Polycopetta pax, Kornicker, Louis S. & Harrison-Nelson, Elizabeth, 2005

Kornicker, Louis S. & Harrison-Nelson, Elizabeth, 2005, Two new species of Ostracoda from hydrothermal vents of Riftia pachyptila aggregations on the East Pacific Rise (Halocypridina; Cladocopina), Zootaxa 1071, pp. 19-38 : 31-37

Polycopetta pax , new species

Figs. 9–13

Etymology. From the Latin pax (peace, tranquility).

Holotype. USNM 1078717, adult female; appendages on slide, separated valves in alcohol.

Paratypes. None.

Type Locality. Riftia Field Site , East Pacific Rise, 9°50.705'N, 104°17.493' W, slightly north of the Tica site, 2500 m bottom depth, temperature up to 20°C, Alvin dive number 3843, sample number RF 2a, December 2002. Sample taken with Bushmaster jr. from Riftia pachyptila aggregation with curved and "rusty" tubes due to iron oxide.

Description of adult female (Figs. 9–13). Carapace oval with concavity in anterior margin (Fig. 9A). Ventral margin with about 25 small teeth and minute spines (or serrations) between teeth. (Valves of holotype were immersed in glycerine and are now decalcified and without surface ornamentation, but valves had surface reticulations prior to immersion.)

Central Adductor Muscle Scars (Fig. 9A): About 6 oval scars.

Carapace Size: Length 0.54 mm, height 0.47 mm.

FIGURE 9. Polycopetta pax , new species, adult female, holotype, length 0.54 mm: A, complete specimen from right side, anterior to right; B, Bellonci Organ and left 1st antenna, mv; C, right 1st antenna, mv; D, Bellonci Organ and left 1st antenna (top, mv), and right 1st antenna (bottom, lv); E, left 2nd antenna, lv (nabs). (lv = lateral view; mv = medial view; nabs = not all bristles shown.)

FIGURE 10. Polycopetta pax , new species, adult female, holotype: A, left 1st antenna, lv; B, endopod left 2nd antenna, lv; C, protopod and exopod right 2nd antenna, lv; D, protopod and endopod right 2nd antenna, lv; E, articles 1–4 exopod right 2nd antenna, mv. (lv = lateral view; mv = medial view.).

First Antenna (Figs. 9B–D, 10A): Article 1 strongly tapered and distally lateral to article 2, with small lateral sclerotized crescent (with anterior spines) near dorsal edge at about midlength. Ventral edges of articles 1 and 2 joined by peculiar, complex, sclerotized structure (Fig. 10A). Article 2 with dorsal spines and long terminal dorsal bristle with few hairs and not separated from article 3 by suture. Inferred articles 3 and 4 not separated by sutures, but distal narrow part may represent article 4; article 3 with dorsal and ventral spines and with narrow spinous lateral ridge near ventral edge; article 4 with ventral spines. Inferred article 5 at right angle to article 4, and separated from it by suture; article 5 broad distally, with dorsal spines at midlength, and 1 short spinous dorsal bristle. Inferred article 6 short, bare, separated from article 5 by weak suture. Inferred article 7 small, with 2 long hirsute bristles. Inferred article 8 small, lateral to article 7, with 3 long hirsute bristles.

Second Antenna: Protopod bare (Fig. 10C,D). Exopod about ¾ length of protopod, with 9 articles (Figs. 9E, 10C); articles 1 to 8 with subequal, medial, natatory bristles about 3X length of stem; article 9 with 3 bristles (ventral bristle hirsute, about 2/3 length of bristle of article 1; dorsal bristles shorter (longer of these hirsute)). Medial bases of bristles of articles 1 to 8 with broad flange­like base (Fig. 10E). Article 1 with lateral spines along terminal margin. Endopod about ¾ length of exopod, with 3 articles without hairs or spines (Fig. 10B,D): article 1 without bristles; article 2 with 1 dorsal bristle with hairs near midlength, and 5 distal bristles (4 long, 1 shorter) with marginal hairs; article 3 with 4 bristles (3 long, 1 short) with marginal hairs, and with bare ventral lobe.

