Pseudosphyrapus azorensis, Larsen, Kim, 2012

Larsen, Kim, 2012, Tanaidacea (Crustacea) from Macaronesia II. The deep-water fauna from the Azores archipelago, Portugal, Zootaxa 3250, pp. 26-42 : 32-37

Pseudosphyrapus azorensis n. sp.

( Figs 3–5 )

Material examined. Holotype Ƥ with rudimentary oostegites. Body length 2.6 mm, MMF 42245. Station L09D20R(S01), 37º43'1536"N. 25º48'5290"W, South of S. Miguel Island, 312 m depth.

Diagnosis. Female. Rostrum with distal denticles. Pleonites with equal in size, laterally pointed epimera. Outer flagellum of antennule with four articles. Mandibular palp with setae only on article 3. Pereopod 1 carpus with two ventral spiniform setae. Pereopod 2 to 6 dactyli with two setae subdistally from unguis insertion.

Male unknown.

Etymology. Named after the Azores archipelago.

Description. Adult female.

Body ( Fig. 3 A,B) about 4.5 times as long as wide. Carapace wider than any pereonite; length including rostrum, longer than combined length of pereonite 1 to halfway on pereonite 3. Without spines but visual elements arranged in a curved spine-form. Rostrum not widening anteriorly, with several small tubercles. Pereonites all wider than long, all widening posterior and with demarcated shoulders. Pleon only slightly longer than carapace. Pleonites slightly narrowing in posterior direction. Lateral edges with spiniform processes. Pleotelson slightly shorter than last three pleonites combined, tapering to blunt apex.

Antennule ( Fig. 3 C) peduncle article 1 longer than rest of antennule, with several simple and setulated setae. Article 2 about 0.3 times as long as article 1, with one setulated and four simple distal setae. Article 3 longer than article 4, with one setulose and two simple distal setae. Article 4 (common article), shorter than other articles, with one simple seta. Inner flagellum with two articles, first article bearing only one simple seta while second article with four simple distal setae. Outer flagellum with four articles, article 2 and 3 with long (longer than twice article length) aesthetascs.

Antenna ( Fig. 3 D) almost as long as antennule. No rudiment of squama. Article 1 wider than following articles, with dorsal crenulated projection and no setae. Article 2 shorter than article 4 but longer than other articles, naked. Article 3 minute, naked. Article 4 longer than other articles, with multiple medial and distal setulated setae. Articles 5–8 of diminishing size, all with simple or setulated setae.

Mouthparts. Labrum ( Fig. 3 E) naked and with flat apex. Mandibles ( Fig. 4 A, B). Mandibular molar tapering slightly. Palp with three articles; article 1 and 2 naked, article 3 with two short and one long (twice as long) setae. Left mandible ( Fig. 4 A) lacinia mobilis with four denticles; incisor blunt and bifurcate; setal row with three tiny and apparently simple setae. Right mandible ( Fig. 4 B) incisor with flat apex; setal row minute with one bifurcate (perhaps rudimentary lacinia mobilis) and three simple setae. Labium ( Fig. 3 F), incomplete, lobe and palp with very few setules; palp with terminal seta. Maxillule ( Fig. 4 C) outer endite with seven spiniform setae and inner row of setules; inner endite with three setulated spiniform setae and two simple setae; palp bi-articulate, distal article with three setae with apical serration. Maxilla ( Fig. 4 D) body with row of inner and outer setae; outer lobe of movable endite with five inner- and two outer- proximally bipinnate, long setae; inner lobe of movable endite with five proximally setulose spiniform and two minute simple setae; outer lobe of fixed endite with three proximally setulose spiniform setae and two trifurcate spiniform setae; inner lobe of fixed endite with row of several distally curved setae as well as scattered longer setae. Maxilliped ( Fig. 4 E) palp article 1 with one longer inner and one shorter outer seta, article 2 with seven inner and one spiniform outer setae, article 3 with two groups of four inner setae each, article 4 with five inner and one outer setae; endites outer corners setulated, distal edge with five apparently simple spiniform setae on inner corners, with one longer- proximally setulose outer seta, inner margin with two coupling hooks; outer margin with three setulated spiniform setae; basal part with, apparently overlapping lobe, with medial setules and three to four outer spiniform setulated processes. Epignath ( Fig. 4 F) body completely naked, terminal seta with minute terminal setulation.

Cheliped ( Fig. 5 A) basis oval, longer than merus, with small ventromedial spiniform seta and ventrodistal simple seta; with tri-articulate exopod, bearing three plumose terminal setae. Merus clearly shorter than carpus, with one ventro-subdistal seta. Carpus shorter than basis, with minute dorsodistal seta, ventrally with five simple setae. Propodus (including fixed finger) longer than basis, with two distally serrated inner setae and two simple setae at dactylus insertion. Fixed finger with three setae ventrally and three setae on inner margin; inner margin with crenulations diminishing in proximal direction. Dactylus as long as fixed finger, without processes, with three medial setae.

