Porroecia spinirostris ( Claus, 1874 )

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 : 84-89

Porroecia spinirostris ( Claus, 1874)

( Figs. 41 A–N, 42)

1874 Conchoecia spinirostris —Claus: 6, pl. I, fig. 8; pl. II, fig. 11.

1887 Conchoecia pellucida —Sars: 80, pl. XI, figs. 1–4; pl. XII; pl. XIII, fig. 1–4.

1890 Conchoecia spinirostris —Claus: 7.

1891 Conchoecia spinirostris —Claus: 56, pl. I, figs. 1–12.

1896 Conchoecia spinirostris —Brady & Norman: 689, pl. LX, fig.22.

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

1920 Conchoecia spinirostris — Skogsberg, 1920: 697, fig. CXXXIV;

1968 Conchoecia spinirostris —Deevey: 80, figs. 38, 39;

1969a Conchoecia spinirostris— Angel: 35, figs. 4–6;

1969b Conchoecia spinirostris— Angel: 173;

1973 Spinoecia spinirostris —Poulsen: 111, fig. 55;

1979 Porroecia spinirostris — Martens, 1979: 329;

1999 Porroecia spinirostris— Angel: 821, 836, fig. 9.112;

2012 Porroecia spinirostris —Drapun & Smith: 152–155, pict. 29, pls. 58, 59, figs. 67, 68.

Examined material. MFFT Kavalerovo, 1980: MIMB 18353 /1, 18353/2 and 18353/3—adult males (1.12, 1. 0 8 and 1.04 mm) and 18353/6, 18353/7—adult females (1.16 and 1.21 mm), station 70, 30°30´N– 140°39´E, layer 100–0 m, sounding?, September 4 ; MIMB 18353 /4 and 18353/5—adult males (1.10 and 1.15 mm), 18353/8— adult female (1.18 mm), 18353/10— 2 females (1.15 and 1.17 mm), station 74, 33°02´N– 139°01´E, layer 100–0 m, depth?, September 5 ; MIMB 18353 /9— 2 males (1.03 and 1.06 mm) and 3 females (1.17–1.19 mm), station?, 33°15´N– 148°27´5´´ E, layer 100–0 m, depth?, August 28.

Additional material see Appendix.

Additional description of adult male. Carapace ( Fig. 41A, B ). The length range is 1.0–1.2 mm in the northwestern Pacific and 1.0–1.1 mm in the north-eastern Pacific (literature data: from 0.9 mm in Skogsberg 1920 to 1.3 mm in Poulsen 1973). The carapace is most rectangular. The height in the anterior and posterior parts is subequal, less than half of the length (about 43–45%) (literature data from Deevey 1968; Skogsberg 1920; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: about the half of the length). The dorso-posterior corner is right-angled. The posterior margin is slightly arched or straight, and the ventral margin is almost straight. The right asymmetrical gland is in its usual location (one aberrant specimen lacked this gland: MFFT Cavalerovo, 1980 from the area of St. 74: 33°2´N, 139°1´E). The left asymmetrical gland is moved from the posterior corner forward along the dorsal margin by about 6–7%. Sculpture of the surface is very faint, restricted to weak cross-striations dorso-anteriorly.

Frontal organ ( Figs. 41C, D ,; 44A ). The capitulum is relatively slim and long (one aberrant specimen has a noticeably short capitulum: collected by MFFT Cavalerovo, 1980 from the region of St 74), almost straight, tapering anteriorly and with a rounded tip. The proximal surface of the capitulum is usually covered with small spines.

First antenna ( Figs. 41 I–M; 44A). Lengths of the first and second segments are similar. Seta-a extends well beyond the suture between these segments to 1/3–4/5 the length of the first segment (summary literature data from Deevey 1968; Skogsberg 1920; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: only reaches to this boundary). Seta-c is slightly longer than the combined lengths of the third, fourth and fifth segments (literature data: equal, slightly shorter or longer). Armature of the seta-e has a comb with 8 “т”-shaped pairs of spines and 13– 15 alternated usual type spines slightly directed proximally (in the above-listed literature: 7–10 pairs and 14–20 alternated spines).

