Tanaella kroyeri Larsen & Araújo-Silva, 2009

Larsen, Kim, Araújo-Silva, Catarina De L. & Coelho, Petrônio Alves, 2009, Tanaidacea from Brazil. I. The family Tanaellidae Larsen & Wilson, 2002, Zootaxa 2141, pp. 1-19 : 9-17

Tanaella kroyeri Larsen & Araújo-Silva n. sp.

( Figs 4–9 )

Material examined. Holotype. non-ovigerous female (DOUFPE -14.023), 2.5 mm, Seillean station 12 R1 (5–10). Allotype. male (DOUFPE -14.024), ATEX station 12 R1 (0–2). Paratypes. 1 male (DOUFPE - 14.025), ATEX station 12 R1 (0–2). 1 male (DOUFPE -14.026), P-34 station 10 R3 (5–10). 1 male (DOUFPE -14.027), P-34 #10 R2 (2–5). 1 non-ovigerous female (DOUFPE -14.028), Seillean station 6 R2 (2–5). 1 nonovigerous female (DOUFPE -14.029)., P-34 station 1 R1 (0–2). 1 non-ovigerous female (DOUFPE -14.030), Seillean station 7 R3 (0–2). 2 non-ovigerous female (DOUFPE -14.031), Seillean station 12 R3 (0–2). 1 nonovigerous female (DOUFPE -14.032), Seillean station 12 R1 (0–2). 2 non-ovigerous female (DOUFPE - 14.033), Seillean station 7 R2 (0–2). 1 non-ovigerous female (DOUFPE -14.034), Seillean station 10 R1 (2–5). 1 non-ovigerous female, 1 male (DOUFPE -14.036), Seillean station 8 R2 (0–2). 1 non-ovigerous female (DOUFPE -14.037), P-34 station 5 R3 (2–5). 1 non-ovigerous female (DOUFPE -14.038), Seillean station 7 R1 (2–5). 1 non-ovigerous female (DOUFPE -14.039), Seillean station 7 R3 (2–5). 1 non-ovigerous female (DOUFPE -14.040), 3Loc Bia4 station 1 R3 (0–2). 1 non-ovigerous female (DOUFPE -14.041). Ext3 Lead2 station 7 R2 (0–2), (dissected). 1 non-ovigerous female (DOUFPE -14.042), Seillean station 5 R3 (0–2). 1 non-ovigerous female (DOUFPE -14.043), Ext3 Lead2 station 3 R3 (0–2). 1 male (DOUFPE - 14.046), 3Loc Bia4 station 12 R2 (5–10) (dissected). Station data given in table 2.

Diagnosis. Female. Somites lateral shield narrower than somites. Pleotelson acorn-shaped and short almost square (l/w ratio 1.06). Maxilliped endites with small lateral spiniform prolongation on distal corner. Cheliped fixed finger with four denticles and inner serrated proximal depression, dactylus without processes. Uropod shorter than pleotelson, basal article two thirds as long as endopod.

Male. Antennule thicker than that of female. Antennule article 2 as long as half of article 1. Cheliped fixed finger with less pronounced serrated depression and denticles. Pleopods present on all pleonites but with simple setae only. Uropod marginally shorter than pleotelson, basal article marginally shorter than endopod.

Etymology. Named in honor of Henrik Nikolai Krøyer, the first author to describe tanaids from Brazilian waters.

Description. female (body of holotype, appendages of dissected paratype)

Body ( Fig. 4 A). Body length 2.5 mm. Cylindrical, 8.3 times as long as broad. Cephalothorax 3 times as long as pereonite 1. Pereonites all wider than long. Pereonite 1 and 6 shorter than other pereonites. Pereonites 2 and 3 shorter than 4 and 5. Pleon all pleonites lacking pleopods. All pleonites subequal, with slightly protuberance on pleonite 3. Pleotelson longer than combined length of three pleonites. Apex blunt.

Antennule ( Fig. 5 G). With four articles and additional minute distal article. Article 1 longer than articles 2–5. Article 1 with one distal simple seta. Article 2 half the length of article 1, with three pinnate setae and one spiniform setae distally. Article 3 less than half length of article 4 with one dorsoproximal simple seta and one ventrodistal spiniform setulated setae. Article 4 length almost half of article 2, with one dorsoproximal simple seta and one ventrodistal spiniform seta. Minute terminal article with three long and one short distal simple setae and one aesthetasc.

