Alexandrella wimdecocki, Springthorpe & Hughes, 2025

Springthorpe, Roger T. & Hughes, Lauren E., 2025, Alexandrella wimdecocki sp. nov. (Stilipedidae Holmes, 1908) and new records for three Australian Abyssal Amphipods (Crustacea: Peracarida), Zootaxa 5636 (3), pp. 538-550 : 542-546

publication ID	https://doi.org/10.11646/zootaxa.5636.3.8
publication LSID	lsid:zoobank.org:pub:88E6D05D-9CA4-466C-BDF4-1384314AED99
DOI	https://doi.org/10.5281/zenodo.15561847
persistent identifier	https://treatment.plazi.org/id/03B36401-A763-FFEA-B2BD-B4BCFCC5FE43
treatment provided by	Plazi
scientific name	Alexandrella wimdecocki
status	sp. nov.

Treatment

Alexandrella wimdecocki sp. nov.

( Figs 1D View FIGURE 1 , 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Type material. Holotype female gravid, 57.5 mm, AM P.100455, eastern Bass Strait , Australia, (39°33'07"S 149°33'11"E to 39°29'46"S 149°35'53"E), Four Metre Beam Trawl, 4197– 4133 m, 23 May 2017, coll. L.E. Hughes, F. Koehler, E.K. Kupriyanova, RV Investigator (INV2017_ V03 _030). GoogleMaps

Etymology. Named for Wim Decock for his dedicated contribution to taxonomy as a data manager with the World Register of Marine Species.

Description. Head. Rostrum weakly developed, anterior margin sinuous, lateral cephalic lobe rounded, eyes unknown. Antenna 1 peduncle article 1 twice length of articles 2 and 3 combined; flagellum with 21 segments; accessory flagellum, 1 articulate, minute. Antenna 2 peduncle article 4 subequal to 5, flagellum articles partially fused, 39 articulate. Upper lip as long as broad, asymmetrically lobed, right lobe much larger than left. Mandible well developed, incisors broad, serrate; right lacinia mobilis robust blade, broad, smooth, with acute facial corner; accessory setal row with slender setae; molar present, raised not triturative; palp three-articulate; article 2 longer than 3, lined with slender setae; article 3 with marginal setae. Lower lip broken. Maxilla 1 inner plate large, lined with setae; outer plate broad, with nine setal teeth; palp 2-articulate, distally broad, length 1.5 times width, lined with 19 short, broad robust setae. Maxilla 2 inner plate length 0.5 times outer plate, margins with long slender simple setae; outer plate with 2 rows of long slender simple setae. Maxilliped inner plate with slender setae; outer plate broad, inner margin straight, lined with short robust setae increasing in length, outer margin with minute setules; palp 4-articulate, short, length 0.80 times outer plate, with few setae; dactylus straight with unguis.

Pereon. Pereonites 1–7 smooth, without dorsal projections. Pereopods 2–6 gills present. Gnathopods 1 and 2 similar, simple; basis margins without setae. Gnathopod 1 with oostegites, coxa anterior margin straight, not produced, anteroventral margin broadly rounded; carpus rectilinear, broader than propodus, length 1.8 times breadth; propodus with long setae; dactylus broad, straight, 0.6 times length of the propodus, with unguis deflexed. Gnathopod 2 coxa anterior margin convex, ventral margin rounded; carpus rectilinear, broader than propodus, length twice breadth; dactylus length 0.8 times propodus, weakly recurved with unguis deflexed. Pereopod 3 coxa margins parallel, posterior margin convex, length twice width. Pereopod 4 coxa posterior lobe rounded. Pereopods 5–6 similar. Pereopod 7 basis proximal margin broadly rounded, posterodistal corner acute; dactylus elongate 0.8 times propodus length, apically rounded.

Pleon. Pleonite 1 without dorsal carina. Pleonites 2–3 with dorsal carina. Epimeron 1 posterior margin broadly rounded. Epimeron 2 posterior margin proximally rounded, posterodistal margin straight, corner without tooth. Epimeron 3 posterior margin straight, posterodistal corner with small acute tooth. Urosomite 1 with carina and dorsal boss (a deep excavation medially). Urosomites 2–3 dorsally smooth, without carina. Uropod 1 longer than uropod 2; biramous, peduncle lines, with medial robust setae, length 1.3 times outer ramus; rami subequal. Uropod 2 inner ramus 0.9 times outer ramus. Uropod 3 peduncle short, slightly longer than broad; rami (regenerating; missing). Telson slightly longer than broad, lobes apically convex, cleft 0.20 times length.

Remarks. Alexandrella wimdecocki sp. nov. is most similar to A. cedrici Souza-Filho et al., 2024 , both these species can be distinguished from the 14 described Alexandrella by the pattern of the carinae on the dorsal margins of the pereonites, pleonites and urosomites.

Alexandrella wimdecocki sp. nov. differs from A. cedrici in the anterior margin of the head is straight (concave in A. cedrici ); the right mandible is a robust smooth blade (serrate in A. cedrici ); gnathopod 1 is with oostegites (without in A. cedrici ); gnathopods 1 and 2 basis setae absent (present on posterior and anterior margins in A. cedrici ). The uropod 1 peduncle is 1.3 time the outer ramus length (subequal in A. cedrici ) and the uropod 1 peduncle is lined with robust setae medially (with only one robust seta medially in A. cedrici ).

At over 57 mm, the present specimen is the largest reported Alexandrella individual. Five other species recorded at 50 mm and over, indicating this may be the maximum size of individuals for the genus ( Table 1 View TABLE 1 ).

The specimen appears senescent based on the fusing of the antenna 2 flagellum articles and the telsonic lobes being uneven with the left lobe cuticle appearing worn and the margins minutely crenulate, presumably where there is a setal fringe which has been abraded away.

Ommatidia were not discerned in the material at hand though may be present as eyes are known to disappear in alcohol for this family ( d’Udekem d’Acoz & Verheye, 2017: 169).