Porroecia porrecta ( Claus, 1890 )

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 : 75-80

Porroecia porrecta ( Claus, 1890)

( Figs. 35 , 36 , 37A and B )

For synonymy before 1906, see Müller 1906.

1906 Conchoecia spinirostris —Müller: 104, pl. XXII, figs. 21–23, 25–28 (partly);

1968 Conchoecia porrecta —Deevey: 83, figs. 40, 41;

1969a Conchoecia porrecta —Angel: 35, figs. 1–3;

1973 Spinoecia porrecta —Poulsen: 114–115, fig. 56;

1977 Conchoecia porrecta adriatica —Gooday & Angel: 139, figs. 7–9;

1979 Porroecia porrecta pacifica —Martens: 329, fig. 13;

2012 Porroecia porrecta —Drapun & Smith: 148–151, pict. 28, pls. 56, 57, figs. 65, 66.

Examined material. RV Akademik Mstislav Keldysh, 22th Cruise: MIMB 18352 /4—adult male (1.42 mm) and 18352/7, 18352/9, 18352/10—adult females (1.70, 1.69 and 1.75 mm), station 2383, sample 83, 18°47.7´N– 155°10.9´W, layer 2000–0 m, depth 5000 m, September 4, 1990 ; MIMB 1 8352/1, 18352/2 and 18352/3—adult males (1.40, 1.40 and 1.43 mm) and 18352/5, 18352/6 and 18352/8—adult females (1.67, 1.67 and 1.72 mm), station 2345, sample 96, 29°9.36´N– 141°16.21´W, layer 200– 100 m , depth 4900 m, September 12, 1990.

Additional material see Appendix.

Additional description of adult male. Carapace ( Fig. 35 A–E). The length ranges 1.30–1.55 mm in the northwestern Pacific and 1.25–1.50 mm in the north-eastern Pacific (literature data: from 1.13 mm in Drapun & Smith 2012 to 1.48 mm in Angel 1969a). The carapace is most rectangular. The height is similar throughout, slightly less than half of the length (about 45–49%) (summary literature data from Deevey 1968; Martens 1979; Drapun & Smith 2012: slightly less, subequal or more). The dorso-posterior corner is right-angled. The posterior and ventral margins are almost straight (summary literature data from Deevey 1968; Gooday & Angel 1977; Angel et al. 2008; Martens 1979; Drapun & Smith 2012: ventral margin straight, slightly concave or barely noticeable convex). The left asymmetrical gland is somewhat moved forward along the dorsal margin by about 6–7%. The surface of the carapace has distinct striae directed from the rostrum to the postero-ventral corner (the above-listed literature: obscure or weakly striated on the rostral shoulders).

Frontal organ ( Figs. 35F ; 36A ). The capitulum is moderately broad (literature data: moderately broad or broad), almost straight and with a rounded tip. Proximal surface of the capitulum usually is covered with small spines.

First antenna ( Figs. 35F, G ; 37A ). The first segment is somewhat shorter than the second segment (summary literature data from Deevey 1968; Gooday & Angel 1981; Angel et al. 2008; Drapun & Smith 2012: shorter, subequal or longer). Seta-a just extends beyond the suture between the segments (summary literature data from Deevey 1968; Gooday & Angel 1981; Angel et al. 2008; Drapun & Smith 2012: extends to or barely reaches). Seta-c is slightly shorter than the combined lengths of the third, fourth and fifth segments (literature data: equal or slightly more). Armature of seta-e has a comb with 13–14 “σ”-shaped pairs of spines and 24–28 alternated usual type spines slightly directed proximally (summary literature data from Deevey 1968; Poulsen 1973; Martens 1979; Gooday & Angel 1981; Drapun & Smith 2012: 8–16 pairs and 20–27 alternated spines).

Second antenna ( Figs. 35 H–K; 37B). Seta-b on the endopodite has one or two long, basal, fine filaments and zero or two medium-length distal setae. The right clasping organ is slightly acutely-angled or almost square, slightly swollen or not, with a pointed or rounded tip. The left clasping organ is right-angled and with a pointed tip.

Mandible. The epipodite has a verruca and a spine-like seta. The ventral margin of the first endopodite segment has one long and one short setae. The disto-dorsal seta of this segment is plumose. The tooth edge of the coxale endite is armed with nine teeth, and the distal tooth-list and proximal tooth-list have 15–17 and 11–13 teeth, respectively. The masticatory pad at most has four rounded flaps, three flat spines and about 25–40 seta-like filaments (20–25 filaments in Poulsen 1973).

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

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

Sixth limb ( Fig. 35L ). The coxale has one long, plumose seta and a rudimentary bare seta. The ventral margin of the basale bears three short, bare setae. The exopodite is short and barely reaches (in Drapun & Smith 2012: or does not reach) the proximal margin of the first endopodite segment.

Caudal furca. There is no unpaired seta.

Copulatory appendage ( Fig. 35 M–O). It is moderately broad, slightly tapered to the end, with nearly parallel anterior and posterior margins; the tip is rounded. The distal seta is thick. The appendage is small, almost triangular and with a rounded tip. The limb has six–ten oblique muscle bands.

