Alijinocaris stactophila, 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 : 1143-1148

publication ID	https://doi.org/ 10.1080/00222930400002499
persistent identifier	https://treatment.plazi.org/id/050D1914-FFE9-FF96-FE60-FDC6FD984EEC
treatment provided by	Carolina
scientific name	Alijinocaris stactophila
status

Treatment

AlIJinocaris stactophila Williams, 1988

( Figures 15–18 View Figure 15 View Figure 16 View Figure 17 View Figure 18 , 29 View Figure 29 ) Alυinocaris stactophila Williams 1988, p 272 (part), Figures 5–7 View Figure 5 View Figure 6 View Figure 7 ; Shank et al. 1999, p 246 (Table 1), 247 (Table 2), Figure 2 View Figure 2 ; Kikuchi and Hashimoto 2000, p 146, 148 (key).

Material examined

Gulf of Mexico. Johnson-Sea-Link: dive 1879, Bush Hill hydrocarbon seep, about 129 km south of Louisiana, 27 ° 46.949N, 91 ° 39.349E, 534 m, 28 September 1986, one male CL 7.0 mm (holotype; USNM 234292 About USNM ) GoogleMaps .

Alυinocaris sp. 1 (allotype of A. stactophila ), same data as for holotype of A. stactophila , one female CL 6.8 mm (USNM 23493).

Description

Body moderately robust for genus.

Rostrum ( Figure 15A View Figure 15 ) directed forward, straight, 0.42 times as long as carapace, slightly reaching beyond distal margin of first segment of antennular peduncle; dorsal margin armed with 16 teeth, including eight teeth on rostrum proper and eight relatively small teeth on carapace posterior to orbital margin, posteriormost tooth arising from 0.28 of carapace length; ventral margin armed with one small subdistal tooth. Carapace ( Figure 15A, B View Figure 15 ) with postrostral median ridge moderately high, extending to 0.60 of carapace length, dorsal angle 170 °; pterygostomian tooth weakly produced anteriorly, slightly exceeding antennal tooth; post-antennal groove shallow; branchial region not particularly inflated.

Third abdominal pleuron unarmed ( Figure 15C View Figure 15 ). Fourth abdominal pleuron with small posteroventral tooth and additional two or three tiny teeth on posterior margin. Fifth abdominal somite similarly armed with strong posteroventral tooth and additional three or four tiny teeth. Sixth abdominal somite 1.38 times longer than height. Telson ( Figure 15D View Figure 15 ) reaching posterior margin of uropodal endopod, 3.00 times as long as anterior width and 4.70 times as long as posterior width; armed with six dorsolateral spines; posterior margin ( Figure 15E View Figure 15 ) moderately convex, armed with eight pairs of spines (longest second pair noticeably curved mesially, mesial six pairs subequal in length).

Antennular peduncle ( Figure 15B View Figure 15 ) moderately stout, second segment 1.80 times longer than wide. Antennal scale ( Figure 16A View Figure 16 ) 0.46 times as long as carapace, 2.00 times longer than wide; lateral margin straight, slightly diverging anteriorly against dorsal median ridge; distolateral tooth directed forward, falling short of broadly rounded distal margin of blade.

First pereopod ( Figure 16B View Figure 16 ) as illustrated; greatest height of palm about 0.40 times length of chela ( Figure 16C View Figure 16 ); dactylus longer than palm. Third pereopod ( Figure 16D View Figure 16 ) moderately slender; dactylus ( Figure 16E View Figure 16 ) with strongly erect accessory spines on ventral margin, of which second and third accessory spines longer than distalmost accessory spine; carpus 0.66 times as long as propodus; merus 7.44 times as long as greatest height.

Size

Only the male holotype has been available for study. CL 7.0 mm. TL ca 25 mm. Distribution and habitat

Known with certainty only from the cold seep area at Louisiana Slope in the Gulf of Mexico ( Figure 28 View Figure 28 ), at a depth of 534 m.

Remarks

Alυinocaris stactophila was described on the basis of nine specimens from the central Gulf of Mexico, of which the holotype male and allotype female have been available for study. The holotype differs from the allotype in several respects, although the sizes are similar to one another (CL 7.0 mm in the holotype, 6.8 mm in the allotype). The ventral margin of the rostrum is armed with one tiny subdistal tooth in the holotype ( Figure 15A View Figure 15 ) , while in the allotype it is unarmed ( Figure 17A View Figure 17 ). The fourth abdominal pleuron bears three (left) or four (right) teeth on the posterior margin (including the posteroventral tooth) in the holotype (cf. Figure 15C View Figure 15 ), but it is only bluntly pointed at the posteroventral angle in the allotype ( Figure 17C View Figure 17 ). The posterior margin of the telson is armed with eight pairs of spines, of which the second pair are longest and mesially curved in the holotype ( Figure 15E View Figure 15 ), rather than having two pairs of lateral spines and 12 long plumose setae in the allotype ( Figure 17E View Figure 17 ). The second segment of the antennular peduncle is more slender in the holotype than in the allotype ( Figures 15B View Figure 15 , 17B View Figure 17 ). The chela of the first pereopod in the male holotype is much stouter than in the female allotype ( Figures 16B, C View Figure 16 , 18B, C View Figure 18 ). The third to fifth pereopods are more slender in the holotype than in the allotype ( Figures 16D View Figure 16 , 18D View Figure 18 ). The accessory spines on the dactylus of the third pereopods of the holotype are more strongly erect, of which the second and third spines are longer than the distalmost spine ( Figure 16E View Figure 16 ). In the allotype , the accessory spines are less erect and increase in length distally ( Figure 18E View Figure 18 ). Although only two specimens have been available for comparison, the differences in the armature on the posterior margin of the telson and the armature of the dactylus of the third pereopod, at least, strongly suggest that they represent two separate species. Therefore , the allotype is here treated as a species of uncertain taxonomic status. A final decision will be made when an adequate series of adult specimens from the Gulf of Mexico is available for study. Here A. stactophila is re-diagnosed on the basis of the holotype .

As mentioned before, the possession of spines other than two lateral pairs on the posterior margin of the telson links A. stactophila to A. lusca and A. breυitelsonis. Differences among the three species are discussed under ‘‘Remarks’’ for A. lusca .

Alυinocaris stactophila somewhat resembles A. aeilliamsi particularly in the short rostrum. Other than the armature on the posterior margin of the telson, the less stout antennular peduncle and the fourth abdominal pleuron armed with more than one posterolateral tooth distinguish A. stactophila from A. aeilliamsi .