Alijinocaris markensis, Williams, 1988

Komai, Tomoyuki & Segonzac, Michel, 2005, A revision of the genus AlIJinocaris Williams and Chace (Crustacea: Decapoda: Caridea: Alvinocarididae), with descriptions of a new genus and a new species of AlIJinocaris, Journal of Natural History 39 (15), pp. 1111-1175 : 1128-1132

AlIJinocaris markensis Williams, 1988

( Figures 6 , 7 , 14A , 29 )

Alυinocaris markensis Williams 1988, p 264 , Figures 1 , 2 , 7 [MARK vent, Snake Pit, Mid-Atlantic Ridge, 23 ° 22.099N, 44 ° 57.129W, 3437 m]; Dixon and Dixon 1996, p 9, Figures 1–3 ; Vereshchaka 1996, p 577; Shank 1997, p 192; Shank et al. 1998, p 89; Shank et al. 1999, p 246 (Table 1), 247, Figure 2 ; Kikuchi and Hashimoto 2000, p 146 (table), 148 (key); Desbruyères et al. 2000, p 209 (Table 4).

Alυinocaris muricola: Shank et al. 1999, p 246 (Table 1). Not Alυinocaris muricola Williams, 1988 .

Alυinocaris aff. markensis: Desbruyères et al. 2001, p 1335 (Table 3).

Material examined

Mid-Atlantic Ridge. DS Alυin: dive 1683, stn 1, MARK vent, Snake Pit, 23 ° 22.099N, 44 ° 57.129W, 3437 m, 30 May 1986, scoop, one female CL 4.2 mm (holotype; USNM 234286 ); same data, one female CL 6.7 mm, one juvenile CL 4.4 mm (paratypes; USNM 234287 ) .

Hydrosnake (DS Nautile): HS 03, site Elan, Snake Pit, 3515 m, 21 June 1988, 4 males CL 9.5–12.9 mm (MNHN-Na 14279); HS 10, site Les Ruches, Snake Pit, 23 ° 22.139N, 44 ° 57.139W, 3482 m, 28 June 1988, slurp gun, one female CL 18.9 mm, one juvenile (badly damaged) (MNHN-Na 15049).

MAR 93 (DS Alυin): M11/2619, site Les Ruches, Snake Pit, 23 ° 22.139N, 44 ° 57.139W, 3482 m, 20 June 1993, one male CL 6.9 mm, two females CL 6.1, 6.2 mm (MNHN-Na 14280); same data, one female CL 18.3 mm (MNHN-Na 14281) .

Microsmoke (DS Nautile): dive MS 08, site Les Ruches, Snake Pit, 23 ° 22.139N, 44 ° 57.139W, 3480 m, baited trap, 21 November 1995, one male CL 10.2 mm, 13 females CL 7.3–16.7 mm (MNHN-Na 14282); same dive, two females CL 9.4, 12.8 mm, five specimens (sex undeterminable because of lack of abdomens) CL 10.0–12.0 mm (MNHN- Na 15050); dive MS 16, same site, 3500 m, 29 November 1995, one female CL 22.3 mm (MNHN-Na 14283); same data, four females CL 13.7–18.1 mm (MNHN-Na 15051) .

Atos ( ROV Victor): dive 119-17, Tour Eiffel, Lucky Strike, 37 ° 13.489N, 32 ° 19.429W, 1693 m, 16 July 2001: one ovigerous female CL 13.0 mm (MNHN-Na 14284); dive 104-02, 25 June 2001, GBT1, site Rainbow, 36 ° 13.7599N, 33 ° 54.1699W, 2292 m, one male CL 10.1 mm (MNHN-Na 14285); three juveniles, dive 107-05, same site, 30 June 2001, slurp gun, one female CL 8.3 mm, one juvenile CL 4.9 mm (Ifremer) .

Seahma 1: dive 186-04, Rainbow, 36 ° 13.7599N, 33 ° 54.1699W, 2292 m, 8 August 2002, slurp gun, one female CL 13.0 mm ( CBM-ZC 7041 ) .

