Eusarsiella tryx Kornicker 1996

Eusarsiella tryx

ETYMOLOGY.—From the Greek tryx (new wine).

HOLOTYPE.—Undissected ovigerous female in alcohol, QM W20745.

TYPE LOCALITY.—Calliope River and Auckland Creek area, near Gladstone, Queensland, Australia.

PARATYPES.—Type locality: USNM 157969B, ovigerous female on slide and in alcohol; USNM 194121, undissected ovigerous female in alcohol; USNM 194969C, undissected females plus juveniles in alcohol.

DISTRIBUTION.—Collected only at type locality.

DESCRIPTION OF ADULT FEMALE (Figures 34, 35).—Carapace oval in lateral view, with long slender posteroventral caudal process (Figure 34).

Ornamentation: Dorsal margin with 1 large triangular process near midlength and 3 smaller processes anterior to it (Figure 34); alate rib extending from near valve midlength and midheight (in vicinity of central adductor muscle attachments) to posterodorsal corner, where it extends past valve edge (Figure 34). Surface of both valves and rib with abundant minute papillae (not shown); edges of valves and processes with minute broad triangular papillae (not shown) and small U-shaped scales (2 scales shown near ventral edge in Figure 35b). Anterior and ventral margins with numerous slender bristles with bases along inner side of valve edge, some bristles broad at base or near midlength (Figure 35a); about 12 bristles along posterior edge of valves (5 shown in Figure 35b); bristles extremely sparse elsewhere on valve surface. Valves without gel-like coating.

Infold: Anterior infold with minute bristle near valve midheight (Figure 35a). Infold of caudal process with 7 small spine-like bristles (Figure 35b); few minute bristles along inner edge of infold in vicinity of caudal process; posterior infold with 2 setal bristles dorsal to caudal process (Figure 35b).

Carapace Size (length (L) including caudal process, height (H), in mm): QM W20745 (holotype), L = 1.29, H = 1.31. USNM 157969B, L = 1.48, H = 1.32; width including alate ribs = 1.00. USNM 194121, L = 1.22, H = 1.11.

First Antenna (Figure 35c,n): 1st joint bare. 2nd joint with proximal row of spines on dorsal margin and with dorsal bristle with few indistinct minute spines. 3rd joint fused to 4th joint, with 2 bristles (1 small ventral, 1 dorsal); 4th joint with 3 bristles (1 dorsal, 2 ventral). Ventral bristle of 5th joint long, with minute proximal filament and minute terminal papilla (only proximal part of bristle shown). 6th joint fused to 5th joint, with short medial bristle near dorsal margin, bristle bare except for slender subterminal hair. 7th joint: a-bristle about twice length of bristle of 6th joint, bare except for slender subterminal hair; b-bristle almost 3 times length of a-bristle, with minute terminal papilla; c-bristle same length as bristle of 5th joint, with 1 minute proximal filament and minute terminal papilla (bristle not shown). 8th joint (bristles not shown): d- and e-bristles very slightly shorter than c-bristle, bare with blunt tips; f-bristle very slightly shorter than c-bristle, with minute terminal papilla; g-bristle same length as c-bristle, with minute terminal papilla.

Second Antenna: Protopodite bare (Figure 35d). Endopodite 1-jointed, with 2 proximal ringed anterior bristles and minute spine-like terminal bristle (Figure 35d). Exopodite: 1st joint with terminal medial minute curved tubular bristle; bristles of joints 2–8 with natatory hairs, no spines; 9th joint with 2 bristles (1 short dorsal, 1 long ventral) with natatory hairs; joints 3–7 with 1–4 minute medial spines along distal edges near dorsal margin.

Mandible (Figure 35e): Coxale endite represented by small bifurcate spine; coxale with slender ventral spines. Basale: ventral margin with 6 small bristles (4 medial, 2 lateral); dorsal margin with 1 short bristle distal to midlength and 2 ringed subterminal bristles. Exopodite absent. 1st endopodial joint with spines on medial surface and terminal dorsal margin and with stout ventral claw with narrow transparent flange (not shown) along proximal of dorsal margin (small part of flange near base divided into row of few indistinct spines) and few minute spines near base of ventral margin. 2nd endopodial joint with small dorsal bristle and stout ventral claw with narrow transparent flange (not shown) along proximal to of ventral and dorsal margins. 3rd endopodial joint with stout terminal claw (without flanges) and 3 minute bristles (2 ventral, 1 dorsal).

