Nannoniscus brenkei, 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 : 1061-1063

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

( FIG. 23 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: AF031C17-94B8-4274-A079-D113BC1423BC.

Type fixation: Holotype, preparatory female, ZMH K-55370, 2.5 mm, designated here.

Material examined: Holotype: preparatory female (NB12_Iso070), 2.5 mm, CCZ, equatorial NE Pacific, BIONOD expedition, RV L’Atalante, EBS, station 33 (start: 11°51’44’’N, 117°3’10’’W, 4133 m; end: 11°51’54’’N, 117°3’8’’W, 4133 m), date: 07/04/2012, ZMH K-55370.

Paratypes: Preparatory female (Na03), CCZ, equatorial NE Pacific, JPIO SO239 expedition, RV Sonne, EBS, station 20 (start: 11°50’9’’N, 117°58’29’’W, 4093 m; end: 11°50’11’’N, 116°58’0’’W, 4093 m), date: 21/03/2015, ZMH K-55369; ovigerous female (Na24), CCZ, equatorial NE Pacific, JPIO SO239 expedition, RV Sonne, EBS, station 24 (start: 11°51’19’’N, 117°1’30’’W, 4093 m; end: 11°51’31’’N, 116°58’0’’W, 4093 m), date: 22/03/2015, ZMH K-55371; male (?), badly damaged (MA14_Iso258), CCZ, equatorial NE Pacific, MANGAN 14 expedition, RV Kilo Moana EBS, station 21 (start: 11°49’44.52’’N, 117°00’27.06’’W, 4132 m; end: 11°49’56.76’’N, 116°59’40.62’’W, 4136 m), date: 10/05/2014, ZMH K-55368.

Etymology: The name of the new species ( brenkei, Latin genitive, male) is dedicated to Nils Brenke, builder of the Brenke sledge (“Berta”), in recognition of his passion for deep-sea isopod taxonomy.

Distribution: The species is only known from four stations in the eastern German claim of the CCZ (type locality) between 4093 and 4136 m depth.

Diagnosis: Body slender, length about 5.0 × pereonite 1 width; Mxp epipodite reaching mid of palpal article 3; Mxp lateral margin with a fringe of setae; molar process of both Md each with only a few (≤ 5) distal spines; Md incisor teeth rounded; pereonite 2 anterolateral tergites each with robust seta; pereonite 7 without ventral spine; Op with a ventral posteriorly bent spine, posterior margin with numerous (≥ 14) long simple setae; Urp biramous, not projecting beyond Plt posterior margin; Urp endopodite length ≤ 5.8 exopodite length; Plp 3 exopodite 0.6 endopodite length, length 2.5 width, strongly tapering in width distally.

