Cacoheterotanais rogerbamberi, Morales-Núñez, Andrés G. & Heard, Richard W., 2015

Morales-Núñez, Andrés G. & Heard, Richard W., 2015, Cacoheterotanais rogerbamberi, a new genus and species of leptocheliid Tanaidacea (Crustacea: Peracarida) from shelf-waters of the Gulf of Mexico, Zootaxa 3995 (1), pp. 169-188 : 172-185

Cacoheterotanais rogerbamberi sp. n.

( FigS 1–9; 10G, I; 11G, I)

Synonymy. “ Pseudonototanais sp. B”: sensu Heard et al. (2004); Morales-Núñez & Heard (2013). Material examined. Holotype - Adult male, length 1.9 mm, ( USMN 1273215), Station (Stn) 2318: 29º 05ʹ00.8ʹʹ N; 83º 45ʹ00.5ʹʹ W, depth 20 m, substrata: “medium sand”, 11 September 1977.

Paratypes - one male ( USMN 1273217), two females ( USMN 1273216); one male and five females ( GCRL 06532), same collection data as for holotype. Additional specimens from the type locality are in the collection of the authors.

Additional material: three males, 42 female /neuters, Stn 2102, 26º24ʹʹ59.6ʹʹN, 82º 23ʹ59.6ʹʹW, depth 18 m, fine sand, Cruise 22, September 1975; four females, Stn 2102, Cruise 23, depth 18 m, fine sand, September 1977; two males, ten female/neuters, Stn 2207, 27º57ʹʹ00.4ʹʹN, 83 º 09ʹ00.3ʹʹW, Cruise 22, depth 19 m, fine/very fine sand, September 1975; two females, Stn 2208, 27º56ʹ00.5ʹʹN, 83 º 27ʹ29.6Wʹʹ, Cruise 23, depth 30 m, clayey sandy silt, August 1976; two males, ten female/neuters, Stn 2318, 29º05ʹ00.8ʹʹN, 83º 45ʹ00.5ʹʹW, depth 20 m, medium sand, 9 November 1977; three males, 21 female /neuters, Stn 2318, Cruise 22, depth 20 m, medium sand, August 1975; five males, 98 female /neuters, BLM Stn 2419, 29º46ʹ59.8ʹʹN, 84º 05ʹ00.2ʹʹʹW, Cruise 22, depth 10 m, medium fine sand, August 1975; three females, Stn 2423, 29º37ʹʹ00.8ʹʹN, 84º 17ʹ 00.8ʹʹW, depth 19 m, silty fine sand, November 1977.

Etymology. Named in honour of our colleague the late Roger Bamber, in recognition of his expertise and extensive research and publications on the crustacean order Tanaidacea and arachnid class Pycnogonida.

Type locality. Gulf of Mexico Eastern Continental shelf, 29 05’00.8”N; 83 45’00.5,” depth 20 m, substrata: “medium sand”

Distribution. North America, Gulf of Mexico Eastern Continental shelf at depths of 10 to 30 m ( Fig. 12 ).

Description. Adult Male. Body ( Figs 1 A −B): Length about 1.7 to 1.9 mm, slender, about 6.2 times as long as wide, slightly smaller than female,

Cephalothorax ( Figs 1 A −B): Narrower than that of female anteriorly, slightly more than 20% of TL, length about 1.7 times depth, longer than combined lengths of pereonites 1–3, sub-rectangular with simple seta on each mid-lateral face. Ocular lobes with well-developed, pigmented eyes, visual elements present.

Pereon ( Figs 1 A −B): About 55% of TL; pereonites sub-rectangular, and wider than long; pereonites 1 to 4 becoming progressively longer; pereonite-5 same length that as pereonite-4; pereonite-6 same length as pereonite- 3; pereonite-1 with two simple seta distally.

Pleon ( Figs 1 A −B): About 20% of TL; combined lengths of pleonites 1 to 5 shorter to that of pereonites 5 and 6 combined; all pleonites sub-equal, much wider than long, with two short, epimeral, simple seta ( Fig. 1 A).

Pleotelson ( Figs 1 A −B): About 5% of TL; about same length as pleonite-5, with lateral margins each having single small seta, with four subapical setae (two broom and two simple), and pair of simple setae on apical lobe.

