Pleuroprion chuni

Pleuroprion chuni (zur Strassen, 1902)

(Figs 1 – 8)

Antares chuni zur Strassen, 1902: 687 – 688, fig. 4.

Pleuroprion chuni.—zur Strassen, 1903: 31.—Barnard, 1914: 216.— Kensley, 1975: 38 (in table).— Kensley, 1978: 33–34, fig. 15E.

Material examined: Paralectotype (herein designated), female, 10 mm, German Deep-Sea Expedition 1898/99, station 104, cat. number ZMB 19154. Lectotype, male, same data as holotype.

Other material: Non-ovigerous female, length not recorded, South Africa, Still Bay, 35ºS, 22ºE, 200 m (station SST-11-D-5), SAM A14025.

Description of paralectotype (female) (Figs 1–4): Body (Fig. 1A; completely broken, head, pereonite 1 and pleotelson missing) width of pereonites subparallel (pereonites completely broken and squeezed, thus no widthlength relationship is given). Pereonites 2–7 with large lateral extensions, pereonite 4 with 2 dorsal spines. Pereonites 5–7 subparallel and of similar length and width. Pereonite 5–7 each with 2 dorsal spines. Pleonite 1 not fused to pleotelson, without middorsal spines, lateral extension present. Remaining pleotelson with 1 dorsal spine and lateral extensions on anterior part.

Antennula (Fig. 1B) peduncle article 1 wide and short, narrowing towards distal end; distally with 2 penicillate setae; article 2 0.7 times width of article 1, with 2 penicillate setae and few slender setae; flagellum article 1 short, with 1 long, slender seta distally, article 2 2.6 times longer that article 1, 2.8 times longer than wide, with 8 aesthetascs, 1 penicillate seta and 4 slender setae distally.

Antenna (Fig. 1C) flagellum distally with long unguis.

Labrum (Fig. 1D) with fine setae.

Right mandible (Fig. 2A) molar smooth, slightly dentate on anterior edge, with some longer setae. Lacinia mobilis like structure lobate. Spine row comprising 3 dentate spines. Incisor with 2 lobes and 3 smaller teeth. Left mandible (Fig. 2B) molar serrated, with 3 pappose setae, outside densley fringed with numerous fine small setae. Lacinia mobilis with two major lobes and one small indication of third lobe. Spine row comprising presumably 1 dentate spine; incisor 4-toothed.

Pereopod 4 (Fig. 2C, carpus to dactylus missing) basis, ischium and merus with long slender setae distally on inferior margin.

Pereopod 5 (Fig. 3A), stout, with sparse setae; inferior margin of basis with 5 broom like setae; carpus and merus similar in length, carpus distally with one broom like seta, propodus 1.3 times longer than carpus and distally with one broom like seta. Dactylus partly broken.

Pereopod 6 (Fig. 3B) similar in shape to pereopod 5, stout, with sparse setae; basis with 5 broom like setae; carpus and merus similar in length, propodus 1.2 times longer than carpus and 1.6 times longer than dactylus. Dactylus with 1 unguis and three stout setae (one setule, two broken).

Pereopod 7 (Fig. 3C) similar in shape to pereopod 6, stout, with sparse setae; basis with at least 4 broom like setae; carpus and merus similar in length, propodus 1.3 times longer than carpus. Dactylus broken off.

Pleopod 1 (Fig. 4A) peduncle with 9 coupling hooks; mesial margin of endopod and lateral margin of exopod fringed with plumose setae.

Pleopod 2 (Fig. 4B) mesial margin of endopod and lateral margin of exopod fringed with plumose setae.

Pleopod 3 (Fig. 4C) with expanded exo- and endopods; rami apically rounded.

Uropod (Fig. 4D, E) slightly truncated anteriorly, tapering posteriorly with 6 plumose setae. Exopod very short, with one short robust seta, endopod tiny, with one robust seta.

Lectotype male (Figs 5–8): Body (Fig. 5A, B) maximum length 9.8 mm; length 5.6 times largest width (pereonite 3) (excluding spines), width of pereonites subparallel. Body flattened in dorsal view with asellote appearance, with dorsal spines and lateral extensions. Pattern of spination as in female. Head fused to pereonite 1, suture absent; anterolateral spines in front of eyes; anterodorsal pair of spines. Eyes prominent, bulbous.

Pereonite 1 lateral margin deep, convex, with one spine; middorsal pair of spines. Pereonites 2–4 of similar length, with lateral extensions and 2 dorsal spines each. Pereonite 2 0.8 times length of pereonite 4, pereonite 3 0.9 times length of pereonite 4. Pereonite 4 0.1 times body length; anterior and posterior parts constricted, ventral margin not notched (Fig. 5C). Pereonites 5–7 with lateral extensions and 2 dorsal spines each. Pereonite 5 0.7 times length of pereonite 4, pereonite 6 0.6 times length of pereonite 4, pereonite 7 0.5 times length of pereonite 4.

Pleonite 1 not fused to pleotelson, without middorsal spines, lateral extensions present. Pleotelson with two dorsal spines and lateral extensions on anterior part; posterior end of pleotelson pointed and slightly dorsally orientated.

Antennula (Fig. 6A) peduncle article 1 wide and short, narrowing towards distal end; distally with 2 penicillate setae; article 2 0.8 times width of article 1, medially with 3 penicillate setae and few slender setae; flagellum article 1 short, with 1 long, slender seta mediodistally, article 2 4.1 times longer that article 1, 4.9 times longer than wide, with 17 aesthetascs distally on lateral margin; few slender setae in between.

