Atlantistylis borealis, Shalla & Bishop, 2005

Shalla, Salma H. & Bishop, John D. D., 2005, First record of the genus Atlantistylis Reyss, 1975 (Crustacea: Cumacea) from the North Atlantic, with the description of a new species, Journal of Natural History 39 (18), pp. 1483-1489 : 1484-1488

publication ID	https://doi.org/ 10.1080/00222930400001582
persistent identifier	https://treatment.plazi.org/id/03AA87F7-B625-AD22-E680-FC3BEF96FB4F
treatment provided by	Felipe
scientific name	Atlantistylis borealis
status	sp. nov.

Treatment

Atlantistylis borealis View in CoL sp. nov.

( Figures 1 View Figure 1 , 2 View Figure 2 )

Type material

Holotype: preparatory ♀, length 4.5 mm; White Zone 55204 # 2, co-ordinates: 59 ° 40.65 9 N, 08 ° 42.27 9 W, depth 1295 m; NMSZ 2000.249 .0004 . Paratypes: one brooding ♀, two immature „„, one manca, AFEN 54579 # 2A, NMSZ 1999.238.0076; one brooding ♀, one preparatory ♀, one immature „, AFEN 54580 # 1A/B, NMSZ 1999.238 .0077.

Other material. Five brooding ♀♀, two preparatory ♀♀, Institute of Oceanographic Sciences ( IOS), Discovery collections 9753 # 7 .

Diagnosis

Pseudorostrum long, with four to six spines on either side of the dorsal margin (i.e. a double row) and minute teeth on the ventral margin; frontal lobe with a crescent-shaped group of spines, pseudorostral lobe with a row of spines extending on to the lateral lobe, dorsal crest with a double row of spines on the anterior half; first pereopods very long; telson small, one-quarter the length of the uropod peduncle and with two small apical acuminate setae only; uropodal endopod longer than exopod; male without pleopods.

Preparatory and brooding-form females ( Figure 1A View Figure 1 ). Body length 4.5–4.9 mm. Carapace depth 0.47–0.50 times carapace length. Pereon 0.7–0.8 times carapace length. Pleon 1.75– 1.95 times carapace length, pleonite 6 0.5 times the length of pleonite 5.

Carapace ( Figure 1A View Figure 1 ). Laterally compressed, deep, no antennal notch, antero-lateral corner not defined. Dorsal crest with a double row of ca seven very small spines on the anterior half, a few denticles on the posterior half. Frontal lobe with small narrow eyelobe with no eyes, a crescent shaped group of ca 8–10 spines and a few scattered denticles. Pseudorostrum long, 0.46 times length of remainder of carapace, tapering to a narrow point in undamaged material. Dorsal margin with double row of four to six spines, ventral margin with small teeth continuing past the antero-lateral corner and to the posterior portion of the ventral margin. Pseudorostral lobe with a row of ca seven to nine spines extending on to the lateral lobe.

First antenna ( Figure 1B View Figure 1 ). Long, exceeding the length of the pseudorostrum. Peduncle and flagellum both three-segmented. First segment of the peduncle 1.1 times the length of the second segment, third segment 1.2 times the length of the first segment. Three-segmented accessory flagellum 0.6 times the length of the main flagellum.

Third maxilliped ( Figure 1C View Figure 1 ). Slender, basis 0.88 times the length of the distal articles combined, with very fine teeth on the ventral margin. Exopod slender, shorter than basis, basal segment with minute teeth on the lateral margin.

First pereopod ( Figure 1D View Figure 1 ). Very long and slender, carpus exceeding the tip of the pseudorostrum. Basis 0.48 times the distal articles combined, with very fine teeth on the lateral and ventral margins. Dactyl 0.5 times propodus. Exopod slender, 0.7 times length of basis.

Second pereopod ( Figure 1E View Figure 1 ). Basis strongly curved, 0.5 times the distal articles combined. Ischium 0.4 times merus, carpus subequal to propodus plus dactylus. Exopod slender, subequal to basis.

Third pereopod ( Figure 2A View Figure 2 ). Basis long and cylindrical, 1.7 times distal articles combined. Exopod rudimentary, two-segmented, 0.2 times basis.

Fourth pereopod ( Figure 2B View Figure 2 ). Basis 1.3 times length of distal articles combined. Exopod rudimentary, two-segmented, 0.3 times basis.

Fifth pereopod ( Figure 2C View Figure 2 ). Basis 0.9 times length of distal articles combined. No exopod.

Uropods and telson ( Figure 2D View Figure 2 ). Uropod 0.24 times body length, peduncle 1.25 times the length of the endopod. Exopod shorter than endopod, extending 0.72 of way along endopod. First segment of endopod 1.1 times the length of second; second and third segments subequal. Number of setulose stout setae on median margin: peduncle, five; segment 1 of endopod, two; segment 2 of endopod, two; segment 3, one and one long simple terminal seta. Terminal seta of segment 3 of endopod 1.75 times the length of the segment. Median margin of the endopod segments 2 and 3 with serrated edge. First segment of exopod relatively long, 0.5 times segment 2. Exopod distal segment with four setulose stout setae on the median margin and three setae terminally. Telson very short, slightly wider than long, 0.4–0.5 times the length of pleonite 6, with a single pair of terminal acuminate setae; postero-lateral border serrated.

Immature male. Body length 3.7–3.8 mm. Carapace depth 0.6–0.7 times carapace length. Pereon 0.7–0.8 times carapace length. Pleon 1.7–1.9 times carapace length. Carapace dentition ( Figure 1F View Figure 1 ) similar to that of female. Second antenna reaching 0.75 of the way along the ventral margin of the carapace; flagellum with few segments ( Figure 2E View Figure 2 ). Exopod present on maxilliped 3 and pereopods 1 to 4, absent from pereopod 5 ( Figures 2F, G View Figure 2 for pereopods 3 and 4). No pleopods, pleon similar to that of female. Uropod resembling that of female, i.e. with three-segmented endopod.

Etymology

The name borealis refers to the northern occurrence of the new species.

Remarks

The telson in Atlantistylis borealis sp. nov. is relatively inconspicuous and the species could be mistaken for a leuconid.

The only other two species in the genus are Atlantistylis chauvini Reyss, 1975 , from the tropical Atlantic, and A. japonica Gamô, 2001 from the Pacific. The new species is referred to Atlantistylis because it shares with A. chauvini the combination of (1) the absence of pleopods in males; (2) the small telson lacking lateral setae; and (3) the three-segmented uropodal endopod of females. The description of A. japonica Gamô, 2001 is based on a single adult male with an incomplete pleon (the first two pleonites only). The latter shares with A. chauvini and A. borealis sp. nov. the absence of pleopods in males. The species of the genus Atlantistylis Reyss, 1975 can be separated by the following key.