Paranarthrura angolensis, Guerrero-Kommritz, Jürgen, Schmidt, Anja & Brandt, Angelika, 2002

Guerrero-Kommritz, Jürgen, Schmidt, Anja & Brandt, Angelika, 2002, Paranarthrura Hansen, 1913 (Crustacea: Tanaidacea) from the Angola Basin, description of Paranarthrura angolensis n. sp., Zootaxa 116, pp. 1-12 : 3-11

Paranarthrura angolensis n. sp. ( Figs. 1­3 )

Holotype: one female of 2.96 mm length, ZMH K­ 40073, DIVA M­48 Stn 345 (KG2 16°16.98´S 5°27.00´E; 5434 m).

Paratypes. 12 males of 1.51 ­ 2.57 mm; 20 females of 1.27 ­2.98 mm and nine mancas of 0.96 – 1.27 mm length.

ZMH K­ 40074 five females: 2.84 mm; 2.96 mm; 2.96 mm; 2.98 mm, 1.27 mm one manca: 1.12 mm; DIVA M­48 Stn 348 (EBS; 16° 18.10´S 5°27.20´E ­ 16°19.30´S 5°27.20`E; 5380 m).

ZMH K­40075 one female: 2.78 mm DIVA M­48 Stn 345 (KG4; 16°16.98´S 5°27.12´E; 5434 m).

ZMH K­40076, two females: 2.12 mm; 1.93 mm; one male: 2.00 mm DIVA M­48 Stn 340 (EBS; 18°18.30´S 4° 41.30´E ­ 18° 19.40´S 4° 41.90´E; 5395 m).

ZMH K­40077, one male: 1.75 mm DIVA M­48 Stn 341 (KG6; 17°07.96´S 4°41.99´E; 5465 m).

ZMH K­40078 two males: 1.51 mm; 1.63 mm, one female: 2.48 mm DIVA M­48 Stn 341 (KG8; 17°08.06´S 4°41.90´E; 5464 m).

ZMH K­40079 one male: 2.57 mm DIVA M­48 Stn 345 (KG3; 16°16.99´S 5°25.06´E; 5433 m).

ZMH K­40080 two males: 2.18 mm; 2.12 mm; two females: 1.90 mm; 2.03 mm; two mancas: 0.96 mm; 1.27 mm DIVA M­48 Stn 336 (KG1; 18°16.60´S 4°44.36´E; 5437 m).

ZMH K­40081 one male: 2.15 mm DIVA M­48 Stn 350 (EBS; 16°14.30´S 5°26.80´E; 16°14.90´S 5°26.70`E; 5389 m).

MCZ 16714 one manca: 1.06 mm, Atlantis II cruise 42 Stn. 190 (AD; Walvis Bay 23°5´S 12°45´W, 979 m).

MCZ 16723 eight females: 1.54 mm; 2.18 mm; 2.09 mm; 1.69 mm; 2.24 mm; 2.09 mm; 2.06 mm; 1.72 mm; four males: 2.03 mm; 1.57 mm; 1.93 mm; 1.93 mm; five mancas: 1.24 mm; 0.96 mm; 1.21 mm; 1.21 mm; 1.18 mm; Atlantis II cruise 42 Stn. 190 (AD; Walvis Bay 23°5´S 12°45´W, 979 m).

MCZ 16732 one female: 2.06 mm, Atlantis II cruise 42 St 187 (AD; Walvis Bay 22°58´S 13°1´W, 631 m).

Diagnosis

Cephalothorax as long as pereonites 1 and 2 together. Pleotelson triangular in shape, caudal apex pointed. Inner margin of labium rounded. Pereopod 5 longer than pereopod 4. Uropod endopod of two articles with three setose terminal seta, First article 1.2 times longer than second.

