Amphithyropsis shanti Gasca & Suárez-Morales & Hendrickx 2021, sp. nov.

• Main Authors: Gasca, Rebeca, Suárez-Morales, Eduardo, Hendrickx, Michel E.
• Format: Text
• Language: unknown
• Published: Zenodo 2021
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Amphipoda; Amphithyridae; Amphithyropsis; Amphithyropsis shanti; Antarctic; Pacific; New Zealand; Thumb; Morales; Middle Head; Antarc*
• Online Access: https://dx.doi.org/10.5281/zenodo.5516614; https://zenodo.org/record/5516614

Amphithyropsis shanti sp. nov. (Figs. 4‒8) Type material . Holotype, 1 male, TALUD III. St. 19B (25°18’24”N, 109°18’36”W), August 20, 1991, I-K from surface to 600 m (TD, 1890 m) (ECO-CH-Z-10545). Allotype, 1 gravid female, TALUD IV, St. 25A2 (24°54’N, 108°59’W), August 26, 2000, BS from surface to ca. 800 m (ECO-CH-Z-10546). Type locality . Central Gulf of California, SW of Topolobampo, Sinaloa (25°18’24”N, 109°18’36”W). Distribution . Known only from two localities, in the central Gulf of California, Mexico (Fig. 9). Etymology . The Sanskrit noun shanti means peace. It is feminine as the genus gender, which ending on the suffix – opsis is to be treated as feminine (Oren & Schink 2016). In this way, we manifest our wish for world peace. Description of adult male . Body . Body (Fig. 4A) robust, weakly curved, total length, 2.66 mm. Surface of whole body sculptured with hexagonal and pentagonal polygons. Head . Longer than high, hemispheric, representing 0.15 x of total body length (0.40 mm), not notoriously deeper than body. Eyes (Fig. 4B) covering most of head surface except for triangular frontal space in front of head. Antenna 1 (Fig. 4C, 5A) prominent; peduncle 1-segmented, flagellum with large callynophore armed with transversally arranged rows of aesthetascs crossing the ventral zone, distal segment armed with spines and aesthetascs. Antenna 2 (Fig. 5B, C) peduncle with dorsally flat and ventrally round first segment, as high as long; succeeding four segments zig-zagged, folded below eyes and thorax; segments with row of setae along anterior margins; terminal segment with setae extending to the tip, directed anteriorly. Segment 3 about 0.75 x length of segments 2, terminal article about 0.83 x the length of precedent. Mandible (Fig. 5D) about 0.75 x length of first mandibular palp. Mandibular palp (Fig. 5E) 3-segmented, middle segment being longest (0.15‒0.20 x of segments 1 or 3 length). Maxilliped (Fig. 5F) fully sculptured, developed inner lobes completely fused, with two spines on the external apical margins (Fig. 5G). Maxillae sculptured; maxilla 1 inner lobe wide and truncated, outer lobe triangular with long apical spines; maxilla 2 both lobes pyramidal, about 2 x as long as maxilla 1, with spines both along inner margin and apically (Fig. 5H). Pereon (Fig. 4A) length about 2 x eyes diameter, all segments distinctly separate. Pereopods 1 and 2 (Fig. 6A, B) bases longer than combined length of distal segments; carpus sub-rectangular, lacking anterodistal projection; propodus with rounded, thumb-like antero-distal projection. Pereopod 1 simple (ca. 0.41 mm), with long slender basis, straight anterior margin, and bulging posterior margin; isquium bent to the front, forming the internal part of an elbow (similar in pereopods 1–4); propodus 0.4 x narrower than carpus, thumb-like in posterodistal section; dactylus claw-shaped, ornamented with teeth-like processes and short spines. Pereopod 2 like pereopod 1, about 1.2 x its length, basis 1.3 x length of basis of pereopod 1; propodus narrower than carpus, with thumb-like process on postero-distal end. Pereopods 3 and 4 (Fig. 6C, D) (0.7 mm) longer than 1 and 2 (ca. 0.50 mm). Pereopod 3 approximately 1.6 times as long as pereopod 1. Basis with weakly concave anterior margin and convex posterior margin; 70% wider than the widest portion of pereopod 1 basis. Pereopod 4 basis with straight anterior margin, posterior margin regularly convex, propodus almost 2 x as long as carpus, dactylus nearly half length of propus, bent backwards, with postero-proximal hump. Pereopod 5 (Fig. 6E) being the longest leg (about 1 mm), 2 x as long as pereopod 2, basis 2 x as long as wide, with anterodistal lobe overlapping ischium, inserted terminally to basis, bent towards posterior end; carpus and propodus with short spines along anterior margin (seen at 400 magnification); propodus long, slender; dactylus short (0.1 x propodus length). Pereopod 6 (Fig. 6F) basis longer than wide, with fissure but lacking telsonic groove; isquium inserted in ventral rounded socket of basis; merus dorsal margin approximately 0.5 length of anterior margin, with similar and regularly distributed spines along anterior margin; carpus about 0.5 x as long as merus width; propodus less than 0.5 carpus width; dactylus finger-shaped, 0.3 x propodus length. A strong structural union of isquium to basis appears like a separating segment. Pereopod 7 (Fig. 6G) basis more than 3.5 x as long as wide, plus one additional crinkled segment, about 0.2 mm total length. All coxae , except seventh, separate from thorax, coxae 1‒5 rectangular, with rounded margins; coxa 6 