Rimicaris exoculata, WILLIAMS & RONA, 1986

Martin, Joel W. & Haney, Todd A., 2005, Decapod crustaceans from hydrothermal vents and cold seeps: a review through 2005, Zoological Journal of the Linnean Society 145 (4), pp. 445-522 : 467-469

RIMICARIS EXOCULATA WILLIAMS & RONA, 1986

Type locality: North Atlantic Ocean , MAR, TAG vent field; 26°08.3′N, 44°49.6′W; 3620–3650 m .

Known range: North Atlantic Ocean, MAR, from hydrothermal vent fields at the Snake Pit, TAG, Broken Spur, Lucky Strike, Logatchev and Rainbow sites, 1700–3650 m ( Williams & Rona, 1986; Van Dover et al., 1988; Galkin & Moskalev, 1990a; Segonzac, 1992; Segonzac, 1997, in Desbruyères & Segonzac, 1997; Segonzac et al., 1993; Vereshchaka, 1997a; Gebruk et al., 2000a; Turnipseed et al., 2004).

Material: type locality, NOAA VENTS Program, R / V Researcher; 3 August 1985; dredge haul. USNM 228443 (holotype male), USNM 228444 (allotype female), USNM 228445 (paratypes, 5 males, 6 females), USNM 228446 (paratypes, 69 males), USNM 228447 [paratypes, 64 females, (1 ovigerous)], USNM 228448 (paratypes, 14 juveniles), USNM 228449 (nontype, 1 male, fragmented), USNM 228450 (non-type, 1 female, fragmented), USNM 228451 (unsexed fragments) ( Williams & Rona, 1986) .

– Rainbow hydrothermal vent field; 36°13.40′N, 33°54.07′W; 2285 m; PICO, Nautile dive 1264; 30 June 1998; slurp gun; CBM-ZC 6446 (1 male, 1 female) ( Komai & Segonzac, 2003) .

– TAG hydrothermal vent field, 26°8′N, 44°49′W; 3630 m ( Van Dover et al., 1988, specimen data not provided) .

–Snake Pit hydrothermal vent field, Elan site, site 649, Hole 649H; 23°22.160′N, 44°57.072′W; 3522 m; JOIDES, D/ V Resolution, leg 106; 17 December 1985, USNM 228525 (2 males, 2 females) ( Williams, 1987). –Elan site; 23°22.20′N, 44°57.08′W; 3500 m; MICRO- SMOKE; dive 01; 14 November 1995; MNHN-Na, registration number not provided (6 juveniles) ( Komai & Segonzac, 2003). –Les Ruches site; 23°22′N, 44°56′W; HYDROSNAKE, Nautile dives 03, 08 and 10 ( Segonzac et al., 1993).

Williams & Rona (1986) indicated that 2 males and 2 females would be sent to each of the following: LACM, MCZ, BMNH, RMNH, MNHN. At least two paratypes were deposited at MNHN, as noted by Watabe & Hashimoto (2002). Nuckley et al. (1996) mentioned additional material from Alvin dives 2613, 2618 and 2623.

–As Rimicaris aurantiaca : North Atlantic Ocean, MAR, Snake Pit hydrothermal vent field, Moose vent (Elan) site; 23°22.1′N, 44°57.0′W; 3520 m (type locality for Rimicaris aurantiaca ); R / V Atlantis II cruise 129- 7, Alvin dive 2618; 3520 m; 19 June 1993; LACM 93- 46.3 (holotype: female), LACM 93-46.2 (paratypes, 17 adults) ( Martin, Signorovitch & Patel, 1997; mentioned also by Martin et al., 1998b).

–As Iorania concordia : North Atlantic Ocean, MAR, TAG vent field, point ‘D’, sta. 3415; 26°09′N, 44°50′W; 3650 m (type locality for Iorania concordia ).

34th cruise of R / V Akademik Mstislav Keldysh for British–Russian Programme BRAVEX-94, Mir-1, Mir- 2; 3650 m; 24 September 1994; slurp gun; Oceanology Institute (Moscow) (holotype, female), Oceanology Institute (Moscow) (paratypes, 30 females) ( Vereshchaka, 1996b). Vereshchaka (1996b) additionally indicated that one female paratype (of I. concordia ) would be transferred to each of the following collections: ZMUC, MNHN, RMNH.