Antennule ( Fig. 2 A): Peduncle with three distinct, unfused articles. Article-1 length about 2.8 times as long as wide, with three broom setae along mid-lateral margin, with simple subdistal seta on dorsal and lateral margins. Article-2 with length about 2.3 times as long as wide, with four setae (one simple and three broom) on ventrolateral subdistal margin. Article-3 length about 1.8 times depth, with dorso-lateral simple setae distally. Flagellum with three articles. Article-1 with proximal and distal cluster of aesthetascs. Article-2 with single distal cluster of aesthetascs. Article-3 minute terminating in four simple setae of varying length.

Antenna ( Fig. 2 B): Article-1 reduced, asetose, much deeper than long. Article-2 with length about 1.3 times depth, dorsal margin bearing two setiform setae, one medial and one distal; ventrodistal margin with setiform seta (stout). Article-3 with length about 1.3 times depth, with small thorn seta on disto-dorsal margin. Article-4 with length and depth about subequal, slightly shorter than combined length of articles 1 to 3, broom seta on sub-distal dorsal margin, simple seta subdistal seta on lateral margin, and two subdistal, simple setae on ventral margin. Article-5 length about 3.0 times depth, two long simple setae distally. Article-6 minute, terminating in four (three long and one short), simple setae.

Mouthparts: Vestigial, appearing non-functional.

Maxilliped ( Fig. 2 C): Reduced, apparently non-functional, palps fused, forming attenuated lobes.

Cheliped: Lateral aspect ( Figs 1 B, 2F): Coxal sclerite triangular, Basis with simple seta on mid-lateral margin. Inner aspect ( Figs 7 D–E): Basis length about twice depth. Merus triangular, posterior margin with three simple setae of unequal length. Carpus length about two-thirds length, with anterior margin having two small spiniform setae (one sub-proximal and one sub-distal); posterior margin with two simple setae of unequal length. Chela forcipate; fixed finger directed downward, nearly at right angle to posterior (ventral) margin of propodus; dactylus reaching to or beyond tip of fixed finger. Propodus, length about twice that of depth, distal margin with two subacute process on either side of dactylus insertion; fixed finger with low tooth of apophysis midway along incisive margin, with cluster of six (three anterior and three posterior) simple setae between tooth and sclerotized tip; row of eleven comb-setae on sub-distal margin near to base of dactylus, ventral-most seta much longer than others. Dactylus, posterior margin with row of five spiniform setae along cutting edge, unguis forming small subacute tip, with one simple seta near anteroproximal margin.

Pereopod-1 ( Fig. 3 A): Longer than other pereopods. Coxa with simple seta on anterodistal margin. Basis length about 4.4 times maximum width; anteroproximal margin with simple seta. Ischium wider than long with simple seta on posterior margin. Merus asetose, length about 1.1 times width, having oblique articulation with carpus. Carpus length about equal to that of merus; anterodistal margin with simple seta; posterodistal margin with two small simple setae. Propodus length about 3.8 times width, slightly shorter than combined lengths of ischium, merus, and carpus; anterior margin with one sub-distal spine, three sub-distal simple setae of unequal length. Dactylus elongate, styliform, asetose; together with unguis longer than propodus. Unguis longer than dactylus with minute duct opening at tip.

Pereopod-2 ( Fig. 3 B): Coxa with simple setae on anterodistal margin. Basis with length about 3.7 times width; Ischium wider than long with simple seta on posterior margin. Merus asetose, with length about 1.3 times width. Carpus with length about equal to that of merus; anterodistal margin with simple seta; posterodistal margin with small spiniform and simple seta on posterodistal posterior margin. Propodus length about 3.4 times width, slightly shorter than combined lengths of merus and carpus; anterior margin with sub-distal simple setae. Dactylus and unguis with combined length slightly more than 1/2 that of propodus; dactylus longer than unguis with simple seta on anterior margin. Unguis not curved, with minute duct opening at tip.

Pereopod-3 ( Fig. 3 C): Similar in form to pereopod-2, except basis, merus to unguis shorter.

