Comprehensive Description

provided by Smithsonian Contributions to Zoology
Eusarsiella fallomagna

ETYMOLOGY.—From the Latin fallo (lie, deceive) plus the Latin magnus (large, great). So named because of the similarity of the species to E. magna Poulsen, 1965.

HOLOTYPE.—Undissected ovigerous female in alcohol in the collection of the Museum of Victoria.

TYPE LOCALITY.—Slope 1, 34°59.52′S, 151°5.94′E, New South Wales, off Nowra; depth 204 m.

PARATYPES.—Slope 1: USNM 193944, adult female on slide and in alcohol; 2 undissected ovigerous females in alcohol (1 with bryozoan on shell). Slope 40: USNM 193989, 1 partly dissected adult nonovigerous female in alcohol; 1 undissected adult female in alcohol. Slope 56:7 adult females (6 ovigerous) in alcohol.

DISTRIBUTION.—Slope 1,204 m. Slope 40, 400 m. Slope 56, 429 m.

DESCRIPTION OF ADULT FEMALE (Figures 76–78).—Carapace round in lateral view with ovoid posterodorsal processes large in some specimens (Figures 76a, 78c,d, and smaller in others (Figure 78f), and a paratype from slope 1 with bulge only on right valve (Figure 78e); posteroventral caudal process with rounded tip (Figure 76d,e). Some specimens with many large secondary calcareous concretions.

Ornamentation: Surface with widely separated oval fossae with short stout spines (Figure 76b) and minute spines between fossae (Figure 76c,e). Short and long undivided bristles, some with broad bases, very sparsely distributed on lateral surface but more abundant along anterior and ventral margins (Figure 76c,e). Outer surface without gel-like coating.

Infold: Anterior infold with minute bristle near inner margin (Figure 76c). Infold of caudal process with 7 or 8 bristles; few small bristles along inner margin of infold in vicinity of caudal process (Figure 76d,e). Posterior infold with 2 setal bristles at about midheight (Figure 76d); 4 darker unevenly spaced ovoid areas just anterior to infold of caudal process (Figure 76d,e).

Central Adductor Muscle Attachments (Figure 76f): Comprising 18–20 ovoid attachments.

Carapace Size (length including caudal process, height in mm): Slope 1: holotype, 2.2, 2.1, width 1.6; USNM 193944, 2.3, 2.0; 2 unnumbered specimens: 2.1, 1.9; 2.2, 1.9 (specimen with bryozoan on shell). Slope 40, USNM 193989, 2.53, 2.10. Slope 56, unnumbered specimen, 2.38, 2.08. (Note considerable variation in size.)

First Antenna (Figure 76g,h): 1st joint bare. 2nd joint with few proximal dorsal spines and plumose dorsal bristle. 3rd joint fused to 4th, with ventral bristle about half length of dorsal bristle; 4th joint with 4 spinous bristles (3 ventral, 1 dorsal). Ventral bristle of 5th joint with 1 minute proximal filament and 1 terminal filament. 6th joint fused to 5th, with small spinous medial bristle. 7th joint: a-bristle about 3 times length of bristle of 6th joint, with short marginal spines; b-bristle about longer than a-bristle, with pointed tip; c-bristle about same length as bristle of 5th joint, with minute terminal filament 8th joint: d- and e-bristles shorter than c-bristle, bare with blunt tips; f-bristle slightly shorter than c-bristle, with minute terminal filament; g-bristle same length as c-bristle, with 2 minute proximal filaments and minute terminal filament.

Second Antenna: Protopodite bare. Endopodite with 2 bare proximal bristles and 1 minute spinous terminal bristle (about length of proximal bristles) on small terminal node (Figure 76i). Exopodite: 1st joint with small, terminal, medial, straight, tubular bristle; bristles of joints 2–8 and long bristle of 9th joint with natatory hairs, no ventral spines; short bristle of 9th joint with slender hair-like spines; some joints with few minute spines along distal edges.

Mandible: Coxale endite single, stout, pectinate (Figure 77a); ventral margin of coxale with long slender spines. Basale: ventral margin with 6 short bristles; dorsal margin with small bristle near midlength and 2 terminal bristles (Figure 77a). 1st endopodial joint with medial spines, spines on distal dorsal corner, and stout ventral claw (Figure 77b). 2nd endopodial joint with minute dorsal bristle and stout ventral claw. 3rd endopodial joint with stout terminal claw and 2 or 3 small bristles (1 or 2 ventral, 1 dorsal).

