Nannoniscus magdae, Kaiser, Brix & Jennings, 2021

Kaiser, Stefanie, Kihara, Terue Cristina, Brix, Saskia, Mohrbeck, Inga, Janssen, Annika & Jennings, Robert M., 2021, Species boundaries and phylogeographic patterns in new species of Nannoniscus (Janiroidea: Nannoniscidae) from the equatorial Pacific nodule province inferred from mtDNA and morphology, Zoological Journal of the Linnean Society 193, pp. 1020-1071 : 1042-1048

NANNONISCUS MAGDAE KAISER, BRIX & JENNINGS , SP. NOV.

( FIGS 11–14 )

Zoobank registration: urn:lsid:zoobank.org:act:B36BAA31-FE02-4E33-BB83-CA8444FB91E5 .

Type fixation: Holotype, preparatory female, ZMH K-55375, 2.2 mm, designated here.

Material examined: Holotype: preparatory female (Na26), 2.2 mm, CCZ, equatorial NE Pacific, JPIO SO239 expedition, RV Sonne, EBS, station 171 (start: 14°2’41’’N, 130°5’57’’W, 5024 m; end: 14°3’12’’N, 130°4’36’’W, 5017 m), date: 17/04/2015, ZMH K-55375.

Paratypes: Preparatory female (Na12), CCZ, equatorial NE Pacific, JPIO SO239 expedition, RV Sonne, EBS, same station as holotype, ZMH K-55374; preparatory female (NB12Iso99), CCZ, equatorial NE Pacific, BIONOD expedition, RV L’Atalante, EBS, station 67 (start: 14°3’4’’N, 130°4’36’’W, 5021 m; end: 14°3’10’’N, 130°4’27’’W, 5021 m), date: 19/04/2012, ZMH K-55373; ovigerous female (Na28), CCZ, equatorial NE Pacific, JPIO SO239 expedition, RV Sonne, EBS, same station as holotype, ZMH K-55376; juvenile male (Na49), CCZ, equatorial NE Pacific, JPIO SO239 expedition, RV Sonne, EBS, same station as holotype, ZMH K-55377.

Etymology: The new species ( magdae, Latin genitive, feminine) is named in honour of Magdalena Błażewicz for her invaluable help onboard the SO239 Ecoresponse voyage, and her contributions to the taxonomy and biodiversity of deep-sea peracarids.

Distribution: Based on the material available (four specimens), this species has a restricted distribution and is only known from the French licence area of the CCZ, between 5017 and 5024 m depth.

Diagnosis: Body slender, length about 4.8 × pereonite 1 width; Mxp lateral margin with numerous small setae; Mxp epipodite reaching mid of palpal article 3; molar process of both Md with ≥ nine distal spines each; Md incisor teeth rounded; pereonite 2 anterolateral tergites devoid of setae; pereonite 7 without ventral spine; Op with ventral posteriorly bent spine, posterior margin with numerous (≥ 17) long simple setae; Urp biramous, not projecting beyond Plt posterior margin; Urp endopodite length about 2.1 exopodite length.