Description

Non ovigerous females: Body ( Fig. 1A, 1 B) elongated, cylindrical, 6.7 times longer than broad, length 1.27 – 2.98 mm. Cuticula heavy sclerotised and covered with very fine setules (see detail in Fig. 1 B). Cephalothorax ( Fig. 1A, 1 B, ventral view Fig. 1 E) about as long as pereonite 1 and 2 together, 0.2 of body length, 1.3 times longer than broad.

Pereon ( Fig. 1A ) about 0.6 of body length, six free pereonites. Last pereonite shortest, pereonites 2, 4, and 5 longest pereonites and equally long. Pereonite 3 only slightly shorter than pereonite 2. Pereonite 1 broadest. Pereopod shoulders (see dorsal view in Fig. 1 B) well developed. Hyposphenian frequently present.

Pleon ( Fig. 1A, 1 B) short, about 0.05 of body length, composed of five free pleonites, narrower than pereon and pleotelson, as long as pereonite 5, pleopods absent. Pleonite 1 longest, pleonites 2, 3, 4 and 5 subequal in length. Pleotelson as long as preceding three pleonites together, apex triangular.

Antennula ( Fig. 1 F, 1G) long, about 0.2 body length, and 0.8 cephalothorax length, with four articles, first article longest with three simple and one distally setose seta. Second article as long as fourth, and as broad as first, 0.6 of length of first, with three distolateral seta, two simple seta of different length and 1 distally setose seta. Third article shortest, slightly narrower than second, with two long simple seta and one short setose seta. Fourth article with five terminal, long and one simple short seta and one aesthetasc.

Antenna ( Fig. 1 H, 1I) 0.6 of length of antennula, composed of six articles, first article reduced and fused with cephalothorax. Article 2 rectangular, shorter than article 5, with one distolateral simple seta. Article 3 without seta, 0.5 times as long article 2. Article 4 longest, longer than 2 and 3 together, with three simple subterminal seta (one not illustrated). Article 5 slightly larger than 2, with one terminal simple seta. Article 6 shortest, with 5 simple terminal seta of various lengths.

Labrum ( Fig. 2 B) stout, with fine marginal setules, without special ornamentation.

Mandible ( Fig. 2 A) molar process week (reduced), minute.

Maxillula ( Fig. 2 D) endite with ten distinct simple, smooth thick seta, one of these very slender, palp with two long simple seta, one of these as long as palp article.

Maxilla ( Fig. 2 C) triangular, twice as broad as long.

Labium ( Fig. 2 G) pointed, medially with short setules and a weak spinelike process on the outer margin.

Maxilliped ( Fig. 2 F) endite basally fused, endites slightly shorter than basis, reaching midpoint of second palp article, with two distal short seta. Palp 0.9 length of basis and endites, consisting of four articles. First article longest and broadest, roughly rectangular, without seta, naked; second article 0.6 length of article 1, with three simple and one setose seta; third article about as long as first, with four strong simple seta; last article almost as long as second, with five distal setulated seta, and one medioventral simple seta, medially with a row of fine setules.

Epignath ( Fig. 2 E) falciform.

Cheliped ( Fig. 3 A) basis fused to cephalothorax; without seta and with a fine subdivision; merus of triangular shape, with one small simple seta; carpus longest article, twice as long as broad, with two ventral and one dorsal simple seta; chela well developed, twice as long as broad, with a dorsal keel, two seta near incisive process of propodus, one ventral seta; propodus roughly twice as long as dactylus.

Pereopod 1 ( Fig. 3 B) coxa with one seta; basis without seta; ischium 0.1 of basis length, no seta; merus 0.3 length of basis, one distodorsal simple seta; carpus 0.5 length of basis, with one distodorsal simple seta and a strong ventral setose seta; propodus (twisted in Fig. 3 B) 0.6 length of basis, with two distal simple seta and two rows of ventral short setules; dactylus 0.2 length of basis; unguis with rounded tip, 1.5 times dactylar article length.