Pereopod-4 ( Figs 3 D, F–G): Shorter than other five pereopods. Basis expanded, length about 2.3 times width, with broom seta on mid-posterior margin. Ischium wider than long with two simple setae on posterior margin. Merus with length about 1.8 times width; slightly longer than carpus, with two posterodistal small stout spiniform setae. Carpus length about 1.4 times width; anterodistal margin with simple seta; posterodistal margin with three stout spiniform setae each distally setulate ( Fig. 3 F). Propodus length about 3.3 times width; anterior margin with four small modified spiniform setae, with three pectinate spiniform setae of unequal length on disto-dorsal margin; posterior margin with two short, stout pectinate, spiniform setae sub-distally. Dactylus and unguis having combined length more than half that of propodus; dactylus longer than unguis. Unguis minute, curved and unequally bifid ( Figure 3 G).

Pereopod-5 (not figured): Similar to pereopod-4, except longer and unguis not bifid.

Pereopod-6 ( Fig. 3 C): Similar to pereopod-5, except by basis and carpus longer. Basis with simple seta on mid-posterior margin. Propodus with simple seta having length less than that of dactylus and unguis combined, and four pectinate spiniform setae on anterodistal margin.

Pleopods ( Fig. 4 D): Five similar, but more strongly developed than in female with longer natatory setae. Basal article broad, with small simple seta on inner margin. Endopod with inner and distal margins usually bearing eight long plumose setae, distal-most seta modified, greatly attenuated and filament-like distally; lateral margin medially with strongly developed plumose seta. Exopod with inner and distal margins bearing about 17 long plumose setae, outer margin asetose.

Uropod ( Fig. 4 E): Biramous. Basis asetose. Exopod unarticulated, small, less than one third length of endopodal article-1, simple seta on outer proximal margin and two distal simple setae, outer longest extending posteriorly to distal end of endopodal article-2 and inner seta about one third length of outer. Endopod with three sub-equal articles. Article-1 with simple seta on inner distal margin. Article-2 with broom setae on inner distal margin. Article-3 slightly longer than article-1, distally with five simple setae of unequal length.

Adult Female. Body ( Fig. 5 A): Length about 1.9 mm, about 6.5 times width.

Cephalothorax ( Fig. 5 A): About 20 % of TL, longer than first two pereonites combined, about 1.4 times width; ocular lobes with eyes having visual elements present (pigmented with 7–10 ommatidia).

Pereon ( Fig. 5 A): About 56 % of TL; pereonites 1–4 and 6 sub-rectangular, wider than long; pereonite-5 quadrate.

Pleon ( Fig. 5 A): About 19% of TL; combined length of pleonites 1 to 5 shorter to that of pereonites 5 and 6 combined; all pleonites subequal, much wider than long, with two simple epimeral seta.

Pleotelson ( Fig. 5 A): About 4 % of TL, same length of pleonite-5; with lateral margins each having single small seta, with four subapical simple setae (2 not shown), and pair of simple setae on apical lobe.

Antennule ( Fig. 6 A): Relatively long (slightly shorter than length of cephalothorax) with three distinct articles and minute terminal article. Peduncle article-1 with length about three times depth of lateral face, longer than articles 2–4 combined, with two broom setae and two clusters of three (near to middle) and four (distally) broom setae along lateral margin, with two simple setae (1 on mid-dorsal margin and 1 on distodorsal margin). Article-2 length about 1.8 times as long as wide with dorsal (long) and ventral (small) simple seta, distally. Article-3 length about 2.4 times as long as wide with three simple distal setae (unequal in length) and one aesthetasc. Article-4 minute, with four simple setae, one longer than others.

Antenna ( Fig. 6 B): Article-1 short, asetose. Article-2 as long as wide, with dorsal and ventral thorn seta, distally. Article 3 as long as wide with thorn seta on distodorsal margin. Article-4 about 3.1 times as long as wide equal in length to that of article-2 and -3 combined with three distal or subdistal simple setae. Article-5 about 2.0 times as long as wide with broom and simple seta on sub-distal dorsal margin; with two simple setae (1 sub-distal and 1 distal) on ventral margin. Article-6 minute with five (four long and one short) simple setae.