Description of holotype and paratype female: Habitus ( Figs 11B, D , 14A–C ), body length 4.8 pereonite 1 width. Coxae not visible in dorsal view. Cephalothorax ( Figs 11B , 14D–E ) as long as wide (measured from lateral view). Anterior margin straight, posterior and lateral margins slightly rounded. Antennae inserting frontolaterally in deep fold. Pereonites 1–4 gradually flattening, then abruptly flattening from pereonite 4 to 5. Pereonites 1–3 of similar width, gradually decreasing in width from 3 to 7; pereonite 1 length 0.4 width. Pereonite 2 width 0.5 pereonite 1 width, length 1.2 pereonite 1 length. Pereonites 2 and 3 of similar length; pereonite 4 length 1.1 pereonite 1 length. Pereonites 1–4 anterior margins frontally directed, without setation. Pereonite 5 length 1.1 pereonite 1 length, anterior margin straight. Pereonites 6–7 dorsomedially fused, pereonite anterior margin slightly convex. Plt length 0.2 body length, length 1.5 width; width 0.7 pereonite 1 width, posterior margin strongly rounded; anterior margin straight. Urp length 0.3 Plt length, not projecting beyond posterior margin. AI ( Fig. 11A ) length 0.1 body length, with five articles. First article circular and broadest, with one small broom seta distally. Second article length twice width, with three broom setae (one broken off) and one small simple seta distally. Article 3 minute, length 0.2 article 2 length, as long as wide. Article 4 length 0.3 article 2 length, with long distal projection reaching mid of article 5, with two simple setae of varying size distally. Article 5 length 0.9 article 2 length, length 1.6 width, with one aestetasc terminally. AII ( Fig. 11C ) length 0.4 body length, with six podomere and seven flagellar articles. Podomere articles 1–4 short; article 1 with one simple seta distally; article 3 with two simple setae distally, article 4 with one simple seta distally. Article 5 longest, length 1.3 articles 1–4 length, length approximately 4.1 width, with two simple setae laterally. Article 6 length 0.8 article 5 length, length 3.3 width, with two broom setae of varying size and one long simple seta distally. Flagellar article 1 longest, conjoint with two setal positions (fusion of three articles), length 0.9 podomere article 6 length, length 4.6 width, with two simple setae laterally. Flagellar articles 2–7 decreasing in length and width distally; each article with 1–3 short simple setae distally. Article 7 with 5 long slender setae terminally. Md ( Fig. 11E, F ), palp of left and right mandible well developed, consisting of three articles reaching mid of incisor. Palpal article 2 of rMd length 1.7 article 1 length, with two simple setae laterally. Terminal article length 0.4 article 2 length, tapering distally, with several (≥ nine) small setae ventrally and three somewhat longer setae terminally. Incisor process of rMd with three rounded teeth, incisor of lMd with rounded three teeth. Lacinia mobilis of lMd with three teeth. Spine row of rMd with 10 robust spines and several slender setae in between; dentation decreasing and setal size increasing proximally. Spine row of lMd with ten robust spines and several slender setae in between, dentation decreasing, seta length increasing proximally. Molar of rMd and lMd triangular; molar of rMd and lMd each with nine long, serrate spines distally. Mxp ( Fig. 11G ), left and right Mxp connected by three retinacula. Epipodite smooth, triangular, slender, length 3.1 width, reaching mid of palpal article 3. Palpal article 1 short, width 1.6 length, with several small setae lateral. Article 2 length 1.9 article 1 length, as long as wide, with several small setae laterally. Article 3 length 1.6 article 1 length, width 0.9 length, with four robust sensory setae distally and two simple setae laterally. Article 4 as long as article 1, width 0.5 length, with distal projection reaching mid of article 5, with three slender setae distally. Article 5 length 0.6 article 1 length, width 0.4 length, with three slender setae terminally. Endite distal margin with some robust, dentate setae and several fine setae laterally. Basis triangular, length 0.7 width. PI ( Fig. 12C ) basis length 2.7 width. Ischium length about half basis length, length 2.2 width, with two simple setae distodorsally, with one simple seta ventrally. Merus length 0.7 ischium length, length 1.4 width, with two simple seta distodorsally, with one long simple setae distoventrally. Carpus length 1.6 merus length, length 2.4 width, with one simple seta distodorsally, with row of six simple setae ventrally. Propodus length 0.9 carpus length, length 3.8 width, with one simple seta dorsally, with numerous small setae, membranously embedded, and two small unequally bifid setae in between ventrally. Dactylus length about half propodus length, length 4.5 width, with one small simple setae medially. Unguis length half dactylus length, with two long, slender setae underneath unguis. PII ( Fig. 12D ) basis length 3.7 width, with one simple seta distoventrally. Ischium length about half basis length, length twice width, with five simple setae dorsally, with one simple seta distodorsally. Merus length 0.8 ischium length, length 1.5 width, with one simple seta (broken off) distodorsally, with one simple seta distoventrally. Carpus length 2.3 merus length, length 3.9 width, with six long slender simple setae and two long robust setae ventrally. Propodus length 0.6 carpus length, length 3.7 width, with two simple setae dorsally, with numerous small setae, membranously embedded, and three simple setae in between ventrally. Dactylus length 2.4 propodus length, length 3 width, with two simple setae medially, with numerous small setae ventrally. Unguis length 0.7 dactylus length, with two slender setae underneath unguis. PIII ( Fig. 12E ) damaged between basis and ischium. Basis length 4.4 width. Ischium length about half basis length, length 2.3 width, with one simple seta distodorsally, with one simple seta ventrally. Merus length 0.8 ischium length, length 1.8 width, with one small seta distodorsally, with one somewhat longer seta distoventrally. Carpus length 2.3 merus length, length 4.5 width, with 11 long slender setae (four broken off) ventrally. Propodus length 0.7 carpus length, length 4.3 width, with three long simple setae dorsally. Dactylus length 0.3 propodus length, length 2.3 width. Unguis damaged, as long as dactylus. PIV ( Fig. 12F ) basis length 5.9 width, with one simple seta ventrally. Ischium length 0.6 basis length, length 3.8 width. Merus length 0.6 ischium length, length 2.2 width, with one small simple seta distodorsally, with one long simple seta distoventrally. Carpus length 2.2 merus length, length 4.7 width, with nine long slender simple setae ventrally. Propodus length 0.7 carpus length, length 5 width, with numerous small setae and four simple seta ventrally. Dactylus length 0.4 propodus length, length 3.5 width. Unguis length 0.6 dactylus length, ventral claw length 0.3 ungius length. PV ( Fig. 12G ) basis length 4.9 width. Ischium length 0.8 basis length, length 3.1 width, with two long simple setae dorsally. Merus length about half length, length 1.8 width, with three simple setae (two long, one somewhat shorter) distodorsally. Carpus length twice merus length, length 3.6 width, with four long slender simple setae dorsally, with six long slender simple setae ventrally. Propodus length 0.6 carpus length, length 3.2 width, with four long simple setae dorsally, with five long simple setae ventrally. Dactylus length half propodus length, length 3 width. Unguis length 0.8 dactylus length, ventral claw length 0.6 ungius length. PVI ( Fig. 12H ) basis length 5.1 width, with three long simple setae ventrally. Ischium length 0.7 basis length, length 3.4 width. Merus length half ischium length, length 1.6 width, with two long simple setae distodorsally. Carpus length 2.4 merus length, length 4.1 width, with four long slender simple setae (one broken off) ventrally. Propodus length 0.6 carpus length, length 3.5 width, with seven long simple setae dorsally, with two simple setae of varying size ventrally. Dactylus length half propodus length, length 2.2 width. Unguis length 0.6 dactylus length, with two slender setae of varying size underneath unguis. PVII ( Fig. 12I ) slightly damaged between ischium and merus. Basis length 3.2 width. Ischium length 0.8 basis length, length 2.9 width, with one simple seta distodorsally. Merus length 0.4 ischium length, length 1.3 width, with one seta (broken off) distodorsally. Carpus length 2.4 merus length, length 3.1 width, with five slender simple setae (four long, one somewhat shorter) ventrally. Propodus length 0.7 carpus length, length 3.8 width, with seven long simple setae dorsally. Dactylus length 0.4 propodus length, length 4.5 width, with three simple setae medially. Unguis length 0.9 dactylus length, with two slender setae underneath unguis. Op ( Fig. 11H ) length 1.2 width, with strong ventral spine, posteriorly bent. Lateral margin rounded, posterior margin almost straight, with several (≥ 17) simple setae, setal size 0.3 Plt length. PlpIII ( Fig. 11I ), protopodite length 0.7 proximal width, length 0.4 endopodite length. Exopodite 0.5 endopodite length, length 1.6 width, width tapering distally, with numerous short simple setae laterally and one somewhat longer distally. Endopodite 1.2 length 1.5 width, with three long plumose setae distally, distal margin strongly rounded. PlpIV ( Fig. 11J ), protopodite rectangular, as long as wide, length 0.4 endopodite length. Exopodite slender, length 0.7 endopodite length, length 5 width, with several thin setules laterally (outer margin) and one long robust plumose seta distally. Endopodite ovoid-shaped, length twice width. PlpV ( Fig. 11K ), small oval lobe, without setation. Length twice proximal width, width gradually tapering towards distal end. Urp ( Fig. 11L ) biramous, length 0.2 Plt length, not projecting beyond Plt posterior margin. Protopodite length 1.5 proximal width, with three long simple setae distally. Exopodite length 0.5 protopodite length, length 4.5 width, with two long simple setae terminally. Endopodite length 2.1 exopodite length, length 3.8 width, with two simple setae (broken off), two long simple setae and two long broom setae terminally.

