Parthenoecia parthenoda ( Müller, 1906 ) 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 : 95-96

Parthenoecia parthenoda ( Müller, 1906) comb. nov.

( Figs. 46–49 )

1906 Conchoecia parthenoda— Müller: 78, pl. XVI, figs. 24–29;

1968 Conchoecia parthenoda— Deevey: 71, figs. 33–35;

1969b Conchoecia parthenoda— Angel: 56, figs. 7–9;

1970 Conchoecia parthenoda— Deevey: 815, fig. 7;

1969 Conchoecia parthenoda— Poulsen: 153, fig. 10;

1973 Spinoecia spinirostris— Poulsen: 117–121, fig.58;

1993 Conchoecia parthenoda— Angel: 200, fig. 74;

2012 Porroecia parthenoda— Drapun & Smith: 144–147, pict. 27, pls. 54, 55, figs. 63, 64.

Examined material. RV Vityaz, 57 th Cruise, 1975: MIMB 18351 /1 and 18351/3—adult males (1.47 and 1.62 mm) and 18351/4, 18351/5 and 18351/6—adult females (1.75, 1.72 and 1.73 mm), station 7229, sample 23, station 7229, sample 22, 5°21´7–5°00´04 N and 124°21´7–124°04´4 W, layer 50-0 m, sounding 5734 m, February 24–25 ; 18351/2—adult male (1.61 mm), station 7236, sample 37, 5°57´1–6°00´0 N and 123°40´1–124°01´1 W, layer 200- 100 m, sounding 4760– 3830 m, February 26–27 1975. FT Pelamida, 30 th Cruise, 1976: 18351/7—adult female (1.70 mm), station 91, sample 134, 32°30´N– 138°00´E, layer 100–0 m, sounding?, August 30.

Additional material see Appendix.

Additional description of adult male. Carapace ( Fig. 46 A–D). Length range is 1.50–1.75 mm in the northwest Pacific and 1.40–1.70 mm in the north-eastern Pacific (plus two larger males: 1.8 and 1.95 mm) (literature data: from 1.30 mm in Poulsen 1973 to 1.80 mm in Poulsen 1969). The carapace is almost rectangular and untapered, so the height is consistently 47–50% of the length (summary literature data from Müller 1906; Deevey 1968; 1970; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: is 45–51% the length). The posterior margin is almost straight or slightly arched, and the ventral margin is slightly concave. The right asymmetrical gland opens at the posterior ventral corner. The left asymmetrical gland is on the dorsal margin by about 1 1–12 % of the carapace length anterior to the posterior dorsal corner (literature data from above-listed works: about 12–16%), It opens on a bump that clearly projects above the margin. Sculpture on the carapace has weak concentric striae.

Frontal organ ( Fig. 46 E–G). It is downward bent. The capitulum is relatively slim (literature data from Deevey 1968; 1970; Drapun & Smith 2012: moderately broad), slightly curved and with a rounded tip. Proximally its surface is covered with small spines.

First antenna ( Fig. 46 E–H). Lengths of the first and second segments are similar. Seta-a is convoluted so barely reaches the suture between the first two segments (literature data from Deevey 1968; 1970; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: barely reaches or extends beyond this boundary but if straight it can reach 2/5 the length of the first segment). Seta-c is about equal to the combined lengths of the third, fourth and fifth segments (literature data from Deevey 1970; Angel et al. 2008: can be slightly longer). Armature of the seta-e has a comb with 13–14 distal pairs of usual type spines and 19–21 proximal alternated ones slightly directed proximally (total 46–49 spines) (summary literature data from Deevey 1968; 1970; Poulsen 1973; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: 8–10 pairs and 13–22 alternated ones).

Second antenna ( Fig. 46 I–L). Seta-b on the endopodite has one or two long basal filaments and two long distal, fine filaments (in the literature: 1–2 and 1–3, respectively) and also with short filaments distally. Right clasping organ is squared with the distal angle curved, and has a noticeably swollen tip (literature data: without or with slightly visible swollen), left clasping organ is right-angled. Tips of both organs are pointed (literature data Deevey 1968; Angel 1993; Angel et al. 2008: without or with a terminal spine).

Mandible ( Figs. 45M ; 47 A–D). The epipodite has a well developed seta. The ventral margin of the first endopodite segment bears one long and one short setae. The disto-dorsal seta of this segment is plumose. The coxale endite is armed with nine or ten teeth; the distal and proximal tooth-lists have 14–16 and 17–19 teeth, respectively (in Poulsen 1973: 9–12, 13–16 and 15–19). The masticatory pad is armed with three or four (also in literature) rounded flaps, four or six flat spines and about 15–25 seta-like filaments (in Poulsen 1973: 20 filaments).

Maxilla. The first endopodite segment has six anterior and three posterior setae. All anterior setae are in the usual locations. Along the distal edge of this segment is a line of four–six long spines (also in above-listed literature).

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

Sixth limb ( Fig. 47E ). The coxale has two setae, one long and plumose, the other short, bare and rudimentary ( Poulsen 1973 illustrates only one long plumose seta). The ventral margin of the basale has one long, plumose proximal seta and one to four short, bare setae. The exopodite seta is short and barely reaches to the first endopodite segment.

Caudal furca. There is no unpaired seta (but according to Drapun & Smith 2012 one is present).

Copulatory appendage ( Fig. 47 G–J). It is broad (literature data: moderately broad in Deevey 1968), tapered anteriorly, broader in the middle and with a rounded tip. The distal seta is thick. The appendage is small, rounded, sclerotized and armed with a distal row of teeth. The limb has eight to ten oblique muscle bands (in Drapun & Smith 2012 with six–seven bands).

