Nasoecia, 2011

Chavtur, Vladimir G. & Angel, Martin V., 2011, Revision of Metaconchoecia (Ostracoda: Halocyprididae) and the designation of two new tribes Conchoeciini and Metaconchoeciini 2857, Zootaxa 2857 (1), pp. 1-87 : 47-52

NASOECIA Chavtur & Angel , n.gen.

Synonymy

1906a Conchoecia ‘rotundata’ group—Müller, p. 79 (part).

1953 Conchoecia —Iles, p. 270 (part).

1955 Metaconchoecia —Howe, p. 118 (part).

1970 Conchoecia —Deevey, p. 810 (part).

1974 Conchoecia —Deevey, p. 364 (part).

1973 Metaconchoecia —Poulsen, p. 70 (part).

1980 Conchoecia rotundata group—Deevey & Brooks, p. 85 (part).

1981 Conchoecia skogsbergi species complex—Gooday, p. 141 (part), 159 (part).

1981a Conchoecia —Angel, p. 47 (part).

1982a Conchoecia —Deevey, p. 484 (part).

1986 Metaconchoecia —Kempf, p. 498 (part).

1992 Metaconchoecia —Kock, p. 68 (part).

1999 Metaconchoecia —Angel, Figs 9.58 –76 (part).

Etymology. The name is derived from Latin nasus, -i, meaning nose, since the LAG opens on the rostrum, and “- oecia” derived from the Greek word “οƖκοσ” meaning house, from which the terms ecology and economy have been derived, and is the ending that has become standard for Conchoeciinae genera.

Type species. Conchoecia nasotuberculata ( Müller, 1906a) .

Composition. This genus is monospecific, Nasoecia nasotuberculata ( Müller, 1906a) being the sole species.

Differential diagnosis. The species is small (0.74–0.88 mm) and globose ( CH is 52−62%CL). The LAG opens on the rostrum, anterior to the anterior end of the carapace hinge. The RAG opens on the posterior margin about 10% CH below the hingeline. In females there is a large lateral tubercle on each valve close to the posterior dorsal corner. In males similar lateral tubercles are present, but are much smaller. In some specimens there is a faint concentric pattern of sculpturing. The A1 e-seta armature in males consists of 10−12 pairs of slim spines.

Description. Males. Carapace: The length range is 0.74–0.90 mm. The carapace is rather globose, being short and relatively high, with a maximum height of 52–58%CL. The breadth is also ≥50%CL. Laterally on each valve close to the posterior dorsal corner there is a weakly developed tubercle (the tubercles are much more obvious features in females). In ventral aspect the curve of the carapace is indented just posterior to the shoulder vaults. This character immediately distinguishes this species from all the other small, globose species other than K. kyrtophora . Lrost is 10%CL, and LC3 is 9.5%CL. The LAG opens on the rostrum only 2–6%CL behind the tip (variously reported as 2.2% ( Angel 1981a), 5.2% ( Müller 1906a) and 6.1% ( Gooday 1981)). It opens anterior to the anterior hinge between the valves of the carapace; an attribute unknown in the other genera of Metaconchoeciini . The RAG opens on the posterior margin 8–13% CH below the dorsal margin. The surface of the carapace often has weak concentric striations.

Frontal organ: The shaft is segmented and its length is 38%CL, which is the same as the A1 limb. The capitulum is long (16–17%CL), broad, slightly concave, finely spinose, and down-turned, with a rounded tip. The shaft is a little shorter than the A1, but the capitulum extends well beyond its end.

First antenna: The limb (37–38%CL) is similar in length to the shaft of the frontal organ and just over double that of the capitulum. Its segmentation is clear, with the first segment being slightly shorter than the second. The aseta is simple, S–shaped and slightly swollen near its base. It is quite long (21–22%CL) and extends beyond the suture between the first two segments. The c-seta is short (4–5%CL), but only slightly shorter than the combined lengths of the third, fourth and fifth segments. The armature of the e-seta consists of 12–14 pairs of short, thin spines that lie parallel with the seta, pointing basally. The e-seta is 52%CL and nearly 1.5x times the length of the limb; it is also slightly longer than both the d-seta (46%CL) and the b-seta (44%CL).

Second antenna: The protopodite is quite long (50%CL). The exopodite is short, about 55–58% the length of the protopodite, and is of medium thickness. The a- and b- setae are subequal, slightly curved and finely spinose. The c- and d-setae are slim and short, and the e-seta is minute. The g- and f-setae are 46%CL and 41%CL respectively, and may be slightly flattened terminally. The sensory setae (h-, i-, and j-setae) are 16%CL, and just over a third the length of the g-seta. The hook appendages are slim, curved, and terminally rounded with some traces of subterminal ridging. The left hook is the smaller, and its distal arm is only slightly curved.