Second antenna ( Figs. 41 H–M; 44B). Seta-b on the endopodite has two long posterior fine filaments (fig. 40N). The right clasping organ is curved obliquely distally ( Fig. 40N, P ) (summary literature data from Deevey 1968; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: squared or oblique), with a slightly swollen and rounded tip. The left clasping organ is right-angled or barely oblique distally and with a pointed tip (literature data: a rounded tip only in P. spinirostris in Müller 1894 and in P. pellucida in Sars 1887 ).

Mandible ( Figs. 41N ; 42C ). The epipodite has a tiny verruca and a rudimentary spine-like 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 tooth edge of the coxale endite is armed with eight or nine teeth, the distal tooth-list has 11–12 teeth, and the proximal tooth-list has 13–15 teeth (in Poulsen 1973: 10, 11 and 9–18, respectively).The masticatory pad at most has four rounded flaps, three flat spines and about 15–20 seta-like filaments (in Poulsen 1973: 10–12).

Maxilla. The first endopodite segment has six anterior and three posterior setae.

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 lateral seta is obscure; the distal dorsal seta (vestige of the exopodite) is long, reaching the end or just beyond the end of the limb. The first endopodite segment bears two ventral setae and one dorsal seta.

Sixth limb ( Fig. 44A ). The coxale has one long plumose seta and a tiny rudimentary bare seta. The ventral margin of the basale has one short, bare seta (summary literature data from Poulsen 1973 and Drapun & Smith 2012: zero or one seta). The exopodite seta is very short, barely reaching (in Drapun & Smith 2012: does not reach) the proximal margin of the first endopodite segment.

Caudal furca ( Fig. 42D ). There is no unpaired seta.

Copulatory appendage ( Fig. 42D, E ). It is moderately broad, slightly tapered to the end, with almost parallel anterior and posterior margins, and with a rounded tip (summary literature data from Deevey 1968; Skogsberg 1920; Drapun & Smith 2012: it is broad or mid-broad, either with parallel margins or is slightly convex, being broader in the middle or distal portion). The distal seta is thick. The appendage is small and almost rounded (summary literature data from Skogsberg 1920; Deevey 1968; Poulsen 1973; Drapun & Smith 2012: large or small, triangular or rounded). The limb has eight oblique muscle bands (summary literature data from Poulsen 1920; Drapun & Smith 2012: 6–8).

Additional description of adult female. Carapace ( Fig. 42 F–H). Length range is 1.10–1.30 mm in the northwestern Pacific and 1.05–1.25 mm in the north-eastern Pacific (summary literature data from Skogsberg 1920; Angel 1993; Angel et al. 2008; Deevey 1968; Poulsen 1973; Martens 1979; Drapun & Smith 2012: generally 0.95– 1.30 mm, but according to Poulsen (1973) up to 1.50 mm). It is more elongated and rounded than the male, and noticeably tapers anteriorly. The maximum height is about 47–49% of the length (summary literature data from Skogsberg 1920; Angel 1993; Angel et al. 2008; Deevey 1968; Drapun & Smith 2012: 47–52%). The dorsoposterior corner is slightly rounded. The posterior margin is clearly arched, and the ventral margin almost straight or with a slight concavity. The left asymmetrical gland is moved forward along the dorsal margin by about 6–7%. The number and locations of glands (except the postero-dorsal medial glands) and sculpture are the same as in the male.

Frontal organ ( Fig. 42I, J ). It is straight. The capitulum is straight and fused with the stem and slightly broader than it. Its tip has a clear spine (summary literature data from Skogsberg 1920; Angel 1993; Angel et al. 2008; Drapun & Smith 2012: tip with small or relatively long spine or pointed).

First antenna ( Fig. 42I, J ). The suture between the first and second segments is distinct. The first segment is shorter than the second one. The limb has no dorsal seta. Setae-a–d are shorter than the shaft of the limb. Seta-e is armed with proximal medium-length or long fine filaments on the anterior side and short filaments distally along the posterior side ( Fig. 42I ).

Second antenna. The first endopodite segment is about 39–41%, 52–54% and 55–56% the lengths of setae-g, - f and –h, respectively.

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

Sixth limb ( Fig. 42K ). The coxale has two unequal long plumose setae. The basale bears five ventral, long, plumose setae and has one lateral short, plumose seta. The exopodite is represented by a short seta.

