Dautzenbergia concavipalma Zettler & Hendrycks & Freiwald 2022, sp. nov.
Creators: name: Zettler, Michael L.
name: Hendrycks, Ed A.
name: Freiwald, André
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Pontogeneiidae
Dautzenbergia
Dautzenbergia concavipalma

description: Dautzenbergia concavipalma sp. nov.
Figs. 2–8
Diagnosis. Gnathopod 1 propodus subchelate, broadly triangular, length 1.7 x width, palm relatively straight, clearly distinct from posterior margin, dactylus exceeding palm, with inner margin serrated. Gnathopod 2, propodus massive, dorsal margin strongly convex, length 3.36 x width, palm strongly concave, densely setose, occupying nearly the complete length of the propodus, delimited by a strong tooth of the ventrally directed posterior margin and distal margin with a flanged, bidentate cusp near insertion of dactylus, dactylus very powerful, strongly curved, elongate, fitting palm. Pereopods 3–7, dactyls short and strongly curved, inner margins smooth. Pereopod 7 basis short, length 1.4 x width. Epimeron 3 lacking a strong posteroventral tooth. Telson subovate, broad, length 1.4 x width, incised one-sixth of length, lobes not separated.
Type material. Holotype: male, 11.0 mm, photographed and figured, (CMNC 2022 -4376), South Atlantic, off Angola, Stn 20927, Buffalo Mound, 9.7003°S, 12.7303°E; water depth 349 m; associated with hexactinellid sponges (Sympagella sp. and Aphrocallistes sp.) within a Desmophyllum pertusum gallery, leg. 21 st January 2016.
Allotype: female, 10.8 mm, photographed and figured, (CMNC 2022-4377), data same as holotype.
Paratypes: male, 9.2 mm, (CMNC 2022-4378), data same as holotype. 7 specimens, (ZMB 32994), data same as holotype; 2 specimens, (CMNC 2022-4379), South Atlantic, off Angola, Stn. 20913, Anna Ridge, 9.78827°S, 12.77335°E; water depth 307 m, leg. 18 th January 2016; 1 specimen, (ZMB 32995), South Atlantic, off Angola, Stn. 20930, Scary Mound, 9.82287°S, 12.77393°E; water depth 374 m, leg. 22 nd January 2016.
Locus typicus. South Atlantic, off Angola, 110 km south-southwest of Luanda, Buffalo Mound, 9.7003°S, 12.7303°E; water depth 349 m. Ambient seawater temperature and oxygen concentration was 11.3°C and 0.76 ml/l.
Etymology. The species is named in reference to the strongly concave shape of the palm of the gnathopod 2 (especially in males), which is highly distinctive.
Description.
Holotype. Male, 11.0 mm, CMNC 2022-4376.
Colour (Figs. 2–3). Mostly white, with some light brown highlights in the head, mouthparts and gnathopods.
Head (Figs. 2–4). With rostrum weakly developed, eyes prominent, luminescent in the living state; lateral cephalic lobe slightly angular, broad, not projecting strongly.
Body (Figs. 2–4). Smooth, lacking dorsal teeth, humps or carinae, urosome 2 not dorsally occluded, subequal in length to urosome 3 (Figs. 4, 8).
Antenna 1 (Figs. 2–4, 6). Long, about three-quarters of the body length; peduncular articles short, article 1 sparsely setose dorsally, article 2 three-quarters length of article 1, article 3 short, about two-fifths length of article 2, accessory flagellum absent; flagellum broken but with over 30 remaining articles, normally 40–50 articulate (see Figs. 2–3).
Antenna 2 (Figs. 2–4, 6). About two-thirds length of antenna 1, with weak setation, gland cone prominent and acute, extending past peduncular article 3, peduncular articles 4–5 subequal; flagellum ~ 30-articulate.
Labrum (Fig. 5). Unevenly bilobed, with a shallow, oblique incision, inner margin of the right lobe finely serrate.
Mandible (Fig. 5). Incisor toothed, 6–7 dentate, left lacinia mobilis 5-dentate, right lacinia present and toothed; accessory spine row with 8 (right mandible) and 12 pectinate spines (left mandible); molar subovate, projecting, large and triturative; palp 3-articulate, elongated, article 1 0.44 x length of article 2, article 2 with 8 B2-setae, article 3 long, 1.6 x length of article 2, with 8 A3-setae, the distal third with about 19 fine, comb-like teeth posteroventrally, covered with a row of ~ 18 D3-pectinate setae of equal length and 4 long E3-pectinate setae.
Labium (Fig. 5). Outer plates densely setose, distal inner margins slightly excavated.
Maxilla 1 (Fig. 5). Inner plate narrowly subovate, finely setose, with two strong and 2 tiny pinnate setae; outer plate with 7 toothed and forked spine-teeth, plate sparsely covered with setae; palp narrow, two segmented with 5–6 stout spines and 5 setae distally.
Maxilla 2 (Fig. 5). Inner and outer plates subequal, inner slightly shorter, distally rounded, covered in fine setae, some strong, pinnate setae distally on both plates, inner plate distomedially with 1 strong, pectinate seta.
