Akanthoparapseudes alfaroae, Heard, Richard W. & Morales-Núñez, Andrés G., 2011

Heard, Richard W. & Morales-Núñez, Andrés G., 2011, Akanthoparapseudes alfaroae, a new genus and species of apseudomorphan tanaidacean (Crustacea: Malacostraca: Peracarida) from Puerto Rican coastal waters, Zootaxa 3111, pp. 49-63 : 53-62

Akanthoparapseudes alfaroae , n. sp.

( Figs. 2–7 )

Material examined. Holotype: subadult female ( USMN 1160079), 18˚16’21.81’’N, 65˚19’09.01’’W, 3.2 km Southwest of Culebra Island, Puerto Rico, depth 28 m, collected between October 2002 /2003. – Paratypes (same collection data as for holotype): two subadult females ( USMN 1160080). Additional specimens from the type locality are in the collection of second author.

Diagnosis. As for genus.

Etymology. The species is named in honor of Mónica Alfaro Lozano in recognition of her support and encouragement of our studies on the Tanaidacea from Puerto Rican waters.

Type locality. 18˚16’21.81’’N, 65˚19’09.01’’W, 3.2 km Southwest of Culebra Island, off eastern Puerto Rico, depth 28 m, soft substrata (sand).

Distribution. Presently known only from the type locality.

Description. Subadult female

Body ( Fig. 2 A): Length 4.5 to 5 mm, about 4.8 times longer than wide.

Cephalothorax ( Figs. 2 A, H): Slightly more than 22% of body length. Carapace smooth, longer than wide, subquadrate in dorsal aspect, slightly longer than pereonites 4 and 5 combined, with three simple setae on distolateral margins. Rostrum triangular, apically subacute. Eye lobe distinct unarmed; eyes poorly developed, lacking distinct pigment, with about eight poorly formed ommatidia. Epistomal spine relatively small, directed antero-ventrally.

Pereon ( Figs. 2 A–C): Slightly less than 55% of body length, generally decreasing slightly in width posteriorly; first pereonite widest, subquadrate, with two or three small simple setae on anterolateral corners, posterolateral corners rounded; first, third and fifth pereonites subequal in length; pereonites 2 and 6 slightly shorter than other pereonites with small spine on posterolateral corners; pereonite 2 with small simple setae on anterolateral corners and one small simple seta on posterolateral corners; third to fifth pereonites 3 to 5 with a row of several small simple setae on anterolateral corners; pereonite 4 longer than other pereonites; pereonite 5 slightly smaller than fourth; pereonite 6 trapezoidal, with several simple setae on mid-lateral margin.

Pleonites ( Figs. 2 A, D–E): Compressed, slightly less than 15% of body length, shorter than carapace length; pleonites 1 to 4 each decreasing slightly in width posteriorly, each pleonite about twice as wide as long, with few small simple setae laterally, each pleonites with lateral lobes, each lobe with five simple setae, three long, one short, and one very small, on tip and one very small simple seta on mid-ventral margin ( Fig. 2 D); pleonite 5 wider than other pleonites, without lateral lobes, having small simple setae dorsally and five simple setae, one long, three short, and one very short, on distolateral margin ( Fig. 2 E).

Pleotelson ( Figs. 2 A, F): About 8% of total length, subquadrate, about as long as wide, widest posteriorly just above lateral insertion of uropods, slightly longer than pereonite 3; pair of long, submarginal setae originating in anterior third; small protuberance on mid-lateral margin with cluster of three simple setae of varying length; pair of submedial simple setae in med-region; pair of long, submedian, simple setae in posterior one third, reaching wellpast posterior margin of pleotelson.

Antennule ( Fig. 3 A): Peduncle article 1 with length about 3.3 times width, with three sensory setae (two proximal and one on medial along lateral margin), three simple setae mid-dorsally and cluster of simple setae subdistally on both margins; article 2 about half length of article with cluster of 8 to 10 simple setae distolateral margin and row of 4 simple setae subdistally on inner margin; article 3 slightly more than half length of article 2, with three or four simple setae distally on both margins Article 4 (common article) two thirds length of article 3. Accessory flagellum about two thirds length of main flagellum, with seven articles. Main flagellum with 14 articles, distal margins of articles 6, 8, 10 and 12 each with single aesthetasc.

