Neotanais guskei, Weigmann, Simon & Guerrero-Kommritz, Jürgen, 2009

Weigmann, Simon & Guerrero-Kommritz, Jürgen, 2009, New species of Neotanais Beddard, 1886 (Crustacea, Tanaidacea) from the deep sea of the tropical and southern East Atlantic Ocean, Zootaxa 1992, pp. 20-36 : 28-35

Neotanais guskei sp. n.

( Figures 5 to 7)

Material examined: 7 individuals. Holotype ZMH K- 42024, RV Meteor 63-2, St. 43, one neuter. Paratypes ZMH K- 42025, RV Meteor 63-2, St. 42, one male, ZMH K- 42026, RV Meteor 63-2, St. 37, one manca I, ZMH K- 42027, RV Meteor 63-2, St. 41, three manca I and one female.

Other material examined: type Neotanais serratispinosus hadalis Wolff, 1956 . ZMUC-CRU-6649, Galathea expedition, St. 649, Kermadec Trench, 8210 m, one female, ZMUC-CRU-9353, same locality, one male.

Diagnosis: female. Antennula with six to seven articles. Chela with low dorsal crest. Propodus of pereopods 1 to 3 with serrate, pinnate setae and a dorsally serrated grooming seta. Dactylus of pereopods 4 to 6 with one serrated shield. Dactylus and ungius of pereopods 4 to 6 with a ventral row of spinules. Pleonites 1 to 3 with minute ventral projections. Pleopods short. Pleotelson heptagonal. Uropods inserted laterally. Uropod’s endopod with up to nine articles.

Description: non-ovigerous female.

Body ( Fig. 5 A, B): long and slender, seven times as long as wide, dorsoventrally flattened.

Cephalothorax ( Fig. 5 A, B): 1.5 times as long as wide, anterior end tapering towards the antennulae, comprising 0.2 of body length.

Pereon ( Fig. 5 A, B): composed of six free pereonites, comprising 0.55 of body length. Pereopods attached laterally. All pereonites with one to three lateral setae on both sides. Pereonite 1 shortest, two and a half times wider than long; pereonites 1 to 3 slightly triangular on dorsal view; pereonites 4 to 6 rectangular; pereonites 2 to 6 slightly wider than long; pereonites 3 and 4 of the same length; pereonite 5 longest; pereonites 2 and 6 of the same length, shorter than pereonites 3 to 5 and longer than pereonite 1.

Pleon ( Fig. 5 A, B): comprising 0.25 of body length, composed of five free pleonites and a pleotelson. All pleonites of almost equal length. Pleonites 1 to 3 with minute ventral projection. All pleonites with two setae on the right side. Pleotelson heptagonal and without setae. Uropods inserted laterally.

Antennula ( Fig. 6 K): composed of six or mostly of seven articles. Article 1 longest, longer than the other articles of the antennula together, 3.8 times as long as wide, with one broom and one broken seta proximoventrally and several setules near insertion of body; distal third with a row of six simple setae, two long, two middle and two short ones and one ventral and one distal broom seta. Article 2 twice as long as wide, with two short distodorsal simple setae, a row of four ventral simple setae, one middle and three long ones, and a distolateral row of four broom setae, perpendicular to antennula axis. Article 3 almost square, with one short simple seta distoventrally and one short simple seta and two broom setae distodorsally. Article 4 three times as long as wide, with one terminal multiarticulated aesthetasc and one terminal short simple seta. Article 5 almost square, with one terminal multiarticulated aesthetasc and one terminal and two distolateral short simple setae. Article 6 twice as long as wide, with three terminal simple setae. Article 7, if present, short, with three terminal simple setae. In this case the setation of former articles changes: article 4 nude, article 5 with one terminal multiarticulated aesthetasc and one terminal short simple seta, article 6 with one terminal multiarticulated aesthetasc and one terminal and two distolateral short simple setae.

Antenna ( Fig. 6 J): composed of nine articles. Article 1 cone-shaped, short and wide, with one broken terminal seta and few setules distodorsally. Article 2 longest, three times as long as wide, with one long simple seta dorsally. Article 3 almost square, with one simple seta dorsally. Article 4 twice as long as wide, with one broom seta distolaterally. Articles 5 to 9 three times as long as wide. Article 5 with two broom setae distoventrally and two long and two short simple setae and one plumose seta distally. Article 6 with two short distal simple setae. Article 7 with three short simple setae distally. Article 8 with two short distal simple setae. Article 9 with four terminal simple setae.

