Makrokylindrus (M.) abyssalis, Mühlenhardt-Siegel, Ute, 2014

Mühlenhardt-Siegel, Ute, 2014, Deep-sea Bodotriidae, Diastylidae and Pseudocumatidae (Cumacea, Crustacea) from the southeastern Atlantic, Zootaxa 3815 (3), pp. 301-341 : 323-325

Makrokylindrus (M.) abyssalis sp. n.

( Figures 17–19 )

Holotype ovigerous female, ZMH: K 43922 .

Type locality: E Atlantic, Guinea Basin, 0° 13,27' S 2° 29,91' W, 5054 m depth, DIVA II, EBS #64. paratype ovigerous female (dissected), type locality, ZMH K 43923 ;

Etymology. The new species is named after its environment, the abyssal plains

Diagnosis. Carapace with numerous small teeth, the largest ones at frontal lobe; no teeth at pseudorostral lobes; Maxilliped 3 has strong teeth along the inner margins and a swelling at the distal inner margin, outer distal prolongation is beset with six long pappose setae; pereiopod 2 with merus longer than carpus; telson longer than uropod peduncle and praeanal part of telson shorter than uropod peduncle, postanal part of telson with five pairs of lateral cuspidate setae.

Description. Holotype ovigerous female (ZMH: K 43922 ), 10.7 mm long ( Fig. 17 ).

Carapace with numerous small teeth, the largest ones at frontal lobe, highest elevation in posterior region of carapace, 1.6 times as long as free thoracic segments; pseudorostral lobes meeting in front of ocular lobe; siphonal tube not protruding; ocular lobe reduced; no eye lenses.

Antennal notch not discernable; anterolateral tooth missing; anteroventral margin of carapace with large teeth, smaller in ventral part.

Integument calcified.

Five free thoracic segments visible, the first shortest.

Pleon longer than carapace and free thoracic segments combined.

Telsonic segment (pleonite 6) slightly shorter than uropod peduncle, 1.2 times longer than wide.

Telson 1.1 times longer than peduncle, with two stout terminal setae; postanal part with five lateral setae, one third of the length of preanal part.

Paratype ovigerous female (ZMH K 43923 ). Antenna 1 ( Fig. 18 , A1): relative length of peduncle articles 1 to 3: 37/37/26; article 1 with a long tooth, a long pappose seta and numerous short hair-like setae along margins; article 2 with a pappose seta and seven simple setae, three composed setae (slightly damaged) at distal margin; article 3 with two simple setae; tri-articulated accessory flagellum longer than basal article of main flagellum, with three simple setae terminally; main flagellum tetra-segmented, with one aesthetasc, one long, and two short simple setae.

Maxilliped 1 ( Fig. 18 , Mxp1): B/R ratio 0.8, relative length of articles I to D: 0/23/ 38/29/10; ischiobasis and merus with a pappose seta each; carpus with three comb-like setae along inner margin, one long and seven short pappose setae; propodus with a long pappose and a short hand-like seta; dactylus with a long terminal and a short sub terminal simple seta.

Maxilliped 2 ( Fig. 18 , Mxp2): B/R ratio not given, basis broken, relative length of articles I to D: 5/22/32 /26/14; basis damaged in basal part, distally with four pappose setae; merus with one pappose seta; carpus with six pappose setae; propodus with a broken and four pappose setae; dactylus with a terminal and a sub terminal simple seta.

Maxilliped 3 ( Fig. 18 , Mxp3): B/R ratio 1.2, relative length of articles I to D: 11/13/25 /28/23; basis dilated distally, with six teeth, seven pappose setae and fringes of hair-like setae along margins; ischium with two teeth and a pappose seta; merus with one tooth and three pappose setae; carpus with two simple and three pappose setae; propodus with one simple and two pappose setae; dactylus with one terminal and two sub terminal simple setae; exopod present (not figured).

Pereiopod 1 broken off, not figured.

Pereiopod 2 ( Fig. 18 , P2): B/R ratio 0.6, relative length of articles I to D: 5/34/18 /9/34; basis with 11 teeth, two simple and two pappose setae; ischium with one tooth; long merus with 14 teeth and one pappose seta; carpus with five teeth and three stout simple setae; slender dactylus tapering, with seven simple setae; exopod long and slender.