Antenna ( Fig. 3 B): Peduncle with five apparent articles. Article 1 with three distolateral simple setae. Article 2 with three simple setae on inner margin and two simple setae on outer margin; squama slightly longer than combined length of articles 3 and 4, bearing 14 to 16 simple setae of varying lengths. Article 3 with simple seta on inner distal margin. Article 4 distinctly longer than article 3, with three sensory setae (one proximal on outer margin, and two distally on inner margin); article 5 about twice length of article 3 with four sensory setae (one distal on inner margin, and three on outer margin), and four simple setae, two on inner medial margin and two on subdistal margin. Flagellum with six articles having simple setae.

Labrum: not recovered.

Mandibles ( Figs. 4 A–D). Left mandible, incisor process with tip having four teeth; lacinia mobilis tridentate; setiferous lobe with six bifurcate setae. Molar process thick and relatively short, with grinding surface having welldeveloped micro-denticles. Palp with 3 articles; first article shortest bearing six to seven simple setae; second article longest, about twice as long as first, with six setae, five setulose and one simple, on distal margin; third article same length as first article, but slightly more slender with five to seven setulate setae on distal margin, and three long simple setae and two short plumose setae distally ( Fig. 4 A). Right mandible with reduced bidentate lacinia mobilis distinct from setiferous lobe; setiferous lobe with six bifurcate setae; incisor and molar process similar to that of left mandible.

Maxillule ( Figs. 4 E–F): Inner endite with five setulate distal setae, both margins finely setose. Outer endite with 12 spiniform setae (at least one being serrate) and two subdistal setulate setae, margins finely setose (setae longer on lateral margin); palp biarticulate with three subdistal and one distal whip-like “cleaning” setae.

Maxilla ( Fig. 4 G): Outer lobe of fixed endite with two to three pectinate and three trifurcate setae; inner lobe of fixed endite with row of about 23 to 26 basally swollen setae; outer lobe of movable endite with five to seven simple setae and two long setulose setae on distal outer margin; inner lobe of movable endite with 11 to 14 simple setae.

Labium ( Fig. 4 H): with outer margin serrate, inner margin setulose. Palp with row of fine lateral setules and three spiniform distal setae.

Maxilliped ( Figs. 5 A–B): Basis slightly longer than broad, outer face with small short simple seta near inner distal margin. Endite (inner plate) with inner margin having three coupling hooks, row of 11 to 13 basally-swollen setulate setae proximally and distally with row of apically bidentate or grooved spiniform setae, innermost short, distinctly bidentate, becoming longer and distally bent and grooved laterally; relatively long, finely setulate spiniform seta present subdistally ( Fig. 5 B). Palp (outer face): article 1 length about two thirds width, inner margin with long seta (slightly shorter than article 2); small short simple seta near distal inner margin; outer margin with stout spiniform seta, less than half length of article 2 ( Fig. 5 A). Article 2 slightly longer than broad, inner margin with row of 14 to 16 small to medium-sized setae along distal two thirds of article, three long attenuated simple setae medially and three long attenuated setae distally near base of article 3; distal corner of lateral margin with stronglydeveloped spiniform seta extending to mid region of article 4 ( Fig. 5 A); article 3 about twice as wide as long; inner and distal margins combined with 17 to 20 simple attenuated setae ( Fig. 5 A); outer margin naked. Article 4 about as long as wide, slightly less than half width of, and inserted laterally in, article 3; distal margin having six simple attenuated setae becoming longer laterally.

Epignath ( Fig. 5 C): Suboval, cup-shaped with short, stout seta on inner distal margin and two small simple setae on inner mid-margin.