Mandible: Coxa endite bifurcate distally ( Fig. 11 B). Basis with 1 lateral bristle with long spines at midlength near base of exopod and 4 stout ventral bristles with long spines along distal ½. Endopod with 2 articles: article 1 with 3 ventral bristles (1 slender proximal bristle (bare or with few indistinct marginal hairs) with base slightly lateral to bases of 2 stouter spinous bristles), 2 long dorsal terminal bristles, and few long proximal ventral and distal dorsal hairs. Article 2 with 2 long terminal bristles with long spines at midlength (dorsal of the 2 bristles also with long spines at tip). Exopod interpreted to have 2 articles, but without suture separating articles ( Fig. 11 A,B): article 1 broad and with 1 terminal bare bristle; article 2 with proximal spines and funnel­like tip.

Maxilla (Maxillula): Precoxa endite with 5 bristles ( Fig. 12 A,D). Coxa with 2 endites (II, III) ( Fig. 11 C): proximal endite with 3 terminal bristles; distal endite with 2 terminal bristles. Ventral margin of coxa with 2 or 3 long bristles ( Figs.11 C, 12A). Basis: ventral margin with 2 long terminal bristles; dorsal half of basis with long backward projection; medial side of basis with long hairs near dorsal end of terminal margin ( Fig. 11 C). Endopod with 3 articles ( Figs. 11 C, 12A): article 1 with long distal ventral bristle; article 2 with 2 dorsal bristles and 1 ventral bristle adjacent and proximal to short triangular process; article 3 with 4 long bristles (not shown). Exopod with proximal end set well back from suture separating basis and article 1 of endopod ( Figs. 11 C, 12A,B); distal end with 8 long bristles ( Fig.12 C); dorsal margin with rows of hairs. Groups of intrinsic muscles present with insertions at proximal end of backward extension of basis ( Figs. 11 C, 12A); dorsal group extends into exopod, the other into endopod. Endopod of holotype at right angle to coxa.

Fifth Limb ( Fig. 12 E): Epipod with about 12 bristles. Precoxa and coxa not separated by suture, but indentation in dorsal margin indicates place of separation. Precoxa with short distal bristle. Coxa with long hairs, short proximal bristle, and terminal, spinous, triangular process. Basis: dorsal margin with 3 long hirsute bristles and few marginal spines; ventral margin with 2 distal bristles (1 long, 1 short), 1 long terminal bristle, and marginal spines. Exopod well­developed, with 4 terminal spinous bristles (3 long, 1 short). Endopod with 1 narrow article with short spinous terminal bristle and short adjacent terminal spine.

Furca ( Fig. 13 A): When holotype received all long claws missing from furca; 2 small unringed spine­like bristles present at posterior end of ventral margin of right lamella. Number of processes along ventral margin of each lamella indicates 6 long claws had been present.

Bellonci Organ (Fig. 9B,D): Spinous bristle divided at midlength.

Upper Lip ( Fig. 13 B): With few spines.

Gut Content: Brown particles, some round or disc­like, and a few fragments of tubular structures.

Eggs (Figs. 9A, 13A): Holotype with several unextruded eggs.

Comparisons. Three species of Polycopetta have been described previously: P. monneroni Chavtur 1979 and P. curva Chavtur 1979 from the vicinities of Japan and the Commander Islands at depths of 60 to 70 m ( Chavtur, 1981: 56), and P. bransfieldensis ( Hartmann, 1987) [transferred from Polycope by Chavtur, 1981] from Bransfield Strait, Antarctica, at a maximum depth of 420 m ( Hartmann, 1987:138–140). The Bellonci Organ of the new species P. pax differs from that of P. monneroni in being divided at midlength rather than distal to midlength. The carapace of P. p a x differs from that of P. c u r v a and P. bransfieldensis in having about 25 small teeth along the ventral margin of each valve compared to about 11 teeth along the anteroventral margin of P. c u r v a, and 9 teeth along the anteroventral margin of P. bransfieldensis . Having only a female P. pax in the present collection, male characters could not be compared with males of the two species described by Chavtur (1979:97).

Figures

FIGURE 11. Polycopetta pax, new species, adult female, holotype: A, right mandible (coxale endite missing) lv; B, left mandible, mv; C, right maxilla, mv. (lv = lateral view; mv = medial view.)

FIGURE 12. Polycopetta pax, new species, adult female, holotype: A, left maxilla, lv (nabs); B, right maxilla drawn on body, lv (nabs); C, exopod right maxilla, lv; D, precoxal endite I of maxilla, anterior to left; E, 5 th limb. (lv = lateral view; nabs = not all bristles shown.)

FIGURE 13. Polycopetta pax, new species, adult female, holotype: A, posterior of body from right side showing unextruded eggs (claws of furca missing); B, upper lip and esophagus.