Labrum: not recovered, lost during dissection.

Mandibles ( Fig. 6 B, C): pars incisiva of left mandible with two teeth; lacina mobilis with four teeth and two bipinnate setae; pars molaris long, with two protuberances. Pars incisiva of right mandible with a large sharp cutting edge and two small teeth; lacina mobilis with one blunt bipinnate seta and two bipinnate setae; pars molaris with eight teeth around crushing surface.

Maxillula ( Fig. 6 A): composed of two endites. Outer endite’s terminal part with eight distal setae, two middle and four long spiniform and two serrated setae, as well as several setules on outer margin. Inner endite with one long setulose seta and three stout setulose setae distally, outer margin with several distal setules.

Maxilla ( Fig. 6 F): basal lobe with several comb setae, also on the margins. Inner lobe of fixed endite with twelve hooked setae. Outer lobe of fixed endite with two bifurcated spiniform and four simple setae. Inner lobe of movable endite with six simple setae of different lengths. Outer lobe of movable endite with three long simple setae.

Labium ( Fig. 6 H): basal plate with inner lobes and long setules; palps elongated, with several setules.

Maxilliped ( Fig. 6 D, E): basis not fused, broad, with two basal simple setae; endite’s inner margin with several setules and three to four setulose setae, four distal spiniform setulose setae and one short simple and two setulose setae distally; palp insertion with one medial simple seta on outer margin. Palp, article 1 widening distally, without setae. Article 2 with one bipinnate and six simple setae on inner margin and one distal simple seta on outer margin. Article 3 with eight simple setae on inner margin. Article 4 with two simple setae laterally and one simple and seven bipinnate setae distally.

Epignath ( Fig. 6 G): both ends pointed and with many fine and long setules, forming brushes.

Cheliped ( Fig. 5 E): basis spherical, 0.8 times as long as chela. Ischium slender. Merus triangular, with one ventral simple seta. Carpus twice as long as wide, with two ventral simple setae and eleven simple setae dorsally in a row. Propodus smooth, twice as long as dactylus, with a low crest dorsally; fixed finger with two distoventral and three dorsal simple setae and one simple seta at the basis of dactylus insertion; cutting edge with a proximal serrated part and five distal teeth. Dactylus smooth, with one proximodorsal seta and one seta at the dorsal insertion of dactylus.

Pereopod 1 ( Fig. 7 A): coxa simple. Basis long, about as long as ischium. Merus und carpus together, dorsally with five short simple and two broom setae. Ischium with one short and one middle simple seta. Merus with one row of four and two additional bipinnate setae. Carpus with one row of seven and one row of five very slender and long bipinnate setae, as well as two additional bipinnate setae. Propodus with one distal row of six slender and long bipinnate setae and one lateral row consisting of seven serrate, pinnate setae and one biserrated seta, whose size increases constantly towards distal end; also with one dorsal broom seta, one short terminal simple seta and one terminal grooming seta, which has five ventral teeth and is dorsally serrated. Dactylus and ungius without setae. Ungius about 0.4 times as long as dactylus.

Pereopod 2 ( Fig. 7 B): coxa simple. Basis four times as long as wide, dorsally with one short simple seta and three broom setae. Ischium with one short and one middle simple seta. Merus twice as long as wide, with one row of three bipinnate setae and one single bipinnate seta (not illustrated). Carpus laterally with one row of eight and one row of eight very slender and long bipinnate setae, whose size increases constantly towards distal end (only partially shown), as well as one short and one middle (not illustrated) bipinnate seta; propodus laterally with one row consisting of six serrate, pinnate and five bipinnate setae and one row of eight very slender and long bipinnate setae, whose size increases constantly towards distal end (only partially illustrated); also with one dorsal short simple seta and one terminal grooming seta, which has five ventral teeth and is dorsally serrated. Dactylus with two short rows of spinules ventrally. Ungius without setae, about 0.3 times as long as dactylus.

Pereopod 3 ( Fig. 7 C): coxa simple. Basis dorsally with two short simple setae and one broom seta, ventrally with one broom seta. Ischium with one short and one middle simple seta. Merus with one row of three bipinnate setae and one single bipinnate seta (not illustrated). Carpus laterally with one row of nine and one row of seven very slender and long bipinnate setae, whose size increases constantly towards distal end (not illustrated) and two short bipinnate setae; propodus with one row consisting of three serrate, pinnate and six bipinnate setae and one row of nine very slender and long bipinnate setae, whose size increases constantly towards distal end (only partially illustrated); also with one terminal grooming seta, which has five ventral teeth and is dorsally serrated. Dactylus with two short ventral rows of spinules. Ungius without setae, about 0.4 times as long as dactylus. For details of propodus, dactylus and ungius see figure 7 D.

