dcsimg

Comprehensive Description

provided by Smithsonian Contributions to Zoology
Eusarsiella chessi

ETYMOLOGY.—The species is named for James R. Chess who collected the specimens.

HOLOTYPE.—USNM 193616, adult male on slide and in alcohol.

TYPE LOCALITY.—Enewetak lagoon, midwater trawl off Bokandretok Island.

PARATYPE.—Enewetak lagoon: Composite sample, USNM 193609, 1 instar II on slide and in alcohol (sex unknown).

DISTRIBUTION.—Enewetak Atoll.

DESCRIPTION OF ADULT MALE (Figures 48, 49).—Carapace elongate with shallow incisur and elongate caudal process (Figure 48, 49a); stout lateral process overhanging incisur (Figure 49b); ventral margin with lateral overlap (Figure 49b).

Ornamentation (Figures 48, 49a): Each valve with lateral ribs: lower rib just ventral to central adductor muscle attachments, extending from process overhanging rostrum to spinous process just anterior to caudal process; dorsal rib extending from spinous process at anterodorsal corner of valve to spinous process near posterodorsal edge of valve; posterior ends of dorsal and ventral ribs connected by thin vertical rib; left valve with narrow rib just within dorsal margin terminating posteriorly on low spinous process (Figure 49a). Ventral margin with 5 spinous processes; narrow low rib extending from 1st ventral process to the rib just ventral to central adductor muscle attachments; low spinous lateral process proximal to 4th ventral process; caudal process with low spinous lateral process near midlength (Figure 49a). Valve surface with shallow fossae having minute inward-pointing peripheral bristles with fairly blunt tips (Figure 48). Similar bristles, some longer than others, widely distibuted over valve surface, spinous processes, and ribs; tip of most short bristles pyramidal, but some tips slightly bulbous; anterior end of valve dorsal to incisur with abundant bristles 2 or 3 times length of shorter bristles and with bulbous tips (bulbous tips not shown in Figure 48 but are shown in enlarged detail in Figure 49b); most spinous processes with abundant short bristles and also with 1 or more long pointed bristles (Figure 48); outer edges of anteroventral margin and anterior 2/3 of ventral margin with abundant long pointed bristles, some with broad part near base. Tip of caudal process with short slender pointed bristles and 2 longer pointed bristles, 1 near ventral and 1 near dorsal corners of process. Long pointed bristles sparsely distributed on lateral surfaces of valve. Valve coated with gelatinous substance covering all except the long pointed bristles.

Infold (Figure 49b): Anterior infold with minute bristle posterior to incisur, just ventral to valve midheight. Infold of caudal process with 4 small bristles forming vertical row near anterior end, and 1 or 2 additional bristles near inner margin of infold; posterior infold with 2 setal bristles.

Selvage: Broad lamellar prolongation with smooth outer edge along free margins (detail in Figure 49b); prolongation cut squarely at tip of caudal process.

Carapace Size: USNM 193616, length without caudal process 1.10 mm, length with caudal process 1.31 mm, height 0.78 mm.

First Antenna (Figure 49c,l): 1st joint bare. 2nd joint with 1 dorsal bristle. 3rd joint short, fused to 4th joint, with 2 bristles (1 dorsal, 1 minute ventral); 4th joint with 2 bristles (1 dorsal, 1 ventral). 5th joint wedged ventrally between 4th and 6th joints; sensory bristle with broad proximal cup with abundant thin filaments (filaments not shown) and long stem with 4 short distal filaments and bifurcate tip (filaments and tip of stem with terminal papilla). Long 6th joint with short proximal concavity on ventral margin and short terminal medial bristle near dorsal margin. 7th joint: a-bristle slightly longer than 6th joint, with marginal spines; b-bristle slightly longer than a-bristle, with terminal papilla; c-bristle long with 4 short distal filaments with terminal papilla and stem with 2 terminal papillae. 8th joint: d-and e-bristles long, bare, with blunt tips; f-bristle long with 4 short distal filaments with terminal papilla and stem with 2 terminal papillae; g-bristle long with 4 short distal filaments with terminal papilla and stem with 2 terminal papillae.

