"HOLOTYPE—USNM 127264, gravid female, length 2.70 mm. Valves and some appendages in alcohol, remaining appendages on slides.
TYPE-LOCALITY—Eltanin Cruise 7, station 480, Atlantic Quadrangle, Antarctic Ocean.
ETYMOLOGY—The specific name "tetrathrix" from the Greek "tetra" [ = four] and "thrix" [= hair] refers to the four bristles on the 2nd joint of the endopodite of the female 2nd antenna.
PARATYPES—USNM 127265, juvenile female, length 2.48 mm, height 1.47 mm; USNM 127269, 31 juveniles. Paratypes from same sample as holotype.
ADDITIONAL SPECIMENS—USNM 128506, juvenile female, length 2.19 mm, height 1.37 mm; USNM 128507, N-l male, USNM 128612, adult female; USNM 128613, 2 juveniles; USNM 135048a, 1 N-l male; USNM 135048b 1 N-2 male, length 1.63 mm, height 0.90 mm; USNM 136090, gravid female; USNM 138147, 1 adult female; USNM 138148, 10 adult females without eggs + 15 juveniles; USNM 138152, 1 adult female, length only 2.68 mm; USNM 138030, 1 juvenile. USNM 128506, 128507 from Eltanin Cruise 5, station 216; USNM 128612, 128613 from Vema Cruise 14, station V-14-25; USNM 135048a, 135048b, from Vema Cruise 17, station V-17-8A; USNM 136090 from Vema Cruise 18, station V- 18-27; USNM 138147, 138148 from Eltanin Cruise 7, station 475; USNM 138030 from Eltanin Cruise 5, station 216.
DIAGNOSIS OF FEMALE—Carapace with truncate posterior; length 1.92-2.78 mm (generally 2.61- 2.78 mm).
First antenna: 2nd joint without ventral bristle, but with 1 or 2 dorsal bristles and 1 lateral bristle.
Second antenna: 2nd endopodial joint with 4 bristles.
Mandible: Dorsal margin of basale with 5 bristles.
Seventh limb: Each limb with 26-33 bristles; 2 or 3 pegs present opposite comb.
Furca: Each lamella with 10 claws.
DESCRIPTION OF FEMALE—Carapace with prominent rostrum, broad incisur and truncate posterior; anterior corner of rostrum slightly rounded, inferior corner well rounded.
Ornamentation: Carapace smooth with bristles along anterior, ventral, and posterior margins, and sparsely distributed on lateral surface; faint reticulate structure visible in transmitted light.
Infold: Infold broad along anterior and posterior parts of shell and narrow ventrally; infold on rostrum with 25-29 bristles, some double and hirsute; 1 minute bristle present on infold posterior to incisur; anteroventral part of infold with about 15 striae and 16 to 18 bristles; no bristles present along middle part of ventral infold; posteroventral and posterior infold with numerous small bristles along raised list (about 80 bristles, many forming groups of 3); 4 to 7 scattered bristles present between list and posterior edge of shell; 5 or 6 bristles present on infold just within posterior edge of caudal process.
Selvage: Lamellar prolongation with marginal fringe present along anterior, ventral, and posterior margins; prolongation with typical segmentation present along rostrum and incisur; long bristles with bases on lateral side of prolongation present on prolongation below incisur.
Size: USNM 127264, gravid female, length 2.70 mm, height 1.87 mm; USNM 128612, length 2.61 mm, height 1.77 mm; USNM 136090, length 1.92 mm, height 1.14 mm; USNM 138147, length 2.78 mm, height 1.86 mm.
First antenna: 1st joint with spines forming clusters on lateral and medial surfaces; 2nd joint with numerous clusters of spines and 2 or 3 spinous bristles, 1 or 2 dorsal, 1 lateral; 3rd joint short with 3 spinous bristles, 2 dorsal, 1 ventral; 04th joint with 1 spinous dorsal bristle and 4 ventral bristles, 3 long stout, 1 shorter and slender, surface of joint without spines; 5th joint with few spines forming clusters on surface; sensory bristle of 5th joint with 3 marginal filaments and tip consisting of 5 long filaments; medial bristle of 6th joint one-half to three-fourths the length of sensory bristle of 5th joint. Seventh joint: abristle spinous about two-thirds length of sensory bristle, b-bristle with 1 proximal and 3 terminal filaments; c-bristle with 4 proximal and 5 terminal filaments. Eighth joint: d- and e-bristles long bare, slightly shorter than sensory bristle of 5th joint; f-bristle with 4 proximal and 5 terminal filaments; g-bristle with about 3 proximal and 5 terminal filaments.