Pereopod 4 ( Fig. 7 E): coxa simple. Basis four times longer than wide, dorsally with one short simple seta and two broom setae, ventrally with five broom setae. Ischium with one middle and two short simple setae. Merus twice as long as wide, with two rows of three bipinnate setae each (only partially illustrated). Carpus laterally with one row of eight (only partially illustrated) and one row of nine bipinnate setae; also with one terminal bipinnate seta. Propodus laterally with one row of five and one row of eight bipinnate setae, as well as one broom seta dorsally. Dactylus with a terminal serrated shield and a ventral row of spinules. Ungius about 0.7 times as long as dactylus and laterally serrated, with one row of spinules ventrally. Details of dactylus and ungius in figure 7 F.

Pereopod 5 ( Fig. 7 G): similar to pereopod 4, except basis with two dorsal und two ventral broom setae; ischium with one short and one middle simple seta; carpus with one row of eight and one row of ten bipinnate setae.

Pereopod 6 ( Fig. 7 H): coxa simple. Basis four times longer than wide, dorsally with two broom setae. Ischium with one middle and two short simple setae. Merus with two rows of two bipinnate setae each (only one row illustrated) and one dorsal short simple seta. Carpus laterally with one row of six and one row of eight bipinnate setae (only partially illustrated), as well as one terminal short bipinnate seta. Propodus laterally with one row of four and one row of seven bipinnate setae, two broken terminal setae and a row of seven spiniform setae. Dactylus with a terminal serrated shield and a ventral row of spinules. Ungius about 0.7 times as long as dactylus and laterally serrated, with one ventral row of spinules.

Pleopod ( Fig. 6 I): all pairs similar. Basal article longer than wide, with two ventral and one to three dorsal plumose setae. Exopod with three dorsal and ten distal plumose setae. Endopod with four dorsal, three ventral and seven distal plumose setae.

Uropod ( Fig. 5 G): uropod’s surface covered by minute setules. Basal article about twice as long as wide. Exopod composed of two articles, about 0.75 the length of article 1 of endopod. Article 1 with one distal simple seta. Article 2 with two terminal simple setae. Endopod composed of nine articles. Article 1 longest, three times longer than wide and almost three times longer than the second article, distally with one simple seta and three broom setae. Article 2 almost square and 0.4 times as long as the first, with one distal simple seta. Article 3 three times as long as wide and twice as long as article 2, distally with one short simple seta, one broken simple seta and two broom setae. Article 4 about as long as article 2, with one broken distal simple seta. Article 5 as long as article 3, with one long simple and two broom setae distally. Article 6 almost as long as article 3, with one distal simple seta. Article 7 almost as long as article 1, distally with two long simple and two broom setae. Article 8 as long as article 3, with one long distal simple seta. Article 9 as long as article 7, terminally with four simple and two broom setae.

Neuter: like non-ovigerous female, without oostegites.

Male ( Fig. 5 C, D, E): cephalotorax longer, pleonites broader and pleopods larger than in females. Pereonites with strong shoulders and with one to two lateral setae on both sides. Pleonites with one lateral setae on the right side. Cheliped ( Fig. 5 E): basis almost spherical. Ischium compressed. Merus triangular, building a shield, with one simple ventral seta. Carpus long and slender, three times longer than wide, with two short ventral and two short simple dorsal setae. Propodus twice as long as dactylus, dorsally slightly serrated; fixed finger almost straight with two prominent blunt teeth and two small distal teeth, as well as three dorsal and two distoventral simple setae and one simple seta at the basis of dactylus insertion. Dactylus with one proximodorsal simple seta, two large teeth with blunt cutting edges and one simple seta at the dorsal insertion of dactylus.

Manca I: up to 2.8 mm.

Type locality: South Atlantic Ocean, Cape Basin, RV Meteor 63-2, st. 43, 28°1.2'S 007°17.9'E – 28°4.9'S 007°21.6'E, 5078 m.

Etymology: this species is dedicated to the memory of the late grandfather of the first author, Kurt Guske.