Second Antenna: Protopodite bare. Endopodite 2-jointed (Figure 49d): 1st joint with 2 small proximal anterior ringed bristles; 2nd joint elongate with 2 minute terminal ringed bristles. Exopodite: 1st joint with small recurved medial terminal spine; bristle of 2nd joint long, with 8–11 stout proximal ventral spines, few proximal dorsal hairs, and distal natatory hairs; bristles of joints 3–8 long, with few proximal dorsal hairs, distal natatory hairs, and with following number of stout proximal ventral spines on bristles of each successive joint: 7–9, 4–6, 5 or 6, 2, 2, 3; joint 9 with 2 bristles (1 long ventral with natatory hairs, no spines; 1 short dorsal with short marginal hairs); joints 3–7 with small spines forming row along distal margins.

Mandible (Figure 49e): Coxale endite represented by small proximal medial spine. Basale: proximal ventral corner with 5 small ringed bristles (3 medial, 2 on margin); medial surface with 1 small ringed bristle near ventral margin just proximal to joint midlength; dorsal margin with 1 short bristle distal to midlength and 2 terminal bristles (medial long stout; lateral shorter and slender); all basale bristles with slender unringed knife-like tips. Exopodite well developed, hirsute, with base on lateral side of basale and tip extending onto medial side of 1st endopodial joint. Endopodite: 1st joint: dorsal margin with proximal indentation to accomodate exopodite; medial surface with abundant long hairs near dorsal margin, long hairs forming proximal transverse row, short spines forming 6 transverse rows (distal row extending onto dorsal margin), and also 1 short terminal row near ventral margin; ventral margin with stout unringed terminal claw (with minute proximal perpendicular spines along dorsal and ventral margins) and 2 small ringed bristles (with slender unringed knife-like tips) medial to base of claw. 2nd joint: dorsal margin slightly undulate, with 1 slender ringed bristle (with slender unringed knife-like tip) proximal to joint midlength; ventral margin with stout unringed terminal claw (with minute perpendicular dorsal and ventral spines); medial surface with small spines forming terminal row. 3rd joint with stout unringed terminal claw (with few indistinct minute proximal spines along ventral margin), 2 small ringed bristles ventral to base of claw, and 1 minute indistinct unringed spine-like bristle medial to dorsal edge of claw. (Rings of ringed bristles not shown.)

Maxilla: Minute with weakly developed bristles.

Fifth Limb (Figure 49f,g): Protopodite with 37 spinous bristles. Single endite with 1 small bristle. Exopodite small (Figure 49g): 1st joint with 2 bristles; 2nd joint with 3 bristles; 3rd, 4th, and 5th joints with indistinct sutures separating them, hirsute, and with total of 5 bristles. Small ?glandular process on margin just distal to epipodite.

Sixth Limb (Figure 49h): Single endite with 3 small ringed bristles (2 medial, 1 terminal). End joint with 2 hirsute posterior ringed bristles separated by short space from 13 anterior ringed bristles (5 long with medial bases, long proximal hairs, and short distal spines; 7 long with lateral bases and long marginal hairs; not all spines and hairs shown on Figure). Lateral surface of limb with spines forming rows, medial surface hirsute.

Seventh Limb (Figure 49i): Very long with 4 bristles on terminal segment, each with 6 or 7 bells and no marginal spines. Terminal segment with smooth distal margin.

Furca (Figure 49j): Each lamella with 5 claws; claw 1 nonarticulated, others articulated; all claws with teeth along posterior edges, some longer than others, especially on claws 1 and 2; claw 4 with teeth along anterior margin similar in size to those along posterior margin; claw 5 with few indistinct minute posterior teeth; left lamella with 4 stout spines following claw 5, none on right lamella; anterior margin of right lamella with few minute spines. Right lamella anterior to left by width of base of claw 1.

Bellonci Organ (Figure 49k): Elongate, broadening distally, with rounded tip.