Maxilla (Figure 35f): Endites I and III each with 6 bristles (not all bristles shown); endite II (not shown) with about 4 bristles. Usual dorsal bristle of coxale not observed (probably broken off or obscured). Basale with short dorsal bristle near exopodite. Exopodite with 3 bristles (1 long, 2 short). Endopodite: 1st joint with spines along anterior margin and spinous and pectinate alpha- and beta-bristles (bristles broken on illustrated limb); 2nd joint with 2 small a-bristles, 1 small c-bristle, and 5 stout pectinate end bristles (middle bristle shorter; anterior bristle ringed distally; posterior bristle broken off of limb illustrated).

Fifth Limb (Figure 35g): Single endite with short bristle. Exopodite: 1st joint with 2 bristles; joints 2–5 fused, with total of 9 bristles (interpretation: 2nd joint with 3 bristles; 3rd joint with 3 bristles (1 minute) on inner lobe and 1 bristle on outer lobe; fused 4th and 5th joints with total of 2 bristles).

Sixth Limb (Figure 35h): Single endite with 2 short bristles. End joint with 12–14 spinous bristles followed by space and 2 broad plumose posterior bristles.

Seventh Limb: Proximal group with 4 bristles, 2 on each side, each with 3 or 4 bells (mostly 3); terminal group with 6 bristles, 3 on each side, each with 3–5 bells (mostly 5); all bristles without marginal spines. Terminal segment with opposing combs, each with about 9 indistinct teeth (Figure 35i).

Furca (Figure 35f): Each lamella with 5 claws; claw 1 nonarticulated; all claws with teeth along posterior edge; those of claws 2 and 3 unusually long, greater than width of claw at base. Right lamella anterior to left lamella by width of base of claw 1; right lamella with spines along anterior edge; left lamella with spines along edge following claw 5.

Bellonci Organ: Short (length less than width of base of 1st joint of 1st antenna), cylindrical, with broadly rounded tip (Figure 35c,k,n). Tip bulbous on USNM 194121 (Figure 35n).

Eyes: Medial eye bare, with brown pigment (Figure 35c,k,n). Lateral eye absent, but a triangular process (with minute unpigmented round cell near tip) (Figure 35l) in place where lateral eye is usually present in other species of the genus may represent a sight organ.

Upper Lip: Not seen with certainty (may be attached to mounted left mandible of USNM 157969B).

Genitalia: Not observed.

Posterior of Body: Evenly rounded, bare.

Y-Sclerite (Figure 35m): Typical for subfamily except for curvature of proximal part.

Number of Eggs: QM W20745 (holotype) with 9 eggs in marsupium. USNM 157969B with 10 eggs in marsupium and with large unextruded eggs; length of 1 extruded egg (appendages visible) 0.189 mm, length of 1 unextruded egg 0.185 mm. USNM 194121 with 6 eggs in marsupium and with large unextruded eggs; length of 1 extruded egg 0.181 mm.

COMPARISONS.—The carapace of E. tryx resembles that of E. saengeri in that both have a stout alar rib. The carapace of E. tryx (length 1.22–1.48 mm) is smaller than that of E. saengeri (length 1.77–1.89 mm) and does not have strongly scalloped anterior and ventral margins. The seventh limb of E. saengeri bears 13 bristles in the proximal group compared to four for E. tryx, and the Bellonci Organ is cone-like rather than cylindrical. The teeth along the posterior edges of the furcal claws are well developed in both E. saengeri and E. tryx, but the teeth are longer in the latter. Also, the lateral eye is better developed in E. saengeri than in E. tryx. The carapace of E. tryx is smaller than that of E. serrata (Hall, 1987) (the length of the latter is 1.84–2.11 mm), the seventh limb has fewer proximal bristles (four compared to seven), and the exopodite of the maxilla has three instead of two bristles. Also, the lateral eye has six ommatidia in E. serrata but is either absent or minute in E. tryx.