Diastylis andeepae, Alberico, Natalia & Mühlenhardt-Siegel, Ute, 2010

Alberico, Natalia & Mühlenhardt-Siegel, Ute, 2010, Two new Diastylis (Cumacea: Diastylidae) from Antarctic waters: Diastylis andeepae and D. catalinae, Zootaxa 2440, pp. 33-48 : 34-40

publication ID	https://doi.org/ 10.5281/zenodo.194934
DOI	https://doi.org/10.5281/zenodo.6208582
persistent identifier	https://treatment.plazi.org/id/03AE1C51-FF86-FFF9-FF5E-F9B4FDFDFA2D
treatment provided by	Plazi
scientific name	Diastylis andeepae
status	sp. nov.

Treatment

Diastylis andeepae n. sp.

( Figures 1−4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. R/V “Polarstern”. ANDEEP I (ANT XIX/3). West Weddell Sea, Sta. 46−7, 60º38.35´S, 53º57.36´W, 2893.6 m, 30 January 2002: 1 manca ( ZMH K- 42178). ANDEEP III (ANT XXII/3). East Weddell Sea, Sta. 80−9, 70º39.07´S, 14º43.36´W, 3103 m, 23 February 2005: 1 preparatory ♀ (with an isopod on basis of pereopod 1) (holotype ZMH K −42179).

Diagnosis. Carapace with small tubercles all over, inferior margin serrated; anterior part with an arched row of teeth on each side of the pseudorostrum, an oblique row of three teeth on each side of the frontal lobe fissures, and two middorsal rows of small teeth. Pereopod 2, ischium with four strong teeth. Pereopods 3 and 4 without rudimentary exopods. Telson with five cuspidate setae on each side. Uropod endopod of two articles.

Description of the preparatory female (based on the holotype ZMH K −42179) Total length: approximately 11.75 mm.

Carapace ( Figures 1 View FIGURE 1 A, B) approximately 1.3 times as long as wide, surface with small tubercles all over, inferior margin serrated; anterior part with: (1) an arched row of teeth, extending from each side of the pseudorostrum and disappearing a short distance before reaching the inferior margin of the carapace, (2) an oblique row of three teeth on each side of the frontal lobe fissures, and (3) two rows of small teeth in the middle of the frontal lobe, running posteriorly from ocular lobe and reaching approximately middle of the carapace. Ocular lobe approximately as long as wide, without lenses. Pseudorostrum approximately 4 times as long as the ocular lobe. Antennal notch shallow and smooth.

Pereon ( Figures 1 View FIGURE 1 A, B) approximately 0.4 times as long as the carapace. Pereonites 1, 2, 3 subequal in length, pereonite 4 the longest, postero −lateral angles of the pereonite 5 rounded in dorsal view. Pereonites 2−5 with dorso −lateral teeth: pereonite 2 with four, pereonites 3 and 5 with two, and pereonite 4 with two rows of four.

Pleon ( Figure 1 View FIGURE 1 A) approximately 0.8 times as long as the cephalothorax, pleonites 1−6 with two small dorso −lateral teeth each.

Telson ( Figure 4 View FIGURE 4 C) approximately twice as long as last pleonite, with several sinuate setae on dorsal surface. Each side with five cuspidate setae and distal end with two long stout cuspidate setae.

Antenna 1 ( Figure 1 View FIGURE 1 C), peduncle, articles 1, 2 and 3 with thin sinuate setae; article 1 approximately 0.9 times as long as articles 2 and 3 combined, inner distal corner with one setulate seta and one large tooth, outer distal corner with one large seta with tiny setulae; article 2 approximately 1.2 times as long as article 3, with one setulate seta, one broom seta and two small simple setae; article 3 with three broom and two simple setae distally. Main flagellum of three articles; article 1 slightly longer than articles 2 and 3 combined, articles 2 and 3 with one aesthetasc each. Accessory flagellum almost reaching middle of the article 1 of the main flagellum; of three articles, article 2 the longest.

Antenna 2 ( Figure 1 View FIGURE 1 D) of four articles, article 1 the longest, article 4 minute. Article 1 with two setulate setae, articles 2−4 with one setulate seta each.

Right mandible ( Figure 2 View FIGURE 2 A) boat-shaped, pars incisive with 16 setae. Left mandible not dissected.