Mouthparts: Labrum ( Fig. 6 C): Sub-quadrate and distal edge finely setose. Mandibles ( Figs 6 D–E): Left mandible, incisor having mid margin with two low denticles; lacinia mobilis crenulate with four blunt denticles ( Figure 6 D). Right mandible with broad incisor with weakly bifid tip and crenulate upper margin ( Fig. 6 E). Molar process with ridged, grinding surface in both mandibles ( Figs 6 D–E).

Labium ( Fig. 6 F): Bilobed, outer lobe setulate distally.

Maxillule ( Fig. 6 G): Endite with eight relatively stout distal spines and sub-distal cluster of simple setae. Palp bearing two long terminal setae of unequal length (not shown).

Maxilla ( Fig. 6 H): Irregularly sub-quadrate.

Maxilliped ( Fig. 7 A): Basis having proximal third fused, distal margin with three pairs of long simple setae. Endites unfused with simple seta (reaching to proximal region of palp article-3); inner half of distal margins with two tooth-like, modified setae; inner distal margins each with denticle-like spiniform seta; inner sub-distal margin each with two very small (vestigial?) coupling hooks. Palp: Article-1 asetose. Article-2, outer margin having simple seta; inner sub-distal margin with four well-developed simple setae of unequal length. Article-3 outer margin asetose; inner margin with five strongly-developed simple setae. Article-4 with five strongly-developed, simple setae on inner and distal margin.

Epignath: Not recovered.

Cheliped: Lateral view ( Fig. 7 B): Coxal sclerite triangular, dorsally inserted, asetose. Basis length about 1.7 times depth, with sub marginal simple seta sub-distally. Merus sub-triangular, with two simple setae of unequal length on posterior margin. Carpus length about 2.1 times depth, anterior margin with two small seta, one subproximal and one subdistal; posterior margin with four sub-distal, simple setae of varying lengths. Propodus length about 1.1 times depth; simple seta arising near mid-margin just anterior to articulation with dactylus, extending distal for over half length of dactylus. Fixed finger of propodus with three simple setae sub-marginal to incisive edge; posterior margin with three subdistal simple setae, distal most less than half length of other two; unguis (nail) small, sub-conical, arising just distal to small seta on subdistal posterior margin and extending just past tip of finger. Dactylus plus small unguis nearly same length than length of propodus. Inner face ( Fig. 7 C): Propodus having three short setulate (comb) setae (posterior most distinctly longest) just anterior to medial articulation with dactylus. Dactylus with simple seta proximally on near anterior margin.

Pereopod -1 ( Fig. 8 A): Distinctly larger and longer than other five pereopods. Coxa with simple seta on anterodistal margin. Basis with length about 3.8 times maximum width; anteroproximal margin with simple seta. Ischium wider than long with simple seta on posterior margin. Merus asetose, length about 1.1 times as long as wide, having oblique articulation with carpus. Carpus length about equal to that of merus; anterodistal margin with simple seta; posterodistal margin with two small simple setae. Propodus length about 3.2 times as long as wide, slightly shorter than combined lengths of ischium, merus, and carpus; anterior margin with one sub-distal spine, three sub-distal simple setae of unequal length, and simple distal seta; posterior margin with sub-distal simple seta. Dactylus elongate, styliform, asetose; together with unguis longer than propodus. Unguis longer than the dactylus with minute opening of duct at tip.

Pereopod-2 ( Fig. 8 B): Coxa with simple setae on anterodistal margin. Basis with length about three times width; anteroproximal margin with simple seta. Ischium wider than long with simple seta on posterior margin. Merus with length about 1.1 times width, simple spiniform seta on posterodistal margin. Carpus with length about equal to that of merus, small spiniform seta on posterodistal margin. Propodus with length about 3 times width, slightly shorter than combined lengths of ischium, merus, and carpus; anterior margin with four small modified spiniform setae and two sub-distal simple setae. Dactylus and unguis with combined length slightly more than 1/2 that of propodus; dactylus longer than unguis with simple seta medially on anterior margin. Unguis not curved, with minute duct opening at tip.

Pereopod-3 ( Fig. 8 C): Similar in form to pereopod-2, except basis, merus, and propodus shorter. Basis without simple seta on anteroproximal margin. Merus without spiniform seta. Propodus with one sub-distal simple seta on anterior margin.