Description

Body moderately robust.

Rostrum ( Figure 6A, B ) directed forward or slightly descending, nearly straight or slightly curved dorsally, 0.45–0.70 of carapace length, usually reaching to second segment of antennular peduncle; dorsal margin nearly straight or slightly concave in general outline, armed with 14–19 teeth, including 8–12 on rostrum proper and five to seven moderately large teeth on carapace posterior to level of orbital margin, posteriormost tooth arising from 0.24–0.31 of carapace length; ventral margin armed with six to nine small teeth on anterior 0.30–0.50. Carapace ( Figure 6A, C ) 0.52–0.65 times as wide as long; postrostral median ridge relatively high, strongly compressed laterally, extending to 0.75–0.80 of carapace length with dorsal angle 150 °; pterygostomian tooth larger than antennal tooth, distinctly exceeding antennal tooth; post-antennal groove shallow; branchial region not particularly inflated.

Third abdominal pleuron smooth or bearing few minute denticles posteriorly. Fourth abdominal pleuron ( Figure 6D ) with one to four (most frequently two or three) teeth posteriorly. Fifth abdominal pleuron similarly armed with one strong posterolateral tooth and one to three additional teeth on posterior margin. Sixth somite about 1.50–1.70 times longer than proximal height. Telson ( Figure 6E ) narrowed posteriorly, not reaching or reaching posterior margin of uropodal endopod, length 2.60–2.90 times anterior width and 4.90–5.10 times posterior width; armed with six to eight dorsolateral spines; posterior margin ( Figure 6F ) always convex, armed with two pairs of lateral spines and 12–14 plumose setae all longer than mesial pair of lateral spines.

Antennular peduncle ( Figure 6B ) moderately stout, second segment 1.79–2.05 times longer than wide. Antennal scale ( Figure 7A ) 0.48–0.51 times as long as carapace, 1.91–2.04 longer than wide; lateral margin straight, slightly diverging anteriorly from dorsal median ridge; distolateral tooth directed forward, falling short of distal margin of blade.

First pereopod ( Figure 7B, C ) as illustrated; greatest height of palm about 0.40 times length of chela; dactylus longer than palm ( Figure 7C ). Third pereopod ( Figure 7D ) moderately slender; dactylus ( Figure 7E ) with accessory spinules notably increasing in size distally; carpus 0.65–0.70 times as long as propodus; merus about 7.00 times as long as greatest height.

Size

Largest male 12.9 mm; largest female 22.3 mm, ovigerous female 13.0 mm. Maximal TL ca 82 mm.

Variation

The shape and armature of the rostrum is rather constant in the present material of this species. The armature of the third to fifth abdominal pleura is variable as in A. longirostris (cf. Kikuchi and Ohta 1995).

Distribution

The occurrence of this species is confirmed at the three locations on the Mid-Atlantic Ridge: Snake Pit, 3484–3515 m; Lucky Strike, 1693 m; and Rainbow, 2292 m ( Figure 29 ). Shank et al. (1999) recorded A. markensis from hydrothermal vents of Broken Spur (3300 m), TAG (3650 m) and Logatchev (3010 m).

Ecology

Observations made from video films taken by DS Nautile during the cruises Hydrosnake and Microsmoke on the site Snake Pit (Les Ruches, 3480 m and Elan, 3515 m), and by the ROV Victor during the cruises Atos on the site Lucky Strike (Tour Eiffel, 1693 m) and Seahma 1 on the site Rainbow (2292 m), are consistent with the previous report from Snake Pit and Logatchev ( Segonzac et al. 1993; Gebruk et al. 2000a, 2000b). This species always lives solitary at the base of the active chimneys or on the walls of the few active chimneys ( Figure 14A ), close to aggregates of Rimicaris exoculata or on mussel beds. The trophic mode is necrophagous, as capture of the shrimps by baited traps indicates. However, the gut contents examined generally contained much mineral particles.