Second antenna: Protopodite with abundant long slender hairs along dorsal margin and short spines forming clusters on dorsal part of medial surface; few spines also present on ventral margin. Endopodite 2-jointed: 1st joint with 6 bristles, 5 proximal, 1 distal; 2nd joint with 1 long and 2 short spinous ventral bristles and 1 long recurved bare terminal filament. Exopodite: 1st joint with short medial spine; bristle of 2nd joint reaching beyond 9th joint and with 6 ventral spines near middle; bristles of joints 3 to 5 unbroken, with few ventral spines near middle and without natatory hairs; bristles of joints 6 to 8 and 4 long bristles of 9th joint broken; 9th joint with 4 long, 1 medium, 2 short bristles, medium and short bristles with slender marginal spines; distal margins of joints 2-8 with comb of short spines; spines forming clusters present on medial surfaces of joints 2 to 6; small basal spines present on joints 2 to 8, spine on 8th joint about three-fourths length of 9th joint.
Mandible: Coxale with spines forming clusters on surface; endite spinous, pectinate, with bifurcate tip; short slender bristle present near base of endite. Basale: medial surface with 6 short proximal bristles, 3 stout pectinate, 3 slender spinous; lateral surface with 5 short spinous bristles forming row near ventral margin; ventral margin with 2 or 3 medium, spinous, distal bristles; dorsal margin with 5 long spinous bristles, 1 near middle, 2 distal to middle and 2 terminal; lateral and medial surfaces of joint with numerous spines forming clusters. Exopodite three-fourths length of dorsal margin of 1st endopodite joint, with 2 terminal bristles (inner bristle slightly longer than outer bristle, both with marginal spines). Endopodite: 1st joint with 4 spinous ventral bristles, and few short terminal spines on dorsal corner; medial and lateral surfaces of 2nd joint with spines forming clusters; dorsal margin with spinous bristles in 2 groups, proximal group with 2 or 3 bristles, distal group with 6; ventral margin with 2 groups of spinous bristles, each with 3 bristles; end joint with 3 claws and 4 spinous bristles, dorsal short claw bare, other 2 with few small teeth along middle of ventral margin.
Maxilla: Precoxale and coxale with fringe of hairs along anterior margin; 1st endite with 10 spinous bristles; 2nd endite with about 6 bristles; 3rd endite with about 8 terminal bristles and 2 slender proximal bristles on lateral side of coxale; coxale with stout plumose bristle; exopodite with 1 short proximal bristle and 2 long terminal bristles; distal margin of basale with 3 long bristles (inner bristle spinous, 2 outer bristles with few short spines and with bases close together on medial surface near anterior margin). Endopodite: 1st joint divided by faint suture into 2 parts; 1 long spinous medial bristle present on distal margin of proximal part; anterior margin of 1st joint with long hairs and 1 spinous a-bristle; distal margin with 4 6-bristles, bare or with few spines; end joint with 3 bare a-bristles, 2 b-bristles (anterior b-bristles spinous, inner bristle clawlike, pectinate), 3 bare c-bristles, 3 pectinate d-bristles (2 anterior d-bristles clawlike).
Fifth limb: Epipodial appendage with 54 to 67 bristles; 1st endite with 7 bristles; 2nd endite with about 9 bristles; 3rd endite with about 8 bristles. Endopodite: anterior distal margin of 1st joint with 2 bristles near middle; protuberance in front of main tooth consisting of 2 teeth, proximal tooth about half length of distal tooth; main tooth consisting of 3 pectinate teeth followed by a smooth spine and 1 spinous bristle; large triangular tooth of 2nd joint with 1 or 2 nodes on inner margin; outer margin of tooth faintly serrate; posterior surface of joint with usual group of 3 bristles, all with spines, 1 spinous c-bristle, and 1 small spinous bristle near outer corner of large tooth; inner lobe of 3rd joint with 3 spinous bristles, outer lobe with 2; 4th + 5th joints hirsute with 6 spinous bristles.