Remarks: Rimicaris exoculata is perhaps the most extensively studied vent decapod to date. It is known only from sites along the MAR, where it occurs in active swarms that may be as dense as 2500 individuals per square metre and on chimney walls where temperatures range from 15 to 30 °C. The density and unusual eye morphology and function have resulted in photographs and brief articles on the species appearing in a large number of popular as well as scientific articles (e.g. Monastersky, 1989; Tunnicliffe, 1991: 337, fig. 4B, 1992b; Van Dover, 1995: 262, fig. 3a, d; Copley et al., 1997, 1999; Herring, Gaten & Shelton, 1999). Renninger et al. (1995) studied sulphide as a chemical stimulus in this species, Vereshchaka et al. (2000) reported on carbon and nitrogen composition, and general physiology was reviewed by Childress & Fisher (1992). Feeding biology and ecology were studied by Van Dover et al. (1988) and Rieley et al. (1999); feeding morphology and behaviour were further investigated by Gebruk et al. (1993, 2000b), Casanova et al. (1993), Segonzac et al. (1993) and Polz et al. (1998). In part because bacteria are involved with feeding in this species, the associated bacteria have been examined by many workers (e.g. see Raguénès et al., 2003). Lipid fatty-acid composition was studied in a series of papers by Pond, Dixon & Sargent (1997b), Pond et al. (1997a, c, 2000a, b), Allen Copley, Tyler & Varney (1998), Allen Copley, Copley & Tyler (2001) and Rieley et al. (1999). Carotenoid pigments were analysed by Nègre-Sadargues et al. (2000). The morphology and function of the novel eye structure in this species, consisting of rhodopsin-containing organs beneath the transparent dorsal cuticle of the carapace, and the question of what these organs might be perceiving, have been the subject of several studies, including those of Pelli & Chamberlain (1989), Van Dover et al. (1989), Chamberlain (2000), Chamberlain et al. (1994a, b), Johnson et al. (1995), O’Neil et al. (1995), Curra et al. (1996), Nuckley et al. (1996, as Rimicaris sp. ), Kuenzler et al. (1996, as? Chorocaris [juveniles]), Jinks et al. (1998), Gaten et al. (1998a, b), Herring et al. (1999) and others (see also Meyer-Rochow, 2001). Dixon et al. (2001) studied rates of cell division, Compere et al. (2002) studied sulphide detoxification, Galchenko et al. (1989) studied CO 2 assimilation, Lallier & Truchot (1997) examined haemocyanin properties, and Geret et al. (2002), Larsen et al. (1997; arsenic) and Martins et al. (2001; mercury) investigated the bioaccumulation or presence of metals. Studies of allozyme data from populations at TAG and Broken Spur sites showed no significant genetic differentiation, suggesting gene flow among these sites is not restricted ( Creasey, Rogers & Tyler, 1996). Ramirez- Llodra et al. (2000) addressed aspects of reproductive biology. The organ of Bellonci and sinus gland were described by Charmantier-Daures & Segonzac (1998). Larvae and postlarvae of alvinocaridids, some of which undoubtedly belong to this species, have been collected at a distance from MAR vents (Herring, 1998; Herring & Dixon, 1998; see also Dixon et al. 1998). Martin et al. (1998b) examined the carpal cleaning brush of this species in comparison with that of other vent shrimp species (see also comments above under R. aurantiaca concerning this brush).

The very different coloration (usually bright orange, in large part due to the four-fold increase in carotenoids; see Nègre-Sadargues et al., 2000) and morphology of juveniles of R. exoculata have led to taxonomic confusion (e.g. see comments and discussion in Murton, Van Dover & Southward, 1995; Creasey et al., 1996; Polz et al., 1998; Vereshchaka, 1996a, b, 1997a). Several authors were convinced early on that the small orange shrimp found at many MAR sites was a distinct species until it was shown (mostly by Shank, Lutz & Vrijenhoek, 1998b; Shank et al. 1999) that some of these were simply juveniles of R. exoculata . Indeed, juveniles of R. exoculata were given at least two different names, Rimicaris aurantiaca (by Martin et al., 1997) and Iorania concordia (by Vereshchaka, 1996b).

The genus Iorania and the species Iorania concordia , both described by Vereshchaka (1996b), were based on juveniles of Rimicaris exoculata , according to genetic studies by Shank et al. (1998b, 1999). Thus, all distributional and collection records of Iorania can be combined with those of R. exoculata . This finding of course brings up questions about the morphological differences noted by Vereshchaka (1996b), especially those larger differences (such as the extended ‘lash’ on the first maxilliped) that he attributed to generic significance. Ontogenetic studies of this species are needed to resolve this issue.

The species described as Rimicaris aurantiaca by Martin et al. (1997) was, like Iorania concordia , also based on juveniles of R. exoculata , which, as noted above, differ from adults dramatically in coloration and to a lesser extent in morphology. Thus, there are three names in the literature that all refer to one species ( Rimicaris exoculata ): R. exoculata , R. aurantiaca and Iorania concordia , only the first of these is still a valid name. Interestingly, characters of the carpal brush cleaning setae on the cheliped of ‘ Rimicaris aurantiaca ’ (the juvenile of R. exoculata ) were intermediate between what is found in Chorocaris (with a well-developed carpal brush) and what is found in adult Rimicaris exoculata (which lacks a carpal cleaning brush) ( Martin et al., 1998b). The original conclusion of Martin et al. (1998b) – that characters of ‘ R. aurantiaca ’ were morphologically intermediate between those of Chorocaris species and Rimicaris exoculata – must now be reinterpreted as an ontogenetic progression; Rimicaris exoculata has a poorly developed carpal brush as a juvenile but loses it by the adult stage.

T. Komai and M. Segonzac (pers. comm.) inform us that indeed the postlarval stages of R. exoculata can be roughly divided into three ontogenetic stages based on morphology, thus explaining to some degree the previous confusion.