Pereopod-4 ( Figs 8 D, G): Shorter than other five pereopods. Basis expanded, asetose, with length about 2.1 times width. Ischium wider than long with two simple setae on posterior margin. Merus with length about 1.5 times width; slightly shorter than carpus, with two posterodistal small stout spiniform setae. Carpus with length about 1.4 times width; anterodistal margin with simple seta; posterodistal margin with three stout spiniform setae each distally setulate ( Fig. 8 G). Propodus with length about 2.2 times width; anterior margin with small spiniform seta sub-distally, two simple setae about same length as dactylus and unguis combined, and one pectinate spiniform seta (stout) on anterodistal margin; posterior margin with two short, stout pectinate, spiniform setae sub-distally. Dactylus and unguis having combined length more than half of propodus; dactylus longer than unguis. Unguis minute, curved.

Pereopod-5 ( Fig. 8 E): Similar to pereopod-4, except basis, carpus, and dactylus longer. Basis broad with broom seta on mid-anterior margin

Pereopod-6 ( Fig. 8 F): Similar to pereopod-5, except basis, merus, carpus, and propodus slightly longer. Propodus with anterodistal margin having three pectinate spiniform setae.

Pleopods ( Fig. 9 A): Five similar, well-developed, biramous pairs. Basal article broad, with simple seta on inner margin. Endopod and exopod with lengths slightly more than twice width, both with inflated plumose seta on proximal inner margin adjacent to articulation with basis. Endopod with inner and distal margins usually bearing seven long plumose setae, distal-most shortest, attenuated distally into single filament; mid-lateral margin with strongly developed plumose seta. Exopod with inner and distal margins bearing about 16 long plumose setae, outer margin asetose.

Uropod ( Fig. 9 B): Similar to that of male, except by basis with simple seta on sub-distal inner margin. Endopod with article-1 asetose. Article-2 with two broom setae on inner subdistal margin.

Remarks. Cacoheterotanais rogerbamberi is distinguished from other six species within the Pseudonototanais complex by a combination of characters including (1) both the male and female having a uropodal endopod with three articles of about equal length, (2) the male antennule having a flagellum with three articles, (3) a male antennal article-3 with small thorn seta on dorsodistal margin, and (4) the male chela compressed, forcipate, having downwardly directed fixed finger with low tooth or apophysis subdistally on the grasping margin. The following key may be used to further distinguish the males of the Pseudonototanais complex.

Cacoheterotanais rogerbamberi gen. et sp. n. Figures modified from: A, Shiino 1978; B. Morales-Núñez & Heard 2013; C, Krøyer 1842; D, F, and H, Guţu 2012; E, Esquete et al. 2013; G and I, Morales-Núñez & Heard (this study). Not to scale.

Figures

FIGURE 2. Cacoheterotanais rogerbamberi gen. et sp. n., holotype male. A, antennule, lateral view; B, antenna, lateral view; C, maxilliped, ventral view; D, left cheliped, inner view; E, enlargement of left chela, inner view; F, enlargement of left chela, lateral view. Scale line: 0.1 mm for A – D.

FIGURE 4. Cacoheterotanais rogerbamberi gen. et sp. n., holotype male. A, pleopod; B, uropod. Scale line: 0.1 mm.

FIGURE 6. Cacoheterotanais rogerbamberi gen. et sp. n., paratype female. A, antennule, lateral view; B, antenna, lateral view; C, labrum; D, left mandible; E, right mandible; F, labium; G, maxillule; H, maxilla. Scale line: 0.1 mm.

FIGURE 8. Cacoheterotanais rogerbamberi gen. et sp. n., paratype female. A – F, pereopods 1 – 4; G, enlargement of carpus spine of pereopod- 4. Scale line: 0.1 mm for A – F.

FIGURE 9. Cacoheterotanais rogerbamberi gen. et sp. n., paratype female. A, pleopod; B, uropod. Scale line: 0.1 mm.

FIGURE 12. Map of eastern Gulf of Mexico (Mississippi, Alabama, Florida) indicating the 60 stations sampled seasonally with a modified Reineck box core during 1975, 1976, and 1977. Open squares indicate Cape Town Dredge sampling sites; open circles indicate box core stations; filled (red) / bold circles indicate the six box core stations where Cacoheterotanais rogerbamberi gen. et sp. n., occurred.