Maxilliped (Fig. 5). Inner and outer plates short, outer plate broader than inner, reaching about 0.3 x length of article 2 of palp, with setae distally and medially; inner plate reaching distal end of article 1 of palp, with 2 stout spines distomedially; palp raptorial, very prominent, 4-articulate, article 2 very long and densely setose medially, article 3 narrow and setose, dactylus falcate, well developed, longer than article 3 and with a distal seta.
Gnathopod 1 (Fig. 6). Coxa strongly produced anteriorly in a subacute lobe, basis with long posterior marginal setae; ischium-merus subequal with strong distoventral clusters of setae; carpus length 0.86 x length of propodus, ventral margin densely setose; propodus subchelate, broadly triangular, length 1.7 x width, with several groups of dorsal and ventral marginal clusters of setae, palm relatively straight, distinct from posterior margin, with spines and setae, dactylus slightly exceeding palm, with inner margin serrated.
Gnathopod 2 (Fig. 6). Coxa subrectangular, broader than long; basis widening distally, posterior margin with long setae proximally, with a rounded flange/lobe anterodistally; ischium with a rounded flange/lobe on anterior margin; merus twice as long as ischium, with a strong cusp distoventrally; carpus very short, length 0.1 x propodus, cup-shaped, with a very weak distal lobe; propodus powerful, massive, subchelate, subovoid, dorsal margin strongly convex, length 3.36 x width, palm strongly concave, nearly the complete length of the propodus, delimited by a strong tooth of the ventrally directed posterior margin carrying a spine and distal margin with a strong, flanged cusp near insertion of dactylus, palm entirely lined with a dense covering of setae; dactylus very powerful, strongly curved, proximally widened, inner margin smooth, elongate, fitting palm.
Pereopod 3 (Fig. 7). Slender; coxa rectangular, length 1.35 x width, ventral margin straight; basis slender, length 5.9 x width, margins with very small spines and long setae anterodistally and posteroproximally; merus slightly longer than carpus, margins weakly spinose; propodus posterior margin with 5 pairs of spines; dactyl short, strongly curved, smooth.
Pereopod4(Fig.7).Coxa narrowing ventrally,anterior margin straight, posterior margin excavated,posteroventral lobe small; rest of pereopod as in pereopod 3 except basis with a strong cluster of long setae anteroproximally.
Pereopod 5 (Fig. 7). Shorter, 0.89 x length of pereopods 6–7, coxa larger than coxa 6, strongly posterolobate, with anterodistal lobe shallow and broadly rounded, posterodistal lobe slightly narrowed; basis expanded, length 1.46 x width, ovate, anterior margin slightly concave, with small spines and proximally with long setae, posterior margin convex, smooth with minute setules, posterodistal lobe narrowly rounded and not reaching distal margin of ischium; merus about subequal in length to carpus, produced posteriorly into a long pointed lobe, margins spinose; carpus expanded distally, anterior margin with 5 clusters of strong spines; propodus curved, anterior margin with 5 pairs of spines; dactylus short and strongly curved, smooth.
Pereopod 6 (Fig. 7). Subequal in length to pereopod 7; coxa with anterodistal lobe narrow, posterodistal lobe broad; basis expanded, length 1.32 x width, ovate, with 5 surface setae, anterior margin with small spines and proximally with long setae, posterior margin convex, smooth with minute setules, posterodistal lobe narrowly rounded and not reaching distal margin of ischium; merus about subequal in length to carpus, produced posteriorly into a long pointed lobe, margins spinose; carpus expanded distally, anterior margin with 5 clusters of strong spines; propodus curved, anterior margin with 5 pairs of spines; dactylus short and strongly curved, smooth.
Pereopod 7 (Fig. 7). Subequal in length to pereopod 6; coxa small, subovate; basis expanded, length 1.4 x width, ovate, anterior margin with small spines and proximally with long setae, posterior margin nearly straight, smooth with minute setules, posterodistal lobe broadly rounded and reaching distal margin of ischium; rest of pereopod as in pereopod 6.
Gills (Fig. 7). Present on gnathopod 2 to pereopod 6. Subovate, largest on pereopod 4.
Epimeron 1 (Fig. 7). Subovate, slightly subacute ventrally, posterior margin convex.
Epimeron 2 (Fig. 7). Narrowly subquadrate, ventral margin convex, posterodistal angle very weakly pointed, posterior margin nearly straight.
Epimeron 3 (Fig. 7). Subquadrate, ventral margin evenly convex, posterodistal angle very weakly pointed, posterior margin slightly convex.
Pleopods 1–3 (Fig. 7). Long, peduncle with ~ 5 proximal clothespin spines; rami lined with marginal plumose setae.
Uropod 1 (Fig. 8). Peduncle long, subequal to rami, with marginal spines; rami slender, lanceolate, subequal, with marginal spines, apices lacking spines.
Uropod 2 (Fig. 8). Peduncle length 0.74 x outer ramus, both margins spinose; rami slender, lanceolate, outer ramus length 0.95 x inner ramus, both rami margins spinose, apices lacking spines.
