Metapolycope hartmanni Kornicker & Morkhoven 1976

Metapolycope hartmanni

HOLOTYPE.—USNM 151164, adult female.



TYPE-LOCALITY.—Atlantis II, cruise 31, station 167.

ETYMOLOGY.—The species is named for Dr. Gerd Hartmann, who has done much work on the Cladocopa.

ALLOTYPE.—USNM 151163, adult male.

PARATYPES.—USNM 152857, 1 adult male; USNM 152858, 1 A–1 male; USNM 152859, 1 adult female; USNM 152860, 1 adult male; USNM 152861, 1 adult male; USNM 152862, 7 juveniles; USNM 152864, 1 right valve (?).

LOCALITIES.—USNM 151163, 152859, 152860, 152861; 152864 from type-locality; USNM 152857, 152858, 152862, from Atlantis II, cruise 31, station 169 A.

DISTRIBUTION.—Western part of South Atlantic at depths of 587–1007 m.

DESCRIPTION OF ADULT FEMALE (Figures 2–5, 20a).—Except for slight anterior concavity, carapace round in lateral view (Figures 2a,f, 4a); each valve more-or-less evenly rounded in anterior view (Figure 2b), posterior view (Figure 2d), dorsal view (Figure 2c), and in ventral view (Figure 2e): carapace widest in middle.

Ornamentation: Carapace reticulate except in middle part of valve, in area of central adductor muscle scars (Figure 2a); 3 or 4 continuous more-or-less straight ridges present just within valve edge on anterodorsal margin; in vicinity of anterior concavity the ridges become discontinuous forming short segments (Figures 2a,b,e,f, 3b,j); lower end of each segment with oblique or vertical ridge forming reticulations along anteroventral margin and giving valve serrate appearance in lateral view (Figures 2a, 3b); reticulations absent along concavity in anterior margin, and the anterodorsal and posterior margins (Figures 2b–d, f, 3e).

Pores: 2 types of pores present: small open pores without bristles (Figure 3c–e,g,j), and noded open pores containing 1 or 2 bristles (Figure 3a, e–i).

Selvage: Outer edge of lamellar prolongation of selvage along ventral margin of valve fringed (Figure 3k, l.)

Central adductor muscle scar (Figure 4a): Consisting of central ovoid scar and 7 additional scars forming half of a rosette with convex part of rosette oriented posteriad; an 8th slender crescentic muscle scar, less visible than others, present anterior to lowermost scar.

Infold: Wide infold present except along hinge area.

Hinge: Short, straight; position of soft parts suggests that hinge has posterodorsal position when living animal swims.

Size: USNM 151164, length 1.00 mm, height 0.96 mm; USNM 152859, length 1.07 mm, height 1.00 mm.

First antenna (Figure 4a,b): Limb with 5 distinct joints; 1st joint short spinous, with long dorsal bristle with long proximal and short distal spines; 2nd joint long, spinous, with distal spinous ventral bristle, and 2 dorsal processes, each with spinous bristle; 3rd joint very short, bare; 4th joint elongate with 3 short distal bristles, 2 ventral, 1 dorsal; 5th joint short with 5 long bristles having rings and long spines proximally.

Second antenna: Protopodite triangular (Figure 4c) with cluster of long hairs distal to middle of dorsal margin and extending onto medial and lateral sides; medial surface of protopodite with closely spaced spines forming 2 rows proximal to endopodite. Exopodite 9-jointed; 1st joint with spines along ventral margin; joints 1–8 with long bristles having rings on proximal part; ringed section with proximal spines and distal natatory hairs; 9th joint with 3 bristles: 1 long similar to bristles on other joints, 1 medium with proximal spines but no natatory hairs, and 1 short with short marginal spines; joints 2–8 with short spines forming row along distal margin. Endopodite 3-jointed (Figure 4d): 1st joint long with 1 spinous terminal bristle on ventral margin; 2nd joint with 1 ventral bristle with long proximal and short distal spines, and 5 long terminal bristles with proximal rings and spines; 3rd joint with 4 long bristles with proximal widely spaced spines; bristles of endopodite without closely spaced long natatory hairs present on exopodite; suture between 2nd and 3rd joints not well defined.

Mandible (Figure 4e): Coxale endite with large weak inner tooth with fringed margins and large strong outer tooth with smooth margins; 2 short teeth and 1 short spine present between inner and outer teeth; distal half of posterior margin of endite knurled. Basale with 4 spinous ventral bristles and 1 short, spinous, distal, dorsal bristle. Exopodite with 2 spinous bristles. Endopodite 2-jointed: medial surface of 1st joint hirsute; ventral margin with 3 spinous bristles, 2 proximal, 1 distal; dorsal margin with 3 spinous bristles, 1 proximal, 2 distal; end joint with 2 bristles with long proximal and short distal spines; dorsal bristle of end joint clawlike.