Mandible ( Fig. 2J ): The first endopodite segment has a subterminal dorsal seta that is either finely bare or with fine setules, and on its inner ventral margin it has two moderately long setae both of which extend to the end of the limb. The longest of the seven terminal setae on the third segment is 22%CL and is similar in the length to the limb. The exopodite process is quite large and bears a short, relatively slim, seta with long setules. The coxale is long and is 80% of the length of the endopodite.

Maxilla: The first segment of the endopodite has 4 anterior setae, a lateral seta, three posterior setae, and terminally there are three small spines. The end segment has the usual three terminal hook setae and two slim, subterminal lateral setae.

Fifth limb: The epipodial appendage carries three groups of four setae. The basale has two pairs of setae on the ventral edge, a single lateral seta, and dorsally a long bare seta that reaches to the end of the limb, and a shorter seta with long setules. Drapun (pers. comm.) observes an additional pair of lateral setae in specimens from the Indian Ocean. The limbs of both specimens dissected were somewhat damaged, and this probably account for the apparent disparities between the setation of the female and male limbs. The first endopodite segment has two medial ventral setae and a single medial dorsal seta. All three setae extend to just beyond the end of the segment. The terminal claw setae on the last segment have length ratios of 75:100:65, the longest being 8.3%CL and 80% of the limb.

Sixth limb: The epipodial appendage carries three groups of plumose setae (6 dorsal + 5 + 5). The basale has two pairs of setae on the ventral surface, one lateral seta, but apparently no dorsal seta (i.e. no vestige of an exopodite). The first segment has just a single, short, ventral seta, whereas the second segment has a very short medial seta on both the dorsal and ventral surfaces. The three terminal setae on the third segment are subequal and long (44.5%CL and 125% the limb itself). All three terminal setae have long setules along the distal one-third of their lengths.

Copulatory appendage: Its breadth is 34–35% of its length. It is straight, parallel-sided and has a rounded tip; it has three oblique muscle bands.

Caudal furca: The caudal furca has the usual eight pairs of hook spines that diminish in size posteriorly; the first and longest pair of claws is 15%CL. In some specimens there is an unpaired seta at the back of the furca between the two lamellae, however, Angel 1981a (his fig 2G) did not illustrate the seta nor does it appear in Arabian Sea specimens (Drapun pers. comm.).

Females. Carapace: The length range is 0.74–0.90 mm. The carapace is rather globose; the maximum height of 53–63%CL is in the posterior half. In ventral aspect the flanks curve smoothly with the maximum width a little anterior to midlength. The most striking features are the large lateral tubercles that are situated close to the posterior dorsal corner. (Note: The caption to Müller’s original (1906a) drawing (Pl. 17, fig. 2) shows these tubercles, but is erroneously attributed to Conchoecia kyrtophora ). The rostrum and incisure are similar to those of the male. The opening of the LAG is uniquely placed on the rostrum, 0.5–8%CL behind its tip [0.6% (Angel 1981), 4.2% ( Poulsen 1973), 4.2% ( Deevey 1970) 6.8% (Chavtur unpublished), 8.0% ( Deevey 1974)] but always anterior to the anterior end of the hinge. The RAG opens on the posterior margin 11–17% CH below the dorsal margin (i.e. 5– 8%CL). As in the male, there may be weak, concentric sculpturing.

Frontal organ: The frontal organ is fused, but the straight capitulum is slightly broader than the shaft, terminally rounded, and finely spinose along its ventral margin. The overall length of the frontal organ is 30–32%CL, i.e. 1.5–2x the length of the limb of the first antenna and similar in length to the e-seta.

First antenna: The segments are fused, and the overall length is 16–18%CL. The sensory setae (a- to d-) are simple and quite short (13–16%CL). The length of the e-seta is about 32%CL, i.e. 1.7–2.3x the length of the limb and 2–2.5x the sensory setae. Distal to the ends of the sensory seta, the e-seta carries minute fine spines along its trailing edge.

Second antenna: The protopodite is 42–44%CL. The first exopodite segment exopodite is 17–19%CL and of medium thickness. It appears to lack the terminal seta that is present on the male exopodite. Segments 2–9, which carry the swimming setae, are about half the length of the first segment, so overall the exopodite is quite short and is only around 60–65% the length of the protopodite. The terminal setae on the endopodite are subequal and unflattened; their lengths are 19–23%CL (i.e. 50% of the protopodite).