Maxilla 1, outer endite with 14 cuspidate distal setae and one small seta on outer margin, inner endite with four unequal and two small simple setae distally (not drawn but very much alike to the maxilla 1 of Diastylis fabrizioi presented by Alberico and Roccatagliata 2008).

Maxilla 2, outer endite with three serrate and three serrulate setae, inner endite with three serrate and one serrulate setae (not drawn but very much alike to the maxilla 2 of Diastylis fabrizioi presented by Alberico and Roccatagliata 2008).

Maxilliped 1 ( Figure 2 View FIGURE 2 B), basis with seven setuloserrulate setae on inner distal margin. Endite with seven setae (simple, setuloserrulate and setulate). Carpus, inner margin with a row of six setuloserrate setae and simple setae (not drawn), inner distal corner with one setulate and one setuloserrulate seta, outer distal corner with one large setulate seta. Propodus with many simple setae (only basis drawn), two long and one short setulate setae and two setuloserrulate setae. Dactylus with simple and serrulate setae.

Maxilliped 2 ( Figure 2 View FIGURE 2 C), basis approximately as long as remaining articles together, with eight setulate setae (four of them with thicker setulae) and one short simple seta on outer margin and distally. Merus with three setulate setae distally. Carpus with three unequal setulate setae on outer distal corner and six setulate setae on inner margin. Propodus, outer margin with two setulate setae, inner margin with nine barely setulate setae (distal half finely serrulate). Dactylus with serrulate and simple setae distally.

Maxilliped 3 ( Figure 3 View FIGURE 3 A), basis −carpus with several thin sinuate setae. Basis approximately 1.6 times as long as remaining articles together, inner margin with setulate setae and several teeth, distal process with five stout setulate setae (one of them shorter). Ischium distal margin with one tooth, inner margin with three small teeth and three setulate setae. Merus with two teeth, outer margin with one and inner margin with two setulate setae. Carpus inner margin with two setulate setae and one tooth, dorsal surface with a row of three setulate setae and outer distal corner with two setulate setae. Propodus with three barely setulate setae on inner margin and one simple seta distally. Dactylus with several simple and serrulate setae. Exopod with flagellum of six articles.

Pereopod 1 ( Figure 3 View FIGURE 3 B), basis −propodus with thin sinuate setae. Basis 0.85 times as long as remaining articles together, with setulate setae on both margins and distally, and teeth on both margins and on dorsal surface. Ischium and merus combined approximately 0.6 times as long as carpus. Merus with two teeth on dorsal surface and two setulate setae. Carpus with one setulate seta. Merus and carpus combined 0.76 times as long as propodus and dactylus combined. Dactylus approximately as long as propodus. Last two articles with simple setae only. Exopod with flagellum of seven articles.

Pereopod 2 ( Figure 3 View FIGURE 3 C), all articles with thin sinuate setae. Basis approximately 0.8 times as long as remaining articles together, with setulate setae on inner and distal margins, and teeth on both margins and on dorsal surface. Ischium distal margin with four large teeth on inner corner and four smaller teeth on outer corner. Ischium and merus combined approximately 0.7 times as long as carpus. Merus, distal margin with three setulate setae and one tooth on each corner. Carpus approximately 1.4 times as long as propodus and dactylus combined. Last three articles with simple setae only. Exopod with flagellum of seven articles.

Pereopod 3 ( Figure 4 View FIGURE 4 A), basis −merus with thin sinuate setae. Basis slightly longer than remaining articles together; inner margin with three setulate setae, one broom seta and several small simple setae; distal outer corner with one setulate seta. Ischium and merus with two simple (annulate?) setae each. Carpus slightly longer than merus, with two simple (annulate?) setae basally (one broken, not drawn) and four annulate setae distally. Propodus with one annulate and one broom seta distally. Dactylus with one small simple seta near middle of article and two simple setae distally (one minute, one large). Without exopod.

Pereopod 4 as pereopod 3 except for: basis approximately 0.8 times as long as remaining articles together, inner margin with one tooth basally, distal outer corner without seta. Carpus slightly shorter than merus, with four simple (annulate?) setae basally.

