Microcope denticulata, Malyutina, Marina V., 2008

Malyutina, Marina V., 2008, Microcope gen. nov. — a new deep-sea genus of Munnopsidae (Crustacea, Isopoda, Asellota), with description of two new species from the Southern Hemisphere, Zootaxa 1866, pp. 555-574 : 558-567

Microcope denticulata sp. nov. ( Figs. 1–6 )

Material examined

Holotype, female (1.8 mm), ( ZMH K- 41423), ANDEEP III St. 21–7–S, 29 January 2005, 47°39.87’- 38.52’ S 04°15.79’ -14.94’ W, 4574 m.

Paratype, preparatory female (2.2 mm), same data as holotype ( ZMH K- 41424), dissected for description.

Additional material: female with 8 eggs (2.2 mm), ( ZMH K- 41425), DIVA 2 St. 41–2–E, 28°3.98’S, 07°20.49’E, 5054 m.

Etymology. Denticulata refers to the serrulated anterior margins of pereonites 1–4.

Description. Body ( Fig. 1 ) length 1.7–1.9 width of pereonite 5, body height 0.35 of body length. Head length 2 times width, antennulae inserted with narrow gap between, clypeus 1.8 as wide and as long as labrum. Pereonite 1 1.3 as wide as head, anterior transparent flange overhanging head and basal part of antennae, pereonite 2 longest, slightly longer than pereonite 1, pereonite 3 slightly shorter than pereonite 1, TABLE 1. Distribution of some characters in selected munnopsids genera.

Pereonites 1 and 2 in longer subequal subequal subequal longer subequal subequal or

comparison to 3 and 4 longer

Pereonites 2-4 lateral sinuate straight straight straight sinuate straight straight

margin

pereonite 4 shortest, length about half of pereonite 1; anterolateral margin of pereonites 1–4 serrated; pereonites 2–4 anterolateral projections distinctly protrude in dorsal view, distal stout seta long; coxae anterior lobe acute, equal in size to anterolateral projections of pereonite, lateral margin of coxa with 3 setae. Natasome length 0.75 body length, width 2.1 head width; pereonite 5 lateral length 1.5 lateral length of pereonites 6 and 7 together; pereonite 7 lateral length 0.1 pereonite 5 length. Pleotelson length 0.7 width, 0.3 body length, pleopodal cavity width 0.4 of pleotelson width, cavity length 0.6 pleotelson length.

Antennula ( Fig. 2 ) one third of body length; article 1 as long as wide, with 4 whip medial, 3 short stout lateral setae, and 1 dorsal broom seta, distomedial lobe with 3 distal stout setae; article 2 length 0.3 of article 1, with 2 distal broom and 1 stout setae; article 3 length 1.3 of article 2, with long whip seta; flagellum of 8–10 articles, article 4 length 0.2 article 3 length, with distal broom seta, following articles shorter than article 3, with 2 small distal setae each, last three articles with aesthetasc.

Antenna incomplete on all specimens ( Fig. 2 ): articles 1–3 subequal in size, with row of stout ventrodistal setae, scale on article 3 narrow in dorsal view and broad triangular in lateral view, with 4 distal setae; article 4 smaller than preceding articles.

Mandible ( Fig. 2 ) pars incisiva with 5 cusps; lacinia mobilis of left mandible slender, length 0.8 length of pars incisiva, with 4 teeth; spine row with 3 and 4 spines on left and right mandibles respectively; condyle length 0.4 molar process length; palp as long as mandibular body, article 1 with 2 long distal setae, article 2 twice as long as article 1, with 5 slender medial and 2 stout distal setae, article 3 with row of slender distal setae. Maxilla 1 ( Fig. 3 ) lateral endite width 1.2 mesial endite width, almost all 12 distal spine-like setae denticulate, 2 longest distolateral setae slightly longer than endite width. Maxilla 2 ( Fig. 3 ) middle endite shortest, lateral endites longest, with 2 long and 2 short distal setae each; mesial endite as wide as middle and lateral endites together, with 10 comb-like and numerous distal setae. Maxilliped ( Fig. 3 ) basis length 2.5 width, endite with 3 coupling hooks, distal margin serrated, with 5 stiff setae and numerous simple slender setae; palp article 2 lateral margin straight, length 1.5 length of medial margin, medial margin with 3 long whip setae; article 3 medial margin dentate, with whip setae, medial length equal to lateral length of article 2; articles 3–5 subequal in length laterally, medial lobe of article 4 almost as long as article 5, convergent, with broad basis, with 4 long distal setae; article 5 with 5 long setae. Epipod length 3 times width and as long as basis.

