Makrokylindrus
Creators: name: Mühlenhardt-Siegel, Ute
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Cumacea
Diastylidae
Makrokylindrus

description: Makrokylindrus (A.) sp. 1
(Figures 20–22)
Material. 1 manca, locality: SE Atlantic, Angola Basin, 05°47.532' S 09°42.655' E, 3147 m depth, BIOZAIRE 3, KGS #79. MNHN-IU-2012-1355.
Description. Manca, 7.6 mm long (MNHN-IU-2012-1355; Fig. 20).
Carapace smooth, without armature like tubercles, spines or teeth; pseudorostral lobes 0.3 times as long as rest of carapace; siphonal tube not protruding; ocular lobe roundish; no eye lenses.
Antennal notch missing; anterolateral angle missing; anteroventral margin of carapace appears smooth, may be due to long storage time in formalin.
Integument strongly decalcified due to fixation and long conservation in formalin.
Five free thoracic segments visible, the first shortest.
Pleon excluding telson slightly shorter than carapace and free thoracic segments combined.
Telsonic segment shorter than wide.
Telson cylindrical, 0.8 times as long as pleon, clearly longer than uropod peduncle, reaching beyond the end of uropod endopod, praeanal part with small teeth along the margin, minute postanal part not projecting beyond the anal valves, without lateral setae, two tiny setae terminally.
Antenna 1 (Fig. 21, A1): relative length of peduncle articles 1 to 3: 41/30/29; article 1 with fringe of hair-like setae along outer margin, a simple and a pappose seta; article 2 with four simple setae; article 3 with a simple seta; accessory flagellum bi-articulated, half as long as basal article of main flagellum; main flagellum tri-articulated, with one aethetasc and a simple seta.
Maxilliped 3 (Fig. 21, Mxp3): B/R ratio not given because basis damaged during dissection, relative length of articles I to D: 10/20/24 /25/21; basis with at least one short and three long and a short teeth, two pappose setae and fringes of hair-like setae along margins; merus with one pappose seta, carpus with four pappose setae and a long tooth; propodus with one pappose seta; dactylus with six simple setae; exopod broken off during dissection, not figured.
FIGURE 21. Makrokylindrus (A.) sp. 1, manca; A1: antenna 1; Mxp3: maxilliped 3; P1: pereiopod 1; P2: pereiopod 2; scale bars: 0.1 mm.
Pereiopod 1 (Fig. 21, P1): B/R ratio not given because basis damaged during dissection, relative length of articles I to D: 5/ 12/35/31 /17; basis with a simple and six pappose setae, a fringe of hair-like setae along inner margin and one tooth; merus and carpus each with a pappose and two simple setae; propodus with three simple setae; dactylus with six simple setae; exopod broken off during dissection, not figured.
Pereiopod 2 (Fig. 21, P2): B/R ratio 0.5, relative length of articles I to D: 5/ 13/41/11 /30; basis with a tooth; ischium with a simple seta; merus with four simple setae; carpus with two teeth and two simple setae; propodus with a simple seta; dactylus with four simple setae; exopod present.
Pereiopod 3 (Fig. 22, P3): long and slender, B/R ratio 1.0, relative length of articles I to D: 11/34/ 35/7/13; basis with seven teeth and a pappose seta; ischium with a simple seta; merus with four teeth, a simple and a pappose seta; carpus with two terminally annulated setae; propodus with a terminally annulated seta; dactylus with a long terminal and two shorter simple setae; rudimentary exopod present.
Pereiopod 4 (Fig. 22, P4): long and slender, B/R ratio not given because basis damaged during dissection, relative length of articles I to D: 9/33/ 36/9/13; basis with eight teeth and two pappose setae; ischium with a broken seta; merus with five teeth and a broken seta; carpus with two terminally annulated setae; propodus with one terminally annulated seta; dactylus with a long simple seta terminally and two short simple setae; rudimentary exopod present
Pereiopod 5: not yet developed.
Uropod (Fig. 22, U): peduncle shorter than telson, with small teeth along the margins; exopod 1.2 times longer than endopod, with long terminal seta; endopod tri-articulated, basal article longer than the two distal articles combined, with two slender setae at inner margin, article 3 with a slender seta terminally and sub terminally.
Distribution. Angola Basin, 3147 m depth.
Remarks. Makrokylindrus (A.) sp. is unfortunately represented only by a manca stage as the fifth pair of pereiopods are missing. The telson is clearly longer than the uropod peduncle with a tiny postanal part like in M. fagei B ӑcescu, 1962 (off Madagascar) and M. tubulicauda (Calman, 1905) (northern Atlantic).
In the present specimen the telson reaches beyond the end of the uropod endopod. However, the telson is longer than the uropod endopod in the specimen described by Calman (1905), which seems also to be a manca due to the small size (5.4 mm) and the lack of pereiopod 5, but shorter than the uropod endopod in the adult specimen (15 mm long) figured by Fage (1929).
B ӑcescu (1962) placed his new species M. fagei close to M. tubulicauda with respect to the telson characters and proposed the spinulose surface as the most striking character to divide the two species. Additionally, the basis of pereiopod 3 is longer than the rest of the extremity in M. fagei (male), whereas in M. tubulicauda the basis of pereiopod 4 is shorter than the rest of the extremity as figured in Fage (1929). Unfortunately, pereiopod 4 is not figured in B ӑcescu (1962). However, he stated the extremities in his species to be shorter and stouter than in M. tubulicauda, maybe due to the fact that the description of M. fagei is based on a male.
As the present manca does not show a single trace of spines, neither at the carapace surface nor at its ventral margin, and as the few spines or teeth at the extremities and the telson are very tiny, it likely that this manca belongs to a new species; however, due to the young stage of the single specimen, it has to remain in open nomenclature. Nevertheless, it is closely related to M. tubulicauda and M. fagei.
description: Published as part of Mühlenhardt-Siegel, Ute, 2014, Deep-sea Bodotriidae, Diastylidae and Pseudocumatidae (Cumacea, Crustacea) from the southeastern Atlantic, pp. 301-341 in Zootaxa 3815 (3) on pages 328-332, DOI: 10.11646/zootaxa.3815.3.1, http://zenodo.org/record/227328