Sixth limb: 3 short spinous bristles present in place of epipodial appendage; 1st endite with 3 spinous bristles (1 long terminal, 2 short medial); 2nd endite with 4 spinous bristles (3 long terminal, 1 short proximal and medial); 3rd endite with 9 or 10 spinous bristles (8 or 9 long terminal, 1 short proximal and medial); 4th endite with 9 spinous bristles (8 long terminal, 1 short proximal and medial); end joint with 27 to 30 bristles of which posterior 7 to 9 (or more) are plumose, others spinous; both surfaces of limb with long hairs forming clusters.
Seventh limb: Limb with 26-33 bristles (1 small specimen from Vema station V-17-27 with 19-21 bristles), 5 in distal group (3 + 2), 21-28 in proximal group, each bristle with 5 to 8 bells, some bristles with few marginal spines distally; terminal comb with 10-13 alate teeth; 2 or 3 fairly long, tapering, closely spaced pegs present opposite comb.
Furca: Each lamella with 10 claws; claws 1 to 4 primary, claws 5 to 10 secondary; hairs present medially at bases of claws and following last claw.
Eyes and rod-shaped organ: Lateral eyes small with 2 or 3 ommatidia. Medial eye large, pigmented. Rod-shaped organ elongate, 1-jointed with rounded tip.
Upper lip: Lip hirsute ventrally with several spines on anterior tip.
Brushlike organ: Organ consisting of about 8 minute bristles above genitalia.
Posterior of body: Long hairs present near middle of posterior margin.
Anterior of body: Single large triangular process present on anterior above upper lip.
Eggs: 6 eggs present in brood chamber of USNM 127264; USNM 128612 with 8 eggs.
Parasites: Cuplike stemmed protistans abundant on appendages. Clusters of ovoid protistans on USNM 128506.
DESCRIPTION OF N—1 MALE—Carapace shape similar to that of adult female. Size: USNM 128507, length 2.01 mm, height 1.19 mm; USNM 135048a, length 1.97 mm, height 1.32 mm.
Second antenna: Endopodite 3- jointed: 1st joint with 4 bristles, 2nd joint elongate with 3 ventral bristles; 4th joint elongate with 1 long proximal bristle and 2 short terminal bristles.
Mandible: Dorsal margin of basale with 5 bristles.
Seventh limb: Well developed.
Lateral eye: Well developed with about 20 small ommatidia.
Parasites: Cuplike stemmed protistans on appendages.
DESCRIPTION OF N-2 MALE (USNM 135048b)—Carapace similar in shape to
N—1 male except caudal process more rounded. Size: 1.63 mm, height 0.90 mm.
Second antenna: Endopodite 3-jointed: 1st joint with 4 bristles; 2nd joint elongate with 2 ventral bristles; 3rd joint elongate with 1 long proximal bristle and 1 short terminal process.
Mandible: Dorsal margin of basale with 5 bristles.
Seventh limb: Well developed.
Lateral eye: Well developed with many minute indistinct ommatidia.
Parasites: Cuplike stemmed protistans abundant on appendages.
DISCUSSION OF SPECIMEN (USNM 136090) FROM Vema STATION V-18-27—A single gravid female of the species in this sample differed from specimens from elsewhere in being smaller (length 1.92 mm, height 1.14 mm) and in having fewer bristles on the 7th limb (19 to 21 with 5 distal and 14 to 16 proximal).
COMPARISONS—The absence of a ventral bristle on the 2nd joint of the 1st antenna, and the presence of 4 bristles on the 2nd joint of the endopodite of the 2nd antenna, 5 bristles on the dorsal margin of the mandibular basale, and the abundance of bristles on the 7th limb, which bears 2 or 3 pegs, distinguishes this species from those previously described.
DISTRIBUTION—This species was collected only in the American Quadrant in Antarctic, Subantarctic, and Subantarctic-to-35°S regions at depths of 566 to 3382 m." (Kornicker 1975, p.255-262)
Philomedes tetrathrix is een mosselkreeftjessoort uit de familie van de Philomedidae.[1] De wetenschappelijke naam van de soort is voor het eerst geldig gepubliceerd in 1975 door Kornicker.
Bronnen, noten en/of referenties