Distribution: deep sea of the South Atlantic Ocean: Cape Basin.

Remarks: oostegites appear on the first four pereopods, as shown in figures 7 A, B, C, E. No ovigerous female was observed, that is why the shape of fully developed oostegites is still unknown. One of the antennulae of the dissected animal has six articles unlike all other described species of Neotanais , which have a seven-articulated antennula; the other antennula has seven articles. A six-articulated antennula has only been reported for mancas before ( Gardiner 1975), but never for adult individuals.

The serrated shield on the dactylus of pereopods 4 to 6 clearly distinguishes this species from Neotanais rotermundiae . Such a serrated shield can also be found in Neotanais antarcticus Kussakin, 1967 , but this species differs from N. guskei in several other characters:

In neuters and females the cheliped of N. guskei has a merus with one ventral simple seta, a carpus with eleven dorsal simple setae and the fixed finger of propodus has two ventral simple setae. In N. antarcticus the merus has two ventral simple setae, the carpus three dorsal simple setae and the fixed finger of propodus one ventral simple seta. The first article of the antennula is 3.8 times longer than wide in N. guskei and 4.9 times longer than wide in N. antarcticus . The dactylus’ shield of N. guskei on pereopod 4 is finely serrated while in N. antarcticus it is composed of big spines. The shield of N. guskei resembles the shield present in males of N. antarcticus on the same pereopod. The males of these two species can easily be differentiated by means of the cheliped, in N. guskei the carpus has two very short ventral and only two dorsal simple setae, the fixed finger is almost straight and the dactylus has two prominent teeth. In N. antarcticus the cheliped’s carpus has two long and brown ventral and seven dorsal simple setae, the fixed finger of porpodus is strongly bent and has a prominent distal tooth next to the end point and the dactylus has one prominent distal and one small proximal tooth.

Further differences between Neotanais guskei and N. rotermundiae can be found in the shape of the pereonites, of which the first three are slightly triangular in the neuter of N. guskei and only the first one is slightly triangular in the female of N. rotermundiae , as well as the dorsal crest of the cheliped, which is flat in N. guskei and sharp and pointed forward in N. rotermundiae and the shorter pleopods of N. guskei . Compared with Neotanais rotermundiae , N. guskei also has a heptagonal and not pentagonal pleotelson, laterally and not ventrally inserted uropods and a lower number of articles in the uropod’s endopod – nine instead of 14 to 15. Besides that Neotanais guskei has a dorsally serrated grooming seta on the propodus of pereopods 1 to 3 and a ventral row of spinules on the dactylus and ungius of pereopods 4 to 6, whereas N. rotermundiae has a dorsally setulated grooming seta and a double row of spinules. Furthermore the ungius of pereopods 4 to 6 is laterally serrated in Neotanais guskei and not serrated in N. rotermundiae .

The antennula of Neotanais guskei has a row of four broom setae on article 2. Only Neotanais bacescui Lang, 1968 has a similar setation, but with five setae. The propodus of pereopods 1 to 3 has a special kind of setae which is serrated and also pinnated. This type of setae has never been reported for Neotanais previously. The male and the neuter of Neotanais guskei are the largest tanaids sampled from the South Atlantic Ocean to date.

Figures

FIGURE 5. Neotanais guskei, A – B. Neuter holotype, ZMH K- 42024 A. Body, dorsal view, B. Body, lateral view. C – E. Male paratype, ZMH K- 42025 C. Body, lateral view, D. Body, dorsal view. Scale bars 5 mm. E. Cheliped. Scale bar 5 mm. F – G. Female paratype, ZMH K- 42027 F. Cheliped. Scale bar 1 mm. G. Uropod. Scale bar 0,5 mm.

FIGURE 6. Neotanais guskei, female paratype, ZMH K- 42027 A. Maxillula, B. Left mandible, C. Right mandible, D. Maxilliped 1, E. Maxilliped 2, F. Maxilla, G. Epignath, H. Labium. Scale bar 0,2 mm. I. Pleopod 1, J. Antenna, K. Antennula. Scale bars 0, 5 mm.

FIGURE 7. Neotanais guskei, female paratype, ZMH K- 42027 A. Pereopod 1, B. Pereopod 2, C. Pereopod 3, D. Detail of pereopod 3, E. Pereopod 4, F. Detail of pereopod 4, G. Pereopod 5, H. Pereopod 6. Scale bar 0, 5 mm.