Paraleptognathia gracilis (Krøyer, 1842) Guerrero-Kommritz, 2004

Guerrero-Kommritz, Jürgen, 2004, A revision of the genus Paraleptognathia Kudinova-Pasternak, 1981 (Crustacea: Tanaidacea) and description of four new species, Zootaxa 481 (1), pp. 1-63 : 25-30

Paraleptognathia gracilis (Krøyer, 1842) new combination ( Figs 9 , 10 )

Synonymy: Akanthophoreus gracilis Sieg, 1986

Tanais gracilis Krøyer, 1842

Tanais islandicus G. O. Sars,1877

Leptognathia Sarsii Hansen, 1913

Leptognathia Sarsii Hansen, 1909

For complete synonymy see Lang (1957) and Sieg (1983)

Material examined: 1964 individuals. ZMH K­40584­ ZMH K­40587 RV ”Porsild” Mellemfjord 1998, 499 individuals, ZMH K­40588­ ZMH K­40599 RV ”Porsild” Mellemfjord 1999, 1033 females, 279 juvenile males, two adult males. ZMUC CRU 3945 East Iceland, Breidals Vig , 6 fm (11 m) 8.06.1900, 24 females, four juvenile males, ZMUC CRU 3946 North Iceland, RV ”Ingolf” St. 126, 67° 19´N 15° 52´W, 293 fm (536 m), three females, one juvenile male, two neuters, ZMUC CRU 3947 Norway, 1898 of Sars , nine females, four juvenile males, ZMUC CRU 3948 Faroe , Bordoy Island, Klaksvig, 15 fm (27 m), 5.1.1899, 54 males, eight females, ZMUC CRU 3949 North Iceland, RV ”Ingolf” St. 128, 66° 30´N 20° 02´W, 194 fm (106 m), one female, ZMUC CRU 3950 North Iceland, RV ”Ingolf” St. 124, 67° 40´N 15° 40´W, 495 fm (905 m), three females, one juvenile male, ZMUC CRU 3951 East Iceland, Bakkefjord (Bakkafloi), RV ”Diana”, 6 fm (11 m), eight females, ZMUC CRU 3952 East Greenland, Steward Land , 70° 0´N, 158 fm (289 m), two females, ZMUC CRU 3653 East Iceland, Seydis Fjord , 6 fm (11 m), five females, ZMUC CRU 3954 Greenland, Angmagsalik , 65° 51´N, 19.6.1902, two females, one juvenile male, one neuter, ZMUC CRU 3955 Greenland, Cap Dalton , 69° 24.6´N 23° 30´W, 9–11 fm (16–20 m), two females, two juvenile males, ZMUC CRU 3956 Greenland, Turner Sound , 69° 44´N, 3 fm (5 m), II Amdrup Exp., one female, ZMUC CRU 3957 Greenland, Glasfor , one juvenile male, ZMUC CRU 3958 East Greenland, Sabine Island , 74°3´N 19° 45´W, 3–5 fm (5–9 m), Daffliste Exp., 12.9.1900, eleven females, one juvenile male. ( ZMUC CRU 3946 to 3958 were indentified previously as L. Sarsii) .

Diagnosis: cheliped carpal shield medium to small or absent, dactylus with crenulation.

Description: non­ovigerous female from Mellemfjord, west Greenland. Body ( Fig. 9a, b ): long, about eight times longer than broad. Body length 1.4 to 4.0 mm. Cephalothorax ( Fig. 9a, b ): shorter than pleon, about 1.3 times longer than broad. Pereon ( Fig. 9a, b ): pereonite 6 shortest, pereonite 1 longer than 6 and shorter than 5. Pereonite 2 and 3 equal in length and longer than pereonite 4. Pleon ( Fig. 9a, b ): pleonite equal in length, pleonite 5 shortest; pleotelson rounded with one small lateral apophysis on each side in some individuals pointed, in others rounded; apex with a terminal tubercule.

Antennule (not illustrated): article 1 longest with one long simple and four short simple distal setae; article 2 with one long and one short distal setae; article 3 shortest with one distal simple short seta; article 4 with five terminal setae.

Antenna ( Fig. 9d ): article 1 short semifused to cephalothorax; article 2 as long as broad, with one short spiniform seta; article 3 with one dorsal simple seta; article 4 longest, with two long simple terminal and two short simple setae; article 5 with one terminal simple seta; article 6 shortest, with four terminal simple setae.

Labrum ( Fig. 10d ): hood­shaped, with a row of setules on the distal margin.

Mandible ( Fig. 10c ): well calcified, pars molaris bent downwards; lacinia mobilis spiniform.

Maxillula ( Fig. 10a ): endite with three ventral rows of setules, two pinnate, and seven simple terminal spiniform setae.