Cheliped ( Figs. 5 D–F): Basis moderately inflated distally, constricted proximally with three to folur small setae anteroproximally near junction with coxa; anterior margin slightly concave; posterior margin convex, rounded with stout spiniform seta, and four, two long and two short, distal setae near posterodistal margin. Merus length about three times width, having cluster of three simple subdistal setae on anterolateral face near proximal junction with carpus; two long simple setae medially on or near posterior margin, and posterodistal margin with cluster of seven to eight simple setae of varying lengths. Carpus elongate, narrow (length about five times width, inserted anterodistally into merus; midposterior margin with four simple setae (one long, reaching to junction with propodus), posterodistal margin with cluster of three simple setae, one of these long (reaching to middle of fixed finger), two pairs of simple setae on, or near, anterior and posterior distal margins. Propodus with three attenuated simple setae on anterodistal margin of palm adjacent to articulation with base of dactylus, posterior margin of fixed finger with row of 8 to 10 simple setae (two distal most short, curved distally); lateral aspect ( Fig. 5 E): outer face of palm near junction pollex (fixed finger) and dactylus (movable finger) with small sub-marginal simple seta near upper base of fixed finger; fixed finger with semicircular row of 15 to 18 sub-marginal setae; propodus inner aspect ( Fig. 5 F): four submarginal setae (three simple and one small and setulate) medially at junction with movable finger, base of fixed finger near cutting edge with three simple setae, seta medially in distal third; unguis horn-colored. Dactylus slightly less than half length of palm, with three simple setae just proximal to unguis; unguis small, horn-colored, with bidentate tip. Exopod with three articles, third article bearing four plumose setae.

Pereopod 1 ( Figs. 6 A–B): Coxa with anteriorly directed process, but reduced to rounded protuberance (not observable from dorsal aspect) bearing five to eight simple setae distally. Basis length slightly more than 1.5 times width; anterior margin with proximal two thirds having row of six simple setae with proximal-most smallest, and strongly-developed, spiniform seta (just distal to row of simple setae); posterior margin with three stout spiniform setae, and cluster of three long simple setae on distal margin immediately adjacent to distal most spiniform seta). Ischium much wider than long, with three simple setae, one short and two long, on posterodistal margin. Merus widest distally, length less than 1.5 times width, length subequal to that of carpus and propodus combined; anterior margin with simple seta subdistally and strong spiniform seta on distal margin; posterior margin with four simple setae near mid-margin, simple seta on subdistal margin, and stout, conical, spiniform seta distally. Carpus slightly longer than wide; anterior margin having stout spiniform seta and four simple setae; posterior margin with two stout conical spiniform setae, distal-most largest, and two simple setae. Propodus narrower and slightly shorter than carpus; anterior margin with sensory seta on mid-margin and three simple setae,(two medial and one sub-distal), and two (one subdistal and one distal) stout conical spiniform setae becoming shorter proximally; posterior margin with four stout conical spiniform setae becoming longer distally with four simple setae interspersed between them, and small, stout, finely setulose setae between distal-most spiniform seta and articulation with dactylus. Dactylus slightly shorter than propodus; with two minute anterior setae proximal to junction with unguis; posterior margin having four small teeth; unguis simple, about one third total length of dactylus. Exopod with three articles; article 1 very small, article 3 bearing six terminal or subterminal plumose setae.

Pereopod 2 ( Fig. 6 C): Basis with length slightly less than three times width, anterior margin having well-development upturned spine on medial margin, plus 11 to 12 marginal or submarginal simple setae of varying length, most clustered proximally; posterior margin with proximal spiniform process armed with two small simple setae, mid-margin with two simple setae (larger about twice length of smaller), five simple setae, two short and three long, on posterior distal margin. Ischium about twice as wide as long, anterior margin with spiniform seta. Merus about half length of carpus, posterior margin with one spiniform seta distally, with six setae of varying length and one simple setae on subdistal lateral face; anterodistal margin with one spiniform seta and four, two relatively long and two short, simple setae. Carpus slightly longer than propodus; anterior distal and subdistal margin with cluster of seven or eight simple distally attenuated setae and sub-marginal spiniform seta; posterodistal margin with four simple setae, sub-marginal spiniform seta on medial face. Propodus subequal in length and narrower than carpus; anterior margin with large sensory setae in mid-region, distal half of margin with seven to nine simple distally attenuated setae of varying length and, with two (one medial and one subdistal) short spiniform setae and long spiniform setae, latter about four fifths length of dactylus; posterior margin with three subequal spiniform setae and six simple setae. Dactylus about half length of propodus with weakly dentate distoventral margin, and two minute setae on anterior margin; unguis simple, about one third total length of dactylus.