Antenna ( Fig. 5 H). With five articles and fusion line, length 0.3 times as long as antennule. Article 1 broader than following articles, with two dorsodistal simple setae and laterodistal simple seta. Article 2 shorter than article 1 with one dorsodistal simple seta. Article 3 with clear fusion line, longer than other articles, with one setulated dorsodistal seta, one mediodistal simple seta, two ventrodistal spiniform setae and one ventrodistal simple seta. Artcle 4 shorter than article 1, with one distal seta. Article 5 shortest article with four long and one shorter distal setae.

Mouthparts. Labrum ( Fig. 5 D) almost rectangular with setules at apex. Left mandible ( Fig. 5 E), lacinia mobilis long, narrow, incisor broad with three distal and one inner denticles. Molar process with five denticles and one bifurcated. Right mandible ( Fig. 5 F) incisor with three denticles. Labium ( Fig. 5 B) simple M-shaped. Maxillule ( Fig. 5 C) with ten distal spiniform setae of which five are setulose. Maxilla (not recovered). Maxilliped ( Fig. 5 A) basis with one seta near palp insertion. Endites with spiniform prolongation on outer distal corner, one mediodistal denticle and one simple inner distal seta. Palp article 1, naked. Article 2 with three inner setae of which two are setulated and one seta on outer margin. Article 3 with four inner setae of wich two are setulated, small scales present on mediodistal margin of article 3 and 4. Article 4 with three setulated setae on inner margin, two distal spiniform setae and one mediodistal seta. Epignath not recovered.

Cheliped ( Fig. 4 B). Basis not divided equally by sclerite, shorter than carpus. Merus triangular with one medioventral simple seta. Carpus longer than propodus with two ventral and two dorsal simple setae. Propodus with one simple seta between fixed finger and dactylus and four setae on inner margin. Fixed finger with proximal serrated depression and four rounded denticles, with three ventral setae on inner margin and two medioproximal simple setae on fixed finger. Dactylus with one simple seta on inner margin.

Pereopod 1 ( Fig. 6 A). Coxa naked. Basis longer than three succeding articles combined, with one dorsoproximal setulated seta. Ischium with one ventral seta. Merus shorter than carpus, widening distally with one distal spiniform seta almost reaching end of carpus. Carpus shorter than propodus, rectangular, with one ventrodistal and one dorsodistal spiniform setae and one simple mediodistal seta. Propodus longer than half of basis, ventral margin with small spines, with one ventrodistal seta. Dactylus and unguis naked.

Pereopod 2 ( Fig. 6 B). As pereopod 1 except: coxa with one dorsodistal simple seta. Basis with two dorsoproximal setulated setae. Carpus with two ventroproximal setae and two dorsoproximal spiniform setae. Dactylus and unguis combined shorter than propodus.

Pereopod 3 ( Fig. 6 C). As pereopod 2 except: coxa naked. Basis with one dorsoproximal setulated seta. Carpus with one spiniform and one simple ventral setae and one dorsal spiniform seta.

Pereopod 4 ( Fig. 6 D). Without coxa. Basis slightly wider and shorter than on pereopods 1–3, with one dorsoproximal setulated seta. Ischium with two ventral simple setae. Merus with two spiniform ventrodistal setae, shorter than carpus. Carpus with one small modified seta and four spiniform distal setae. Propodus with one dorsodistal and two ventrodistal spiniform setae and spiniform prolongated on dorsal view. Dactylus and unguis combined longer than propodus and with rows of small setules.

Pereopod 5 ( Fig. 6 E). As pereopod 4 except: basis naked.

Pereopod 6 ( Fig. 6 F). As pereopod 5 except: Ischium with one ventral seta. Carpus with two dorsodistal and one spiniform ventrodistal setae. Propodus with three dorsodistal spiniform setae and two ventrodistal setae.

Uropods ( Fig. 5 I). Shorter than pleotelson. Basal article with one setulated seta on distal margin, two simple seta, one long and short. Endopod slightly, longer than basal article, with two setulated setae on inner margin, two long and one short distal setae, and two long simple setae subdistally on outer margin.

Male (where differing from female).

Body ( Fig. 7 A). Body length 2.26 mm. Cylindrical, 13.6 times as long broad. Cephalothorax 2 times as long as broad as pereonite 2. Pleon all pleonites subequal, all with pleopods.