Maxilla (Figure 4f):Suture separating precoxale and coxale not well defined; both joints with total of 10 or more bristles. Basale: ventral margin with 3 spinous bristles; dorsal margin with large proximal hump to which is attached internally a muscle extending into exopodite. Exopodite 1-jointed with 9 bristles, most with spines near middle. Endopodite 3-jointed: 1st joint with 2 long spinous bristles; 2nd joint with 4 terminal ventral bristles and 1 dorsal bristle (dorsal bristle missing on both limbs of USNM 151164 but represented by hole); end joint with 4 bristles.

Fifth limb (Figure 4g): Epipodial appendage with 16 hirsute bristles; coxale hirsute, with 10 bristles; basale with 9 bristles (3 medial bristles not shown in Figure 4g); exopodite without hairs, with 4 terminal bristles; endopodite larger than exopodite, hirsute, with 6 terminal bristles. (Interpretation of which distal lobe is the exopodite and which the endopodite is based on the description of Polycope setifera Skogsberg, 1920, in which he stated (p. 769) that the exopodite of the fifth limb is bare and the endopodite hirsute; additional study is necessary to verify this interpretation.)

Furca (Figure 4j): Each lamella with 7 slightly curved claws; claws decreasing in length proximally along lamella; each claw with minute spines on lateral surface proximal to long spines along posterior margin, and few short hairs along anterior margin; posterior spines longer on shorter claws and decrease in length distally along claw; except between claws 6 and 7, a triangular process present anterior to claw 1, between all claws, and following claw 7; processes bear short terminal spines: lateral side of each lamella with short spines forming 4 rows near anterior margin; each row of spines parallel to ventral margin of lamella; unpaired bristle with short spines along anterior margin present posterior to claw 7 and about same length as claw.

Upper lip: Helmet shaped, spinous, with indication of glandular openings in anteroventral corner (Figures 4i, 5).

Head region: 2 spinous bristles present in head region posterior to attachment of 1st antennae (Figure 4c,i,h); long hairs forming cluster present posterior to bristles.

Posterior of body (Figure 4j): With 7–8 (only 5 distinct) transverse segments with short spines forming row near distal margin of each segment; 5th segment from furca with cluster of very long hairs or spines on posterior corner. (Posterior segments appear to be surface features similar to those on thaumatocyprids, and are not true segments such as those on platycopids.)

DESCRIPTION OF ADULT MALE (Figures 6–11, 14b, 20b.)—Reticulations of carapace more evident than on female, especially in vicinity of central adductor muscle scar, which appears slightly raised in SEM photographs (Figure 6b); carapace otherwise similar to that of female (Figures 6–10, 11a).

Size: Slightly smaller than female; USNM 151163, length 0.91 mm, height 0.92 mm; USNM 152860, length 0.92 mm, height 0.87 mm; USNM 152861, length 0.97 mm, height 0.95 mm; USNM 152857, length 0.94 mm, height 0.89 mm.

First antenna (Figure 11b): Lateral side of 1st joint with elongate sensory process; proximal edge of tip of process folded over proximal part giving appearance that sensory process is 2-jointed; except for sensory process, 1st joint, and also 2nd and 3rd joints, similar to those of female; 4th joint with 1 spinous dorsal bristle and 4 ventral bristles, 2 with marginal spines and 2 with 7–8 minute discs; end joint with 4 long bristles with rings and widely spaced spines proximally. (The end joint could be interpreted as consisting of 2 minute joints, each with 2 bristles.).

Second antenna: Protopodite and exopodite similar to those of female (Figure 11b). Endopodite 3-jointed (Figure 11d): 1st joint with short spines along ventral margin and 2 distal bristles (inner of these with bulbous base); 2nd joint with 1 long and 2 short bristles near ventral margin and 6 dorsal and terminal bristles with widely spaced spines proximally; 3rd joint with sclerotized hook-shaped clasping organ and about 4 bristles with widely spaced spines proximally.

Mandible: Similar to that of female (Figure 11e).

Maxilla (Figure 11f): Precoxale and coxale with total of 16–17 bristles. Basale, exopodite, and endopodite similar to those on female maxilla.

Fifth limb (Figure 11g): Epipodial appendage with about 15 hirsute bristles; coxale hirsute with 11 bristles; basale with 9 bristles (3 medial bristles not shown in Figure 11g); exopodite and endopodite similar to those on female 5th limb.

