen 1973; Blachowiak-Samolyk & Angel 2004).

Adult male. Carapace. Length is between 2.00–2.60 mm. The carapace is tapered anteriorly. Locations of asymmetrical glands is usual for the subtribe. Lateral corner glands are present.

Frontal organ. The capitulum is slightly bent downwards and relatively narrow and with a rounded tip.

First antenna. Armature of seta-e has a comb with about 50–70 pairs of small and directed proximally spines; the lengths of spines are clearly shorter than the diameter of the seta supporting the comb.

Second antenna. Seta-b of the endopodite lacks fine filaments. The right clasping organ is slightly acute-angled and oblique proximally, rather thick and with a pointed tip. The left clasping organ is strongly acute-angled and with a pointed tip.

Mandible (based on Poulsen 1973). The lateral tooth on the basale endite is present. The epipodite is without a seta. The ventral margin of the first endopodite segment has only with one long seta.

Maxilla (based on Poulsen 1973). The first endopodite segment has six anterior setae and three posterior setae. All anterior setae are located along the anterior margin.

Fifth limb (based on Poulsen 1973). The basal segment has a proximal group of three–four setae ventrally, a medio-lateral group of two and a distal group of two or three setae, a lateral seta, and a distal seta dorsally.

Sixth limb (based on Poulsen 1973). Ventral margin of the basale has five setae: two long proximal setae (one of which is plumose), three shorter distal setae and one lateral seta.

Adult female. Carapace. Length is between 2.40–3.10 mm. The carapace has a subrectangular outline that is more rounded than that in the male and tapers anteriorly.

Frontal organ. The capitulum is strongly bent downwards and has a rounded tip.

First antenna. The dorsal seta on the second segment is developed. Seta-e is bare proximally and with short spinules distally.

Second antenna. Seta-b is almost twice the length of seta-a and has rather weak spines. Setae-f and-g are not widened distally (description of this limb is insufficient in the above-listed literature).

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

Sixth limb. The basale has five ventral plumose setae and one lateral plumose seta.

Description of genus. Adult male. Carapace. Length is between 2.00–2.60 mm ( Poulsen 1973). The carapace is tapered anteriorly. The height is greater posteriorly and about half of the length of the carapace. Shoulder vaults are well developed. The posterior margin is slightly arched. The postero-ventral corner is visibly curved. The right asymmetrical gland is placed at the postero-ventral corner, and the left asymmetrical gland is placed near the postero-dorsal corner. Each valve has one lateral gland near the postero-ventral corner and one near the posterodorsal corner. Sculpture consists mainly of concentric lines, but it is not always noticeable.

Frontal organ. The stem is straight. The capitulum is slightly bent downwards and relatively narrow and has a rounded tip.

First antenna. First and second segments are subequal in length. Seta-a does not reach the boundary between the first and the second segments. Seta-c is noticeable longer than the combined lengths of the third–through fifth segments. Armature of seta-e has a comb with about 50–70 pairs of small and directed proximally spines; lengths of spines are clearly shorter than the diameter of the seta supporting the comb.

Second antenna. Seta-b of the endopodite is without fine filaments. The right clasping organ is slightly acuteangled and oblique proximally, rather thick and with a pointed tip. The left clasping organ is strongly acute-angled and has a pointed tip.

Mandible. The lateral tooth on the basale endite is present. The epipodite has no setae. The ventral margin of the first endopodite segment has only one long seta. The disto-dorsal seta of this segment is non-plumose. The tooth edge of the coxale endite is armed with nine teeth, and the distal tooth-list and proximal tooth-lists have 11 and 12 teeth respectively. The masticatory pad is armed with three rounded flaps, four flat spines and about 13–35 seta-like filaments.

Maxilla. The first endopodite segment has six anterior setae and three posterior ones. Along the distal edge of this segment is a line of seven long spines.

Fifth limb. The basal segment has a proximal group of three or four setae ventrally, a medio-lateral group of two and a distal group of two or three setae. Laterally, the basal segment is with a seta and has distal seta dorsally (vestige of the exopodite), which reaches or extends 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 ventral margin of the basale bears five setae: two long proximal setae (one of which is plumose), three shorter distal setae and one lateral seta. The dorsal seta (vestige of the exopodite) reaches the proximal margin of the first endopodite segment.

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

Copulatory limb. It is spindle-shaped, with a rounded tip, tapered to the end and broadest at the middle. The appendage is very small, narrow and squared-shaped. The distal seta is thin. It has six oblique muscle bands.

Adult female. Carapace. Length is from 2.40 mm ( Skogsberg 1920) to 3.10 mm ( Poulsen 1973). The carapace has a subrectangular outline that is more rounded than that of the male and tapers anteriorly. The carapace height is somewhat more than half of the length (about 55%). The postero-dorsal and postero-ventral corners are rounded, with the posterior margin more arched than in the male. Locations of asymmetrical and lateral corner glands and carapace sculpturing are similar to those of the male.

Frontal organ. The stem is straight. The capitulum is strongly bent downwards and has a rounded tip.

First antenna. The dorsal seta on the second segment is developed and extends well beyond the boundary of the shaft of the limb. Setae-a–d are shorter than the shaft of the limb. Seta-e is bare proximally and with short spinules distally.

Second antenna. Seta-b is almost twice the length of seta-a and has rather weak spines. Setae-f and-g are not widened distally (description of the limb is insufficient in the above-listed literature).

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

Sixth limb. The coxale has two long, plumose setae. The basale bears five ventral plumose setae and one lateral plumose seta. The exopodite reaches to 1/3–1/2 the length of the first endopodite segment.

Comparison ( Table 2). Parvidentoecia Chavtur , gen. nov. differs from all other genera of the new subtribe in having only one long seta on the ventral margin of the first endopodite segment. It is close to Lophuroecia Chavtur , gen. nov., but the carapace is more tapered anteriorly, the left clasping organ is strongly oblique in the male, the capitulum of the frontal organ in the female has a rounded tip, there is no row of closely spaced long and narrow gland cells at the postero-ventral corner of the left valve, and there is a seta on the epipodite of the mandible in both sexes.

Distribution. Parvidentoecia parvidentata is recorded in the Atlantic, Indian and Pacific Oceans ( Müller 1906; Skogsberg 1920; Poulsen 1973; Deevey 1970; 1974; 1978a; 1978b; 1982; 1983; Martens 1979; Drapun 1983). It is known from 47°N–60°S at a depth range of 0–3750 m.