Maxilla: Coxale with dorsal bristle with few short spines. Diaphanous lobe near coxale (edge of lobe stippled in Figure 77d). Endite I with 5 bristles (Figure 77c); endite II with 4 bristles (Figure 77c); endite III with 6 bristles (Figure 77d). Basale with spinous bristle near exopodite. Exopodite with 3 spinous bristles (1 short, 1 medium, 1 long). 1st endopodial joint with slender pectinate ringed alpha- and beta-bristles. 2nd endopodial joint with 2 slender ringed a-bristles, 1 slender ringed spinous c-bristle, and 5 pectinate end bristles (middle bristle shorter, anterior bristle ringed distally, others unringed claw-like).

Fifth Limb: Epipodite with 43 bristles. Single endite with 1 short bristle (Figures 76k, 78g). Exopodite (Figures 76j, 78g): 1st joint with 3 bristles; joints 2–5 fused: 2nd joint with 4 bristles; joints 3–5 with total of 6 bristles.

Sixth Limb (Figure 76l): Single endite with 3 short bristles. End joint with considerable posterior extension, 14 or 15 bristles (with short spines) followed by long space, then 2 broad bristles with abundant thin hairs; posterior margin hirsute.

Seventh Limb: USNM 193944: proximal group with 11 bristles (5 or 6 on each side), each bristle with 4 or 5 bells; terminal group with 6 bristles (3 on each side) (Figure 77e), each bristle with 4–7 bells (terminal bell minute; Figure 77g). Terminus with opposing combs, each with 11–13 teeth (24 total) (Figure 77e). Illustrated limb of USNM 193944 with small triangular process between combs (Figure 77e,f), but process not present on opposite limb. USNM 193989: proximal group with 14 or 15 bristles (6–8 on each side).

Furca (Figure 77h): Each lamella with 5 claws; claw 1 nonarticulated; all claws with long and short teeth along posterior edges and bare along anterior edges; claw 1 with row of transverse spines near base; minute spines on lamellae following claws; right lamella anterior to left by width of base of claw 1; anterior edges of lamellae with minute spines.

Bellonci Organ (Figures 77i,j, 78h): Short, cylindrical, with rounded tip.

Eyes (Figures 77i, 78h): Medial eye bare, unpigmented. Lateral eye smaller than medial eye, unpigmented with 5 (4 well developed lateral, 1 poorly developed medial) ommatidia.

Upper Lip (Figure 78a): With 2 elongate anterior projections.

Genitalia (Figures 77h, 78b): USNM 193944 with small sclerotized ring without spermatophore on each side of body anterior to furca.

Posterior of Body: Evenly rounded, bare; USNM 194944 with small unpaired process near posterodorsal corner (Figure 78b) (not present on USNM 193989).

Y-Sclerite (Figures 77h, 78b): Typical for genus.

Number of Eggs: Holotype with 9 eggs in marsupium; lengths of 2 eggs measured through shell 0.36 mm, 0.46 mm (outlines of 4 eggs shown in Figure 78c). USNM 193944 with about 7 unextruded eggs; length of largest egg 0.26 mm (1 egg shown in Figure 77h, another in Figure 78b).

Epizoa: Ovigerous female from Slope 1 with bryozoan (without soft parts) on left shell (Figure 78e) (identified as bryozoan by Alan H. Cheetham).

COMPARISONS.—Externally the carapace of E. fallomagna resembles E. magna Poulsen (1965, fig. 25a). Viewed internally the valves of both species have 4 dark ovoids anterior to the caudal process, but they are evenly spaced in magna and unevenly spaced in fallomagna (Figure 76d,e). Appendages of E. fallomagna also differ from E. magna in having a 1st antenna with no spines on the ventral margin of the 2nd joint, and an extremely long ventral bristle (about 3 times the length of the 5th joint) on the 4th joint, an endopodite of the 2nd antenna with a terminal node and proximal bristles much stouter than the terminal bristle, a mandible with numerous medial spines on the 1st endopodial joint, and terminal combs of the 7th limb with a total of about 24 teeth (40 on E. magna).
bibliographic citation
Kornicker, Louis S. 1994. "Ostracoda (Myodocopina) of the SE Australian Continental Slope, Part 1." Smithsonian Contributions to Zoology. 1-200. https://doi.org/10.5479/si.00810282.553