Hymenodora chacei Wasmer 2022, n. sp.
Creators: name: Wasmer, Robert A.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Oplophoridae
Hymenodora
Hymenodora chacei

description: Hymenodora chacei, n. sp. (Figs. 1—4)
Material examined. Holotype: ♀, CL 25 mm (LACM:DISCO:21317), ALCYONE 5, Station 135, 14 October, 1985, 31º N, 159°W, 10 m 2 MOCNESS Trawl, 4200 m; paratype, ♀, CL 18 mm (LACM: DISCO:21319), ALCYONE 5, Station 135, 14 October, 1985, 31°N, 159º W, 10 m 2 MOCNESS Trawl, 4200 m; paratype, ♀, CL 10 mm (LACM: DISCO:21320), EVE Station 198, 23 June, 1987, 31°N, 159º W, 10 m 2 MOCNESS Trawl, 4200 m; paratype, ♀, CL 11 mm (LACM:DISCO:21322), ALCYONE 5, Station 184, 1 November, 1985, 31°N, 159º W, 10 m 2 MOCNESS trawl, 4200 m; paratype, ♀, CL 7.0 mm (LACM: DISCO:21321), EVE Station 198, 23 June, 1987, 31°N, 159º W, 10 m 2 MOCNESS Trawl, 4200 m.
All the specimens examined are damaged to a greater or lesser degree, with appendages missing or damaged, but have eyes with corneas unpigmented, and much narrower than the relatively short ocular peduncles. The gastric region of the carapace is corrugated, with subtle folds and ridges.
Description of holotype. Integument thin and fragile. Carapace (Fig. 1a—1c) bluntly carinate anteriorly on dorsum, with one tooth on rostrum proper anterior to level of orbital margin, with four teeth on anterior carapace. Rostrum overreaching eyes, acute at tip. Dorsal surface of gastric region of carapace with corrugated appearance, with folds and ridges. Small pterygostomial spine present. Carapace weakly sulcate laterally as shown; no hepatic spine.
Abdomen bent and twisted. Abdominal somites not dorsally carinate, without posteromesial teeth, 6 th somite longer than 5 th. Telson (Fig. 2a, 2b) shallowly sulcate, with five or six pairs of dorso-lateral spines; terminating in a pair of large terminal spines (missing, but inferred from sockets) and a distally rounded spatulate endpiece with sockets for 24 smaller missing spines.
Eyes (Figs. 1b—1d) with corneas unpigmented, narrower than ocular peduncle. Cornea set laterally at end of peduncle; peduncle short, nearly as long as broad at base, with large pointed tubercle at inner distal end overreaching cornea.
Scaphocerite (Fig. 1e) narrowing distally, truncate at tip, distolateral spine reaching beyond end, without teeth proximal to distolateral spine.
Mandibles with incisor process toothed along entire opposable margins, molar process of right mandible (Fig. 2c) with transverse distal surface triangular, compressed and sub-linear on left (Fig. 2d).
Palp of first maxilla (Fig. 2e) with large spine on median surface.
Second maxilla (Fig. 2f) with proximal endite lacking papilla and submarginal lamella.
First maxilliped (Fig. 2g) with slender central lobe with only one transverse suture.
Second maxilliped (Fig. 2h) with distal segment somewhat ovoid, attached diagonally to preceding segment; epipod without podobranch.
Exopods of third maxillipeds and pereopods neither foliaceous nor rigid.
Third maxillipeds extending anteriorly slightly beyond distal end of antennal scale.
First through fourth pereopods incomplete; fifth pereopods reaching anteriorly to one-half the length of antennal scale.
Color. Color in life not known; colorless in preservative.
Variation. The number of teeth on the anterior dorsal region of the carapace and on the rostrum proper of Hymenodora chacei n. sp. varies: a ♀ paratype, CL 18.0 mm (LACM:DISCO:21329), has a total of seven teeth (three rostral and four on the anterior dorsal carapace (Fig.3a, b); a ♀ paratype, CL 10.0 mm (LACM:DISCO:21320) has no teeth on the rostrum proper and two on the anterior dorsal carapace (Fig. 4a, b). All of the paratypes either have no telsons, or telsons missing the distal portion.
Distribution. Known only from the type locality in the central North Pacific (31°N, 159°W) at a depth of 4200 m.
Etymology. It gives me great pleasure to name this species in honor of the late Zoologist Emeritus in the Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Dr. Fenner A. Chace, Jr. (1908—2004), who was “one of the most influential carcinologists of the 20 th century” (Lemaitre, 2005: 622). His taxonomic work on caridean shrimps, and particularly on the oplophorid shrimps (Chace, 1936, 1940, 1947, 1986) did much to further our understanding of this family of shrimps.
Remarks. While Dr. Chace’s taxonomic work was voluminous, he early on coauthored several papers on the eye structure of bathypelagic caridean shrimps (Welsh & Chace, 1937, 1938). It is unfortunate that he did not live to make any comments about the reduced eyes of Hymenodora chacei n. sp. I found him willing to answer questions in 1966 when I was an unknown graduate student at a small college in eastern Washington where I was working on midwater shrimps for a Masters dissertation, through my doctoral work at Oregon State University where I described a new species of Hymenodora, (H. acanthetelsonis Wasmer, 1972) and finally as a university professor in suburban Washington, D. C., where I found him always willing to review manuscripts for me, and to visit when I came down to the museum on other business. I especially appreciate his helpful suggestion about where in the crustacean collections of the USNM I might find additional specimens of a new species of the shrimp genus Systellaspis (Systellaspis eltanini Wasmer, 1986) when I was working on oplophorid shrimps from the Southern Ocean.
description: Published as part of Wasmer, Robert A., 2022, A new species of Hymenodora (Crustacea: Decapoda: Oplophoridae) from abyssopelagic depths of the central North Pacific Ocean, pp. 589-599 in Zootaxa 5155 (4) on pages 590-593, DOI: 10.11646/zootaxa.5155.4.8, http://zenodo.org/record/6691812