Eyes (Figure 49k): Medial eye unpigmented, bare. Lateral eye smaller than medial eye, with 7 amber-colored divided ommatidia.

Upper Lip (Figure 49l): Evenly rounded, bare.

Genitalia (Figure 49j): Elongate lobes on each side of body anterior to furca; distal lobe with elongate hook-like sclerotized terminal process with tooth at base and 2 bristles along concave margin. Seminal vesicles appearing as amber-colored ovals when viewed in transmitted light (stippled in Figure).

Posterior of Body (Figure 49j): Evenly rounded, bare.

Y-Sclerite (Figure 49j): Typical for subfamily.

DESCRIPTION OF INSTAR II (Figures 50, 51).—Carapace oval in lateral view with long narrow caudal process (sex unknown) (Figure 50).

Ornamentation (Figures 50, 51a): Posterodorsal margin with 2 projecting processes each with dense covering of short bristles and a long terminal bristle; anterior and ventral margins, each with 3 similar processes perpendicular to valve edge, each with covering of small bristles and 1 or 2 long terminal bristles (long bristle missing from posterior ventral process of illustrated right valve, but present on left valve); lateral surface of each valve with 2 indistinct weakly developed horizontal ribs (1 above and 1 below valve midheight); ribs with high density of short bristles on them (density similar to that on processes), each rib terminating posteriorly on small process covered with short bristles (only process on lower rib with long terminal bristle), and terminating anteriorly on upper and lower processes of anterior margin; upper rib with row of 2 or 3 long bristles along anterior half; lower rib with row of 2 or 3 long bristles; anterodorsal margin dorsal to upper anterior process with single long bristle on low node. Tips of short bristles bulb-like and coated by continuous gelatinous film; long bristles on processes and ribs slender and tapering from base to tip; some bristles (shorter than long bristles on processes but longer than short bristles with bulb-like tips) along anterior and ventral valve edges have broad part near base or at bristle midlength (Figure 51a); 1 or 2 bristles of that type also on anterior and ventral processes. Small bristles with bulb-like tips widely scattered over valve surface between ribs and processes (not all shown in Figure 50). Posterior edge of caudal process with 2 short pointed bristles projecting posteriorly (Figures 50, 51b); 2 bristles on caudal process (1 on dorsal margin, other on ventral margin) have thin thread-like tips (Figure 50, 51b). (Fossae not visible on decalcified shell of USNM 193609 but few curved lines on shell suggest that they might have been present when it was calcified.)

Infold: Anterior infold with small bristle near inner margin ventral to valve midheight (Figure 51a). Infold of caudal process with 2 small bristles near anterior end and 1 small bristle on list ventral to process (Figure 51b). Posterior infold just dorsal to caudal process with 2 setal bristles (Figure 51b).

Selvage: Wide lamellar prolongation with smooth outer edge present along anterior, ventral, and posterior margins of valve; posterior end of prolongation at tip of caudal process forms square (Figure 51b).

Central Adductor Muscle Attachments (Figure 51k): Comprising 11 ovoid attachments.

Carapace Size: USNM 193609, length including caudal process 0.81 mm, length excluding caudal process 0.64 mm, height 0.55 mm.

First Antenna (Figure 51c): 1st joint bare. 2nd joint with few indistinct dorsal spines and short distal dorsal bristle. 3rd and 4th joints fused; 3rd joint short with 2 bristles (1 ventral, 1 dorsal) reaching 5th joint [note ventral bristle of 3rd joint not short as on adult male]; 4th joint with 1 dorsal bristle reaching midlength of 5th joint. Sensory bristle of long 5th joint with 3 minute filaments and terminal papilla. 6th joint fused to 5th, with short medial bristle near dorsal margin. 7th joint: a-bristle about 3 times length of bristle of 6th joint; b-bristle slightly longer than a-bristle, bare with terminal papilla; c-bristle slightly longer than sensory bristle of 5th joint, with 2 minute filaments and terminal papilla. 8th joint: d- and e-bristles slightly shorter than sensory bristle, bare with blunt tips; f-bristle about twice length of b-bristle, with terminal papilla; g-bristle same length as sensory bristle, with 2 minute filaments and terminal papilla. Not all filaments shown on bristles of joints 5, 7, and 8.