Pereopod 2 ( Fig. 3 C) coxa with one seta; basis without seta; ischium 0.07 of basis length, with one simple seta; merus 0.3 length of basis, with two distodorsal simple seta; carpus 0.5 length of basis, with one distodorsal strong setulate seta and two ventral seta, one strong, and setulate, the other simple and shorter; propodus 0.6 length of basis, with one distoventral simple seta and a row of ventral short setules, dorsal margin with 3 minute spines; dactylus 0.2 of length of basis; unguis with rounded tip, 1.5 times as long as dactylar article.

Pereopod 3 ( Fig. 3 D) coxa with one seta; basis without seta; ischium 0.1 basis length, without seta; merus 0.3 length of basis, with two ventral simple seta; carpus 0.5 length of basis, with one distodorsal simple strong seta and two ventral seta, one setulate, and strong, the other one simple and shorter; propodus 0.5 length of basis, with one distoventral simple seta and a row of ventral short setules; dactylus 0.2 of length of basis; unguis with rounded tip, 1.4 times as long as dactylar article.

Pereopod 4 ( Fig. 3 E) coxa with one seta; basis without seta; ischium 0.07 basis length, with one simple seta; merus 0.3 length of basis, with one short seta; carpus less than half as long as basis, with three distoventral strong seta; propodus 0.7 length of basis, with one distoventral simple seta, and one minute distal spine; dactylus 0.3 length of basis; unguis with rounded tip, as long as dactylar article.

Pereopod 5 ( Fig. 3 F) coxa with one seta; basis without seta; ischium 0.07 basis length, with one seta; merus 0.3 length of basis, with two distoventral short seta, one setose, one simple; carpus less than half as long as basis, with three setulate seta, two distoventral and one dorsal; propodus with four seta, two long, one short dorsally and one long setose ventrally, three minute spines on dorsal surface. Dactylus about 0.25 of basis length, ungius as long as dactylus and pointed.

Pereopod 6 ( Fig 3 G) very similar to pereopod 5, but merus with two strong setose seta.

Pleopods in female absent.

Uropods ( Fig. 1 J) basis with lateral projection being as long as medial margin of article, with one terminal setose seta. Exopodite reduced. Endopodite composed of two articles; first article 1.3 times longer than second and twice as long as wide with a simple distal seta. Last article twice as long as wide, with three long terminal setose seta and two simple short seta.

Ovigerous female: Similar to non­ovigerous females, pereon slightly more compressed dorsoventrally. Oostegites lamelliform, present on pereonites 1 to 4. Body length 2.18 mm.

Males: ( Fig. 1 C, 1D, 1K) Similar to non­ovigerous female, but pleon well developed, as wide as pleotelson and pereon, pleopods present. Hyposphenian frequently present.

Body length 1.51 – 2.57 mm.

Mancas I: Similar to non­ovigerous females but much smaller. Pereonite 6 is not developed and resembles a pleonite. Hyposphenian frequently present. Body length 0.96 – 1.21 mm.

Mancas II: Similar to non­ovigerous females but smaller. Pereonite 6 is well developed with rudiments of pereopods. Hyposphenian frequently present. Body length 1.18 ­ 1.27 mm.

Type locality: Angola Basin.

Etymology: This species in named after the Angola Basin were the material was sampled.

Remarks

The occurrence of hyposphenian, ventral thornlike projections, is not uniform. Hyposphenian are common in most specimens (31 of 42 specimens). They are present in manca I, manca II, males and females but absent in ovigerous females. They always are directed downwards. Most of the animals of deep water presents hyposphenians on all their pereonites. Males from shallower waters presents hyposphenian only on pereonites 1 to 3, males from deeper water present hyphosbaenian on all 6 pereonites. Not ovigerous adult females on all 6 pereonites. Some mancas have hyposphenian and other lack all of them, this character is highly variable.

In the revision of the genus Paranarthrura by Bird & Holdich (1989), nine species are reported for the Atlantic Ocean most of them from the North Atlantic. Paranarthrura angolensis will be the second species reported for the South Atlantic. The other species P. fortispina is reported from Subantarctic and Antarctic waters.