Remarks

The holotype and two paratypes of Alυinocaris markensis are all juveniles. The species is rediagnosed in this study using supplementary adult specimens from some hydrothermally influenced fields on the Mid-Atlantic Ridge, including topotypic specimens (see ‘‘Material examined’’). The rostrum normally reaching the second segment of the antennular peduncle and the possession of plumose setae on the posterior margin of the telson link A. markensis to A. muricola , A. longirostris , and A. dissimilis sp. nov. Differences among these four species are discussed under ‘‘Remarks’’ for A. dissimilis sp. nov.

Desbruyères et al. (2001) mentioned the occurrence of A. aff. markensis at Lucky Strike on the Mid-Atlantic Ridge. The presence of A. markensis at this site has been confirmed based on one ovigerous specimen collected during the Atos cruise (MNHN-Na 14284).

Figures

Figure 1. Diagrammatic Alυinocaris, showing measurements used in text. (A) Carapace and rostrum, lateral; CL, carapace length; DA, dorsal angle; RL, rostral length. (B) Carapace, dorsal: CW, carapace width. (C) Anterior part of carapace and cephalic appendages, dorsal; L, length; W, width. (D) Sixth abdominal somite, lateral; L, length; H, height. (E) Telson, dorsal; AW, anterior width; L, length; PW, posterior width. (F) Antennal scale, dorsal; abbreviations as in (C). (G) Chela of first pereopod, lateral; PL, palm length; PH, palm height.

Figure 2. Alυinocaris muricola Williams, 1988. Left appendages. (A) Antennal scale, dorsal; (B) mandible, dorsal; (C) maxillule, ventral; (D) maxilla, ventral; (E) first maxilliped, ventral; (F) endopod of first maxilliped, dorsal; (G) second maxilliped, ventral; (H) first pleopod, ventrolateral; (I) endopod of first pleopod; (J) appendices interna and masculina of second pleopod, mesial. (A–H) Female from Régab site, west equatorial African margin (CL 16.8 mm; MNHN-Na 14277); (I, J) male from same locality (CL 15.4 mm; Ifremer).

Figure 6. Alυinocaris markensis Williams, 1988. (A) Carapace and cephalic appendages, lateral; (B) anterior part of carapace and cephalic appendages, dorsal; (C) carapace, dorsal; (D) third to sixth abdominal somite, lateral; (E) telson and right uropod, dorsal; (F) posterior part of telson, dorsal. Female from site Les Ruches, Snake Pit, Mid-Atlantic Ridge (CL 16.7 mm; MNHN-Na 14282).

Figure 7. Alυinocaris markensis Williams, 1988. (A) Left antennal scale, dorsal; (B) left first pereopod, lateral; (C) chela of left first pereopod, outer; (D) left third pereopod, lateral; (E) dactylus and distal part of propodus of left third pereopod, lateral. Female from site Les Ruches, Snake Pit, Mid-Atlantic Ridge (CL 16.7 mm; MNHN- Na 14282).

Figure 14. (A) In situ photograph taken by the submersible Nautile, at a sulphide edifice of vent site Les Ruches, Snake Pit, Mid-Atlantic Ridge (3480 m) during Hydrosnake Cruise (PL 08): on the centre, one individual of Alυinocaris markensis Williams, 1988; other shrimps, Chorocaris chacei. Copyright Ifremer/Hydrosnake. (B) In situ photograph taken by the ROV Victor, at the cold seep site Régab, west equatorial African margin (3150 m) during Biozaïre 2 Cruise (PL 146): aggregation of Alυinocaris muricola Williams, 1988, among mytilid mussels Bathymodiolus sp. and tubeworm pogonophorans Escarpia n. sp.; lower left corner, coiled gastropods Proυanna sp. (fide A. Warén, Stockholm). Copyright Ifremer/Biozaïre 2. (C) Same data, Alυinocaris muricola Williams, 1988, among mussels Bathymodiolus sp. and actiniarians; lower right corner, limpet gastropods Paralepetopsis sp. (fide A. Warén). Copyright Ifremer/Biozaïre 2.

Figure 29. Distribution map of Alυinocaris species known at present.