Mandible: The structure of this limb is similar to that of the male.

Fifth limb: The epipodial appendage has three groups of four setae. The basale has five ventral setae, a group of three near its base and a more distal pair; it has two lateral setae, and dorsally a seta with long setules and a long subterminal seta that extends to the end of the limb. The first endopodite segment has a medial pair of ventral setae and a single medial dorsal seta; all these setae extend to the end of the segment. The end segment carries the usual three terminal setae (dorsal to ventral length ratios 90:100:50). The longest is 7.5%CL and 75% of the limb.

Sixth limb: The epipodial appendage has three groups of setae (6 dorsal + 5 + 5). The basale has four or five ventral setae, a single lateral seta, but no dorsal seta was seen. The first segment has only a ventral medial seta. The second segment has a single medial seta on both its dorsal and ventral margins; both of these setae are quite long and extend to the end of the segment. The lengths of the terminal three setae have ratios of 75:100:50 (ventral). The longest seta is 10%CL and about 60% the length of the limb.

Comparisons. This genus is most closely resembles Kyrtoecia (see below). Some of the characters that discriminate between these two genera are summarized in Table 8 and Appendices 1–3 and illustrated in Figure 2 .

Distribution. Atlantic Ocean and Mediterranean Sea: occurs between 18ºN and 40ºS ( Müller 1906a, 1908; Iles 1953, Deevey 1970, 1982b; Angel 1981a; 1981b, Gooday 1981), and one specimen has been collected from 62ºN, 17ºW (Chavtur, unpublished). Indian Ocean: latitudes 4ºN to 3ºS ( Müller 1906a). Pacific Ocean and Pacific sector of the Southern Ocean: latitudes 22º to 54ºS ( Poulsen 1973; Deevey 1982a, 1983) and from one station situated at 37ºS, 144ºE ( Chavtur 1977a). Overall its reported depth range is 0–2500m. However, the maximum depth is a sampling artifact resulting from fishing non-closing nets as stratified sampling in the North Atlantic shows that it is almost entirely restricted to depths of 100– 400m.

KYRTOECIA Chavtur & Angel n.gen.

Synonymy

1906a Conchoecia ‘rotundata’ group—Müller, p. 79 (part).

1955. Metaconchoecia —Howe, p. 118 (part).

1968 Rotundata group—Deevey, p. 50 (part).

1970 Conchoecia —Deevey, p. 810 (part).

1973 Metaconchoecia —Poulsen, p. 70 (part).

1979 Metaconchoecia —Martens, p. 352.

1981 Conchoecia skogsbergi species complex—Gooday, p.159 (part).

1981a Conchoecia —Angel, p. 53 (part).

1986 Metaconchoecia —Kempf, p. 149 (part).

1992 Metaconchoecia —Kock, p. 68 (part).

1999. Metaconchoecia —Angel, Figs 9.58 –76 (part).

Etymology. The name is derived from Greek κʋρτοσ meaning “arched”, “curved”, and “-oecia” derived from the Greek word “οƖκοσ” meaning house, from which the terms ecology and economy have been derived, and is the ending that has become standard for Conchoeciinae genera.

Type species. Conchoecia kyrtophora Müller, 1906a .

Composition. This genus is monospecific, and includes just Kyrtoecia kyrtophora ( Müller, 1906a)

Differential diagnosis. Small, globose species (carapace length 0.76−0.93 mm). LAG opens 6.0%CL behind the tip of the rostrum and posterior to the anterior edge of the hinge. The RAG opens close to the PDC. In its ventral aspect, the lateral margin of the carapace is constricted just behind the shoulder vaults. The armature of the male A1 e-seta consists of 16–22 square ended spines set at right angles to the seta. These spines are paired distally, but proximally they become alternate.

Description. Males. Carapace: The length range is 0.75–0.90 mm. The carapace is very short and rather globose; its maximum height of 51–59%CL is just posterior to midlength. The breadth is usually slightly less than the height. In ventral aspect the carapace is characteristically constricted posterior to the shoulder vaults; the maximum width is anterior to midlength across the shoulder vaults. Lrost is 6%CL, but LC3 is> 7%CL. The LAG opens just behind the rostrum; posterior to the anterior margin of the hinge, but about level with the hindmost margin of the incisure. The RAG opens almost level with the posterior end of the hinge, and just below the hinge-line, 3–6% CH below the posterior margin. The surface of the carapace is sculptured with very faint concentric striae.