Remarks ( Table 4). The morphology of our specimens is similar to that described in the above-listed literature.

Characteristics Genus Porroecia P. porrecta P. spinirostris P. affinis P. acutirostrata P. vibekensis Male Carapace: Length, mm 1.13–1.55 0.90–1.30 1.25–1.40 1.12–1.20 1.10–1.20 Height, % usually 42–48 44–50 42–43 47–50 about 50 Sculpture barely or distinct striae directed from rostrum to postero-ventral corner slight concentric striae slight concentric striae slight concentric striae distinct concentric striae First antenna: Length of “a”-seta reaches (or not) of 1st segment only reaches or somewhat longer usually reaches proximal end of limb reaches 1/3 of its length reaches 1/3 of its length reaches proximal end of limb Number paired and alternated spines on “e”-seta 8–16 and 22–30 7–10 and 13–20 11–13 and 24–25 11–13 and 24–25 7–9 and 18–22 Second antenna: Number of posterior and anterior “hairs” on “b”-seta of endopodite 1–4 long and 0–4 long 2 long and 0 1–3 long and 0 1–2 long and 0 0 and 3 long

Distribution. It is recorded from all oceans at latitudes lower than 40°, and is a neustonic and shallow mesopelagic species ( Angel et al. 2008). In our materials the species is known from the north-western Pacific at latitudinal ranges of 21°–36°N and from the north–eastern Pacific of 5°–40°N ( Fig. 45 ); all specimens were taken from depths of 0–500 m, but in greatest abundances in the layers 0–100 and 100– 200 m.

Figures

FIGURE 40. Porroecia affinis Chavtur, sp. nov.(Adult female: A, C, and D—18355/7; B and E—MIMB 18355/8; F—MIMB 18355/9) and P. spinirostris (Claus, 1874) (Adult male: G–I, K–M, S, and T—MIMB 218353/2; J, P, and Q—MIMB 18353/4; N, O, and R—MIMB 18353/1). A and B—distal part of frontal organ; C—frontal organ and first antenna; D—endopodite of second antenna; E—proximal part of sixth limb; F—caudal furca.

FIGURE 41. P. spinirostris (Claus, 1874) (Adult male: A–C, E–G, M, and T—MIMB 218353/2; D, J, and L—MIMB 18353/4; H, I, and L—MIMB 18353/1). A—right valve of carapace in lateral view; B—carapace in ventral view; C—frontal organ and first antenna; D—distal half of frontal organ and first antenna; E—proximal part of “a”-seta on first antenna; F and G—arming of “e”-seta on first antenna; H—endopodite of right first antenna; I–L—right (I, J) and left (K, L) clasping organs of second antenna.

FIGURE 42. Porroecia spinirostris (Claus, 1874) (Adult male: A and C–D—MIMB 18353/2; B—MIMB 18353/1. Adult female: F—MIMB 18353/6; G and I–K—MIMB 18353/7; H—MIMB 18353/8). A—distal part of frontal organ and first antenna; B—exopodite and endopodite of second antenna; C—mandibular endopodite (setae shown only for first segment); D—furcal and copulatory appendages; E—distal part of copulatory appendage; F—right valve of carapace in lateral view; G and H—carapace in ventral view; I frontal organ and first antenna; J—distal half of frontal organ and first antenna; Kproximal part of sixth limb.

FIGURE 44. Porroecia acutirostrata Chavtur, sp. nov. (Adult male: A and C—MIMB 18354/1; B—MIMB 18354/3; C— MIMB 18354/2. Adult female: E, F, and H—MIMB 18354/8; G, I, and J—MIMB 18354/6; K and M—MIMB 18354/7; L, N, and O—MIMB 18354/5). A—proximal part of sixth limb; B—caudal furca and copulatory appendage; C and D—distal part of copulatory organ; E and F—right and left valves of carapace in lateral view; G and H—carapace in ventral view; I—frontal organ and first antenna; J–L—capitulum of frontal organ; M—endopodite of second antenna; N—basale, exopodite, and endopodite of fifth limb (setae not shown); O—epipodite, basale, and exopodite of fifth limb.

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