Skogsbergia iota Kornicker 1992

Skogsbergia iota

ETYMOLOGY.—From the Greek iota (anything very small), in reference to small lateral eyes of the species.

HOLOTYPE.—MNHN Os 438, 1 undissected ovigerous female.

TYPE LOCALITY.—Sta 124-S, 12 Apr 1977, Mozambique Channel, SE Glorioso Islands, 11°32′06″S, 47°23′06″E, 24 m.

PARATYPES.—Sta 8-DR: USNM 193746, 1 adult male in alcohol. Sta 124-S: USNM 193739, 1 ovigerous female on slide and in alcohol; USNM 193741, 1 adult male on slide and in alcohol; USNM 193743, 4 ovigerous females in alcohol; USNM 193744, 6 adult males in alcohol; 209 specimens in alcohol including adult males and females and juveniles.

DISTRIBUTION.—Sta 8-DR, W Glorioso Islands, depth 250 m. Sta 124-S, Mozambique Channel, SE Glorioso Islands, depth 24 m. Known depth range 24–250 m.

DESCRIPTION OF ADULT FEMALE (Figures 35–37).—Carapace elongate with convex ventral and dorsal margins and broad caudal process delimited from margin of valve dorsal to caudal process by obtuse angle (Figure 35a); anterior edge of rostrum only slightly convex and with minute lateral projection on tip reaching past valve edge (Figure 35d); narrow line extending from inner end of incisur to anteroventral comer of valve (Figure 35a). Surface smooth.

Infold: Rostral infold with 8 bristles forming outer row, 6 bristles proximal to outer row, 2 closely spaced bristles near inner edge of incisur, and 1 short bristle proximal to inner end of incisur (Figure 35d). Narrow list extending from anteroventral infold, continuing along ventral margin of valve, and then broadening to form wide shelf anterior to caudal process; anteroventral list and anterior end of ventral list with about 32 bristles forming row (only 3 anterior bristles shown in Figure 35d); middle part of ventral infold with 2 or 3 bristles. Broad list at anterior end of caudal process with about 20 protuberances along posterior edge, numerous pore canals perpendicular to edge (Figure 35b,c), and about 45 minute structures forming bead-like row beneath flat surface of broad list at midwidth (not shown).

Selvage: Lamellar prolongation present along anterior and ventral margin, broadest and striated along dorsal edge of incisur, divided at inner end of incisur, and absent along dorsal half of caudal process. Along anterior half of ventral margin prolongation double, with proximal layer about width of total width of both layers and with serrate outer edge.

Central Adductor Muscle Attachments (Figure 35a): Comprising both elongate and ovoid attachments (not all shown).

Carapace Size: MNHN Os 438, holotype, length 1.20 mm, height 0.71 mm. USNM 193739, length 1.21 mm, height 0.72 mm. USNM 193743, 4 specimens: length 1.21 mm, height 0.72 mm; length 1.21 mm, height 0.77 mm; length 1.18 mm, height 0.72 mm; length 1.20 mm, height 0.72 mm.

First Antenna (Figure 35e,f): 1st joint bare. 2nd joint with indistinct minute spines forming few short rows along dorsal margin. 3rd joint short on medial side and longer on lateral side, with 2 short spinous bristles (1 ventral terminal, 1 dorsal with base proximal to midlength). 4th joint with 2 short spinous terminal bristles (1 ventral, 1 dorsal). Sensory bristle of 5th joint with 9 long filaments followed by 2 shorter and slenderer filaments and 1 small subterminal filament. 6th joint with short spinous medial bristle. 7th joint: a-bristle spinous, about same length as bristle of 6th joint; b-bristle 2 length of a-bristle, with 5 short marginal filaments, most with few minute marginal spines; c-bristle (not shown) longer than sensory bristle of 5th joint, with about 9 short filaments, some with few marginal spines. 8th joint: d- and e-bristles (not shown) slightly longer than b-bristle, bare with blunt tips; f- and g-bristles (not shown) similar to c-bristle.

Second Antenna: Protopodite with spinous distal medial bristle (Figure 36a,b). Endopodite single jointed, with 1 or 2 long and 2 short bristles and 1 very long terminal filament (filament on small protuberance that could be interpreted to be a 2nd joint) (Figure 36a,b). Exopodite: bristle of 2nd joint reaching just past 9th joint, aberrant on right limb of USNM 193739 (bristle bare except for subterminal spine), and on left limb bristle with 7 stout ventral spines in addition to subterminal spine; bristles of joints 3–8 with natatory hairs and slender spear-like spines; 9th joint with 3 (aberrance) or 4 bristles (2 long with hairs and spines, 1 medium, 0 or 1 short); joints 2–8 with basal spines increasing in length on distal joints (spine of 2nd joint minute, spine of 8th joint reaching just past distal end of 9th joint); lateral spine of 9th joint about same length as joint; joints 3–7 or 8 with indistinct minute spines forming row along distal edge.