Second Antenna (Figure 51c,d): Protopodite bare. Endopodite 1-jointed, with 1 short proximal anterior bristle, and 1 minute terminal bristle on low node (Figure 51c,d). Exopodite: 1st joint with small recurved medial terminal spine; bristle of 2nd joint long, with numerous slender ventral spines but no natatory hairs; bristles of joints 3–8 long, with stout ventral spines and distal natatory hairs; 9th joint with 2 bristles (1 minute bare dorsal, other long with ventral spines and distal natatory hairs).

Mandible (Figure 51e,f): Coxale endite represented by small medial spine proximally near ventral margin (not shown). Coxale with stiff spines (with bases on lateral side) along ventral margin. Basale with 4 small bristles on or near ventral margin; and dorsal margin with 1 small bristle distal to joint midlength and 2 minute subterminal bristles. Exopodite represented by small terminal process inward from dorsal margin of basale (Figure 51f). Endopodite: 1st joint with medial spines (not shown in Figure 51e but visible in Figure 51f), small terminal spine-like bristle on dorsal margin, and minute bristle near base of main claw; main claw with minute proximal spines along dorsal edge. 2nd joint with minute terminal bristle on dorsal margin and stout ventral claw. 3rd joint with short ventral bristle and minute dorsal bristle, both at base of main claw.

Maxilla (Figure 51g,h,n): Coxale with short anterior bristle (Figure 51h). Endite I with 6 bristles, endite II with 3 bristles; endite III with 6bristles (Figure 51g). Basale with 1 bristle near base of exopodite. Exopodite with 2 bristles (longer bristle with spines). Endopodite (Figure 51h): 1st joint with pectinate alpha-bristle and spinous beta-bristle; 2nd joint with 2 lateral bare a-bristles, 1 medial bare c-bristle, and 5 stout pectinate terminal bristles (middle bristle shorter).

Fifth Limb (Figure 51i): Epipodite with 32 bristles. Single endite with 1 short bristle. Exopodite: 1st joint with 2 bristles; 2nd to 5th joints hirsute, fused, with total of 9 bristles (interpretation of bristle distribution: 2nd joint with 3 bristles; inner lobe of 3rd joint with 3 bristles, outer lobe with 1 bristle, 4th plus 5th joints with 2 bristles).

Sixth Limb (Figure 51j,k,n): Comprising 2 hirsute lobes with long spinous bristle between them.

Seventh Limb (Figure 51k): Small, thumb-like.

Furca (Figure 51k): Each lamella with 5 claws; claw 1 nonarticulated, others articulated; all claws with teeth along posterior edges, some teeth longer than others, especially on claw 1; anterior margin of lamellae with few slender spines; 4 stout spines present on left lamella following claw 5, none on right lamella. Right lamella anterior to left by width of base of claw 1.

Bellonci Organ (Figure 51l,m): Elongate, broadening distally, with rounded tip.

Eyes: Medial eye unpigmented, bare (Figure 51l,m). Lateral eye smaller than medial eye, unpigmented, bare, with 5 small amber-colored ommatidia (Figure 51c).

Upper Lip (Figure 51m): Evenly rounded, bare.

Anterior of Body (Figure 51m): Triangular projection on each side of body just dorsal to insertion of mandible.

Posterior of Body (Figure 51k): Evenly rounded, bare.

Y-Sclerite (Figure 51k): Typical for subfamily.

DISTRIBUTION.—Anscottiella crispata: Sri Lanka, depth unknown; Thailand, 2 m depth; A. tumidicosta: Australia, 2 m depth; A. vertex: Enewetak Atoll, shallow.
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bibliographic citation
Kornicker, Louis S. 1991. "Myodocopid Ostracoda of Enewetak and Bikini Atolls." Smithsonian Contributions to Zoology. 1-140. https://doi.org/10.5479/si.00810282.505