Description of male paratype: Habitus ( Fig. 13 ). Body length 5.3 pereonite 1 width. Coxae not visible in dorsal view. Cephalothorax ( Fig. 13A ) length equals width. Anterior, lateral and posterior margins rounded. Antennae inserting frontolaterally in deep fold. Pereonites 3–6 decreasing in width. Pereonite 1 length 0.3 width. Pereonites 1–2 of similar width; pereonite 2 length 1.6 pereonite 1 length. Pereonites 2–3 of similar length. Pereonite 3 width 0.9 pereonite 1 width. Pereonites 2–5 of similar length. Pereonites 1–4 anterior margins frontally directed, anterolateral tergites of perenonite 1–4 each tipped with simple seta. Pereonites 4–7 of similar width, width 0.8 pereonite 1 width. Pereonite 5 anterior margin straight. Pereonites 6–7 dorsomedially fused, pereonite 6 anterior margin straight. Plt 0.2 body length, length 1.2 width, width 0.8 pereonite 1 width; posterior margin strongly rounded, anterior margin slightly concave. Urp not projecting beyond posterior margin. PlpI ( Fig. 13B ), length 2.5 proximal width. Distal projection width 0.5 proximal width, lateral margins straight. Lateral lobes rounded. Distal margins almost straight, with three simple setae. PlpII ( Fig. 13C ), sympod length 2.2 width, outer margin rounded, with one simple seta distally; inner margin straight. Endopod inserting 0.3 from distal tip of sympod. Stylet length 0.7 sympod length, slightly curved, distal end not extending beyond distal tip of sympod. Exopod short and rounded, inserting 0.1 from distal tip of sympod.