Antennule ( Fig. 8 H). Thicker than that of female. Article 1 as long as rest of antennule, with one ventrodistal simple seta and two ventrodistal setulated setae. Article 3 with two dorsodistal simple setae. Article 4 with one simple and one ventrodistal setulated setae. Minute terminal article with three long setae and one aesthetascs.

Antenna ( Fig. 8 G). Article 1 longer than article 4, with one dorsodistal simple seta and little spines around on dorsodistal view. Article 2 shorter than article 4, with one dorsodistal simple seta. Article 3 longer than other articles, with fusion line, two simple and one setulose ventrodistal setae, one dorsodistal and one dorsomedial setulated setae. Article 4 less than half as long as article 3, with two long simple distal setae. Article 5 shortest, with four long distal simple setae.

Mouthparts. Left mandible ( Fig. 8 C), lacinia mobilis long, incisor broad with three denticles. Right mandible (not recovered). Labrum ( Fig. 8 B). Maxilla ( Fig. 8 D) wider at basis, tapering distally. Palp article 3 with four inner setae of which one is setulated.

Cheliped ( Fig. 7 B). Merus triangular with one ventroproximal seta. Carpus with one medioventral simple seta. Propodus with four setae on inner margin of which the longest is setulose.

Pereopod 1 ( Fig. 9 A). Basis with one dorsomedial setulated seta. Propodus longer than dactylus and unguis, dorsal margin with little spines around, with one mediodistal simple seta.

Pereopod 2 ( Fig. 9 B). As pereopod 1 except for the relative length of the carpal setae.

Pereopod 3 ( Fig. 9 C). As pereopod 2.

Pereopod 4 ( Fig. 9 D). Basis marginally wider than pereopods 1–3, with 1 medioventral setulated seta. Propodus with two rows of small spines around. Dactylus and unguis combined almost twice as long as propodus, with rows of small setules on dactylus.

Pereopod 5 ( Fig. 9 E). As female.

Pereopod 6 ( Fig. 9 F). As pereopod 5 except: Carpus with one simple seta, three ventrodistal spiniform setae. Propodus with four spiniform setae.

Pleopods ( Fig. 8 I). Well developed. Basal article rhomboid. Exopod and endopod both with ten simple setae.

Uropods ( Fig. 8 F). Marginally shorter than pleotelson. Basal article longer and wider than in female, with two simple setae on outer margin. Endopod with two long and two short distal simple setae, two long simple setae on inner margin.

Remarks. By using the keys by Larsen & Heard (2004) and Guerrero-Kommritz & BłaŻewicz- Paszkowycz (2004), this species keys out to Tanaella mclellandi . However the new species can be separated by having: a larger separation between the lateral shields of the somites, maxilliped endites with spiniform prolongation on distal margin; uropod more than two thirds as long as pleotelson (in T. mclellandi about half as long as pleotelson); cheliped fixed finger with four denticles and inner serrated depression. The combination of a uniarticulated uropod endopod, an uropod shorter than pleotelson, and a cheliped dactylus as long as fixed finger and without large proximal process on inner margin, separates the new species from all other Tanaella .

Figures

FIGURE 4. Tanaella kroyeri n. sp., female. A, holotype lateral view, scale bar = 0.5 mm; B, cheliped, scale bar = 0.2 mm.

FIGURE 5. Tanaella kroyeri n. sp., female paratype. A, maxilliped; B, labium; C, maxillule; D, labrum; E, left mandible; F, right mandible; G, antenulle; H, antenna; I, uropod. Scale bars = 0.2 mm.

FIGURE 6. Tanaella kroyeri n. sp., female paratype. A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6. Scale bars = 0.2 mm.

FIGURE 7. Tanaella kroyeri n. sp., male. A, allotype lateral view. Scale bar = 0.5 mm. B, cheliped. Scale bar = 0.2 mm.

FIGURE 8. Tanaella kroyeri n. sp., male paratype. A, maxilliped; B, labrum; C, left mandible; D, maxilla; E, maxillule; F, uropod; G, antenna; H, antennule; I, pleopod. Scale bars = 0.2 mm.

FIGURE 9. Tanaella kroyeri n. sp., male paratype. A, pereopod 1; B, pereopod 2; C, pereopod 3; D, pereopod 4; E, pereopod 5; F, pereopod 6. Scale bars = 0.2 mm.