Addition description of adult female. Carapace ( Fig. 36 A–H). The length range is between 1.30–1.57 mm in the north-western Pacific and 1.30–1.80 mm in the north-eastern Pacific (summary literature data from Deevey 1968; Poulsen 1973; Martens 1979; Gooday & Angel 1981; Drapun & Smith 2012: 1.23–1.75 mm). The carapace is more elongated and rounded than that in the male, and clearly tapers anteriorly, (maximum height is 44–47% of the length). The postero-dorsal corner is slightly rounded. The posterior margin is clearly arched, and the ventral margin is either convex, or almost straight or slightly concave. The left asymmetrical gland is moved forward along the dorsal margin by about 6–7% (in Atlantic Ocean specimens the opening is just anterior to the posterior end of the hinge between the two carapace valves). The number and locations of glands (with exception of the posterodorsal medial ones) and sculpture are same as in the male.

Frontal organ ( Fig. 36 I–K). The whole organ is straight. The capitulum is fused with the stem and slightly broader than it. Its tip has a small spine (summary literature data from Deevey 1968; Martens 1979; Gooday & Angel 1981; Angel et al. 2008; Drapun & Smith 2012: tip with small or relatively long spine or pointed).

First antenna ( Fig. 36I, L ). The suture between the first and second segments is obscure. The limb has no dorsal seta as in literature (only Drapun & Smith (2012) illustrate a rudimentary dorsal seta in their Fig. 56C). Setae-a–d are shorter than the limb. Seta-e is armed with small or medium-length filaments both distally and proximally.

Second antenna ( Fig. 36M ). The first endopodite segment is about 40%, 51% and 58% the lengths of setae-g, - f and –h, respectively in our specimens (summary literature data from Martens 1979; Drapun & Smith 2012: about 40–41%, 51–54% and 53–55%).

Mandible ( Fig. 36 N–P), maxilla, fifth limb and caudal furca are similar to those of the male.

Sixth limb ( Fig. 36Q ). The coxale has two unequal long, plumose setae. The basale bears five ventral long, plumose setae (only four setae in P. porrecta in Poulsen 1973 ), one lateral, short, plumose seta and one short, dorsal, bare seta (exopodite).

Remarks ( Table 4). Morphology of the specimens studied herein is similar to that described in the above-listed literature. However, the species described by Drapun & Smith (2012) is not consistent with P. porrecta , in that the first antenna in the female has a rudimentary dorsal seta, the seta-e armature of the male first antenna has only eight to ten paired spines, and they illustrate the copulatory organ as being broader than that in the descriptions by other authors.

Distribution. It is one of the most dominant species recorded from all oceans, mostly at latitudes lower than 40°; shallow mesopelagic species ( Angel et al. 2008). In our material, the species is known from ( Fig. 38 ): the north-western Pacific—between 5°–41°N, where it was most abundant at depths of 0–200 m; only at one station (St. 7236, RV Vityaz) did it occur in samples from layers of 1088–2000, 2000–3000 and 3214–3500 m (total: from 1088 to 3500 m). In the north-eastern Pacific it occurred between 8°–32°N at depths of 0– 200 m.

Figures

FIGURE 35. Porroecia porrecta (Claus, 1890) (Adult male: A, B, E–H, J, K, M, and O—MIMB 18352/2; C—MIMB 18352/ 4; D, I, L, and N—MIMB 18352/1). A—left valve of carapace in lateral view; B–D—carapace in ventral view; E—posterior part valve of carapace in lateral view; F—distal half of frontal organ and first antenna; G—arming “e”-seta of first antenna; H—left endopodite of second antenna; I—“a”-, “b”- and processus mamillaris of endopodite on second antenna; J and Kclasping organ of endopodite on right second antenna; M—copulatory appendage; N and O—distal part of copulatory appendage.

FIGURE 36. Porroecia porrecta (Claus, 1890) (Adult female: A, F, H, and K—MIMB 18352/5; B and Q—18352/6; C— MIMB 18352/9; D and G—MIMB 18352/10; E—MIMB 18352/7; I, J, and L–P—MIMB 18352/8). A–E—right (A and C–E) and left (B) valve of carapace in lateral view; F and G—carapace in ventral view; H—posterior part of right of carapace in lateral view; I—frontal organ and first antenna; J and K—capitulum of frontal organ; L—distal part of first antenna; Mendopodite of second antenna; N—endopodite of mandible (only main claw and setae on first segment shown); O—masticatory pad of mandibular coxale; P—epipodite of mandible; Q—proximal part of sixth limb.

FIGURE 37. Porroecia porrecta (Claus, 1890) (Adult male: A and B—18352/2); P. cf. porrecta Claus, 1890 (Adult female: C and E—MIMB 18352/13; F and G—MIMB 18352/14. Adult male: D—MIMB 1852/1); and P. affinis Chavtur, sp. nov. Chavtur (Adult male: H and K—MIMB 18355/5; I—MIMB 18355/6; J and L—MIMB 18355/2). A—distal half of frontal organ and first antenna; B—“a”- and “b”-setae processus mamillaris of endopodite on second antenna; C and D—left valve of carapace in lateral view; E—carapace in ventral view; F and G—anterior and posterior parts of right valve of carapace in lateral view; H and I—right valve of carapace in lateral view; J—endopodite of right second antenna; K and L—clasping organs of right and left second antenna.

FIGURE 38. Map showing locations of stations at which Porroecia porrecta (Claus, 1890), P. cf. porrecta (Claus, 1890) and P. affinis Chavtur, sp. nov. Claus, 1890 were sampled.