Alexandrella cedrici Souza-Filho, Guedes-Silva & Andrade 2024, sp. n.
Creators: name: Souza-Filho, Jesser F.
name: Guedes-Silva, Elkênita
name: Andrade, Luiz F.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Stilipedidae
Alexandrella
Alexandrella cedrici

description: Alexandrella cedrici Souza-Filho, Guedes-Silva & Andrade sp. n.
(Figures 18–22)
Material examined
Hototype female, 51.6 mm, Potiguar Basin, MT 85, initial trawl coordinates 4.3559°S, 36.7379°W, final trawl coordinates 4.3669°S, 36.7216°W, Rio Grande do Norte state, Brazil, initial depth 2057 m, final depth 2025 m, 4 May 2011, R / V Seward Johnson col. (MOUFPE 15086).
Type locality
Slope of Rio Grande do Norte state, north-eastern Brazil, between 4.3559°S, 36.7379°W and 4.3669°S, 36.7216°W.
Diagnosis
Mandible incisors fully and strongly toothed, molar absent; right and left lacinia mobilis large and strongly dentate. Maxilla 1 outer plate with 9 robust setae. Gnathopods 1–2 simple, carpus more robust than propodus, both densely setose. Gnathopod 1 lacking oostegite. Pereonite 7 and pleonite 1 lacking dorsal carina. Pleonites 1–3 with a moderately developed dorsal carina. Urosomite 1 with strong dorsal carina.
Description
Based on female holotype, 51.6 mm, MOUFPE 15086. Body as in Figure 18. Head (Figure 19a) lateral cephalic lobe short and blunt, eyes absent. Antenna 1 (Figure 19b) reaching peduncle of antenna 2; peduncle article 1 with a dorsodistal pointed projection; flagellum 27-articulate; accessory flagellum minute, 1-articulate. Antenna 2 (Figure 19c) weakly setose; flagellum 25-articulate. Upper lip (Figure 19d) strongly asymmetrical. Mandibles (Figure 19e–f) incisor fully toothed; molar absent; left lacinia mobilis very large and toothed; right lacinia mobilis almost as large as the left one, strongly toothed; palp 3-articulate, articles 2–3 setose. Maxilla 1 (Figure 19g) inner plate setose, with 5–6 basal pappose setae; outer plate with 9 robust setae; palp 2-articulate, article 2 inner margin widened, with 19 marginal robust setae. Maxilla 2 (Figure 19h) outer plate slightly wider than inner plate. Maxilliped (Figure 19i) inner plate shorter than palp article 1, strongly setose; outer plate strongly exceeding palp, inner margin with row of robust and short setae; palp with marginal setae; article 3 inner margin serrate and bearing a nail distally.
Coxa 1 (Figure 20a) wider than coxa 2 (Figure 20b). Coxa 4 (Figure 21B) with moderate posterior lobe, posterior margin almost straight, ventral margin produced into a rounded lobe. Coxae 5–6 (Figure 21c–d) bilobate, posterior lobe deeper. Gnathopod 1 (Figure 20a) basis slender, setose on both anterior and posterior margin; merus densely setose and slightly longer than ischium; carpus robuster and longer than propodus, setose; propodus setose, 2.5× longer than wide; dactylus inner margin serrate and bearing a nail distally. Gnathopod 2 (Figure 20b) basis slender, anterior margin setose; merus densely setose and slightly longer than ischium; carpus robuster and longer than propodus, setose; propodus setose, 2.7× longer than wide; dactylus inner margin serrate and bearing a nail distally. Pereopods 3–4 (Figure 21a–b) similar in shape, basis slender, merus longer than carpus, anterior margin slightly produced distally; carpus–dactylus with marginal short robust setae. Pereopods 5–6 (Figure 21c–d) basis suboval, posterodistal corner slightly produced into a rounded lobe; merus with posterodistal corner produced into a subacute lobe; carpus–dactylus with marginal short robust setae; dactylus long. Pereopod 7 (Figure 21e) basis with posterior margin strongly excavated, forming a lobe proximally and distally; dactylus about 0.8× the length of the propodus.
Pereonite 7 and pleonite 1 (Figure 18) lacking dorsal carina. Pleonites 1–3 (Figure 22a–c) with a moderately developed dorsal carina. Epimera 2–3 (Figure 22b–c) posteroventral corner produced into a short spine. Urosomite 1 (Figure 22d) with a dorsal well-developed carina, preceded by a distinct ‘U-shaped’ notch. Uropod 1 (Figure 22e) peduncle subequal to outer ramus, with only 1 dorsal robust seta medially; inner ramus broken; outer ramus tapering distally and naked. Uropod 2 (Figure 22f) peduncle 0.8× shorter than outer ramus; only outer ramus with 4 short marginal robust setae. Uropod 3 (Figure 22g) peduncle much shorter than rami, which are broken at tip. Telson (Figure 22h) about 45% cleft, each lobe rounded.
Etymology
The specific epithet is dedicated to Dr Cédric d’Udekem d’Acoz, for his great contribution to the taxonomy of amphipods and more recently to the genus Alexandrella.
Distribution and bathymetry
Known only from the type locality (slope of Rio Grande do Norte state, north-eastern Brazil, 4.3559°S, 36.7379°W and 4.3669°S, 36.7216°W), between 2025 and 2057 m deep (Figure 23).
Remarks
A unique specimen of Al. cedrici sp. n. was collected at 2057 m. The new species resembles Al. inermis Bellan-Santini and Ledoyer, 1987 in presenting antenna 1 shorter than antenna 2, mandible incisors toothed along the entire margin, female gnathopod 1 without oostegite, gnathopods 1–2 simple, pleonite 3 with a short-medium dorsal carina. Even so, Al. cedrici sp. n. can be distinguished from Al. inermis by the following (characters of A. inermis in parentheses): right mandible lacinia mobilis present (absent); pereopod 4 coxa posterior margin almost straight (concave), dactylus long (short); epimera 3 posteroventral corner produced into a short spine (rounded); telson cleft (entire).
Alexandrella cedrici sp. n. also has some characters in common with Al. pulchra Ren in Ren and Huang, 1991 and Al. schellenbergi Holman and Watling, 1983 such as: antenna 1 peduncle article 1 with short dorsomedial tooth; pereopod 4 coxa posterior margin almost straight, dactylus long. The new species can be readily differentiated from the aforementioned species by presenting short-medium dorsal carinae on pleonites 1–3, whereas they present large acute carinae. This is the first record of the family Stilipedidae from Brazil.
description: Published as part of Souza-Filho, Jesser F., Guedes-Silva, Elkênita & Andrade, Luiz F., 2024, Four new species and two new records of deep-sea Amphipoda (Crustacea: Peracarida) from Potiguar Basin, north-eastern Brazil, pp. 1615-1655 in Journal of Natural History 58 (41 - 44) on pages 1643-1648, DOI: 10.1080/00222933.2024.2374404, http://zenodo.org/record/13758699