Pereiopod 3: broken off in paratype, not figured; with rudimentary exopod in holotype.

Pereiopod 4 ( Fig. 19 , P4): B/R ratio not given, basis damaged, relative length of articles I to D: 9/ 48/23/11 /10; basis with three pappose setae; merus long, with three simple setae; carpus with three simple and four terminally annulated setae; propodus with one terminally annulated seta; dactylus with a simple seta terminally and sub terminally, a hair-like seta half way laterally.

Pereiopod 5 ( Fig. 19 , P5): B/R ratio not given, basis damaged, relative length of articles I to D: 8/33/ 35/13/10; basis slightly damaged; merus with two simple setae; carpus with two simple, one broken, and three terminally annulated setae.

Uropods ( Fig. 19 , U), peduncle only 1.1 times longer than pleonite 6; exopod shorter than endopod, reaching well beyond articulation between article 2 and 3 of endopod; endopod tri-articulated, basal article with seven cuspidate setae along inner margin, much longer than the two distal articles combined; second article with three cuspidate setae, third article with two cuspidate setae and a long terminal seta; all three endopod articles and the distal exopod article beset with fringes of short, hair-like setae.

Distribution. Guinea Basin, 5054 m depth.

Remarks. The new species has many spines or teeth on the carapace and a strong tooth at article 1 of the first antenna. In this respect it is similar to the subadult female of M. (M.) tuberculosus Mühlenhardt-Siegel, 2005e from the Angola Basin. However, there are several strong differences between these two species: maxilliped 3 has strong teeth along the margins and a swelling at the distal inner margin, the outer distal prolongation is beset with six long pappose setae (vs. one tooth at distal inner margin and no swelling, outer distal prolongation with three pappose setae in M. tuberculosus ); pereiopod 2 with merus longer than carpus (vs. merus shorter than carpus); pereiopod 4 with merus longer than carpus (vs. shorter than carpus); no teeth at the pseudorostral lobes (vs. a pair of teeth distally at the pseudorostral lobes); telson is longer than the uropod peduncle and the preanal part of the telson is shorter than the uropod peduncle (vs. telson and praeanal part of the telson longer than uropod peduncle); postanal part of the telson has five pairs of lateral cuspidate setae (vs. only 1 pair of lateral setae).

The new species differs from M. (M.) meteorae and M. (M.) reyssii B ӑcescu, 1972, the only species in the subgenus with the merus longer than the carpus in at least pereiopod 2, in the following characters: The pseudorostrum is shorter in the new species and M. meteorae than in M. reyssii ; the telson is longer than the uropod peduncle in the new species and M. meteorae (vs. shorter in M. reyssii ); the preanal part of the telson is 2.8 times as long as the postanal part in the new species (vs. 5 times in M. reyssii and 3.4–3.8 times in M. meteorae ); the number of lateral setae at the postanal part of the telson is five pairs in the new species (vs. four pairs in M. reyssii and two pairs in M. meteorae ); there is no pair of teeth on the pseudorostrum in the new species and M. reyssii (vs. a pair of teeth on the pseudorostrum in M. meteorae ); there are teeth along the basis to carpus of pereiopod 2 in the new species (vs. teeth only at basis in M. reyssi and teeth at basis and one tooth at merus in M. meteorae ).

Figures

FIGURE 17. Makrokylindrus (M.) abyssalis sp. n.: ovigerous female; habitus from lateral, scale bar: 2 mm.

FIGURE 18. Makrokylindrus (M.) abyssalis sp. n., female; A 1: antenna 1; Mxp 1: maxilliped 1; setae in detail (scale bar: 0.1 mm); Mxp 2: maxilliped 2; Mxp 3: maxilliped 3, scale bar: 0.5 mm; P 2: pereiopod 2; scale bars (if not other indicated): 0.5 mm.

FIGURE 19. Makrokylindrus (M.) abyssalis sp. n., female; P 4: pereiopod 4; P 5: pereiopod 5; U: pleonite 6, telson and uropods; scale bars: 0.5 mm.