Uropod 3 (Fig. 8). Peduncle length 0.71 x outer ramus, with 3 marginal spines; rami slender, lanceolate, outer ramus length 0.85 x inner ramus, both rami strongly spinose.
Urosome 1–3 (Fig. 8). Urosome 1 length about 2 x length of urosome 2–3 combined, urosome 2 not dorsally occluded.
Telson (Fig. 8). Subovate, broad, length 1.4 x width, incised one-sixth (17 %) of length, lobes appressed not open, with hint of small distal notches (appear worn down), likely missing the fine, inset spine.
Female.� Allotype, 10.8 mm, CMNC 2022-4377
Similar to male, but differing as follows:
Gnathopod 1 (Fig. 6). Dactylus inner margin, serrations are more pronounced.
Gnathopod 2 (Fig. 6). Basis widening distally, anterior and posterior margins with long setae; propodus powerful, but smaller than male and less curved, subovoid, length 2.6 x width, palm less concave, posterior marginal tooth delimiting palm smaller than male; dactylus less robust and straighter.
Brood plates. Present on gnathopod 2 and pereopods 3–5, largest on pereopod 3, subrectangular, length 3.2 x width, distal end truncated, slightly convex posteriorly, lined with ~ 47 curved brood setae.
Telson (Fig. 8). Apices with small distal notches stronger than in male.
Ecology. As reported for other species of this genus, Dautzenbergia concavipalma sp. nov. is associated with deep-water corals and their sponge assemblages. Species-coral relationships between Dautzenbergia and azooxanthellate scleractinian corals (Caryophylliidae, Isididae, and Oculinidae) and plexaurid gorgonians have been observed and reported previously (Stephensen 1944, Myers & Hall-Spencer 2004, Cartes et al. 2022 and this study). In contrast to other species of the genus, D. concavipalma sp. nov. occurred in water depths between 300–400 m, i.e. much shallower than previously known.
Remarks. Dautzenbergia concavipalma sp. nov. is easily differentiated from all known species by the very distinctive shape and massive size of the propodus of gnathopod 2 (especially in male), with its very strongly concave, setose palm occupying nearly the full length of the propodus and the powerful, strongly curved dactylus. The ventrally directed, strong tooth of the posteroproximal margin of the palm is also very characteristic and does not occur in any of the other congeners. Further, from D. comitari (Myers & Hall-Spencer, 2004), it differs in the much broader propodus of gnathopod 1, length 1.7 x width (vs narrow, length 2.6 x width), the very differently shaped gnathopod 2 and the short, strongly curved, smooth pereopod dactyls (vs toothed dactyls). Dautzenbergia concavipalma sp. nov. is differentiated from D. dentata (Chevreux, 1919) in the broader propodus of gnathopod 1, length 1.7 x width (vs 2.1 x width), the broader basis of pereopods 5–7, basis of pereopod 7 length 1.4 x width, posteroventral lobe broadly rounded (vs 1.8 x width, posteroventral lobe narrowly rounded), and the much shorter and broader telson, length 1.4 x width, incised one-sixth (vs 2.1 x width and widely cleft, greater than one-quarter). From D. grandimana (Chevreux, 1887), our species differs in the smooth pereopod dactyls (vs toothed), the very differently shaped gnathopod 2 and the much shorter and broader telson, length 1.4 x width (vs 2.1 x width). Lastly, D. concavipalma sp. nov. differs from D. megacheir (Walker, 1897) in the broader, subacute distal end of coxa 1 (vs very acutely pointed coxa 1), the different shape of gnathopod 2, the epimeral plate 3 with the posterodistal angle very weakly pointed (vs with a strong tooth at posterodistal corner) and the much shorter and broad telson, length 1.4 x width, incised one-sixth (vs 2.1 x width and cleft, widely, about one-quarter).
The peculiar, comb-like structure that we discovered on the inner margin of the distal third of the mandibular palp, article 3 (see Fig. 5) appears to be also shown by Griffiths (1977) for Dautzenbergia grandimana (see Fig. 3, p. 111). Unfortunately, he did not mention this structure and as far as we know, it has never been reported on. It is a difficult structure to observe due to its small size and the palp D3 setae of the inner margin cover it, so may be easily overlooked. The function of this serrated section of the palp is not known, but perhaps it is related to feeding/ grooming or possibly the structure plays a role in the coral relationship. It is unlikely to be related to mating, as the form is present in both males and females. Whether this morphological character is present in all Dautzenbergia species is unknown and until all the mandibles are examined carefully in these species, this question remains unresolved.
description: Published as part of Zettler, Michael L., Hendrycks, Ed A. & Freiwald, André, 2022, A new amphipod species of the bathyal genus Dautzenbergia Chevreux, 1900 (Amphipoda, Calliopioidea, Pontogeneiidae) associated with cold-water corals off Angola, pp. 49-63 in Zootaxa 5213 (1) on pages 53-59, DOI: 10.11646/zootaxa.5213.1.3, http://zenodo.org/record/7350062