Liuiuristis, Wang & Sha, 2024

Wang, Yan-Rong & Sha, Zhong-Li, 2024, A new genus and one new species of the family Uristidae Hurley, 1963 (Amphipoda, Lysianassoidea) described from hydrothermal vent of the Okinawa Trough, NW pacific, Zootaxa 5447 (3), pp. 413-423 : 415-417

Genus Liuiuristis gen. nov.

Type Species: Liuiuristis thermalis sp. nov. designated herein. Monospecific.

Diagnosis. Antenna 1 peduncular article 1 without anterodistal lobe; accessory flagellum forming cap covering callynophore. Antenna 2 without brush setae. Mandible molar with triturating surface. Maxilla 1 outer plate a well-developed 7/4 crown. Maxilla 2 inner plate shorter than outer plate. Gnathopod 1 parachelate in female and subchelate in male; coxa 1 large, slightly shorter than coxa 2, subrectangular, with concave anterior margin; ischium slightly longer than merus; carpus much shorter than propodus; propodus margins subparallel. Uropod 2 inner ramus not constricted. Telson entire.

Relationships. Liuiuristis gen. nov. is classified in the family Uristidae Hurley, 1963 for the setal-tooth arrangement on the outer plate of maxilla 1 forms a 7/4 crown and have callynophore in both sexes ( Lowry & Stoddart 1989; Lowry & Kilgallen 2014). Most uristids having plumose setae on the rami of uropod 3 ( Lowry & Kilgallen 2014), excepting for seven genera: Caeconyx Barnard & Karaman, 1991 , Galathella Barnard & Karaman 1987 ; Gippsia Lowry & Stoddart 1995 ; Menigrates Boeck, 1871 ; Onisimus Boeck, 1871 ; Paralibrotus Stephensen, 1923 ; Ventiella Barnard & Ingram 1990 (Kudrjaschov 1965; Barnard & Karaman 1987; 1991; Barnard & Ingram 1990; Lowry & Stoddart 1995; Lowry & Kilgallen 2014). Similarly, the new genus also lacks the plumose setae on uropod 3.

Liuiuristis gen. nov. can be distinguished from all above seven genera, except Caeconyx and Onisimus , by the accessory flagellum forming cap that covers the callynophore. Moreover, Liuiuristis gen. nov. differs from Caeconyx , Galathella , Menigrates and Ventiella by having the entire telson. Of the seven aforementioned genera, only three, Gippsia , Onisimus , and Paralibrotus , have an entire telson. Liuiuristis gen. nov. differs from Gippsia by the inner plate of maxilla 2 shorter than outer plate, from Onisimus by the anterior margin of coxa 1 not distinctly concave and from Paralibrotus by the outer plate of maxilla 1 having 11 setal-teeth and gnathopod 1 parachelate in female and subchelate in male ( Lowry & Kilgallen 2014).

Additionally, four other uristid genera, Anonyx Krøyer, 1838 , Caeconyx Barnard & Karaman, 1991 ; Des Lowry & Kilgallen, 2014 and Onisimus Boeck, 1871 , have cap-shaped accessory flagellum. The new genus can be distinguished from above four genera by the combination of the following characters: the peduncular article 1 of antenna 1 not expanded, the gnathopod 1 parachelate in female, and having entire telson ( Barnard & Karaman 1991; Lowry & Kilgallen 2014).

The pairwise inter-generic K2P distances of COI genes ranged from 0.237 to 0.383 within ten uristid genera, and that between the new genus and other nine genera is 0.264 –0.383, well supporting the morphological identification of the new genus. ( Table 2 ). Tree topologies resulting from the BI and ML analyses were highly congruent and generally well supported (fig. 1). The new genus is clustered with Ventiella (BP=73% and PP=0.97), which is a monotypic genus and also reported from vent field ( Barnard & Ingram 1990; Lowry & Kilgallen 2014). Liuiuristis gen. nov. is morphologically well distinguished from Ventiella above.

Etymology. The genus is named in honour of the late Professor Ruiyu Liu (J.Y. Liu) of the Institute of Oceanology, Chinese Academy of Sciences, for his great contributions to Chinese carcinology. The name is masculine in gender.

Tables

TABLE 2. Estimates of p-distances of mitochondrial COI gene between and within 10 genera, including the new genus of the family Uristidae.

	1	2	3	4	5	6	7	8	9	10
1. Abyssorchomene	0.142
2. Anonyx	0.275	0.142
3. Cicadosa	0.326	0.267	n/c
4. Ichnopus	0.324	0.317	0.277	n/c
5. Onisimus	0.257	0.276	0.305	0.358	0.273
6. Parschisturella	0.237	0.239	0.277	0.325	0.262	n/c
7. Tmetonyx	0.301	0.278	0.262	0.304	0.313	0.260	n/c
8. Uristes	0.303	0.262	0.259	0.309	0.295	0.243	0.268	0.239
9. Ventiella	0.298	0.241	0.260	0.315	0.290	0.247	0.312	0.263	n/c
10. Liuiuristis gen. nov.	0.383	0.296	0.306	0.298	0.346	0.312	0.308	0.301	0.264	n/c