Frontal organ: The capitulum is clearly separated from the shaft, which is quite long (35–37%CL). The capitulum is also long (19–22%CL), narrow, slightly concave, and terminally rounded. It has fine spinules along its ventral margin. The shaft is slightly longer than the A1 limb, so overall the frontal organ is considerably longer than the A1 limb.

First antenna: The limb is clearly segmented, with the first segment being slightly shorter than the second. Its overall length is 35–38%CL, about twice the length of the capitulum. The a-seta is S-shaped and unswollen at its base and has no side branch. It is quite long (25–26%CL) and extends well beyond the base of the second segment. The c-seta is short (5%CL), and shorter than or subequal to the combined lengths of the third, fourth and fifth segments. The e-seta is quite long (47–48%CL), longer than both the d-seta (39%CL) and b-seta (37%CL). Its armature is unique in the Metaconchoeciini , in that it consists of 16–22 square-ended pegs that are set at right angles to the seta. Distally they are paired, and become alternate proximally.

Second antenna: The protopodite is 50%CL. The first segment of the exopodite is quite slim (20%CL) and appears to lack a terminal seta. Overall, the other distal exopodite segments are slightly less than half the length of the first segment. On the endopodite the g-seta is nearly 50%CL, and the f-seta is 43–45%CL; both these seta are unflattened and have sharply pointed tips. The sensory setae (h–j) are subequal and 14–15%CL. Both hook appendages are curved and then curve again near their ends, which are ridged with bifid or even trifid points; the left hook is, as usual, the smaller.

Mandible ( Fig. 2H ): The endopodite has a subterminal dorsal seta, and a single inner ventral seta that nearly reaches to the end of the limb. The second segment has three dorsal (1 long) and 2 ventral (1 long) setae. There are the usual seven terminal setae on the third segment. The longest claw seta is>75% the length of the limb and 20%CL. The exopodite consists of just a short, slim, seta with long setules, and there is no process. The coxale is short and about half the length of the endopodite.

Maxilla: The first segment of the endopodite has four anterior setae, a single lateral seta, and three posterior setae; a pattern that is typical of the tribe. There are up to seven small spines on the outer distal margin of the first segment. The end segment carries the usual three terminal spines and two subterminal setae.

Fifth limb: The epipodial appendage has three groups of 4 setae. Proximally the basale has a group of three ventral setae and distally two more setae. It lacks a lateral seta, but dorsally it carries two, one with long fine setules the other a long and subterminal, which is the vestigial exopodite. The first endopodite segment has two ventral and a single dorsal seta, all of which extend to the end of the segment. The terminal segment has three terminal setae (dorsal to ventral length ratios 90:100:50), the longest of which is 8%CL and 65% of the length of the limb.

Sixth limb: The epipodial appendage has three groups of 7+5+?5 setae. The basale has 4 or 5 ventral setae, possibly a single lateral seta, and a short dorsal seta. The first segment has a single short ventral seta, but no dorsal seta. The second segment has a ventral medial seta that reaches halfway to the end of the segment, and a much shorter dorsal seta. The three terminal setae on the third segment are subequal, 45%CL and 150% of the length of the limb. They all carry long setules on the distal third.

Caudal furca: The longest of the eight pairs of hook spines is 18%CL.

Copulatory appendage: The length of the appendage is 33–35%CL. It is almost straight and parallel-sided. The end is obtusely angled. It has 2–3 oblique muscle bands.

Females. Carapace. The length range is 0.76–0.93 mm. It is short and relatively high with the maximum height of 54–59%CL located just posterior to midlength. Viewed ventrally, the flanks are constricted behind the shoulder vaults; this character readily distinguishes females of this species from N. nasotuberculata . Lrost is short (6–8%CL) and LC3 is slightly longer (~8.7%CL). As in the male, the LAG opens just behind the hinge. The RAG opens 4%CL posterior to the posterior end of the hinge and 4% CH below the hinge line. As in the male there is faint concentric sculpturing.

Frontal organ: The frontal organ is fused with an overall length of 29–32%CL and is substantially longer than the A1 limb. The capitulum is almost straight and similar in thickness to the shaft. It is finely spinose along its ventral margin and along the distal half of the dorsal margin. The end is rounded.

First antenna: The limb segments are fused, and its overall length is 17–21%CL. There is no dorsal seta. The sensory setae (a- to d-) are thin-walled and simple (14–17%CL). The e-seta is 26–27%CL, longer than the limb and much longer than the sensory seta. Along its trailing edge, distal to the ends of the sensory setae, it is armed with minute spines.