Mandible: Coxale endite well developed, spinous, with 2 stout terminal spines and small peg between them; small proximal bristle present near base (coxale not shown). Basale: ventral margin with 3 small a-bristles (Figure 36d) (left limb of USNM 193739 aberrant in having only 1 a-bristle, but small socket present where a-bristle present on other limb (Figure 36c)), 1 small b-bristle with base on lateral side of joint, minute medial peg proximal to 2 short c-bristles (1 c-bristle absent on left limb of USNM 193739 but empty socket shows where bristle had been (Figure 36d)), and 1 long spinous d-brisle; dorsal margin with 1 bristle proximal to joint midlength and 2 terminal bristles. Exopodite reaching just past midlength of dorsal margin of 1st endopodial joint, with 2 bristles (distal about length of proximal). 1st endopodial joint with 4 ventral bristles (1 minute, 1 short, 2 long). 2nd endopodial joint: ventral margin with distal pointed bristles forming 3 groups of 1, 1, and 2 bristles; dorsal margin with 4 long bristles, 2 medium bristles (1 proximal and 1 distal to long bristles), 1 short bristle distal to long bristles, and 7 or 8 short cleaning bristles (3rd cleaning bristles from proximal end with longer marginal spines than others). 3rd endopodial joint of USNM 193739 aberrant, with only 2 claws and 4 bristles on left limb (Figure 36e) and with end joint missing from right limb (Figure 36c). (End joint of adult male USNM 193741 normal with 3 claws and 4 bristles, and a normal female assumed to be similar.)

Maxilla: Endite I with 13 bristles (Figure 36f): endite II with 7 bristles (Figure 36g); endite III with 5 bristles (Figure 36h). Dorsal bristle of coxale missing from USNM 193739 (probably broken off during dissection). Basale with short dorsal bristle, long ventral bristle, and short medial bristle (Figure 36i). Exopodite hirsute, with 3 bristles (middle and short outer proximal bristles hirsute (Figure 36j)). 1st endopodial joint with 2 long slender alpha-bristles (Figure 36l) and 2 beta-bristles (medial bristle stout, with long proximal and short distal spines) (Figure 36k). 2nd endopodial joint with 4 a-bristles and 3 stout pectinate claw-like d-bristles (b- and c-bristles obscured on both mounted limbs of USNM 193739).

Fifth Limb: Protopodite with long cylindrical tooth with rounded tip (Figure 37a). Number of endite bristles not determined (not all shown in Figure 37c); endite II with small proximal anterior bristle; endite III with stout pectinate posterior bristle (Figure 37c). 1st endopodial joint: main tooth with smooth proximal peg and 6 constituent teeth (distal tooth with 9 cusps); bristle proximal to peg with few long proximal hairs (Figure 37b); anterior side of joint with 3 bristles (all with long spines, outer bristle stout, pectinate) forming row and 1 bristle with long spines near tooth of protopodite (Figure 37a); 2nd exopodial joint: with 4 pectinate, unringed, claw-like a-bristles (longest with 6 cusps), 3 pectinate ringed b′-bristles, 2 pectinate ringed b″-bristles, posterior c-bristle with long proximal hairs, and anterior stout d-bristle with long spines at midlength (Figure 37b,d). 3rd exopodial joint (Figure 37d): inner lobe with 1 short proximal and 2 long terminal bristles; outer lobe hirsute, with 2 bristles. 4th and 5th exopodial joints fused, hirsute, with 4 bristles, 2 on each side of low rounded process (dashed in Figure 37d) (process absent on right limb of USNM 193739).

Sixth Limb (Figure 37e): 4 short bare epipodial bristles. Endite I with 2 short spinous proximal medial bristles and 1 long spinous terminal bristle endite II with 2 short spinous proximal medial bristles and 2 terminal bristles (1 long spinous, 1 minute); endite III with 1 long spinous proximal medial bristle and 3 terminal bristles (1 long spinous, 1 long bare, 1 short spinous); endite IV with 1 long spinous proximal medial bristle and 4 or 5 spinous terminal bristles (2 or 3 long, 2 short). End joint with 12 or 13 bristles: 2 or 3 short slender at anterior end (1 or 2 ringed and with short spines, 1 unringed with few spines), followed by 1 longer bristle with long proximal and short distal spines, then 2 short bristles with short marginal spines, then 5 longer bristles with long proximal spines or hairs and short distal spines, and 2 longer hirsute posterior bristles. End joint also with medial hairs forming rows and with lateral spines along distal edge.