Furca (Figure 11h,i,k), upper lip, head region (Figure 11l), posterior of body (Figure 11k): Similar to those of female.

Copulatory organ: Consisting of inner setigerous, elongate, pointed, bristlelike process and outer elongate, curved process with sclerotized pointed process at tip (Figure 11i,j).

DESCRIPTION OF A–1 MALE (Figures 12, 13, 14a). —Carapace similar to that of adult male. Size: USNM 152858, length 0.93 mm, height 0.89 mm.

First antenna: Similar to that of adult male except 4th joint with 2 sausage-shaped bristles in place of bristles with discs (Figures 13a, 14a), and 5th joint with 5 long bristles.

Second antenna: Protopodite (Figure 13a) and exopodite similar to those of adult male; endopodite 3-jointed: 1st joint with few hairs along ventral margin and 2 spinous terminal, ventral bristles; 2nd joint with 1 spinous, terminal, ventral bristle and 6 terminal dorsal bristles; 3rd joint with 4 terminal bristles.

Mandible, maxilla, 5th limb, upper lip, head region, posterior of body: Similar to those of adult male and female.

Furca: Similar to that of adult male except with only 6 claws.

Copulatory organ: None present.

Note concerning sex: USNM 152858 is considered to be an A–1 male because of the 2 sausage-shaped bristles on the 4th joint of the 1st antenna, which are interpreted to be the forerunner of bristles with discs that appear on the adult male. Because USNM 152858 is about the same size as the adult males, and because not even a vestigal copulatory organ was observed on the specimen, the interpretation of the specimen as a male is considered tentative.

DESCRIPTION OF A–2 FEMALE.—Carapace similar to that of adult female except smaller. Size: USNM 152862A, length 0.86 mm, height 0.79 mm; USNM 152862B, length 0.85 mm, height 0.81 mm.

First and 2nd antennae: Similar to those of adult female and with same number of bristles on each joint.

Mandible, maxilla, 5th limb, upper lip, head region, posterior of body: Not examined in detail, but similar to those of adult female.

Furca: Each lamella with only 5 claws, otherwise similar to lamellae of adult female.

DESCRIPTION OF A–2 MALE.—Carapace similar to that of A–1 male except smaller. Size: USNM 152862C, length 0.84 mm, height 0.81 mm: USNM 152862D, length 0.83 mm, height 0.81 mm.

First antenna: 1st, 2nd, 3rd, and 5th joints similar to those of A–1 male; 4th joint with 1 spinous dorsal bristle and 3 short ventral bristles.

Mandible, maxilla, 5th limb, upper lip, head region, posterior of body: Not examined in detail but similar to those of A–1 male.

Furca: Each lamella with only 5 claws, otherwise similar to lamellae of A–1 male.

Copulatory organ: Not observed.

SEXUAL DIMORPHISM.—The carapace of the male is slightly smaller than that of the female, and the ornamentation is more distinct, especially in the central part of each valve, near the central adductor muscle attachments. The 4th joint of the 1st antenna of the male bears more bristles than on the female, as follows:

Developmental stage Female Male

A–2 2 3

A–1 no data 4 (2 sausage-shaped)

Adult 2 4 (2 with discs)

The 5th joint of the 1st antenna bears 5 bristles on the adult female but only 4 on the adult male. The same number of bristles (5) is present on the 5th joint of the A–2 instar of both sexes.

The 1st joint of the endopodite of the 2nd antenna of the adult male bears short spines along the ventral margin; the female has hairs in this location. Also, the female has only 1 bristle on the 1st joint, whereas, the male has 2. The 2nd joint of the adult male bears 3 ventral and 6 terminal bristles, whereas, this joint of the adult female bears only 1 ventral and 5 terminal bristles. The 3rd joint of the adult male bears a sclerotized, hooklike clasper that is absent on the female.

ONTOGENY.—All appendages are present on the A–2 instar, which is the youngest stage in the collection. The mandible, maxilla, and 5th limb, although not examined in detail at each stage, appear just as well developed in the A–2 instar as in the adult for both sexes. The number of furcal claws increases by one at each stage of development, from 5 on the A–2 instar to 7 on the adult. The female 1st and 2nd antennae are as fully developed in the A–2 instar as in the adult. The 1st antenna of the A–2 male bears 3 short ventral bristles on the 4th joint. The number increases to 4 on the A–1 instar, and 2 of these are sausage shaped. The 2 sausage-shaped bristles develop into bristles with small discs on the adult. The 5th joint of the 1st antenna of the A–2 male instar bears 5 long bristles. The number decreases to 4 on the A–1 male and on the adult male. The male copulatory organ was observed only on the adult.

KEY TO DEVELOPMENTAL STAGES