Pereopod 3 ( Fig. 7 A): Basis with length slightly less than 2.5 times width; anterior margin naked; posterior margin or sub-margin with four simple setae of variable length, distal cluster of four attenuated setae (longest over ¾ length of basis); cluster of four long attenuated setae on proximal and distal third of outer face. Ischium about as long as wide, anterodistal margin with spiniform seta; posterior margin having four simple setae, one small and three long, distally. Merus length about 1.7 times width; posterior margin having four simple setae (two long) and large spiniform seta; subdistal lateral face with small stout spiniform seta and long simple seta (about length of carpus). Carpus subequal length to merus; anterodistal margin with large spiniform seta and three (one short and two long) simple setae; outer face with three simple setae and spiniform seta sub-distally; posterior margin with three simple setae, one long, two short, and large spiniform seta. Propodus, length little over twice width, slightly longer and narrower than carpus; anterior margin having sensory seta near mid margin, three attenuated simple setae, and three spiniform setae increasing in length distally; outer face with medial small spiniform and simple seta and subdistal small simple seta, posterior margin with three spiniform setae and four simple setae (distal-most, adjacent to dactylus, very small). Dactylus narrow about as long as propodus, two small on anterior margin setae; unguis simple, unguis about 1/3 total length of dactylus.

Pereopod 4 ( Fig. 7 B): Basis with length slightly less than 2.5 times width; anterior margin with three small sensory setae (one proximal and two medial); lateral face with three long and four to five short simple submarginal setae (usually anteriorly directed); posterior margin with small, simple seta subdistally posterodistal cluster of three setae of varying length, longest extending to distal region of carpus. Ischium length about 1.2 times width, anterior margin with one spiniform seta; posterodistal margin with three setae of varying length, longest longer than merus. Merus slightly longer than wide, anterior margin short, naked; posterior margin medially with spiniform seta and five marginal and submarginal simple setae of varying length; anterodistal margin with long simple seta and two spiniform setae; distomedial margin with strongly-developed attenuated seta reaching over twjo thirds length of carpus. Carpus slightly longer than wide; anterodistal margin with three attenuated setae (two over three fourths length of propodus), remaining anterior margin asetose; posterior margin with four rod-like setae becoming larger distally, and three attenuate setae; distal half of outer face with three spiniform setae becoming longer distally, and three simple setae of varying length, small sub-marginal simple seta near mid-point of posterior margin. Propodus length about 3 times width, slightly shorter and narrower than carpus; anterior margin with sensory seta; inner face with one, sub-marginal (more proximal) simple attenuated seta, two simple setae, one short and stout and two subdistal rod-like setae; posterior margin with two attenuated simple setae, long proximal rod-like seta and short spiniform seta distally near base of dactylus; distal margin with three long rod-like setae (nearly as long as dactylus and each with distal setule) and cluster short pectinate setae. Dactylus subequal to length of anterior margin of propodus, with two small dorsal setae; unguis, simple, small, about one fifth total length of dactylus.