Remarks: The new species most closely resembles N. hilario , N. menziesi and N. perunis , but differs from these species by lacking robust setae on the anterolateral tergites of pereonite 2 and a markedly longer uropodal exopodite (Urp endopodite/exopodite length ratio 2.1 vs. ≥ 5.6 in the remaining species). Nannoniscus magdae can be furthermore distinguished from N. hilario as follows: Mxp endopodite reaching mid of palpal article 3 (vs. distal third of palpal article 2 in N.hilario ); Op posterior margin with ≥ 17 simple setae (vs. ≤ 9). Additional characters to distinguish the new species from N. menziesi are: Mxp lateral margin with numerous small setae (vs. Mxp lateral margin lacking setae in N. menziesi ); Md incisor teeth rounded (vs. acute). Nannoniscus magdae is also similar to N. meteori , but can be differentiated as follows: Mxp lateral margin with numerous small setae (vs. Mxp lateral margin lacking setae in N. meteori ). The description of the male characteristics of N. magdae is based on a juvenile specimen, which can differ considerably from the terminal males (Riehl et al., 2012). However, since the specimen is the only male found for the new species, we found it to be a valuable addition to the female description.

Figures

Figure 11. Nannoniscus magdae, (A, C, E–G) paratype female (ZMH K-55373, NB12_Iso099); (B, D) holotype female (ZMH K-55375, Na26); (H–L) paratype female (ZMH K-55374, Na12): (A) AI; (B) habitus, dorsal view; (C) AII; (D) habitus, lateral view; (E) rMd; (F) lMd; (G) Mxp; (H) Op; (I) PlpIII; (J) PlpIV; (K) PlpV; (L) Urp. Scale bars: A, C, E–L = 100 µm; B, D = 200 µm.

Figure 12. Nannoniscus magdae, (A–B) holotype female (ZMH K-55375, Na26); (C–E, I) paratype female (ZMH K-55373, NB12_Iso099); (F–H) paratype female (ZMH K-55374, Na12): (A) habitus, dorsal view; (B) habitus, lateral view; (C–I) PI-PVII. Scale bars: A–B = 200 µm; C–I = 100 µm.

Figure 13. Nannoniscus magdae, paratype male (ZMH K-55377, Na49): (A) habitus, dorsal view; (B) PlpI; (C) PlpII. Scale bars: A = 200 µm; B–C = 100 µm.

Figure 14. Nannoniscus magdae, holotype female (ZMH K-55375, Na26). Confocal laser scanning microscopy images: (A) habitus, dorsal view; (B) habitus, ventral view; (C) habitus, lateral view; (D) mouthparts, ventral view; (E) cephalothorax, lateral view; (F) Plt, ventral view. Scale bars: A–C = 200 µm; D–F = 100 µm.