Antenna (Fig. 6B) peduncle with 5 articles, articles 3 to 5 of similar lengths, inferior margin of penducle fringed with many long slightly plumose setae of same type; flagellum 0.6 times penduncle article 5, flagellum with 2 articles; article 1 distally with 1 long seta, article 2 0.9 length times article 1 length, distally with few slender setae. Claw broken.

Left mandible (Fig. 6C) molar serrated with 2 pappose setae. Outside of molar fringed with numerous fine small setae; spine row with 3 strong dentate spines; lacinia mobilis reduced, one-lobed; incisor process with 6 lobes.

Maxillula (Fig. 6D) lateral lobe with 9 cuspidate apical setae. Mesial lobe apically with 3 pappose setae.

Maxilla (Fig. 6E) mesial lobe oblique margin with 9 robust papposerrate setae; middle lobe with 2 long papposerrate setae; lateral lobe with 2 long papposerrate setae.

Maxilliped (Fig. 6F) endite ventrally with 1 slender setulate seta; distally with several pappose setae and some small simple setae; no coupling hooks visible. Palp article 1 short; article 2 with few long setae mesiodistally; article 3 longest palp article, with long, slender setae mesially; articles 4 and 5 distally with several long papposerrate setae. Epipodite distally pointed.

Pereopod 1 (Fig. 7A) held close to mouthparts; basis distally with few slender setae; ischium short, several long slender setulate setae on inferior margin and distally on ischium; merus short, 0.7 times longer than wide, 4 long slender setulate setae on inferior margin; carpus 0.8 times longer than wide, inferior margin distally pointed, length 1.2 times merus length, inferior margin with long slender setulate setae; propodus length 2.4 times carpus length, 2.5 times longer than wide, numerous slender setulate setae on inferior margin, slender setae distally on superior margin; dactylus with unguis; unguis slender, dactylus and unguis together about same length of propodus.

Pereopod 2 (Fig. 7B) basis short, inferior margin distally with several pappose setae and some single simple setae; ischium short, inferior margin with several pappose setae and some single simple setae; merus short, 1.6 times longer than wide, groups of long, pappose setae and some single simple setae on inferior margin; carpus-propodus long and narrow; carpus 4.9 times longer than wide, length 2.5 times merus length, groups of long, pappose setae and some single simple setae on inferior margin; propodus 9.5 times longer than wide, length 1.3 times carpus length, fringed with long, pappose setae and some single simple setae on inferior margin; dactylus long, slender, length 0.6 times propodus length, unguis present.

Pereopods 3 and 4 (Fig. 7 C–D) similar to pereopod 2.

Pereopods 5–7 (Fig. 7 E–G) similar in shape, stout, with sparse setae; basis of pereopods 5–6 with 6 penicillate setae on superior margin. Pereopod 7 basis with 8 penicillate setae. Carpus and propodus of pereopod 5 with two, respectively 1 penicillate setae, of pereopod 6 and 7 with one penicillate seta each; carpus and merus similar in length, propodus 1.3 to 1.4 times longer than carpus and 1.5 to 1.8 times longer than dactylus. Dactylus with single unguis.

Uropod (Fig. 7H) slightly truncated anteriorly, tapering posteriorly with 12 plumose setae. Exopod very short, with one robust setae (broken), endopod tiny, with one robust setae (broken).

Pleopod 1 (Fig. 8A) peduncle 2.9 times longer than wide, with 5 coupling hooks; exopod laterally with 13 plumose setae and distally with 9 apical plumose setae. Distolaterally with strong groove on its posterior face. Endopod shorter than exopod, laterally with 6 plumose setae and distally with at least 5 apical plumose setae.

Pleopod 2 (Fig. 8B) peduncle with 3 coupling hooks; endopod with about 20 plumose setae apically and distally along mesial margin; exopod with around 31 plumose setae apically and along whole lateral margin; appendix masculina (Fig. 8C) fused as a single penial plate, styliform, straight, apically bifid, pointing sligthly mediodistally, 1.2 times longer than endopod.

Pleopods 3–5 (Fig. 8 D–F) with expanded exo- and endopods; rami apically rounded, fine setae on margins. Pleopod 5 with 3 plumose setae on exopod.

Remarks: The type material stored in the Museum für Naturkunde in Berlin, Germany, consists of three tubes, one with the remaining broken female paralectotype, the second one with some loose dissected parts, and the third one with the male lectotype being in a good shape. The poor condition of the female did not allow a full redescription.

From the remaining part of the female and the male of Pleuroprion chuni no pronounced sexual dimorphism was visible. The lateral extensions of P. chuni are very characteristic for the species, reminding more of an asellote than of a valviferan, this being noted by zur Strassen (1902). Due to the poor condition of the female holotype, there is still uncertainty about the number and shape of the oostegites.

Kensley (1978) stated that the coxae had acute spines. This is erroneous, as this can not be seen from the type material. He illustrated only the habitus (dorsal view, his fig. 15E) of one specimen, but the sex of the specimen was not mentioned (Kensley 1978). This same specimen was reillustrated by G.C.B. Poore in 1999 and provided additional detail. These illustrations revealed the important uropodal rami and the claw on the antennal flagellum, not clear on the types.

Distribution: Off South Africa, Agulhas Bank, Still Bay at 156–200 m (zur Strassen 1902; Kensley 1975; Kensley 1978).