There are five species of Paranarthrura that resembles the new species, one from the Indian Ocean P. bacescui Kudinova­Pasternak, 1986 and other four from the Atlantic Ocean, P. c r a s s a, P. fortispina , P. insignis and P. lusitanus (see table 2). Paranarthrura bacescui differs from P. angolensis in the shape of the mandible, the cutting edge is broader and the molar process is more developed. The antennule has a different setation, the basis is more slender and has no seta on the middle part of it. The labium of P. bacescui has a central groove that is not present in P. angolensis .

Species Location Depth (m)

Paranarthrura borealis Bird & Holdich 1989 Northeast 903­1600

Paranarthrura crassa Bird & Holdich, 1989 Northeast 463­1739

Paranarthrura fortispina Sieg, 1986 Subantarctic 423­1729

Paranarthrura insignis Hansen, 1913 Northeast 582­5000

Paranarthrura intermedia Kudinova­Pasternak, 1982 Northeast 1170 ­4190

Paranarthrura kurchatova Kudinova­Pasternak, 1975 Tropical east 6340­6380

Paranarthrura lusitanus Bird & Holdich, 1989 Northeast 173­641

Paranarthrura subtilis Hansen, 1913 Northeast 582­1739

Paranarthrura tridens Bird & Holdich, 1989 Northeast 4426­4829

Paranarthrura angolensis sp. nov. Southeast 631­5464 Paranarthrura crassa , P. f o r t i s p i n a, P. insignis and P. lusitanus from the Atlantic Ocean resembles P. angolensis in body shape and presence of two articled uropods.

In P. c r a s s a, the shape of the chela is very characteristic, it is more rounded and the terminal spines of the finger and the chela are rounded, the uropods are shorter as in P. angolensis . As a special feature the hyposphenian on P. crassa are pointed frontally while in P. angolensis the hyphosbaenian are pointed ventrally.

In P. fortispina , the chela is more strongly developed and the pleotelson is more rectangulary shaped. The maxilla is almost round and not triangular as in P. angolensis . The strong seta on the propodus of pereopod 1 is very prominent, in P. angolensis it is very small.

In P. insignis the uropod is very characteristic, bearing the typical “ Anarthrura basis” without any seta on top of the projection. The chela is larger than in P. angolensis .

Paranarthrura lusitanus is very similar to P. angolensis . The finger of the chela has a seta on it, pereopod 6 possesses two distal setose seta on the basis, and the maxilliped has two strong seta on its basis. The first article of the antennule is longer in P. lusitanus and the setation is different to P. angolensis . The inner edge of the labium is pointed and in P. angolensis it is rounded. The bathymetrical distribution is different. P. lusitanus is found on shallower waters (to 631 m) and P. angolensis on deeper waters (to 5464 m) (see table 2).

The resemblance of P. angolensis , P. lusitanus and P. fortispina might indicate a close phylogenetic relationship of these species, a future phylogenetic analysis might help to understand the possible colonisation and speciation process of Paranarthrura in the deep Atlantic Ocean.

Figures

FIGURE 2, Paratype ZMH K­ 40074 A Mandibles, B Labrum, C Maxilla, D Maxillula, E Epignath, F Maxilliped, G Labium.

FIGURE 3 Paratype ZMH K­ 40074 A Cheliped, B Pereopod 1, C Pereopod 2, D Pereopod 3, E Pereopod 4, F Pereopod 5, G Pereopod 6. (Scale bar 0.5 mm).

FIGURE 1, A female lateral view, Paratype ZMH K­ 40074, B female dorsal view with detail of cuticula, C Male dorsal view, Paratype ZMH K­ 40081, D pleon male lateral view (Scale bar = 1 mm), E cephalothorax in ventral view, F Antennule, G Detail of antennule tip, H Antenna, I Detail of antenna tip (Scale bar = 0.5 mm), J uropods (Scale bar = 0.05 mm), K Pleopod. (Scale bar = 0.05 mm).