Seventh Limb (Figure 37f): 6 bristles in proximal group (3 on each side), each, bristle with 4 or 5 bells; 11 bristles in distal group (5 on comb side, 6 on peg side), each with 1–7 bells. 1 limb of USNM 193739 with 1 bristle on comb side stouter and much longer than other bristles, and with 7 bells (Figure 37f); on other limb long bristle not present (possibly broken off). Terminus of USNM 193739 obscured on both limbs but approximately as shown in Figure 37f.

Furca (Figure 35g): Each lamella with 7 claws; claw 2 nonarticulated, about same width as claw 1 at base but stouter than claw 1 in distal part; claw 4 narrower than claw 5; all claws with well-defined teeth along posterior edge (not shown); teeth similar in size along each claw; claw 1 with several large distal medial teeth (not shown); right lamella anterior to left by width of claw 1 at base, and with few indistinct spines along anterior edge proximal to claw 1.

Bellonci Organ (Figure 37g): Short, cylindrical, with narrow proximal part and irregular tip.

Eyes: Medial eye unpigmented, bare (Figure 37g). Lateral eye about same size as medial eye, with 27 amber-color ommatidia and brown pigment between ommatidia (Figures 35a, 37g,h).

Upper Lip (Figure 37g,i): Anterior unpaired part with large glandular processes; paired posterior part with large glandular processes along ventral edge, followed by short lobe with 2 glandular processes, and then shorter lobe with 1 glandular process; L-shape sclerite proximally on each side of lip.

Genitalia (Figure 35g): Oval ring with attached elongate spermatophore on each side of body of USNM 193739.

Anterior of Body (Figure 37g): With prominent rounded anterior process between medial eye and upper lip.

Posterior of Body (Figure 35h): Bare rounded bulge present on posterodorsal corner dorsal to dorsal end of girdle. Posterior of body without hairs or spines.

Y-Sclerite (Figure 35h): Typical for subfamily.

Pigmentation: None in carapace or appendages; brown pigment between amber-color ommatidia of lateral eye.

Protistans: USNM 193739 with protistans in “pocket” of caudal process (Figure 35c).

Eggs: In marsupium: MNHN Os 438 and USNM 193739 each with 4 (Figure 35a). USNM 193743, 4 specimens: 1 with 4, 2 with 5, and 1 with 4 embryos with black lateral eyes and with appendages projecting from uncalcified shells.

DESCRIPTION OF ADULT MALE (Figures 38, 39).—Carapace, in general, similar to that of adult female but slightly smaller and caudal process projecting farther (Figure 38).

Carapace Size: USNM 193741, length 1.02 mm, height 0.65 mm. USNM 193744, 6 specimens: length 0.96 mm, height 0.60 mm; length 0.99 mm, height 0.62 mm; length 1.02 mm, height 0.62 mm; length 1.01 mm, height 0.61 mm; length 0.99 mm, height 0.63 mm; length 1.04 mm, height 0.63 mm. USNM 193746, length 1.01 mm, height 0.64 mm.

First Antenna (Figure 39a,b): 1st joint bare. 2nd joint with few indistinct distal ventral spines. 3rd joint shorter on medial side than on lateral side, with 2 spinous bristles (1 short ventral terminal, 1 longer dorsal with base near midlength). 4th joint with short spinous ventral bristle; dorsal bristle absent on both limbs of USNM 193741 (probably aberrant). Sensory bristle of 5th joint with 9 long proximal filaments followed by 3 shorter and slenderer filaments with few marginal spines, and 1 small subterminal filament. Medial bristle of 6th joint with few indistinct marginal spines. 7th joint: a-bristle reaching tip of bristle of 6th joint, with marginal spines; b-bristle almost 4 times length of a-bristle, with stout proximal filament with large transparent sucker, followed by 2 slender filaments each with 2 small suckers, then 1 short slender filament with few small marginal spines, and with few spines on bristle distal to last filament; c-bristle about twice length of b-bristle, with stout proximal filament with very large sucker, followed by slender filament with 2 small suckers, and then about 7 slender filaments, some with spines. 8th joint: d- and e-bristles about same length as b-bristle, bare with blunt tips; f-bristle about 1 times length of b-bristle, with about 7 slender marginal filaments, some with small spines; g-bristle about twice length of b-bristle and about longer than sensory bristle of 5th joint, with about 13 slender filaments, some with small spines.

Second Antenna: Protopodite with spinous distal medial bristle. Endopodite single jointed with 2 long and 2 short proximal bristles and long terminal filament Exopodite: bristle of 2nd joint with proximal hairs followed by 6–9 stout ventral spines and 3 or 4 slender distal dorsal spines; bristles of joints 3 and 4 with stout proximal ventral spines and distal natatory hairs; joints 4–8 with natatory hairs; 9th joint with 4 bristles (dorsal bristle small with few hairs; remaining bristles long and with natatory hairs). Basal spines of joints 2–8, lateral spine of 9th joint, and small spines on joints 3–7 or 8 similar to those of adult female.

