Saurotipleona julii, Bird, 2015

Bird, Graham John, 2015, Tanaidacea (Crustacea: Peracarida) of the northeast Atlantic: Chauliopleona Dojiri and Sieg, 1997 and Saurotipleona n. gen. from the ‘ Atlantic Margin’, Journal of Natural History (J. Nat. Hist.) 49, pp. 1-41 : 30-36

Saurotipleona julii n. sp.

( Figures 14–16 , 17C–E , 19 )

Akanthophoreus sp.1: Holdich and Bird 1989

Akanthophoreus sp.AM#1: Bird 2001

Chauliopleona sp.AM#1: Bird 2014: 28, fig. 11b

Material examined

Holotype. Non-ovigerous ♀, BIOICE Stn 3504, Iceland Basin, 62.02°N, 19.49°W, 1734 m, IINH 29997 .

Allotype. Preparatory ♂, BIOICE Stn 3522, IINH 29996 .

Paratypes. AFEN Stn: non-ov. (possibly post-ov.) ♀ , 54599#1, NMS.Z.2014.169.

BIOICE Stns. One non-ov. ♀ , 2257, IINH 29995 ; one non-ov. ♀ , 2337, IINH 29994 ; one non-ov. ♀ , 2410, IINH 29993 ; one non-ov. ♀ , 3181, IINH 29992 ; one non-ov. ♀ , one post-ov. ♀?, 3504, IINH 29991 ; two non-ov. ♀♀ , 3522, IINH 29990 .

Description

Non-ovigerous female: habitus ( Figure 14A ) slender, eight times ltb; body length 2.84–4.16 mm. Cephalothorax 1.5 times ltb, about as long as pereonites 1–2 (excluding pereonal gap). Pereon 64% of body length, pereonites parallel-sided or with slight lateral process at pereopod attachment; pereonites 1 and 6 shortest, subequal, shorter than broad, pereonites 2–3 longest. Pleon ( Figure 14B ) 13% body length, as long as pereonite-6 and half of pereonite-5 combined; epimera with simple seta; sternites 1–4 with low rounded process; pleonite-5 sternal spur acuminate, slightly hamate in some specimens ( Figure 14C ). Pleotelson as long as two preceding pleonites, smooth, with two simple setae and two PSS on posterior margin.

Antennule ( Figure 14D ) 0.7 times length of cephalothorax, article-1 about half total length, 2.6 times ltb; article-2 1.6 times ltb, about as long as articles 3–4 combined; setation as figured; article-3 with fine distal setules; article-4 with four or five terminal setae and aesthetasc. Antenna ( Figure 14E ) about 0.8 times antennule length; article-2 with inferior and superior setae, superior margin with small setules; article-4 with fusion line. Labrum ( Figure 15A ) typical. Mandibles ( Figure 15B–C ) typical, left and right incisors tricuspid, lacinia of left mandible relatively narrow; molars acuminate-palmate with six–eight terminal spines. Labium ( Figure 15D ) typical, inner lobes distally setulate; outer lobes much reduced with distal setules. Maxillule ( Figure 15E ) endite with combs; terminal array of nine spines (one thinner than rest, four pectinate) and several long setules. Maxilla ( Figure 15F ) just shorter than maxilliped bases, distally setulate. Maxilliped ( Figure 15G ) bases together cardioid, about twice as long as broad, each with one long distal seta; endites with proximal coupling hook, two distal setae, setulate distolateral margins and medial lobe; palp article-1 just shorter than article-2, naked; article-2 with lateral seta and three mesial setae; article-3 about as long as article-2, with four unequal mesial setae; article-4 smaller and thinner than article-3, with superodistal seta and five terminal setae. Epignath not observed.

Cheliped ( Figure 15H–J ) basis with posterior lobe of similar size to anterior mass; carpus fairly slender, 1.8 times ltb (excluding shield), superior margin with setules and two setae, with large, rounded shield (aspect ratio 0.5 on holotype), inferior setae attached medial to this; chela longer than basis and as wide (excluding shield); propodus with two inferior setae attached along ridge or groove, medial comb of about eight spines, and a distolateral seta near the dactylus attachment; fixed finger incisive margin with proximal spine (of group of three) thickest, with low distal teeth; dactylus with smooth superior margin and small proximomedial seta.

Pereopod-1 ( Figure 16A ) coxa with seta; basis as wide as those of pereopods 4–6, as long as ischium, merus and carpus combined, with superior PSS; ischium with small seta; merus twice as long as broad, with distomesial seta and inferodistal (lateral) spine as long as carpus; carpus twice as long as broad, with superior and inferior distal bayonet spines and inferior margin with weak to moderate spinules; propodus four times ltb, with inferodistal spine, superodistal seta and palmate array of spinules, inferior margin with weak to robust spinules; dactylus and unguis subequal, former with accessory seta, together two thirds as long as propodus. Pereopod-2 ( Figure 16B ) similar to pereopod-1 but carpus and propodus slightly shorter, carpus with additional inferodistal spine and mesial seta; (PSS on basis probably detached on drawn specimen). Pereopod-3 ( Figure 16C ) similar to pereopod-2.

Pereopod-4 ( Figure 16D ) basis longer than in pereopods 1–3, with inferior PSS; ischium with two setae; merus about twice as long as broad, with two inferodistal spines; carpus longer than merus, 2.5 times ltb, with weak inferior spinules; propodus narrower than carpus but as long, with weak inferior spinules; dactylus twice as long as unguis, with double row of inferior spinules, together longer than propodus. Pereopod-5 ( Figure 16E ) similar to pereopod-4 but basis with two inferior PSS and propodus with two superodistal spines; dactylus and unguis about as long as propodus. Pereopod-6 ( Figure 16F ) similar to pereopod-4 but propodus with three superodistal spines.

