Eusarsiella merx Kornicker, Iliffe & Harrison-Nelson 2002

Eusarsiella merx

ETYMOLOGY.—From the Latin merx (commodities, goods, wares).

HOLOTYPE.—USNM 194556, dissected adult male on slide and in alcohol.

TYPE LOCALITY.—Sta 95–091, Sugar Cay Blue Hole, Sugar Cay, Andros Island.

PARATYPES.—Sugar Cay Blue Hole, Sta 95-091: USNM 194557, dissected instar IV female on slide and in alcohol; USNM 194559, partly dissected instar III male in alcohol; USNM 194560, partly dissected instar II (sex unknown) in alcohol; USNM 194561, dissected instar I (sex unknown) on slide.

DISTRIBUTION.—Sugar Cay Blue Hole, Sugar Cay, Andros Island, at depth of 22 m.

DESCRIPTION OF ADULT MALE (Figures 33–36).—Anterodorsal and posterodorsal margins of carapace oblique (Figures 33, 34a–c); dorsal margin linear in hinge area; ventral margin slightly scalloped; caudal process with only slight projection. Gel-like coating absent.

Ornamentation: Carapace with upper and lower ribs; upper rib with projecting process at posterior end (Figures 33, 34a). Oblique ridge setback from anteroventral margin and parallel to it (Figure 34b). Bristles sparsely distributed on lateral surface, more abundant along margins (Figures 33, 34b,c). Long bristles forming row along posterior edge of small caudal process (Figure 34c,e).

Infold (Figure 34d,e): Anterior infold with small bristle at shell midheight; posterior infold with 4 bristles within caudal process, and 2 setose bristles near midheight; additional bristles along inner margin of posteroventral and posterior infold.

Central Adductor Muscle Attachments (Figure 34a): Comprising about 13 oval attachments.

Carapace Size (length, height in mm): USNM 194556, 0.85, 0.64.

First Antenna (Figures 34f–k, 35a): 1st joint bare. 2nd joint with spinous dorsal bristle at midlength. 3rd joint fused with 4th; 3rd joint with long dorsal bristle and no ventral bristle; 4th joint with 3 bristles (1 dorsal, 2 ventral). 5th joint wedged ventrally between 4th and 6th joints; sensory bristle with short proximal part with abundant thin filaments (filaments not shown; tip of bristle broken off, remaining part without filaments). 6th joint long with short medial terminal bristle. 7th joint with short slender ringed a-bristle, bare b-bristle about same length as combined joints 6–8, and long c-bristle with 3 marginal filaments. 8th joint with long bare d-bristle, shorter bare e-bristle, and long f- and g-bristles with 3 or 4 marginal filaments.

Second Antenna (Figures 35a–c, 36g): Sclerite attached to posterior edge of protopodite straight (Figure 36g). Protopodite bare. Endopodite 2-jointed (Figure 35a,b): joint 1 with medial and anterior spines and 1 ringed anterior bristle; 2nd joint with 2 or 3 terminal ringed bristles. Exopodite: 1st joint with small terminal medial bristle adjacent to triangular process; bristle of 2nd joint with about 15 slender ventral spines and distal natatory hairs; bristles of joints 3–8 with natatory hairs; 9th joint with 2 bristles (1 long ventral with slender, proximal, hair-like spines and distal natatory hairs, 1 short bare (Figure 35c)); joints 2–7 with row of short terminal spines.

Mandible (Figure 35d–h): Coxale endite represented by small spine (Figure 35f). Basale: ventral margin with short bristle near midlength; medial side near ventral margin with 4 bristles (3 proximal forming cluster) (Figure 35f); dorsal margin with 2 subterminal bristles. 1st endopodial joint: ventral margin with 2 subterminal bristles; medial surface and dorsal margin with spines forming rows. 2nd endopodial joint: ventral margin with terminal bristle; dorsal margin with short subterminal bristle with small medial spine near base. 3rd endopodial joint (Figure 35d,e,h): medial side with 2 minute, indistinct, subterminal, spine-like bristles; distal margin with small ventral bristle and long, bare, terminal claw. Exopodite small indistinct hirsute (Figure 35d,g).


Maxilla (Figure 36a): Extremely reduced with weakly developed bristles.

Fifth Limb (Figure 36b): Single endite with 1 short bristle. Exopodite minute, joints fused, with about 9 indistinct bristles.

Sixth Limb (Figure 36c): Single endite with 3 bristles (2 short, 1 slightly longer hirsute). End joint hirsute with 11 or 12 bristles (6 or 7 broad hirsute bristles along anteroventral margin, 2 hirsute broad posterior bristles, and 3 medial bristles with long proximal and short distal spines).

Seventh Limb (Figure 36d): Small, peg-like.