Pereopod 5 ( Fig. 7 C): Basis about 3 times longer than wide. Two short sensory setae on anteroproximal margin; cluster of seven to eight simple setae of varying of length on proximal anterolateral face; anterior margin with three marginal simple setae and two, one relatively long and one short, submarginal simple setae in distal third; posterior margin with two small setae, proximal-most minute, and anterodistal margin having four simple setae of varying length with longest reaching carpus. Ischium with length about twice width; anterior margin with two, one relatively long and other short, spiniform setae; posterodistal margin with one short and two very long setae, longest reaching propodus. Merus about 2.5 times longer than wide; anterior margin with spiniform seta on distal margin; distal half of posterior margin with cluster of seven or eight simple setae of varying of length (longest three equal to, or greater than, length of carpus), large spiniform seta on distolateral margin and smaller spiniform seta on subdistal margin. Carpus slightly longer than wide; anterior margin naked, inner distal margin with cluster of five simple setae of varying lengths withlongest extending to base of dactylus; inner face with two simple and three rodlike spiniform setae, increasing in size distally; posterior margin with five simple and four rod-like spiniform setae, increasing in size distally. Propodus slightly more than 3.5 times width, about as long as,. but narrower than carpus; anterior margin with large sensory seta medially; one medial and five subdistal or distal rod-like spiniform setae of varying lengths and one medial and three submarginal simple attenuated setae present; posterior margin with three rod-like spiniform setae (becoming larger distally) and two simple attenuated setae. Dactylus slightly shorter than propodus with two minute setae on anterior margin proximal to junction with unguis; unguis simple, slightly less than one-third total length of dactylus.

Pereopod 6 ( Fig. 7 D): Basis swollen, length about twice width, with two short sensory setae and two simple setae proximally, 14 to16 long simple setae on lateral face of adjacent to anterior margin, posterior margin with three (one small) simple setae near to medial margin and 8 to 10 long simple setae, some extending distally to midregion of carpus, on distal margin. Ischium length about twice width, anterior margin with one short and one long spiniform setae; posterodistal margin with five simple setae of varying length (longest extending distally to carpus). Merus proximally attenuated, slightly longer than wide; anterior margin three long setulate setae extending near or beyond junction of carpus and propodus; posterior margin with six to seven attenuated simple setae of varying length and one spiniform seta distally; inner face subdistally with six to seven attenuated simple setae of varying length. Carpus length about twice width, anterior margin with five long setulate setae; oblique subdistal row of six simple attenuated setae originating at anterior margin (becoming shorter posteriorly) and ending medially adjacent to spiniform seta; one long attenuated simple seta medially, extending proximally to propodus; eight to nine simple attenuated setae of varying lengths and three narrow spiniform setae occurring on or adjacent to posterior margin. Propodus with length 3 times width, slightly shorter and narrower than carpus; anterodistal margin with brush seta, three subterminal rod-like spiniform setae (two long, one short), long attenuated seta, and terminal rodlike spiniform seta (slightly more than half length of dactylus); posterior margin with two elongate spiniform setae and compact row of about 18 to 20 small, pectinate setae. Dactylus slightly shorter than propodus with three minute setae, two on anterior margin nd one posterior margin, proximal to junction with unguis; unguis about one third total length of dactylus, with one minute setae on midposterior margin.

Pleopods ( Figs. 3 C–D): Biramous well-developed, becoming only slightly smaller posteriorly. Pleopod 1: basal article with four or five setulate setae on both inner and lateral margins ( Fig. 3 C). Exopod slightly longer than basal article with 11 to 13 plumose plus two small setulate setae on inner proximal margin. Endopod shorter than exopod, about equal in length to basal article, having12 to 14 plumose setae on inner, distal and distal half of lateral margins. Pleopods 2 to 5 with basal article becoming shorter and less setose posteriorly ( Fig. 3 D).

Uropod ( Figs. 2 A, F–G): Basal article with length about 1.7 times width, with one shorter and one longer simple setae on subdistal outer margin, posterior margin having three simple subdistal setae of varying of length, with one shorter and one longer simple setae on subdistal inner margin. Exopod with 8 to 9 articles, distal-most article having four apical simple setae. Endopod with division of articles or pseudoarticles unclear, apparently numbering from 27 to 33, distal-most article with four simple apical setae.

Male and adult female: unknown or recognized.