Pleopod ( Figure 16G ) endopod slightly smaller than exopod, with superodistal seta and distal fringe of seven setae (all finely plumose); exopod with proximal seta on partly demarcated segment, with distal fringe of 13 plumose setae.

Uropod ( Figure 14F ) as long as pleotelson and pleonites 4–5 combined; peduncle twice as long as wide, simple; exopod half as long as segment-1 of endopod, segment- 1 just longer than segment-2; setation typical, as figured; endopod slender, segment-1 just over half total length, five times ltb, with two distal PSS and seta; segment-2 almost seven times ltb, setation as figured.

Post-ovigerous female. Similar to non-ovigerous female but pereon dorso-ventrally compressed, oostegites lost; body length 2.24 mm.

Preparatory male. Habitus ( Figure 14G ) slender, eight times ltb, body length 2.86 mm. Pleon about 15% of body length; pleonite-5 sternal process ( Figure 14H ) similar to female. Antennule ( Figure 14J ) article-1 shorter than rest of articles, 2.2 times ltb; article-4 shorter than broad.

Etymology

For my wonderful son, Julius.

Type locality

Bathyal Iceland Basin, 62.00°N, 19.50°W, ≈ 1000 m .

Distribution records from the AFEN, BIOICE and BIOFAR surveys

Two records from AFEN surveys: one from the Hebrides Slope , 991 m, and one from the northern Rockall Trough , 1886 m. Six records from BIOICE: one from the Irminger Basin, 1209 m, and five from the Iceland Basin, 940–1074 m; temperature range 2.34–4.1°C, with a variety of sediment types including ‘fine sand’, ‘medium sand’ and ‘gravelly sand’ .

Distribution elsewhere

There are 21 records from various surveys ranging from the Rockall Trough to the abyssal South Bay of Biscay, 1400–4829 m (see under C. armata ).

Remarks

As defined for the genus, this species is distinguished by a long, ventrally directed, pleonal spur and two superodistal spines on pereopod-5. The latter character shown for C. hastata by Guerrero-Kommritz (2005, fig. 8l); is possibly an error as pereopod- 6 ( Guerrero-Kommritz 2005, fig. 8m) is shown with only one superodistal spine, when typically for akanthophoreids there are three.

Most records of Saurotipleona julii n. sp. are from south of the main study area, at abyssal depths but with an overall depth range of 991–4829 m. An example is INCAL (Intercalibration) Stn 2.4, sample ØS.04, from the Biscay Abyssal Plain (46.05°N, 10.18°W, 4786 m); sketches of the individual presumed to be S. julii are shown in Figure 17C–E . This distribution pattern suggests a eurybathic tolerance but with some degree of polar emergence.

Key to the species of northeast Atlantic Chauliopleona and Saurotipleona

1. Pleonite-5 spur directed ventrally; pereopod-5 propodus with two superodistal spines ....................................................................................... Saurotipleona julii

– Pleonite-5 spur recurved; pereopod-5 propodus with one superodistal spine ..... Chauliopleona , ................................................................................................... 2

2. Cheliped dactylus superior margin crenate; pereopods 1–3 propodus slender (six times ltb) and scarcely spinulate ......................................................... C. bamberi

– Cheliped dactylus not crenate; pereopods 1–3 propodus not slender (<six times ltb) and densely spinulate ................................................................................. 3

3. Cheliped carpus stout, with deep shield .............................................. C. hastata – Cheliped carpus not stout, with shallow or moderate shield ............................ 4

4. Cheliped carpus shield shallow, subrectangular; pleonal sternites 1–4 with slightly recurved process .............................................................................. C. amdrupii

– Cheliped carpus shield moderate, rounded; pleonal sternites 1–4 with nonrecurved process .................................................................................. C. armata

Figures

Figure 14. Saurotipleona julii n. gen. n. sp. Non-ovigerous female, holotype, BIOICE Stn 3504: (A) habitus; (B) pleonal sternites, lateral. Non-ovigerous female, paratype, BIOICE Stn 3522: (C) pleonite-5 sternal spur; (D) antennule; (E) antenna; (F) uropod. Preparatory male, allotype, BIOICE Stn 3522: (G) habitus; (H) pleonite-5 sternal spur; (J) antennule. Scale bars: (i) 1 mm for A, G; (ii) 0.5 mm for B–C, H; (iii) 0.25 mm for D–F, J.

Figure 15. Saurotipleona julii n. gen. n. sp. Non-ovigerous female paratype, BIOICE Stn 3522: (A) labrum; (B–C) left and right mandibles, respectively; (D) labium; (E) maxillule; (F) maxilla; (G) maxilliped (one palp omitted); (H) cheliped; (J) cheliped carpus inferior setae; (K) cheliped propodus mesial comb and dactylus. Scale bars: (i) 0.25 mm for A–G; (ii) 0.25 mm for H–J.

Figure 16. Saurotipleona julii n. gen. n. sp. Non-ovigerous female paratype, BIOICE Stn 3522: (A–F) pereopods 1–6, respectively; (G) pleopod (setae very finely plumose, omitted for clarity). Scale bar 0.25 mm.

Figure 17. Sketch drawings of Chauliopleona and Saurotipleona. (A) C. hastata?, BIOICE Stn 3187; (B) C. armata sensu lato, Thalassa-73 Stn Z.426; (C–E) S. julii, INCAL ØS.04, cheliped, pleon and pleonite-5 spur, respectively. Not to scale.

Figure 19. Distribution of Chauliopleona bamberi and Saurotipleona julii in the Atlantic Margin area. Filled squares indicate C. bamberi, and filled circles S. julii.