Pereopod 5 ( Figure 4 View FIGURE 4 B), basis, merus and carpus with thin sinuate setae. Basis approximately 0.6 times as long as remaining articles together, with simple setae and one broom seta. Merus with one simple (annulate?) seta. Carpus slightly longer than merus, with three simple (annulate?) setae basally and with three annulate setae distally. Propodus with one annulate seta distally. Dactylus with one small simple seta near middle of article. Without exopod.

Uropod ( Figure 4 View FIGURE 4 C) with several sinuate setae. Peduncle slightly longer than telson, dorsal surface with two −three teeth apically, inner margin with seven −nine cuspidate setae. Endopod approximately 0.8 times as long as exopod, of two articles: article 1 slightly longer than article 2, with three −four cuspidate setae on inner margin and one −two teeth on outer margin; article 2 with four −five cuspidate setae on inner margin and one cuspidate seta, almost reaching end of exopod, distally. Exopod with simple setae on both margins and three unequal simple setae distally.

Male unknown.

Etymology. This species is named after the acronym of the expedition, ANDEEP.

Distribution. Antarctic waters, East and West Weddell Sea, between 2893.6 m and 3103 m depth.

Remarks. To date, a total of 14 species (including the new species herein described) having two articles on the uropod endopod are known for the genus Diastylis . Seven of these species have been described from the Southern Hemisphere, namely D. fimbriata Sars 1873 ( Brazil) , D. horrida Sars 1887 (Kerguelen Is.) , D. argentata Calman 1912 ( Chile) , D. granulata Zimmer 1921 ( Argentina) , D. zimmeri Ledoyer 1977 (Kerguelen Is.) , D. geocostae Băcescu & Petrescu 1991 ( Brazil) , and D. andeepae n. sp (Weddell Sea).

Three of the six above mentioned species are readily distinguished from Diastylis andeepae n. sp.: D. argentata and D. granulata by having on the carapace a pair of antero −lateral horns; and D. geocostae by presenting two oblique ridges enclosing a flat anterior area or plateau. Diastylis zimmeri , D. fimbriata , D. horrida and D. andeepae n. sp. seem to be closely related species. None of these four species has a pair of antero −lateral horns or plateau. However, they can be rapidly separated by the arrangement of their carapace sculptures: D. zimmeri has small teeth, more densely distributed on the anterior part of the carapace, and one groove on each side of it; D. fimbriata has a strong row of teeth on each lateral side of the carapace; D. horrida shows numerous unequal teeth all over the carapace, whereas D. andeepae has on each side of the anterior part of the carapace an arched row of teeth, which extends from pseudorostrum and disappears a short distance before reaching the inferior margin of the carapace. Diastylis andeepae is more similar to D. horrida than to the other two species without antero −lateral horns or plateau ( D. fimbriata and D. zimmeri ). Concerning the carapace sculpture, Ledoyer (1977) noted the variability in the number of spines and teeth in D. horrida from the Kerguelen according to sex and developmental stage; however, he mentioned nothing comparable to the antero −lateral row of teeth as present in the new species. Nevertheless, these two species have further differences: small tubercles all over the carapace in the new species (small and large teeth in D. horrida ); middorsal rows of small teeth at frontal lobe reaching middle part of the carapace in D. andeepae (rows of large teeth and reaching almost the posterior margin of the carapace in D. horrida ); pereonites 3 to 5 of D. andeepae with dorso −lateral longitudinal rows of teeth, particularly distinctive on pereonite 4; whereas D. horrida has “transverse rows of spines” on pereonites ( Sars 1887).

Additional differences between the new species and D. horrida are detectable in the armature of antenna, pereopods and telson: antenna 1 basal article with one strong tooth in D. andeepae (with two strong teeth in D. horrida ); ischium of pereopod 2 with four strong teeth in the new species (with two teeth in D. horrida ); telson with five pairs of lateral cuspidate setae and dorsal surface smooth in D. andeepae (with nine pairs of lateral cuspidate setae and a row of six dorso −median teeth along preanal part in D. horrida ).

In addition to the carapace sculpture, D. andeepae can be distinguished from other members of the genus by having on ischium of pereopod 2 four strong teeth. This is a unique character within the group. As stated above, Diastylis horrida has only two teeth and in the genus we found only one species with several teeth on ischium of pereopod 2 as in the new species, Diastylis jonesi Reyss, 1972 , however only one of these teeth is large and the other four are small.