Pereopod 1 ( Fig. 5 B) twice as long as pereopods 2–6. Coxa with irregular edge (possibly an artifact) and two setae. Basis shorter than three succeeding articles combined, with one seta one each margin and additional one ventrodistal seta; with tri-articulate exopod, bearing four plumose setae. Ischium with ventrodistal seta. Merus longer than carpus, with one dorsodistal seta and ventrally with four simple and one spiniform setae. Carpus half as long as basis, with one dorsodistal and two ventral spiniform setae and scattered simple setae. Propodus shorter than carpus, with four ventral and one dorsal spiniform setae, with three simple dorsal setae. Dactylus and unguis combined as long as propodus; dactylus with weak serration (two spines on left pereopod, three on right pereopod), three times as long as unguis.

Pereopod 2 ( Fig. 5 C) only 1.1 as long as pereopods 3–6. Coxa naked (not illustrated). Basis as long as the three succeeding articles combined, with two ventral setae. Ischium with one seta. Merus shorter than carpus, with three ventral setae. Carpus longer than propodus, with two simple ventral, three simple dorsal, and four distal setae of which one is spiniform. Propodus as long as dactylus and unguis combined, dorsally with one setulose medial and two simple distal setae, ventrally with one simple and three spiniform setae. Dactylus and unguis smooth and with two setae subdistally from unguis insertion. Dactylus three times as long as unguis.

Pereopod 3 ( Fig. 5 D) as pereopod 2 except: basis with one bipinnate seta on each margin as well as one ventrodistal simple seta. Merus with only two ventral setae. Carpus longer than propodus, with two ventral spiniform setae and two simple, distal setae on each margin. Propodus shorter than merus, without dorsal setulated seta.

Pereopod 4 ( Fig. 5 E) basis with five dorsal and one ventral setulated setae proxi-medially, and one ventrodistal simple seta. Ischium with one simple seta. Merus shorter than carpus, with two ventral and one dorsal simple setae. Carpus with multiple ventral and distal setae decreasing in width medially ( Fig. 5 E1), and one ventrodistal spiniform seta. Propodus as long as dactylus and unguis combined, with one setulose dorso medial seta and multiple distal setae with serrated apex. Ventrally with two simple and three bipinnate spiniform setae. Dactylus ( Fig. 5 E1) smooth, with two setae subdistally from unguis insertion, three times as long as unguis. Unguis with ventrodistal serration.

Pereopod 5 ( Fig. 5 F) as pereopod 3 except: with a few extra setae.

Pereopod 6 ( Fig. 5 G) as pereopod 5 except: basis with more setulose setae.

Pleopods ( Fig. 5 H) basal article almost as long as endopod, with one plumose distal seta. Exopod bi-articulate; article 1 with one plumose distal seta, article 2 with five plumose distal setae. Endopod slightly longer than exopod, with one medial and five distal plumose setae.

Uropod ( Fig. 5 I) longer than pleon. Basal article with two distal setae. Endopod with ten articles of which most have simple or setulose distal setae; articles 6, 8, and 10 with long (longer than three articles combined) setae. Exopod with three articles; articles 1 and 2 naked; terminal article with two distal setae longer than exopod.

Remarks. This species is unique within this genus in only having mandibular palp setae on article 3.

The spine-like structures on the proximal part of the maxilliped deserves serious attention. These structures are only reported from the family Sphyrapodidae , but not in all species and not correlated with specific genera. These ‘spines’ are observed in the new species and also found in Pseudosphyrapus siegi ( Viskup & Heard 1989), P. c u s - pidiger (Kaukui et al. 2007), P. centobi (Bäcescu 1981) and P. quintolongus (Kakui et al. 2007) (but only from the female) and are not reported from the other species of the genus. However, this may be an observational mistake as this character is reported from a number of other sphyrapodids: Kudinopasternakia balanorostrata (Kauku et al. 2007) , K. brasiliensis ( Santos 2007) , K. trispinosa ( Santos 2007) , K. dispar ( Lang 1968) , and something that could be interpreted as such spines are illustrated on Sphyrapoides tuberculifrons (Guțu & Heard 2002). The main problem with these structures seem to be their exact location about which there is little consensus. Kakui & Kajihara (2011:57, fig 3B) reports them as origin from the coxa and so does Viskup & Heard (1989:110) although their illustration ( Viskup & Heard 1989:112, fig.4C) suggest they arise from both the coxa and basis. Others report them from both the coxa and basis (Bäcescu 1981, Kaukui et al. 2007) but the later authors also states concern about their true origin (Kaukui et al. 2007:40). This author is convinced that these structures arise from a thin membranous flap covering the proximal part of the maxilliped, partly covering both the basis and coxa making observation of this character difficult.

Figures

FIGURE 3. Pseudosphyrapus azorensis n. sp., holotype, female. A, dorsal view. B, lateral view. scale bar 0.5 mm. C, antennule. D, antenna, scale bar 0.5 mm. E, labrum. F, labium. Scale bar 0.1 mm.

FIGURE 4. Pseudosphyrapus azorensis n. sp., holotype, female. A, left mandible. B, right mandible. C, maxillule. D, maxilla. E, maxilliped. F, epignath. Scale bar 0.1 mm.

FIGURE 5. Pseudosphyrapus azorensis n. sp., holotype, female. A, cheliped. B, pereopod 1. C, pereopod 2. D, pereopod 3. E, Pereopod 4. E 1, same, propodus / dactylus, scale bar 0.1 mm. F, pereopod 5. G, pereopod 6. H, pleopod, scale bar 0.1 mm. I, uropod. Other scale bar 0.5 mm.