Furca (Figure 36e): Each lamella with 5 pointed claws; claw 1 fused to lamella, claws 2–5 separated from lamella by suture; claws followed by paired spines and single spine; left lamella with indistinct spine (not shown) between claws 4 and 5; all claws with teeth along posterior margin, some larger than others; right lamella anterior to left by width of base of claw 1.

Bellonci Organ (Figure 36f,g): Elongate, with rounded tip.

Eyes: Lateral eye with about 12 ommatidia (2 ommatidia near ventral margin larger than others) (Figure 36g). Medial eye about same size as lateral eye, with brown pigment (Figure 36f).

Copulatory Organ (Figure 36h,i): Each limb with about 3 lobes; terminal lobe with foot-like sclerotized hook with 3 or 4 small bristles at inner edge of base; sclerotized medial process present at base of hook; middle lobe with 2 indistinct bristles; small proximal posterior lobe bare.

Y-Sclerite: Typical for family.

DESCRIPTION OF INSTAR IV FEMALE (Figures 37, 38).—Carapace with evenly rounded anterior and dorsal margins and oblique posterior margin (Figure 37a). Caudal process small and forming right-angle. Gel-like coating absent.

Ornamentation: Carapace with distinct crescentic lateral ridge near posterodorsal corner (Figure 37a). Surface with scattered bristles more abundant along margins (Figure 37a). Outer edge of caudal process with row of 8 or 9 bristles (Figure 37b). Several rows of minute lateral spines present just within valve edge.

Infold: Infold of caudal process with 4 small bristles (Figure 37b); additional smaller bristles along inner margin of infold of caudal process; 1 or 2 longer bristles along posterior infold ventral to 2 setal bristles located just ventral to valve midheight.

Central Adductor Muscle Attachments (Figure 37c): Consisting of 11 or 12 large ovoid attachments.

Carapace Size (length, height in mm): USNM 194557, 0.84, 0.74.

First Antenna (Figure 37d): 1st joint bare. 2nd joint with subterminal dorsal bristle. 3rd joint short, fused to 4th, with long dorsal bristle, but without ventral bristle. 4th joint long with 3 bristles (1 dorsal, 2 ventral). Sensory bristle of 5th joint with 2 minute filaments (1 proximal, 1 terminal). Medial bristle of 6th joint short. 7th joint: a-bristle about twice length of bristle of 6th joint; b-bristle almost twice length of a-bristle; c-bristle with minute terminal filament, about same length as sensory bristle of 5th joint. 8th joint: d-bristle bare, same length as c-bristle; e-bristle bare, slightly longer than b-bristle; f- and g-bristles about same length as c-bristle, each with minute terminal filament.

Second Antenna (Figure 37e,f): Protopodite bare. Endopodite 1-jointed with proximal anterior bristle and small terminal node (terminal node could be interpreted to be 2nd joint). Exopodite: 1st joint with minute, terminal, medial bristle; bristle of 2nd joint about two-thirds length of bristle of 3rd joint, with slender, proximal, ventral spines and distal natatory hairs; bristles of joints 3–8 with proximal ventral spines and distal natatory hairs; 9th joint with 2 bristles (ventral bristle long, with proximal ventral spines and distal natatory hairs; dorsal bristle short bare); joints 3–5 with row of minute spines along distal edge.

Mandible (Figure 37g,h): Coxale: endite consisting of minute indistinct spine; ventral margin with slender spines. Basale: medial side near ventral margin with 4 small bristles; lateral side near ventral margin with 2 small bristles; dorsal margin with 2 small subterminal bristles. No exopodite present. 1st endopodial joint: dorsal margin with minute spines forming terminal row; ventral margin with stout terminal claw with minute medial bristle near its base; medial side of joint with about 32 spines (distal spines longer). 2nd endopodial joint with stout, bare, ventral claw and small, terminal, dorsal bristle. 3rd endopodial joint with stout, bare, terminal claw, 2 minute ventral bristles, and 1 minute dorsal bristle.

Maxilla (Figure 37i): Coxale with short anterior bristle. Endite I with 5 bristles; endite II with 4 bristles; endite III with 5 or 6 bristles. Basale with short bristle near exopodite and short transparent flap. Exopodite with 3 bristles (1 longer than others). Endopodite: 1st joint with spinous alpha- and beta-bristles with distal rings; 2nd joint with 2 lateral a-bristles, 1 medial c-bristle, and 5 stout pectinate terminal bristles.

Fifth Limb (Figure 38a): Epipodial appendage with 29 bristles. Single endite with 1 short bristle. Exopodite hirsute: 1st joint with 2 bare bristles; 2nd joint with 3 bristles; joints 3–5 with 4 bristles (1 minute).

