Hyalocoecia hyalophyllum ( Claus, 1890 ) Chavtur & Bashmanov, 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 : 67-70

Hyalocoecia hyalophyllum ( Claus, 1890) comb. nov.

( Figs. 33 , 34 )

1890 Conchoecia hyalophyllum —Claus: 11;

1891 Conchoecia hyalophyllum —Claus: 60; pl. VI, figs. 2–10; pl. VIII, fig. 9;

1896 Conchoecia hyalophyllum —Brady & Norman: 692

1906 Conchoecia hyalophyllum —Müller: 101, pl. XX, figs. 19–26;

1909 Conchoecia hyalophyllum— Fowler: 236, 265, 287; pl XIX, figs. 93–96, 105; pl. XX, figs. 97, 106, 107.

1969a Conchoecia hyalophyllum —Angel: 45–51, figs. 1–3;

1973 Conchoecia hyalophyllum — Poulsen, 1973: 140 –142, fig. 69 a–j;

1993 Conchoecia hyalophyllum —Angel: 162, fig. 55.

Examined material. MFFT Professor Kaganovsky, 2010: MIMB 18350 /1—adult male (1.70 mm), station 81, sample 152, 38°00´N– 164°00´E, layer 200–0 m, sounding 4100 m, April 28, 2010 ; MIMB 18350 /2—adult male (2.72 mm), station 83, sample 154, 39°00´N– 161°00´E, layer 200–0 m, sounding 5200 m, 30 April .

Addition description of adult male. Carapace ( Fig. 33 A–C). The length is between 1.46–1.72 mm (summary literature data from Müller 1906; Skogsberg, 1920, Poulsen 1973; Deevey 1978a; Angel 1993: 1.50–1.70 mm). The carapace is short, rectangular and does not taper anteriorly. The height is 57–59% of the carapace length. The posterior and ventral margins are almost straight. The left asymmetrical gland opens close to the dorsal corner. The right asymmetrical gland is placed in the postero-ventral corner, and left asymmetrical gland near the posterodorsal corner. Each valve has one lateral gland near the postero-ventral corner and one near the postero-dorsal corner. Gland cells beneath the rostral incisures are absent. Sculpture consists mainly of concentric lines.

Frontal organ ( Fig. 33 D–F). The capitulum is bent downwards. It is moderate broad, with a slight dorsal concavity and a rounded tip (pointed tip only in specimens described by Angel 1969; 1993). The capitulum surface is extensively covered with small spines in the basal half, but is bare distally.

First antenna ( Fig. 33D, E, G ). The length of the first and the second segments are subequal. Seta-a reaches to about mid-length of the first segment. Seta-c is about equal to the combined lengths of the third, fourth and fifth segments. Armature of seta-e consists of a comb of about 19–23 pairs of small, directed proximally spines and 13– 14 alternated ones (totalling 52–59) (summary literature data from Poulsen 1973; Angel 1993: 20?, 24–25 pairs of spines and 20–30 alternated ones). Lengths of spines are less than the diameter of the seta at the distal part of the comb.

Second antenna ( Fig. 33 H–L). Seta-b on the first endopodite segment has about six long basal fine filaments (summary literature data from Müller 1906; Poulsen 1973; Deevey 1978a; Angel 1993: with five or six filaments; in Poulsen 1973 only with three posterior and three anterior medium-length filaments). The right clasping organ is right-angled and oblique proximally, slightly swollen and with a spine-like tip. The left clasping organ is moderately thick, not tapered to the end and almost right-angled, with a spine-like tip. Setae-h–j differ in length, but are relatively slim, and slightly tapered towards to their ends. Seta-g is about twice as long as setae-h–j.

Mandible ( Figs. 33M ; 34 A–F). The epipodite has a slightly developed seta on the verruca (in Poulsen 1973 without a seta). The ventral margin of the first endopodite segment bears two setae (one long and one mediumlength). The disto-dorsal seta of this segment is plumose. The toothed edge of the coxale endite is armed with ten teeth; the distal tooth-list and proximal tooth-list are with 14 and 15–16 teeth, respectively (in Poulsen 1973: 9–11, 14 and 16–24 teeth, respectively). The masticatory pad is armed with three rounded flaps, four flat spines and about 24–40 seta-like filaments (only 19 in specimens described in Poulsen 1973).

Maxilla. The first endopodite segment has six anterior and three posterior setae. Anterior setae are located along all of its margin. The distal edge of the first endopodite segment is armed with two to four long spines (five in Poulsen 1973).

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 three setae. Laterally, the basal segment is with a seta and has a distal seta dorsally (vestige of the exopodite), which reaches or barely extends beyond the end of the limb. The first endopodite segment bears two ventral setae and one dorsal seta.

Sixth limb ( Fig. 34G ). The coxale has two long plumose setae. The basale bears four ventral setae: two proximal setae (one long and plumose and one short and bare) and two short distal setae, and is without a lateral seta. The exopodite seta barely reaches the proximal suture of the first endopodite segment.

Caudal furca (34L). Claws are relatively long and slim. An unpaired seta is present and is longer than the eighth pair of claw setae.

Copulatory appendage ( Fig. 34I, K ). It is elongated, broader at the middle, and tapered to a rounded end. The distal seta is thin. The appendage is large, triangular and with a rounded tip. The limb has four or five oblique muscle bands.

Remarks. Morphology of our specimens is generally similar to those reported in the literature ( Müller 1906; Poulsen 1973; Deevey 1978a; Angel 1993), but differs by fewer spines on the armature of seta-e of the first antenna in the male.

Distribution. This s pecies has been recorded from all oceans: in the Atlantic Ocean it is known from 63°N to 55°S, in the Indian Ocean between 5°N and 35°S, and in the Pacific Ocean in a range of about 10°N–56°S at depths from 100–300 m to 3100–3300 m. In our material this species was collected from two areas: in the north-western Pacific between 38°–39°N at depths of 0–200 m, and in the north-eastern Pacific between 18°–31°N at depths of 200–500 m ( Fig. 28 ).

Figures

FIGURE 28. Map showing locations of stations at which Macrochoecilla macrocheira, Lophuroecia lophura, and Hyalocoecia hyalophyllum were sampled.

FIGURE 33. Hyalocoecia hyalophyllum (Claus, 1890) comb. nov. (Adult male: A–E and G–M—MIMB 18350/1; F—MIMB 18350/2). A—left valve of carapace in lateral view; B—posterior part of carapace in lateral view; C—postero-ventral corner of carapace in lateral view; D—frontal organ and first antenna; E—distal half of frontal organ and first antenna; F—capitulum of frontal organ; G—“c”-seta of first antenna; H–J—endopodite of left (H, I) and right (J) second antenna; K and L—right and left clasping organs of second antenna; M—endopodite of mandible (only main claw and setae of first segment shown).

FIGURE 34. Hyalocoecia hyalophyllum (Claus, 1890) comb. nov. (Adult male: A, B, H, I, K, and L—MIMB 18350/1; C–G and J—MIMB 18350/2). A—masticatory pad of mandibular coxale; B—coxale of mandible; C and D—exopodite of mandible, E and F—epipodite of mandible; I—copulatory organ; J and K—distal part of copulatory organ; L—caudal furca.