Halocypretta profunda, Angel, Martin V., 2013

Angel, Martin V., 2013, Planktonic ostracods (Myodocopa: Halocyprididae) from abyssopelagic depths in the Atlantic, North Pacific and Gulf of Oman: Chavturia abyssopelagica (n. gen., n. sp.), Halocypretta profunda (n. sp.), Halocypretta parvirostrata Chavtur and Stovbun, 2008 and Halocypretta striata (Müller, 1906), Zootaxa 3709 (5), pp. 401-431 : 411-415

Halocypretta profunda , n. sp.

( Figs 7–10 )

Type locality. Polarstern station MOC10#2 net#1; 11° 41’N; 20° 45.13’W, depth 4795– 4000 m; 8th November 2007.

Type material. Holotype: male, dissected on slides, NHM registration numbers 2012.1109.

Paratypes: 14 specimens, NHM registration numbers 2012.1110 –2012.1122 (details see appendix).

Etymology. The specific name is derived from the latin for deep.

Male (Holotype).

Carapace ( Fig. 7 A, B). Carapace length 3.16 mm, height 1.92 mm (60.8 % CL); the breadth could not be measured accurately because the specimen was splayed, but it was estimated to be about half the length. There is an overall sculpture of concentric striations and fine pits. The rostra, as measured from the anterior end of the hinge between the valves and their pointed anterior tips, are quite long (18.4 % CL). The incisure depths are about half the lengths of the rostra. On the lower margin of the incisure is the flange which is one of the characteristic features of the genus. The shoulder vaults are slightly humped with a shallow sulcus between them. The posterior dorsal corner is a rounded right angle. The left asymmetrical gland opens just anterior to the posterior end of the hinge between the valves and ~ 0.2 mm anterior to the posterior margin. The right gland opens on the posterior margin slightly above the posterior ventral corner.

Frontal organ ( Fig. 7 C). Before dissection the capitulum was clearly to be seen projecting out between the two rostra. The stem is very short (6.6 % CL) and only a little longer than the first segment of the first antenna. It is divided from the capitulum by a clear suture. The capitulum is long (22.4 % CL), sinuate, slightly down-turned and has a rounded tip.

First antenna ( Fig. 7 C). The limb is five-segmented but is angled down at the joint between the second and third segment. Its length (not accounting for the curvature) is 14.1 % CL. There is a finely spinose curved seta on the dorsal corner, which projects anteriorly beyond the end of the limb. There is a dense covering of coarse setules over the distal margin of the second segment around the base of the dorsal seta. Within the first segment there are several dark pigment granules. The two setae carried on the fourth segment (a- and b- setae) are similar in length to the shorter two terminal setae (c- and d- setae) on the fifth segment (32.9 % CL). The longest terminal seta on the fifth segment (e-seta) is double the lengths of the shorter setae (67.5 % CL) and is sparsely lined with fine setules along its leading edge.

Second antenna ( Fig. 7 D–F). The protopodite is quite short (31.9 % CL) and the first segment of the endopodite is the same length. The segment is slim and slightly curved with a terminal seta that curves around the articulation with the second segment. The remaining segments of the exopodite that carry the swimming setae are 10.2 % CL. The swimming setae are long; the longest being nearly 70 % CL. The first endopodite segment is rectangular and the a- and b- setae are curved and finely spinose ( Fig. 7 E). The second endopodite segment is short and carries the hook appendage with three thin-walled seta attached to its base (32.2 % CL). The hook appendages on the left and right limbs are quite similar; both curve through 180° and end in a ridged, bluntly pointed tip carrying two thorn-like points. The appendage on the right endopodite is only slightly larger than the one on the left ( Fig. 7 E, F). The two longest setae (f- and g- setae) on the second endopodite segment are very long (55.2 % CL and 69.7 % CL respectively).

Labrum. The labrum has a deep narrow rounded cleft and the double row of about 22 flanking filaments. These filaments are unusually stout and their tips are either bifid or trifid.

Mandible ( Figs 7 G, 8A, C). The subterminal seta on the first endopodite segment is finely spinose and only extends to the end of the second segment. On the ventral side of the first segment are four setae, one long and three slimmer and shorter. The second segment has three terminal dorsal setae: one long and claw-like, the other two slim and shorter. On the ventral terminal corner are two long setae. The terminal segment has the usual seven setae, four of which are claw-like. The longest of these setae is 20.7 % CL. The toothed edge of the basale has two bare spine-like teeth: one sharply pointed the other blunt, and six cutting teeth, the first of which is slightly offset. There is also an inner tooth which is relatively tall and narrow. The basale also carries the usual two pairs of seta near the toothed edge and another shorter seta near the articulation with the endopodite ( Figs 7 G, 8A). Along the distal margin close to the articulation is a line of quite long coarse setules. The exopodite is represented by a single stout plumose seta inserted sub-terminally on the outer edge of the basale.

The toothed edge of the coxale consists of a broad tooth and seven more rather rounded teeth that diminish in size along the list ( Fig. 8 C). The outer list consists of two large curved teeth and 14–16 smaller ones and the inner list consists of 19 teeth of assorted sizes.