Sixth Limb (Figure 38b,c): Endite I with 3 short bristles. End joint with 9 or 10 bristles (with short marginal spines) followed by 2 stout hirsute bristles; posterior margin hirsute.

Seventh Limb (Figure 38d,h): Proximal group with 2 tapered bristles, 1 on each side, each with 2 bells; terminal group with 4 tapered bristles, 2 on each side, each with 3 or 4 bells; terminus with opposing combs, each with 2 or 3 minute teeth.

Furca: Right lamella with 5 claws followed by space and small spine (Figure 38e); left lamella with 6 claws with spines between claws 5 and 6 and following claw 6 (Figure 38f); claw 1 continuous with lamella, others separated by suture; anterior margin of right lamella with 3 minute spines; right lamella anterior to left by width of base of claw 1; lamellae without hairs.

Bellonci Organ (Figure 38g): Elongate, with rounded tip.

Eyes: Lateral eye small, with brown pigment and 5 ommatidia (Figure 37f). Medial eye more than twice size of lateral eye, with brown pigment (Figure 38g).

Genitalia: Absent.

Y-Sclerite (Figure 38h): Typical for family.

DESCRIPTION OF INSTAR III MALE (Figure 39).—Carapace shape and ornamentation similar to that of Instar IV female (Figure 39a). Gel-like coating absent.

Infold: Infold of caudal process with 3 or 4 bristles; additional bristles along inner margin of infold (Figure 39c); 2 setal bristles near midheight. Anterior infold with small bristle ventral to midheight (Figure 39b).

Central Adductor Muscle Attachments (Figure 39a,i): Consisting of about 15 oval attachments.

Carapace Size (length, height in mm): USNM 194559, 0.69, 0.54.

First Antenna (Figure 39d,e): 1st joint bare. 2nd joint with subterminal dorsal bristle. 3rd joint fused to 4th, with 1 long dorsal bristle, no ventral bristle. 4th joint with 2 bristles (1 ventral, 1 dorsal). Bristles of joints 5–8 similar to those of instar IV female, but not studied in detail.

Second Antenna: Protopodite bare. Endopodite 2-jointed: 1st joint with 1 short proximal anterior bristle; 2nd joint small with 1 or 2 terminal bristles (Figure 39e–g). Exopodite similar to that of instar IV female.

Mandible (Figure 39h): Similar to that of instar IV female.

Maxilla, Fifth Limb (Figure 39i), and Sixth Limb (Figure 39i,j): Not studied in detail but, in general, similar to that of instar IV female.

Seventh Limb (Figure 39i): Short, bare, thumb-like.

Furca (Figure 39k): Each lamella with 5 claws; claw 1 fused to lamella, claws 1–5 separated from lamella by suture; claws with teeth along posterior edge; left lamella with small spine following claw 5; right lamella anterior to left by three-fourths width of base of claw 1.

Bellonci Organ (Figure 39l): Similar to that of instar IV female.

Eyes (Figure 39a,e,h): Medial eye with brown pigment. Lateral eye about one-half size of medial eye, with 5 ommatidia.

Y-Sclerite: Typical for family.

Genitalia: Absent.

Gut Content (Figure 39m): Large segmented organism near midlength of gut.

Remarks: USNM 194559 is interpreted to be a male because of its having a short 7th limb.

DESCRIPTION OF INSTAR II (sex unknown) (Figure 40a–h).—Carapace shape and ornamentation similar to that of instar IV female (Figure 40a).

Infold and Central Adductor Muscle Attachments (Figure 40a): Similar to those of instar III male.

Carapace Size (length, height in mm): USNM 194560, 0.59, 0.46.

First Antenna (Figure 40b): Differs from that of instar III male in lacking a ventral bristle on 4th joint. Bristles of joints 7 and 8 not examined in detail.

Second Antenna (Figure 40c): Protopodite bare. Endopodite 2-jointed: 1st joint with single proximal anterior bristle; 2nd joint short, bare. Exopodite similar to that of instar III male.

Mandible, Maxilla, and Fifth Limb: Not examined in detail but, in general, similar to those of instar III male.

Sixth Limb (Figure 40d,e): With single bristle adjacent to hirsute node.

Seventh Limb (Figure 40f): Small, bare, thumb-like.

Furca (Figure 40g): Similar to that of instar III male.

Bellonci Organ (Figure 40h) and Eyes (Figure 40a,h): Similar to those of instar III male.

Genitalia: Absent.

Y-Sclerite: Typical for family.

DESCRIPTION OF INSTAR I (sex unknown) (Figures 40i–q, 41).—Carapace similar in shape to that of instar II (Figure 40i). Gel-like coating absent.