Additional description of adult female. Carapace ( Fig. 48 A–K). Length range is 1.65–1.80 mm in the northwestern Pacific and 1.50–1.85 mm in the north-eastern Pacific (literature data: from 1.4 mm in Poulsen 1973 to 1.86 mm in Angel 1993, but Deevey 1968 records a maximum length of 2.10 mm). It is tapered anteriorly. Height is about 48–51% of the length (summary literature data from Müller 1906; Deevey 1968; 1970; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: 47–55%). The postero-dorsal corner of the carapace is distinct, but the posterior margin and the postero-ventral corners are smoothly rounded. The right asymmetrical gland is in the usual location, but the left asymmetrical gland opens on a tubercle on the dorsal margin by about 10–13% of the carapace length anterior to the posterior dorsal corner (literature data from above-listed works: about 10–15%). There is no sculpture.

Frontal organ ( Fig. 48 L–O). It is straight with the capitulum fused with the stem, and is slightly broader than the stem. The capitulum tapers towards a pointed tip, and distally is covered with ventral small spines. This tip may have a terminal spine (literature data from Müller 1906; Deevey 1968; 1970; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: tip pointed or rounded, straight or bent downwards, without or with a terminal spine).

First antenna ( Fig. 48L, M ). The dorsal seta is relatively long, reaching to about 3/5–5/6 of the length of the capitulum (literature data: 1/2–3/4 the length) and is covered with small spines. Setae-a–d are shorter than the shaft of the limb. The anterior margin of the proximal half of seta-e is bare (literature data from Müller 1906; Deevey 1970; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: bare or with small “hairs”).

Second antenna. The first endopodite segment is about 40%, 52–53% and 52–53% the lengths of seta-g, -f and -h, respectively in our specimens (32%, 43% and 46% in Müller 1906; 29%, 41% and 56% in Drapun & Smith 2012). Terminal setae on the endopodite are of even thickness throughout their lengths and have pointed tips.

Mandible ( Fig. 49 D–G). It is same as in the male; the masticatory pad bears 32 seta-like filaments.

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

Sixth limb ( Fig. 49I ). The coxale has two unequal long, plumose setae. The basale bears five ventral plumose setae and one lateral plumose seta (in Poulsen 1973 lateral seta is missing, but in Drapun & Smith 2012 this seta is present). The disto-dorsal exopodite seta is very short and bare.

Remarks. There are some differences between the specimens studied herein and those described in the literature, which are listed below (in brackets literature data on Deevey 1968; 1970; Poulsen 1973; Angel 1993; Angel et al. 2008; Drapun & Smith 2012): the male—seta-e of the first antenna armed with 13–14 paired spines and 19–21 alternated spines (8–10 and 13–18 spines, respectively), the masticatory pad on the mandible has six flat spines (four), the coxale of the sixth limb has a long, plumose seta and one long, thin and bare seta (only with a long plumose seta or additionally with a short rudimentary and bare seta).

Distribution. P. parthenoda is recorded from all oceans: usually at latitudes lower than 40°, and is a shallow mesopelagic species, most abundant at depths 100–500 m ( Angel et al. 2008). In our material, the species is known from ( Fig. 51 ): the north-western Pacific—between 21°–48°N at depths from 0–100 m to 600–800 m, most abundant in layers 100–200 and 200–300 m; the north-eastern Pacific—between 9°–49°N at a depth range from 0– 50 m to 2000 m (and one total catch—from 3000 m to surface).

Figures

FIGURE 45. Map showing locations of stations at which Porroecia spinirostris (Claus, 1874) and P. acutirostrata Chavtur, sp. nov. were sampled.

FIGURE 46. Parthenoecia parthenoda (Müller, 1906) comb. nov. (Adult male: A and D—MIMB 18351/3; B, C, E, F, J, and L—MIMB 18351/1; G–I, K, and N—MIMB 18351/2). A and B—right valve of carapace in lateral view; C—carapace in ventral view; D—posterior part of carapace; E—frontal organ and first antenna; F and G—distal part of frontal organ and first antenna; H—arming on “e”-seta of first antenna; I—endopodite of left second antenna; J—left clasping organ of second antenna; K and L—clasping organ of right second antenna; M—mandibular endopodite (only main terminal claws and setae of first segment shown).

FIGURE 47. Parthenoecia parthenoda (Müller, 1906) comb. nov. (Adult male: A, C, D, H, J, and K—MIMB 18351/2; B, E, F, G, and I—MIMB 18351/1). A and B—coxal endite of mandible; C and D—epipodite of mandible; E—sixth limb; Fseventh limb; G and H—copulatory appendage; I and J—distal part of copulatory appendage; K—caudal furca and copulatory appendage.

FIGURE 48. Parthenoecia parthenoda (Müller, 1906) comb. nov. (Adult female: A, E, and H—MIMB 18351/4; B and I— MIMB 18351/5; C, F, K, and M—MIMB 18351/7; D, G, and J—MIMB 18351/6; L, N, and O—MIMB 18351/4). A–D—left valve of carapace in lateral view; E–G—carapace in ventral view; H–K—posterior part of carapace in lateral view; L and Mfrontal organ and first antenna; N and O—capitulum of frontal organ.

FIGURE 49. Parthenoecia parthenoda (Müller, 1906) comb. nov. (Adult female: A, C, G, I, and J—MIMB 18351/4; B, D–F, and H—MIMB 18351/7). A–C—endopodite of second antenna; D—mandibular endopodite (only main terminal claws and setae on first segment shown); E—masticatory pad on coxal endite of mandible; F and G—epipodite of mandible; H and Iproximal part of sixth limb; J—posterior part of caudal furca.

FIGURE 51. Map showing locations of stations at which Parthenoecia parthenoda (Müller, 1906) comb. nov. and P. aff. parthenoda (Angel, 1971) were sampled.