Lebbeus eludus Jensen, 2006, new species

Lebbeus eludus new species

Figs. 1–3; 4A,B

Type material: Holotype male, postorbital carapace length 6.9 mm. Burrows Channel, Anacortes, Washington (48.29.4°N, 122.41.7°W), suction gun, 14 m, 6 December 1997, G.C. Jensen, collector. National Museum of Natural History, Smithsonian Institution, USNM 1092254. Also allotype, 6.5mm, same location and date, USNM 1092255.

Paratypes collected at the same location as above, and same date except as noted. U.S. National Museum of Natural History (2 males, USNM 1092256); California Academy of Sciences (2 males, l female, 21 November 1997, 16 m, CASIZ 174052); Natural History Museum of Los Angeles County (2 male, 1 female, 21 November 1997, 16 m, LACM CR 1997-140.1); National Science Museum, Tokyo (2 males, 1 female, NSMT-Cr 16842); British Columbia Provincial Museum (1 male, RBCM 006-00056). Female, 12.9 mm cl, Griffith Harbor, west coast of Banks Island, British Columbia, Canada (53.36.04°N, 130.32.55°W), 5–8 m, 20 July 1974, A. Peden, collector, RBCM 974-00383-3.

Description: Integument smooth, thick. Rostrum short, horizontal or descending, 0.31–0.48 carapace length; usually slightly exceeding cornea and reaching 0.66–0.75 length of first article of antennular peduncle. Carapace with two postorbital dorsal teeth, the anteriormost smaller and usually obscured in lateral view by the supraorbital spine. Rostrum lacking dorsal teeth (rarely with one tooth) and usually with one ventral, subterminal tooth. Supraorbital spine massive, with very deep ventral notch; suborbital and antennal spines strong; anterolateral margin extremely convex; pterygostomian spine distinct (Fig. 2 A).

Abdomen smooth except for deep, dorsal, transverse furrow on the second abdominal somite. Dorsal posterior margin of third abdominal somite strongly produced. Pleuron of first abdominal somite with slight anterior lobe; ventral margin rounded. Pleura of abdominal somites 2 and 3 rounded; pleura of fourth and fifth abdominal somites with posteroventral spines; spine on fourth sometimes obsolescent in larger specimens. Sixth somite 1.3–1.6 times length of fifth somite. Telson 1.2–1.38 length of sixth somite, with 3–5 pairs of dorsolateral spinules; tip with three pairs of terminal spinules, outermost similar to dorsolateral series, innermost pair with setules; margin of telson with long dorsomesial plumose setae (Fig. 3 E).

Eye diameter 0.17–0.19 carapace length; cornea pigmented, round, and subequal in diameter to cylindrical stalk; ocellus present.

Basal article of antennular peduncle (Fig. 2 B) with 3–4 distal, dorsal spines and a strong subdistal, ventromesial spine; stylocerite reaching to middle or end of second article of antennular peduncle. Second article with large dorsolateral spine on distal margin; third article with erect dorsal spine. Dorsolateral flagella 0.85–1.0 carapace length, with 16–29 thickened segments; distal portion slender, with 8–13 segments; ventromesial flagella slightly longer than dorsolateral, with 33–42 segments.

Bascicerite of antenna with rounded dorsal lobe and blunt ventrolateral spine; carpocerite slightly exceeding end of third article of antennular peduncle. Antennal scale 2.3–2.7 times longer than wide and 0.56–0.7 carapace length; lateral margin straight, spine exceeded by lamella. Antennal flagellum 2.7–4.7 times carapace length.

Mandibles with sparsely setose, two-segmented palps; incisors slender, with 4–5 distal teeth. Molar of left mandible (Fig. 2 C) large, subcylindrical, with large distal tooth. Right molar with 5–9 teeth on margin.

First maxilla with shallowly bilobed palp, lateral lobe tipped with a slender simple seta and a subterminal slender seta; mesial lobe with a thicker, plumose seta. Distal endite oval, densely armed with spinules and setae on mesial margin; proximal endite with long, stout setae.

Second maxilla (Fig. 2 D) with palp tipped by a long and a short seta. Basal endite bilobed, mesial margin densely setose. Coxal endite very small, with 6–8 long, plumose setae. Scaphognathite densely fringed with plumose setae, longest anteriorly and anteromesially and along posterolateral margin. Anterior lobe of scaphognathite long, subrectangular; posterior lobe rounded.

First maxilliped (Fig. 2 E) with two segmented palp, distal article subequal to proximal. Caridean lobe well developed and fringed with long plumose setae. Exopod long, tipped with setae. Endites well developed, densely setose on mesial margin. Epipod large, bilobed.

Second maxilliped (Fig. 2 F) with ultimate article densely setose on mesial margin; penultimate article with many long setae. Exopod well developed, tipped with long setae. Epipod triangular, with small podobranch.

Third maxilliped (Fig. 2 G) with 8–9 apical and subapical corneous spinules and slightly exceeding antennal scale; mesial margins of ultimate and penultimate articles densely setose. Antepenultimate article with strong distal spinule on lateral margin and small, subdistal, ventrolateral spinule. Hooked epipod present.

Pereopods 1–5 with pleurobranchs. First pereopods (Fig. 3 A) equal, chelate, exceeding antennal scale by about 0.5 length of propodus. Dactyl 0.3–0.46 propodus length; propodus 0.56–0.6 female carapace length, 0.6–0.9 male carapace length; propodus 4.5–4.8 times longer than wide. Antennal cleaning brushes on propodus and carpus. Carpus 1.5–2 times longer than wide; merus length 3.7–4.9 greater than width and 1.9–2.4 length of carpus. Coxa with hooked epipod and setobranch.

Second pereopods equal, chelate, exceeding end of antennal scale by 1–5 distal segments of carpus; dactyl 0.31–0.47 propodus length. Carpus with 7 segments, third from merus longest. Merus 0.59–0.69 length of carpus. Coxa with hooked epipod and setobranch.

Third pereopod (Fig. 3 B, C) dactyl with corneous, bifid tip preceded by 3–4 spinules on flexor margin. Propodus 11.6–14.2 times as long as wide; flexor margin with about 25 small spinules in two indistinct rows, spinules increasing with size distally. Carpus 3.5–5.0 times longer than wide. Merus 7–10 times longer than wide. Coxa with hooked epipod and setobranch. Fourth and fifth pereopods similar to third, but lacking epipods and decreasing in size; setobranch present on coxa of fourth pereopod; fifth pereopod with propodal grooming brush.

Endopod of first pleopod of female reaching middle of exopod. Endopod of first pleopod of male fused with appendix interna; overall length about two-thirds that of exopod. Lateral margin convex with long plumose setae and abrupt shoulder bearing several long setae; fingerlike appendix interna comprising distal 0.2 of length, with cincinnuli at tip; mesial margin somewhat concave with short, curved setae. Second pleopod of male with large appendix masculina (Fig. 3 D), greatly exceeding appendix interna and tipped with numerous long spinules. Uropods subequal in length, both exceeding telson.

Color: Carapace and abdomen a uniform reddish orange with scattered, minute white dots; carapace occasionally with 4–5 faint white or pale blue oblique lines (Fig. 4A). Appendages reddish with no banding. At night the entire shrimp fades to pale pink or lavender (Fig. 4 B).

Distribution: Banks Island, Hecate Strait, British Columbia, Canada to Burrows Channel, Anacortes, Washington, USA; from 5– 20 m.

Etymology: The specific name refers to the very evasive behavior of this shrimp. The common name “elusive lebbeid” is suggested.