Second antenna: The protopodite is 46–47%CL. The first exopodite segment is 17%CL, about double the combined lengths of the three distal exopodite segments; and it lacks a terminal seta. On the endopodite the terminal setae are simple, unflattened, and thick with rounded ends. The longest g-seta is 21–22%CL, and the other setae are subequal at 18–19%CL.

Mandible: Similar to that of the male.

Fifth limb: The epipodial appendage has three groups (4+4 (sometimes 5)+4) of setae. The basale has groups of, 3+2 setae ventrally, 2+2 setae laterally, and dorsally two setae; one moderately long with long setules, the other bare, subterminal, and long extending to the end of the limb. The first endopodite segment has medially two ventral setae and a single dorsal seta. The terminal setae usually have length ratios of 90:100:50. The longest seta is 7.4– 7.7%CL and 65–70% the length of the limb.

Sixth limb: The epipodial appendage has three groups of 5+5+5 setae. The basale has ventrally 4–6 ventral setae arranged in pairs, laterally no seta, and dorsally two setae; one carries long setules and is shorter than the other long bare seta, which barely reached the tip of the limb and so is relatively shorter than in other Metaconchoeciinae species. The first endopodite segment has a single ventral seta and usually a single dorsal seta. The second segment also has a single medial ventral and a longer medial dorsal seta; both these setae extend beyond the end of the segment. The terminal setae have length ratios of 75:100:65. The longest of these setae was 9.5–10%CL and slightly less than 60% the length of the limb.

Comparisons. This monospecific genus is most similar to Nasoecia . The characters that most readily discriminate between these two genera are summarized in Table 8, Appendices 1–3, and illustrated in Figure 2 .

Distribution. In the Atlantic Ocean between 18ºN and 40ºS ( Müller 1906a, 1908; Deevey 1974; Angel 1979, 1981a, 1981b; Angel & Fasham 1975; Gooday 1981). Indian Ocean: reported from 7ºN to 10ºS ( Müller 1906a; Hanai et al. 1980; George & Nair 1980). In the Pacific Ocean it has been reported from the northwest sector between 6ºN and 13°N (Chavtur, unpublished), from the southwest sector around 30ºS, at 71° to 73°W ( Martens 1979), from the southeast sector at two stations 22°S, 166°E and 28°S, 173°W ( Poulsen 1973). So far there have been no reports from the northeastern sector. Its overall depth range is reported to be 0–2500m, but stratified sampling shows it to be almost entirely restricted to subthermocline depths of 50–200m (Angel, Blachiowiak-Samolyk and Chavtur 2008).

Figures

FIGURE 2. Basal segments of the mandibles of eleven species in the tribe Metaconchoeciini, showing the variations in the extent to which the exopodite is developed; in some species there is a process on which a pappose seta is inserted (indicated by *), but in other species there is no process and only the seta is present. A, Juryoecia distoglandula; B, J. abyssalis; C*, Deeveyoecia bathyrotundata; D*, Rotundoecia teretivalvata; E, Clausoecia pusilla; F*, Vityazoecia goodayi; G*, Metaconchoecia crassiseta; H*, Kyrtoecia kyrtophora; I, Muelleroecia glandulosa; J*, Nasoecia nasotuberculata; L, Austrinoecia isocheira. (Note: the mandibles are not sexually dimorphic, so the sex of the specimen drawn does not have to be specified).

FIGURE 9. Juryoecia distoglandula n. sp. Female. A, Lateral view of carapace of holoytype (Museum of Zhirmunsky Institute of Marine Biology, Vladivostok, Russia (IBM 2822) RV Vityaz Cruise 39, Station 5612, 45°43’N, 153°25’E, depth 5000- 6000m) B, ventral view of carapace of holotype; C, ventral view of carapace of one paratype (RV Vityaz Cruise 39, Station 5617; 45°49’N, 153°33’E; depth 6000-7000m); D, and E, ventral and lateral view of the second female paratype (RV Vityaz Cruise 39, Station 5617; 45°49’N, 153°33’E; depth 6000–7000m), F, Posterior dorsal corner of carapace of holotype, showing the opening of the LAG; G, Capitulum of frontal organ of the holotype; H, Frontal organ and first antenna of the holotype, showing side arms on the a-, b-, c- and d-setae; I, Details of the distal end of the first antenna of the holotype, showing the side arms on the sensory a-, b-, c- and d-setae; J, Second antenna of holotype; K, Details of endopodite of the second antenna of the holotype (note b-seta is broken); scales in millimetres.