Infold: Infold fairly well developed, with visible inner margin. Anterior infold with small bristle near midheight (Figure 40j). Infold of caudal process with several bristles along inner margin of infold, but none observed closer to distal end of caudal process (Figure 40k). Usual 2 posterior setal bristles not observed, possibly lost during dissection.

Central Adductor Muscle Attachments (Figure 40i): Consisting of about 13 ovoid attachments.

Carapace Size (length, height in mm): USNM 194561, 0.50, 0.39.

First Antenna (Figure 40l,m): 1st, 2nd, and 4th joints without bristles. 3rd joint with 1 long dorsal bristle. 4th joint with spines forming row in distal dorsal corner. Distal joints fused. Sensory bristle of 5th joint bare. 5th and 6th joints fused. 6th joint with short medial bristle. 7th joint: a-bristle short; b-bristle about 3 times length of a-bristle; c-bristle about same length as sensory bristle of 5th joint, bare. 8th joint: all bristles bare; d-, f-, and g-bristles long, e-bristle short, about one-third length of e-bristle.

Second Antenna (Figure 40n–q): Protopodite bare. Endopodite 1-jointed; left limb of USNM 194560 with unsclerotized pointed tip; right limb with rounded tip. Exopodite 9-jointed: 1st joint with minute terminal medial bristle; bristles of 2nd joint with ventral spines and few long distal hairs; bristles of joints 3–8 with ventral spines and distal natatory hairs; 9th joint with 2 bristles (dorsal bristle short); joints 3–7 with spines forming row along distal edges.

Mandible (Figure 41a): Coxale: endite consisting of small medial spine; ventral margin with few indistinct hairs. Basale: medial side near ventral margin with 4 small bristles; lateral side without bristles near ventral margin; dorsal margin with 2 small subterminal bristles. 1st endopodial joint: dorsal margin with few spines forming terminal row; ventral margin with stout terminal claw with minute, indistinct, medial bristle near its base; medial side with distal spines. 2nd endopodial joint with stout, bare, ventral claw and small, terminal, dorsal bristle. 3rd endopodial joint with stout, bare, terminal claw, 2 minute ventral bristles, and 1 minute dorsal bristle.

Maxilla (Figure 41b–d): Coxale with transparent dorsal fringe, but without dorsal bristle. Endite I with 5 bristles; endites II and III each with 4 bristles. Basale with short bristle near exopodite. Exopodite with 3 bristles. Endopodite: 1st joint with spinous alpha- and beta-bristles; 2nd joint with 2 lateral a-bristles, no medial c-bristle, and 3 stout pectinate terminal bristles.

Fifth Limb (Figures 40i, 41e): Epipodite with 23 spinous bristles. Single endite with 1 short bristle. Exopodite hirsute: 1st joint with 2 bare bristles; 2nd joint with 3 bristles; joints 3–5 with 4 bristles (1 minute).

Sixth Limb (Figures 40i, 41f,g): Hirsute flap without bristles.

Seventh Limb (Figure 41h): Represented by small knob.

Furca (Figure 41i,l): Each lamella with 4 claws fused to lamella followed by stout spines (one of the spines could be interpreted to be an incipient 5th claw); all claws with teeth along posterior edges.

Bellonci Organ (Figure 41j): Elongate, with tapered tip.

Eyes: Medial eye with brown pigment (Figure 41j). Lateral eye about same size as medial eye, with 5 ommatidia and brown pigment (Figures 40i, 41k).

Y-Sclerite (Figure 41l): Anterior branches weakly developed.

Genitalia: Absent.

Posterior of Body (Figure 41l): Row of spines at posterodorsal corner just dorsal to end of girdle.

Gut Content: Unrecognizable brownish particles in posterior part of gut.

ONTOGENY.—Development of appendages of E. merx during ontogeny is normal for the family (Hiruta, 1977:44; 1978:262). The presence of three stout terminal claws on the 2nd endopodial joint of the maxilla of instar I is useful in identifying the first instar of species of the Sarsiellidae; later instars have 5 stout claws. The calculated growth factors of total carapace length between successive stages are as follows: I–II, 1.18; II–III (male), 1.17; III (male)–IV (female), 1.22 ; IV (female)-adult (male), 1.01. The calculated average growth factor of carapace length between the few juvenile instars in the collection is 1.19. This suggests that the adult female would have a length of about 1 mm, which is longer than the adult male length of 0.85 mm.

COMPARISONS.—The 1st antenna of E. merx differs from that of E. ryanae in lacking a ventral bristle on the 3rd joint. Relatively few species of the genus lack a ventral bristle on the 3rd joint (Kornicker, 1986a, table 4). The basale of the mandible of E. merx is without a dorsal bristle distal to midlength that is present on E. absens (Kornicker, 1981c:3).