Apotectonia senckenbergae Momtazi & Riehl 2025, sp. nov.

Apotectonia senckenbergae Momtazi & Riehl sp. nov. Materials Type status: Holotype. Occurrence: catalogNumber: SMF 62823; recordNumber: S 0606 - B 06 - CC 15; recordedBy: R / V FALKOR cruise FKt 231024; individualCount: 1; sex: male; lifeStage: adult; occurrenceID: C55370A3-BE0C-543E-9B7D-E935ECA4B48F; Taxon: scientificName: Apotectonia senckenbergae Momtazi & Riehl; kingdom: Animalia; phylum: Arthropoda; class: Malacostraca; order: Amphipoda; family: Alicellidae; genus: Apotectonia; specificEpithet: senckenbergae; taxonRank: species; scientificNameAuthorship: Momtazi & Riehl; nomenclaturalCode: ICZN; Location: higherGeography: Pacific Ocean; locality: hydrothermal vent fields on the Galápagos Rift, near Rose Garden / Rosebud; verbatimDepth: 2601.6 m; verbatimLatitude: 0°46'16.3"N; verbatimLongitude: 85°55'25.0"W; decimalLatitude: 0.771193; decimalLongitude: - 85.923598; Identification: identifiedBy: Farzaneh Momtazi; dateIdentified: 2024; Event: samplingProtocol: Bio Box mounted on ROV SUBASTIAN, dive # 606; eventDate: 29 / 10 / 2023; habitat: mussel bed; fieldNumber: S 0606 - B 06 - CC 15; Record Level: institutionCode: SMF; basisOfRecord: PreservedSpecimen Description Description of holotype male Body length 15 mm (Figs 20, 21 H). Urosomite 1 with dorsally sharp multifid carina (Fig. 22 Ur); urosomite 3 dorsally with fine seta (Fig. 21 H). Head deeper than long; rostrum absent. Eyes not apparent, but may be faded in ethanol. Lateral cephalic lobe well-developed (Fig. 21 H). A 1 (Fig. 23 A 1), 0.31 body length; peduncular art 1–3 exceed head length; acc flag 5 - articulate; left primary flag 27 - articulate, setal formula 5 L, 2 M, S, 3 M, 16 S (L: large; M: medium, S: small), right primary flag 25 - articulate; aesthetascs on right flag art 1–8. A 2 (Fig. 23 A 2) slender, length 1.1 A 1 length; peduncular art 5 length 0.6 art 4 length; flag 25 - articulate; calceoli absent. Md incisor not symmetrical, right incisor (Fig. 23 RMd) with an inner notch-tooth followed by a plate tooth and ending in three outer notch-teeth; the left incisor (Fig. 23 LMd) with an inner notch-tooth followed by a plate tooth and ending in two outer notch-teeth; right lacinia mobilis tiny, bifid, left lacinia mobilis slightly larger and multitoothed, rakers about 18, molars long, slender, pointed, pubescent; mandibular palps symmetrical, art 3 blade-like, with two apical long simple, four long plumose and 19 medium plumose setae. Mx 1 (Fig. 23 Mx 1) right outer plate with eight spines; inner plate narrow, with plumose setae on the outer margin; palp 2 - articulate and well developed, symmetrical, terminal art with 10 apical robust setae, six subterminal and two lateral setae. Mx 2 (Fig. 23 Mx 2) inner plate shorter than the outer plate; outer plate lateral margin with simple setae; inner plate with a row of simple setae, a row of plumose setae and downward-facing setae on the inner margin. Mxp (Fig. 23 Mxp) inner plate sub-rectangular, with four simple and six plumose apical setae; outer plate large, subovate; palp well-developed; dactylus well-developed, unguis present, surface with small setae. Prn with unplaited gills each with a minor secondary sausage-shaped lobe on C 2–7. P 1 (Fig. 21 P 1), coxa bevelled anteroventrally, ventral margin produced posteriorly, anterior margin 0.75 posterior margin length, with one posteroventral and one superficial robust seta (Fig. 21 C 1); basis L / W ratio 3.0, anterior margin covered with setae; ischium linear, length 0.5 basis length; merus trapezoid, posterior margin with plumose setae; carpus linear, subequal to propodus, posterior margin bearing plumose setae; propodus subtriangular, L / W ratio 2.8; palm straight, finely serrated, defined by pair of robust setae; dactylus short, not reaching to the middle of the palm. P 2 subchelate (Fig. 21 P 2); C 2 larger than C 1, subsimilar in size to C 3, quadrate, with one posteroventral and three superficial robust setae (Fig. 21 C 2); basis L / W ratio 5.5; ischium linear, L / W ratio 3.5; merus trapezoid, shorter than carpus; carpus elongate, length 1.5 propodus length, anterior margin straight, posterior margin covered with plumose setae; propodus subrectangular, posterior margin with plumose seta; palm oblique; dactylus reaching to end of palm. P 3 similar to P 4 (Fig. 22 P 3), slightly stouter, C quadrate with a posteroventral and a superficial robust seta; dactylus simple, short. P 4 (Fig. 22 P 4) C with well-developed posteroventral lobe; dactylus simple. P 5–6 with similar structures, P 6 longer than P 5 and P 7 (Fig. 22 P 5, P 6, P 7). Pleon with Ep 1 (Fig. 22 Ep 1–3) posterodistal corner produced to form sharp tooth; Ep 2 posterodistal corner with one small, rounded tooth, ventral margin with two robust setae; Ep 3 posterodistal corner with medium-sized sharp tooth, ventral margin with three robust setae. U 1 (Fig. 23 U 1) length 1.36 U 2 length, rami lengths subsimilar, subsimilar to peduncle size; U 2 (Fig. 23 U 2) peduncle with three robust setae and two small robust setae; inner ramus length 1.7 peduncle length, inner ramus length 1.3 outer ramus length; U 3 (Fig. 23 U 3) L / W ratio 2.25; rami subequal; inner ramus with robust setae; outer ramus biarticulate, Art 2 asetose. T (Fig. 23 T) deeply cleft (75 %), with two marginal setae in each half, apical margin truncate, each apical margin with one stout seta, each lobe distally notched. Type material Holotype adult male (SMF 62823), ethanol-preserved. Material examined Only known from the type material. Type locality Pacific Ocean, Galápagos Rift, hydrothermal vent fields on the near Rose Garden / Rosebud, 2601.6 m depth. Diagnosis The new species, Apotectonia senckenbergae sp. nov. is characterised by similar lengths of antennae 1 and 2, the epimeral setal formula 0 + 2 + 3, the coxal dorsoventral setal formula 1 + 1 + 1 and two medial robust setae on the posterior margin of the propodus of the first pereopod (gnathopod). Etymology This species’ epithet honours Johanna Rebecca Senckenberg (1716–1743) (maiden name: Riese) from Frankfurt am Main, Germany, who not only guided her husband Johann Christian Senckenberg (1707–1772) in spiritual and charitable matters, but also provided an inheritance that constituted nearly one-third of the funds establishing the Senckenberg Society for Nature Research. Through her much more well-known husband, she was a naturalist and benefactor who supported science and medicine, founding the Dr. Senckenberg Foundation, which later led to the forming of the Senckenberg Society for Nature Research. Distribution Only known from the type locality. Ecology Collected from a mussel bed in the vicinity of a hydrothermal vent. Taxon discussion The genus Apotectonia Barnard & Ingram, 1990 was described as a monotypic genus, based on specimens collected from deep-sea hydrothermal vents on the Galápagos Rift (Barnard and Ingram 1990). It is characterised by a simple first gnathopod, a multifid dorsal process on the first urosomite, a vestigial right lacinia mobilis, a bevelled inner plate of the maxilliped, an unreduced coxa 1 and a shortened outer ramus of the second uropod. The new species, Apotectonia senckenbergae sp. nov., has also been collected from the Galápagos rift, but slightly deeper at 2,601 m depth. The type species, A. heterostegos Barnard & Ingram, 1990, was collected at 2,488 m depth and described, based on the female specimen with 11.73 mm. However, they reported variations on the article number of the accessory flagellum and the setal formula on epimera and uropods in the juvenile specimens with 12.4 mm (Barnard and Ingram 1990). The differentiated characters of A. senckenbergae sp. nov. from A. heterostegos include subsimilar lengths of antennae 1 and 2 (instead of bearing a shorter antenna 1 in A. heterostegos), nine dental spines on the outer plate of the first maxilla (10 in A. heterostegos), the epimeral setal formula 0 + 2 + 3 (1 + 3 + 4 in A. heterostegos), 1 + 1 + 1 distoventral setae on coxae 1–3 (1 + 2 + 2 in A. heterostegos), the serrated inner margin and two robust setae on the outer ramus of the second uropod (asetose in A. heterostegos), two medial robust setae on the posterior margin of the propodus of the first pereopod (gnathopod) and other minute differences (see Table 5). Notes Methods The material studied is part of a donation to the Senckenberg Research Institute and Natural History Museum Frankfurt, Germany from the Schmitt Ocean Institute R / V FALKOR (TOO) research cruise FKt 231024 and the PROJECT ZOMBIE: BRINGING DEAD VENTS TO LIFE – ULTRA FINE-SCALE SEAFLOOR MAPPING. This project surveyed several hydrothermal vent fields on the Galápagos Rift using the remotely operated vehicle (ROV) SUBASTIAN. This cruise studied the vent fields Rose Garden / Rosebud (0.81°N, 86.22°W, 2450–2550 m depth), Tempus Fugit (0.77°N, 85.91– 93°W, 2500–2560 m depth), Iguanas-Pinguinos (2.10°N, 91.89– 94°W, 1650–1700 m depth) and Tortugas (0.95°N, 90.53– 56°W, 1500–1600 m depth) (see Chen et al. (2024)). For animal sampling, a seven-function manipulator arm (Schilling Robotics TITAN 4) and a suction sampler mounted on ROV SUBASTIAN were used. Upon recovery onboard, animals were sorted in cold (4 ° C) seawater. The material used in the present study was collected with a suction sampler from a mussel bed at Tempus Fugit. At the Senckenberg Laboratory, sample dissection was made in glycerol under a stereomicroscope (LEICA M 60). Preliminary drawings were done with a microscope (LEICA DM 2500 LED), equipped with a camera lucida. Illustrations (Figs 21, 22, 23) were made using the methods described by Coleman (2009) using the software Adobe Illustrator CS 6. Measurements were taken from the tip of the first antenna along the dorsal body line until the end of the telson and are given in millimetres. The Discovery Laboratory of the SENCKENBERG OCEAN SPECIES ALLIANCE provided essential facilitation, technical support and logistical assistance that enab