posteriorly expanded, with groove and spines on posterior margin. Pleon . Pleon (Fig. 4A) 1.3 x combined length of pereon segments; epimeral plates rounded, with slightly elongated distal margin, directed backwards (illustrated for female in Fig. 8G); pleonic segments with height similar to thoracic segments, projected downward. Third epimeron with median dorsal and lateral teeth. Pereon and urosome subequal in length (0.70 mm). Urosome first segment about as long as fused segments 2 and 3 (0.19 mm), shorter than telson (0.23 mm). Uropods maximum length about 1.35 x telson length; margins of uropod endopods and exopods serrate; endopod of uropod 3 fused with basis; uropod 1 ca. 0.50 mm long, exopod and basis sub equally long, with serrate margins, exopod 1.25 times as long as endopod, with both margins serrate; uropod 2 about 0.60 mm long, exopod 0.6 x uropod 2 total length, endopod about 0.5 x as long as exopod, with serrate margins specially on endopod; uropod 3 about 0.55 x uropod 1 length, endopod length 2/3 of total uropod 3 length (ca. 0.28 mm), inner and outer rami serrate along inner margins, especially apically. Telson not fused to urosome. Description of allotype female (gravid ) Body (Fig. 4D) smaller than male (2.4 mm). Head . Higher than long (vs. longer than high in male), the longest part in the dorsal portion and not in the middle, head not as rounded as in male. Antenna 1 (Fig. 7A, B) 2-articulated, directed backwards; callinophore resembling a truncate cone, with several transverse tight rows of aesthetascs; terminal segment about 0.35 x preceding one, with distinctive thumb-like projection forming an incomplete “U”, armed with setae. Antenna 2 absent. Pereon . Pereopods (Fig. 8) similar to those of male, but with some variations: carpus of pereopod 1 wider proximally in female (Fig 8A); propodus of female pereopod 5 equally wide along segment (Fig 8E). Urosome and uropods (Fig. 7A) as illustrated. Remarks . Hitherto, the genus Amphithyropsis contained a single species, A . pulchellus , described from a male found off New Zealand, but it was not described in detail. Barnard (1930) pointed out some of its specific characteristics, like the reticulate cuticular sculpturing, and described and illustrated the 4th segment of pereopod 6, specifying that its structure “… seems to be quite distinctive”. Amphithyropsis pulchellus had so far been found in the southwestern Pacific, including waters around New Zealand and Australia and, as stated by Zeidler (2016), it also occurs along the southeast coast of Africa, where specimens show the same attributes as those from the Pacific. The specimens collected in the Gulf of California have the main distinctive generic features of Amphithyropsis but cannot be assigned to A . pulchellus because these specimens possess: 1) different segment proportions in the male antenna 2; 2) a shallower head; 3) pereopods lacking spines; 4) the basis of pereopods 1 and 2 longer than the combined length of distal segments; 5) the middle segment of the male mandibular palp longer than the others; and 6) a female first antenna with a thumb-like projection. All these characters allowed us to distinguish our material from A . pulchellus and propose a new species. Amphithyropsis shanti sp. nov. most closely resembles A. sculpturatus mainly in the body sculpturation, urosome and uropods shape, and in the general structure of pleonite VI. Amphithyropsis shanti sp. nov. , however, is easily distinguished from this species by having segments 4‒6 of pereopods 1 and 2 more rectangular, segment 5 without anterodistal projection, and segment 2 longer than the combined length of distal segments. Amphithyropsis shanti sp. nov. also has the uropod 2 endopod about 0.5 x the length of the exopod, which is longer than basis, and the pleonite VII lacks segments 3‒5. The shape of the female antennae 1 is also a conspicuous distinctive characteristic between the two species. : Published as part of Gasca, Rebeca, Suárez-Morales, Eduardo & Hendrickx, Michel E., 2021, Hyperiids (Amphipoda, Hyperiidea) collected during the TALUD cruises in western Mexico. 5. Family Amphithyridae, with the description of a new species of Amphithyropsis Zeidler, pp. 479-494 in Zootaxa 5039 (4) on pages 485-490, DOI: 10.11646/zootaxa.5039.4.2, http://zenodo.org/record/5515939 : {"references": ["Oren, A. & Schink, B. (2016) Formation of names of genera of prokaryotes that end on - oides or - opsis. A proposal for addenda to Rule 65 (2) and Appendix 9 of the International Code of Nomenclature of Prokaryotes. International Journal of Systematic and Evolutionary Microbiology, 66, 2452 - 2453. https: // doi. org / 10.1099 / ijsem. 0.001031", "Barnard, K. H. (1930) Crustacea. Part XI. Amphipoda. British Antarctic (\" Terra Nova \") Expedition. Natural History Report Zoology, 8 (4), 7 - 454.", "Zeidler, W. (2016) A review of the families and genera of the superfamily Platysceloidea Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), together with keys to the families, genera and species. Zootaxa, 4192 (1), 1 - 136. https: // doi. org / 10.11646 / zootaxa. 4192.1.1"]}