Description of holotype and paratype female: Habitus ( Fig. 23A ). Body length 5.5 pereonite 1 width. Coxae not visible in dorsal view. Cephalothorax ( Fig. 23A ), length 0.8 width. Anterior and posterior slightly rounded, lateral margins straight. Antennae inserting frontolaterally in a deep fold. Pereonites 2–4 decreasing in width, pereonites 4–7 of similar width. Pereonite 1 length 0.3 width. Pereonite 1 and 2 of similar width, pereonite 2 length 1.1 pereonite 1 length. Pereonite 3 length 1.3 pereonite 2 length. Pereonite 4 length 1.2 pereonite 2 length. Pereonites 1–4 anterior margins frontally directed, anterolateral tergites of pereonite 2 each tipped with a robust seta, anterolateral tergites of pereonites 3 and 4 each with a simple seta. Pereonite 5 length 1.5 pereonite 1 length, anterior margin straight. Pereonites 6 and 7 dorsomedially fused, anterior margin of pereonite 6 convex. Plt length 0.2 body length, length 1.4 width, width 0.8 pereonite 1 width, posterior margin strongly rounded; anterior margin slightly concave. Urp length 0.3 Plt length, not projecting beyond posterior margin. AI ( Fig. 23B ), terminal article broken off, inferred from holotype (in situ). Length 0.1 body length, with five articles. First article circular and broadest, length 2.1 width, with one small broom seta and one simple seta distally. Second article length 0.9 article 1 length, length 1.6 width, with three long broom setae and one seta (broken off) distally. Article 3 minute, length 0.2 article 1 length, half as long as wide. Article 4 length 0.3 article 2 length, with a long distal projection, with one long broom seta and two simple setae distally. Article 5 length 0.5 article 1 length, as long as wide. AII ( Fig. 23B ) broken off, only podomere articles 1–4 present; articles quadrangular of similar length and width. Md ( Fig. 23C, D ), palp of left mandible broken off, of right mandible well developed, consisting of three articles extending beyond distal end of incisor process. Palpal article 2 of rMd length 2.5 article 1 length, with one simple seta and two fringes of small setule laterally. Terminal article length about one-third article 2 length, tapering distally, with several small setae ventrally and three somewhat longer setae terminally. Incisor process of rMd with seven rounded teeth, incisor of lMd with five rounded teeth. Lacinia mobilis of lMd with three teeth. Spine row of rMd with nine robust spines of varying size and several slender setae in between; size increasing proximally. Spine row of lMd with nine robust spines, dentation decreasing, spine size increasing proximally. Molar of rMd and lMd triangular; molar of rMd with five, of lMd with four long, serrate spines distally. Mxp ( Fig. 23E ), left and right Mxp connected by three retinacula (one broken off). Epipodite smooth, triangular, slender, length 3.6 width, reaching mid of palpal article 3. Palpal article 2 as wide as long. Article 3 length 0.8 article 2 length, width 1.2 length, with four robust sensory setae and two simple setae distally. Article 4 length 0.3 article 2 length, width half length. Article 5 length 0.2 article 2 length, width about half length, with two slender setae terminally. Endite distal margin with some robust, dentate setae and several fine setae laterally. Basis length 0.7 width. PI ( Fig. 23F ) basis length 4 width, with one simple seta dorsally and two simple setae ventrally. Ischium length 0.6 basis length, length 2.2 width, with one small simple seta ventrally. Merus length 0.6 ischium length, length 1.2 width, with one long simple seta distodorsally and one long simple seta distoventrally. Carpus length twice merus length, length 2.6 width, with one long simple seta distodorsally, with numerous small setae, membranously embedded, and three long unequally bifid setae in between ventrally. Propodus length 0.7 carpus length, length 2.7 width, with one slender simple seta distodorsally, with numerous small setae, membranously embedded, and one small robust unequally bifid seta ventrally. Dactylus length 0.6 propodus length, length 3.1 width, with three slender setae medially, with numerous small setae, membranously embedded ventrally. Unguis length about half dactylus length, with one long, slender seta underneath unguis. Op ( Fig. 23G ) length 1.3 width, with a strong ventral spine, posteriorly bent. Lateral margins rounded, posterior margin almost straight, with several (≥ 14) simple setae, setal size 0.2 Plt length. PlpIII ( Fig. 23H ) protopodite length 1.7 width, length 0.7 endopodite length. Exopodite 0.6 endopodite length, length 2.5 width, strongly tapering in width distally, with numerous short simple setae laterally, with one somewhat longer simple seta distally. Endopodite length 2.1 width, with three long plumose setae distally, distal margin strongly rounded. Urp ( Fig. 23I ), biramous, length 0.3 Plt length, not projecting beyond Plt posterior margin. Protopodite length 1.7 width, with one simple seta distally (broken off). Exopodite length 3.0 width, with two simple setae terminally. Endopodite length 5.8 exopodite length, length 6.0 width, with six setae (three broom setae, three simple of varying length) terminally.

Remarks: The new species is characterized by a slender body, robust spines on the anterolateral tergites of pereonite 2, biramous uropods and a ventral opercular spine, and thus most closely resembles N. hilario , N. menziesi , N. meteori , N. pedro and N. perunis . Nannoniscus brenkei is most similar to N. hilario , but can be differentiated from the latter as follows: molar process of left and right mandible with ≤ five spines distally (vs. ≥ nine spines in N. hilario ); Op distal margin with ≥ 14 simple setae (vs. ≤ nine). Nannoniscus brenkei also resembles N. meteori , but differs from the latter as follows: Mxp lateral margin with numerous small simple setae (vs. setae lacking in N. meteori ); Urp endopodite length 5.8 exopodite length (vs. 3.9). The new species can be differentiated from N. menziesi by the following characters: Mxp lateral margin with numerous small simple setae (vs. setae lacking in N. menziesi ); molar process of left and right mandible with ≤ 5 spines distally (vs. ≥ 12). Nannoniscus brenkei can be distinguished from N. pedro as follows: Md incisor teeth rounded (vs. acute in N. pedro ); Mxp lateral margin with numerous small simple setae (vs. setae lacking); Urp endopodite length ≥ 5.8 exopodite length (vs. ≤ 3.2). Finally, the new species differs from N. perunis by the following features: body length ≥ 5.0 pereonite 1 width (vs. ≤ 4.7 in N. perunis ); Urp endopodite length 5.8 exopodite length (vs. 7.8); pereonites 3–4 tergites each with an anterolateral seta (vs. setae lacking) (see also the identification key, Table 4).

Figures

Figure 23. Nannoniscus brenkei, (A) holotype female (ZMH K-55370, NB12_Iso070), (B–I) paratype female (ZMH K-55369, Na03): (A) habitus, dorsal view; (B) AI, AII peduncular articles 1–4; (C) lMd, details: incisor, lacinia mobilis and spine row; (D) rMd, details: Md palp, spine row spines 1–4; (E) Mxp; (F) PI; (G) Op; (H) PlpIII; (I) Urp. Scale bars: A = 200 µm; B–I = 100 µm.