Remarks. As mentioned in the Remarks for the genus, Akanthoparapseudes alfaroae , n. sp. may be related to “Parapseudid? sp. A” sensu Heard et al. (2004) reported and partially illustrated from the Gulf of Mexico, but it can be readily distinguished from this as-yet-undescribed species by the armature of the first and second pereopods. On A. alfaroae , the first pereopod has the anterior margin of the basis armed with a large distinctive spiniform seta and a single well-developed spiniform seta on the anterodistal margin of the carpus, whereas, on “Parapseudid? species A” the basis lacks a large spiniform seta on the anterior margin and the anterodistal margin of the carpus is armed with two large, distinctive, spiniform setae. Pending the descriptions of additional species attributable to this genus, the specific or generic importance of these pereopod characters remains to be determined.

There is the possibility that A. alfaroae may be a protandric hermaphrodite. The six specimens examined by us appeared to be subadult (non-incubatory) females or possibly non-sexually dimorphic males, though this latter conjecture seems far less plausible. Their chelipeds appear typical of other parapseudid females, but there is no indication of developing oostegites bubs. On the mid-ventral surface of the sixth pereonites of all the specimens we examined, however, an acutely tipped and posteriorly directed penial-tubercle-like process, similar to that for the male of Saltipedis puertoricensis Morales-Nuñez , Heard, & Alfaro, 2010, was present. Adult females of S. puertoricensis , however, were also observed to have a similar, but reduced hyposphenium or vestigial penial-tuberclelike process ( Morales-Nuñez et al. 2010).

Ecological notes. Based on its morphology and the sand substrata (i.e. fine and medium sand, indicating of coralline origin from fragments of algae, shells, and coral) in which it occurs, A. alfaroae appears to be a fossorial, shallow-burrowing, species. It co-occurred with a variety of infaunal and epifaunal invertebrates, including at least 14 other species of Tanaidacea These include the recently described apseudomorphan, Saltipedis (Spinosaltipedis) puertoricensis , and undescribed tanaidomorphans belonging to the genera Paratanais Dana, 1852 , Pseudoleptochelia Lang, 1973 , and a putative new genus similar to Pseudonotanais Lang, 1973.

Figures

FIGURE 2. Akanthoparapseudes alfaroae n. gen., n. sp., subadult female holotype. A, body, dorsal view; B, enlargement of posterolateral margin of pereonite 2; C, enlargement of posterolateral margin of pereonite 3: D, E. enlargement of lateral margins of first and fifth pleonites, repectively, 1; F, enlargement of pleotelson; G, enlargement of uropod; H, lateral view of cephalothorax and pereonite 1. Scale line: A = 1.0 mm; H = 0.2 mm.

FIGURE 3. Akanthoparapseudes alfaroae n. gen., n. sp., subadult female holotype. A, antennule; B, antenna; C, basal article of pleopod 1; D, pleopod 5. Scale line: A – B = 0.2 mm; C – D = 0.1 mm

FIGURE 4. Akanthoparapseudes alfaroae n. gen., n. sp., subadult female paratype. A, left mandible; B, enlargement of tip of molar process; C, enlargement of lacinia mobilis and tip of incisor process; D, enlargement of tridentate lacinia mobilis; E, maxillule; F, enlargement of tip of maxillule; G, maxilla, H, labium. Scale line: A, E and H = 0.2 mm; G = 0.1 mm.

FIGURE 5. Akanthoparapseudes alfaroae n. gen., n. sp., subadult female paratype. A, maxilliped showing setation; B, inner plate; C, epignath; D, left chela, lateral view, E, enlargement of tip of half chela, F, inner aspect of half chela. Scale line: A – D and F = 0.2 mm.

FIGURE 6. Akanthoparapseudes alfaroae n. gen., n. sp., subadult female paratype. A, pereopod 1, lateral view; B, enlargement of tip of propodus; C, pereopod 2, lateral view. Scale line: A – C = 0.2 mm.

FIGURE 7. Akanthoparapseudes alfaroae n. gen., n. sp., subadult female holotype. A, pereopod 3, lateral view; B, pereopod 4, lateral view; C, pereopod 5, lateral view; D, pereopod 6, lateral view. Scale line: A – D = 0.2 mm.