Maxilla ( Fig. 8 B). One basal seta. On the first endopodite segment are three anterior setae, a single lateral seta, and posteriorly a proximal group of five setae and a single distal seta. Terminally on the first segment there is a patch of short stubby spines. The second terminal segment has the usual three terminal claw setae, subtended on the inner surface by a pair of slim setae.

Fifth limb ( Fig. 9 A). The epipodial formula is 5 + 5 + 4. Ventrally the basale has three groups of four, three and two plumose setae (not all shown in Fig. 8 D). There are two lateral setae and dorsally a moderately long plumose seta and a longer subterminal seta. The first segment has two medial ventral setae and a single dorsal seta; all of these setae extend well beyond the end of the segment. The dorsal two of the terminal setae are marginally longer than the penultimate segment and the central seta is the longest (10.3 % CL).

Sixth limb ( Fig. 8 E). The epipodial formula is 7 + 5 + 5. Ventrally the basale has a proximal pair of plumose setae and a distal group of three more plumose setae. The lateral seta illustrated in Fig. 8 E is probably on the basale whose margin was indistinct. Dorsally there is a long plumose seta and a relatively short bare seta that is the vestigial exopodite. The second segment has only a subterminal ventral seta. The third segment has a medial seta both ventrally and dorsally. The terminal segment has the usual three setae; the central one is the longest 13.8 % CL.

Copulatory appendage ( Fig. 9 B, C). The appendage is a slim rectangle with three oblique muscles and a blunt end. Its length is 25.3 % CL.

Caudal furca. There are eight pairs of caudal furca spines, and there is an unpaired seta. The longest pair of claws is missing on the holotype. The other claw setae are relatively straight with pointed tips that are slightly curved. The claw lengths do not diminish very much along the furca. There are fine secondary spines on all the remaining claws. Between the lamellae of the furca is a dense covering of setules.

Female.

Carapace ( Fig. 10 A, B). The female paratype from the same sample as the male holotype has a length of 3.44 mm, and the height is 66.3 % CL and the breadth is 67.4 % CL. The carapace was drawn before dissection but disintegrated as it was being mounted. The rostrum is down-turned and has a small terminal spine. The shoulder vaults are humped. The incisure is shallow and there is a flange on its lower margin which is a typical feature of the genus. The asymmetrical glands are positioned in the same positions as in the male. There is a clear pattern of concentric striae with a covering of small oval pits.

Frontal organ ( Fig. 10 C). As in the male the stem is divided from the capitulum by a clear septum. It is short (6.3 % CL) and only a little longer than the first segment of the first antenna. The capitulum is long (20.8 % CL), bare and slightly sinuate with a bare rounded end. As in the male before dissection the capitulum clearly to be seen poking out anteriorly below the rostra.

First antenna ( Fig. 10 C). As in the male the limb is five-segmented and arches ventrally at the articulation between the second and third segments. The terminal curved dorsal seta on the second segment (3.9 % CL) is finely spinose and relatively a little shorter than in the male. Around the base of this seta there is a dense covering of short setules. The longest terminal seta, the e-seta, is 69.4 % CL and over double the lengths of the other four sensory setae (27–30 % CL).

Second antenna ( Fig. 10 D, F). The protopodite is relatively short (27.5 % CL). In the dissected specimen, the exopodite segments are damaged. The first segment is slightly longer than the protopodite and carries a terminal seta. The first endopodite segment is approximately rectangular and the a- and b- setae are long, curved and finely spinose ( Fig. 10 F). The five terminal setae are quite long; the g-seta is 64.9 % CL, f- seta is 52.9 % CL and the h-, i- and j- setae are 28.7 % CL.

Labrum. Similar to that of the male.

Mandible. Similar to that of the male. The longest terminal seta on the endopodite is 22.7 % CL.

Maxilla. Similar to that of the male.

Fifth limb. The setation is the same as in the male. The longest of the three terminal setae is the dorsal one (10.3 % CL).

Sixth limb ( Fig. 8 D). There is little sexual dimorphism in the sixth limb. The pattern of setation is the same and the central terminal seta is the longest (13.9 % CL).

Caudal furca ( Fig. 10 E). The caudal furca has eight pairs of claw setae and there is an unpaired seta. The lengths of first, longest pair of claws are 16.6 % CL. Between the lamellae is a dense covering of setules.

Figures

FIGURE 7. Halocypretta profunda, n. sp. Male. Holotype. A. Carapace, lateral view; B. Carapace, ventral view; C. Frontal organ and first antenna; D. Second antenna; E. Hook appendage of right second antenna; F. Hook appendage of left second antenna; G. Toothed edge of coxale of mandible. Scales in millimetres.

FIGURE 8. Halocypretta profunda, n. sp. Male. Holotype. A. Mandible; B. Maxilla; C. Toothlists of the mandible; D. Sixth limb of female; E. Sixth limb of male. Scales in millimetres.

FIGURE 9. Halocypretta profunda, n. sp. Male. Holotype. A. Fifth limb; B. Copulatory appendage; C. Tip of copulatory appendage. Scales in millimetres.

FIGURE 10. Halocypretta profunda, n. sp. Female. Paratype. A. Carapace, lateral view; B. Carapace, ventral view; C. Frontal organ and first antenna; D. Second antenna (exopodite broken); E. Caudal furca; F. Second antenna, endopodite. Scales in millimetres.