Maxilla ( Fig. 10f ): rectangular, smooth.

Labium ( Fig. 10e ): composed of two triangular lobes, with simple seta distally.

Maxilliped ( Fig. 10g ): endites not fused, no setae were observed on the basis.

Epignath ( Fig. 10b ): smooth with no special features.

Cheliped ( Fig. 9g ): basis as long as carpus; merus with one simple ventral seta; carpus with one ventral and one dorsal setae, one tubercle near insertion of chela, carpal shield medium to small or absent; propodus twice as long as broad, with three teeth at the cutting edge; dactylus with a row of tubercles dorsally.

Pereopod 1 ( Fig. 9h ): coxa naked; basis three times longer than broad, with one simple seta; ischium short with one simple seta; merus smooth with one spiniform seta; carpus longer than merus, smooth with two spiniform seta; propodus smooth, with one terminal short spiniform seta; dactylus smooth; unguis as long as dactylus.

Pereopod 2 ( Fig. 9i ): as pereopod 1, except carpus with a dorsal and a ventral row of spinules and three spiniform setae; propodus with a dorsal row of spinules and a terminal spine.

Pereopod 3 ( Fig.9j ): as pereopod 1, except basis naked, carpus with three spiniform setae; propodus with a terminal spine.

Pereopod 4 ( Fig. 9k ): basis 3.5 times longer than broad, with a dorsal simple, one setulose and one simple ventral setae; ischium short, with one simple seta; merus with two spiniform setae; carpus longer then merus, with three spiniform setae; propodus smooth with three terminal spiniform setae and one terminal spine; dactylus as long as carpus, unguis sharp.

Pereopod 5 ( Fig. 9l ): as pereopod 4, except carpus and propodus have a ventral row of spinules.

Pereopod 6 ( Fig. 9m ): as pereopod 4, except basis with only one ventral simple seta and propodus with row of ventral spinules, two ventral and two dorsal spiniform setae on propodus.

Pleopods ( Fig. 9f ): exopod with twelve long simple setae, endopod with eight simple setae.

Uropods ( Fig. 9e ): exopod half as long as first article of endopod; article 1 with one simple distal seta, article 2 with one long and one short simple terminal setae. Endopod article 1 with one distal simple seta; article 2 with five terminal setae.

Juvenile male body length 2.0 to 2.8 mm. Antennule ( Fig. 9c ): first article longest, with one long and four short simple setae; article 2 with one long and one short simple setae; article 3 with one simple seta; article 4 shortest, naked; article 5 with four terminal setae.

Manca body length up to 1.4 mm.

Distribution: this species is widely distributed in the Arctic, Greenland, Spitzbergen, Iceland, North Pacific, Alaska.

Remarks: Paraleptognathia gracilis has a very wide distribution in the Arctic. There are numerous population that show a wide range of variation in the size of the lateral pleotelson apophyses, in the size of cheliped carpal shield, and chela crenulation. Some specimens from Iceland, Greenland and Spitzbergen possess large lateral apophyses on the pleotelson. Preparatory males from west and south Greenland posses small lateral apophyses on the pleotelson and a moderated developed carpal shield and some individuals show a weak lateral crenulation on the fixed finger as in P. australis . In the Mellemfjord (west Greenland) individuals stages with short, middle and large apophysis, as well as with lateral crenulation on the fixed finger, and moderated developed carpal shield of the cheliped were found. Some large non­ovigerous females possess also crenulation on the fixed finger but no pleonal apophysis. The observed variability of these characters support the assumption of Lang (1957) making Leptognathia sarsii Hansen, 1909 a synomym of P. gracilis .

The carpal shield in P. gracilis is moderated to weak developed which makes it easy to distinguish from other Paraleptognathia species of the Arctic. Adult males are very scarce, from 1314 individuals of the Mellemfjord examined only 2 were adult (”swimming”) males.

Reports of P. gracilis from the Southern Ocean must be attributed to other species like P. australis or P. antarctica .

Figures

FIGURE 9. Paraleptognathia gracilis ZMH K­40589 a. Body dorsal view, b. Body lateral view. Scale bar 1mm. c. Antennule, d. Antenna, e. Uropod, f. Pleopod, g. Cheliped, h. Pereopod 1, i. Pereopod 2, j. Pereopod 3, k. Pereopod 4, l. Pereopod 5, m. Pereopod 6. Scale bar 0.25 mm.

FIGURE 10. Paraleptognathia gracilis ZMH K­40589 a. Maxillula, b. Epignath, c. Mandibles, d. Labrum, e. Labium, f. Maxilla, g. Maxilliped. Scale bar 0.25 mm for b and e for the rest scale bar 0.1 mm.