Akanthophoreus

Akanthophoreus sp. KK#5

Figures 15–16

Material examined. 1 non-ovigerous female (3.6 mm), station XR-5, 42°23.83’– 42°22.06’N 145°31.06’– 145°27.70’E, 3145–3265 metres, 16 September 2001.

Remarks. This is an elongate species (Fig. 15 A), 7.8 (contracted) - 8.7 (stretched) times as long as broad, with a long cephalothorax (1.47 times as long as broad), no pleotelson spurs and only low pleonal sternal processes (Fig. 15 B). A potentially significant-useful character is the presence of two setae on the pleonite 3 lateral margin. The antennule (Fig. 15 C) is slender but is only 0.72 times as long as the cephalothorax. The cheliped (Fig. 16 A) is relatively ‘ordinary’, but has two distinct spurs on the dorsal crest of the propodus (Fig. 16 B), weak dorsal crenulation on the dactylus, and a distinct, but weak, carpal shield. Pereopods 1–3 (Fig. 16 C) are slender, with sparse minor setation, with a long dactylus/unguis (almost as long as propodus). The posterior pereopods (Fig. 16 D) are unremarkable, but pereopod 6 has three dorso-distal spiniform setae. Akanthophoreus sp.KK#5 has slender uropods, with a long basal article that is weakly crenulate on the dorsal margin (Fig. 15 E).

The closest taxonomic or phylogenetic affinities of this species are not clear but it approaches A. multiserratus in general shape and setation, if not in the degree of cheliped crenulation.

Distribution. Kurile-Kamchatka Trench, 3145–3265 metres.

(restricted synonymy and bibliography)

Chauliopleona Dojiri & Sieg, 1987: 231. Guerrero-Kommritz, 2005: 11 –79–1180. Larsen & Shimomura, 2007: 31 –32. Leptognathia G.O. Sars, 1882 (partim): Hansen, 1913: 79 –82 (for species amdrupii, armata and hastata listed below). Type species: Chauliopleona dentata Dojiri & Sieg, 1997 by monotypy.

Species included (Japanese waters, Kurile-Kamchatka Trench and the Japan Trench species in bold): C. amfti Guerrero-Kommritz, 2005, Angola Basin; C. armata (Hansen, 1913) [?], NE Atlantic; C. amdrupi (Hansen, 1913), Arctic, NW & NE Atlantic; C. dentata, California; C. hansknechti Sieg & Shimomura, 2007; C. hastata (Hansen, 1913), Arctic Ocean; C. nickeli Guerrero-Kommritz, 2005, Weddel Sea; C. paradoxa Guerrero-Kommritz, 2005, Peru Basin.

Diagnosis. See Larsen & Shimomura 2007.

Remarks. Although the type species of the genus C. dentata was described from Californian waters, the most familiar names are those formerly of Hansen’s Leptognathia group “a”, subdivision ‘ γ ’, characterized by a sternal spur on pleonite 5. A revision of the genus by Guerrero-Kommritz (2005) added several new species and confirmed the distinct identity of C. armata and C. hastata that had been considered to be synonymous by several authorities. Recently, Larsen & Shimomura (2007) have described a shallow-water Japanese species, C. hansknechti, and commented that the genus may belong to the family Leptognathiidae. Whichever family Chauliopleona is eventually assigned to, after a phylogenetic analysis, it will be the same as that for Akanthophoreus.