Pereopods 1–4 ( Fig. 4 ): pereopod 1 length 0.5 body length, length ratios of ischium–dactylus to basis: 0.5, 0.2, 0.6, 0.7, 0.2; basis length 4.7 width, with sparse simple setae; ischium length 3.1 width, with 4 stout distodorsal setae and 3 ventral setae; merus length 1.4 width, with 2 distoventral setae; carpus length 6.3 width, with 4 dorsal and 5 ventral setae; propodus length 8.2 width, with 4 dorsal and 7 ventral setae; claw length 0.35 dactylus length. Pereopod 2 length 1.2 pereopod 1 length, length ratios of ischium–dactylus to basis: 0.6, 0.2, 0.9, 0.7, 0.5; basis length 3.9 width, with 4 distoventral setae, 4 short stout ventral setae and 8 dorsal setae; ischium length 2.6 width, with 4 stout distodorsal setae and 3 stout ventral setae; merus length 1.3 width, with 4 distal setae; carpus length 7.2 width, with 5 ventral and 2 dorsal setae; propodus length 8.7 width, with 1 ventral and 5 distal setae; dactylus length 11.2 width, claw length 0.1 dactylus length. Pereopod 3 length 1.6 pereopod 1 length, length ratios of ischium–dactylus to basis: 0.75, 0.3, 1.3, 1.0, 0.6; basis length 3.4 width, with 3 distoventral setae, 3 short stout ventral setae, 5 dorsal setae; ischium length 2.6 width, with 2 dorsal, 5 stout distodorsal setae and 3 stout ventral setae; merus length 1.5 width, with 2 ventral and 2 distodorsal setae; carpus length 10.8 width, with 9 ventral, 2 dorsal and 4 distal setae; propodus length 20 times width, with 6 ventral, 2 dorsal and 2 distal setae; dactylus length 15.5 width, claw length 0.15 dactylus length. Pereopod 4 not complete, length ratios of ischium–merus to basis: 0.9, 0.3; basis length 2.8 width, with 3 distoventral setae, 4 short simple and 2 broom dorsal setae; ischium length 3.1 width, with 1 dorsal, 4 stout distodorsal setae and 7 stout ventral setae; merus length 1.6 width, with 2 distal setae.

Pereopods 5–7 ( Fig. 5 ): Pereopod 5 length 1.1 pereopod 1 length, length ratios of ischium–dactylus to basis: 1.5, 0.5, 2.1, 1.5, 1.5; basis length 1.2 width, with row of 11 ventral setae; ischium length 2.4 width, with 5 ventral and 7 stout dorsal setae; merus as long as wide, with 2 distal setae; carpus length 2.8 width, with 13 ventral and 17 dorsal setae; propodus length 3.2 width with 10 ventral and 13 dorsal setae; dactylus length 10.3 width, claw length 0.1 dactylus length. Pereopod 6 length 1.1 pereopod 5 length, length ratios of ischium–dactylus to basis: 1.6, 0.6, 2.1, 1.5, 1.4; basis length 1.2 width, with 6 ventral setae; ischium length 3 times width, with 3 stout distal setae; merus length 1.6 width; carpus length 2.8 width, with 15 ventral and 17 dorsal setae; propodus and dactylus similar in shape to those of pereopod 5, but slightly longer. Pereopod 7 length 0.95 pereopod 5 length, length ratios of ischium–dactylus to basis: 1, 0.3, 1.3, 1.1, 0.9; basis length 2.6 width, with 6 ventral setae; ischium length 2.8 width, with 2 stout distoventral setae; merus with 2 distal setae; carpus length 2.3 width, with 12 ventral and 16 dorsal setae; propodus length 3.6 width, dactylus as in pereopods 5 and 6. Carpus/propodus length ratios: 1.4, 1.4, 1.1 for pereopods 5–7 respectively; carpus/propodus width ratios: 1.5, 1.6, 1.8 for pereopods 5–7 respectively.

Pleopods ( Fig. 6 ): Female pleopod 2 length 1.3 width, distal margin width 0.7 proximal edge width. Pleopod 3 endopod length 4.8 width of proximal half and 2.5 width of distal half, distal plumose setae as long as endopod together with protopod; exopod 1.3 length and as wide as endopod, basal article with 18 lateral plumose setae and thin setulae basally, distal article separated, length 0.3 basal article length. Pleopod 4 endopod length 1.5 width, exopod length 0.9 endopod length, distal plumose seta as long as exopod. Pleopod 5 length 1.4 width.

Uropod ( Fig. 6 ) 0.2 pleotelson length. Protopod length 2.6 width, medial extension after endopod insertion 0.4 of protopod length; endopod length 0.8 protopod length, with 2 lateral simple setae, 2 stout, 1 broom and 3 simple distal setae; exopod 0.6 of endopod length and width, with 2 stout, 1 broom and 3 simple distal setae.

Male unknown.

Remarks. M. denticulata sp. nov. differs from the two other known species of the genus by serrated anterior margin of pereonites 1–4, more prominent anterolateral projections of pereonites 2–4 and larger and more acute coxae of pereopods 1–4. The characters distinguishing the new species from the most similar M. levissima sp. nov. are discussed after the description of the latter. 14

Distribution. The species is only known from the Cape Basin, between 4574 and 5054 m depth.

Figures

FIGURE 1. Microcope denticulata sp. nov., holotype female, ZMH K- 41423: A, body dorsal view; B, body ventral view; C, body lateral view; paratype female, ZMH K- 41424: D, body dorsal view; E, body lateral view; Additional material from DIVA 2, female, ZMH K- 41425: F, body dorsal view; G, body lateral view; H, lateral margin of ambulosome, ventral view. Scale bar 1 mm.

FIGURE 2. Microcope denticulata sp. nov., female, paratype, ZMH K- 41424: right antennula, dorsal view, antenna 2 dorsal (d) and lateral (l) views and mandibles: dorsal (d), medial (m) and lateral (l) views. Scale bar 0.1 mm.

FIGURE 3. Microcope denticulata sp. nov., female, paratype, ZMH K- 41424: maxillae and maxilliped, ventral view. Scale bar 0.1 mm.

FIGURE 4. Microcope denticulata sp. nov., female, paratype, ZMH K- 41424: pereopods 1 – 4. Scale bar 0.5 mm.

FIGURE 5. Microcope denticulata sp. nov., female, paratype, ZMH K- 41424: pereopods 5 – 7. Scale bar 0.5 mm.

FIGURE 6. Microcope denticulata sp. nov., female, paratype, ZMH K- 41424, pleopods 2 – 5, pleotelson, ventral view (A) and uropod. Scale bar 0.1 mm