Mandible: 3rd endopodial joint with 3 claws (dorsal claw bare, others with proximal ventral spines) and 4 bristles (Figure 39c). Limb otherwise similar to that of adult female described, which has aberrant 3rd endopodial joints.

Maxilla: Coxale with hirsute slender dorsal bristle. Endite I with about 8 bristles; endite II with 6 bristles; endite III with 5 bristles. Basale, exopodite, and 1st endopodial joint similar to those of adult female. 2nd endopodial joint with 4 bare a-bristles (not shown), 2 or 3 pectinate b-bristles, 2 pectinate c-bristles, and 3 stout pectinate d-bristles (Figure 39d).

Fifth Limb: Endite I with 4 bristles; endite II with 5 bristles; endite III with 7 bristles. Protopodial tooth and exopodite similar to those of adult female.

Sixth Limb: With 3 short bare epipodial bristles. Endite I with 2 or 3 short spinous proximal medial bristles and 1 long spinous terminal bristle; endite II with 2 short spinous proximal medial bristles and 2 terminal bristles (1 long spinous, 1 minute); endite III with 1 long spinous proximal medial bristle and 3 spinous terminal bristles (2 long, 1 short between long bristles); endite IV with 1 long spinous proximal medial bristle and 3 spinous terminal bristles. End joint: right limb of USNM 193741 with 9 marginal bristles (1 short anterior unringed with short spines, followed by 1 small ringed with short spines, then 5 short ringed with long proximal and short distal spines, then 2 longer hirsute posterior bristles); left limb of USNM 193741 with 11 bristles (1 short anterior unringed with short spines, followed by 1 short ringed with short spines, then 1 longer with long proximal and short distal spines, 1 short with short spines, 5 short with long proximal and short distal spines, then 2 longer hirsute bristles). End joint also with long medial hairs and lateral spines along distal edge (Figure 39e).

Seventh Limb: 6 bristles in proximal group (3 on each side), each with 3–6 bells; distal group with 11 bristles (5 on comb side, 6 on peg side); both limbs of USNM 193741 with 1 bristle on comb side stouter and much longer than other bristles and with 7 bells; other bristles with 1–7 bells (Figure 39f). Terminus with comb of 2 long teeth in middle, then on each side 3 shorter teeth with rounded tips, and 2 teeth with flat tips (Figure 39g); short sclerotized bar opposite comb with terminal fan with 3 teeth on each side; a sclerotized bar extending from proximal end of bar projecting into comb (detail in Figure 39g).

Furca (Figure 39h,i): Similar to that of adult female.

Eyes (Figures 38a, 39j): Medial eye unpigmented bare. Lateral eye about same size as medial eye, with about 25 ommaddia and brown pigment between ommatidia.

Upper Lip (Figure 39k): Similar to that of adult female.

Genitalia (Figure 39i,l): Elongate copulatory limb on each side of body anterior to furca; internally on each side of body an elongate vas deferens entering posterior end of a globular testis. (Globular seminal vesicle at distal end of vas deferens as on sarsiellids not observed (Kornicker, 1969, fig. 2a,b).)

Anterior of Body (Figure 39j,k): Similar to that of adult female.

Posterior of Body (Figure 39l): Similar to that of adult female but posterodorsal bulge not as well developed.

Y-Sclerite (Figure 39i,l) and Pigmentation: Similar to that of adult female.

COMPARISONS.—The carapace of the female S. iota differs from that of C. calyx in being smaller and in having a higher and narrower caudal process. The lateral eye of S. iota relative to the medial eye is much smaller than that of S. calyx. The 1st antenna of the adult male S. iota differs from those of previously described species of Skogsbergia males, which do not have abundant thin hair-like proximal filaments on the f-and g-bristles (S. galapagensis Kornicker and lliffe, 1989a:8; S. menezi Kornicker, 1970a:10; S. minuta Poulsen, 1962:165; S. curvata Poulsen, 1962:168; S. lerneri (Kornicker, 1958:229; Poulsen, 1962:171 as S. crenulata Poulsen, 1962); S. strophinx Kornicker, 1991:12). The furca of S. iota differs from that of S. squamosa Kornicker, 1974b, fig. 2c in not having claw 3 nonarticulated, and from that of S. costai Kornicker, 1974b, fig. 2n in having claw 2 nonarticulated. The furca of S. iota differs from most known species of the genus in having only 7 claws on each lamella. Although the lateral eyes of S. iota have many ommatidia the diameter of the eye is relatively small and, because it is visible through the shell, provides a means of easily separating it from other species of Skogsbergia in the present collections.