Haploops truncata Kaim-Malka & Bellan-Santini & Dauvin 2021, spec. nov.

Haploops truncata spec. nov.

(Figures 5–8)

Type material. HOLOTYPE. One female without oostegite. Length: 5.57 mm (Fig. 5). BIOICE: Station 3140; one specimen, 25 August 1999, depth: 768 m, 67°51.90’N – 22°14.89’W, bottom: sediment type unknown. Holotype IINH 42245 + slides IINH 42247. The specimen is deposited in the Icelandic Museum of Natural History in Reykjavik (IMNHR).

BIOICE material. The specimens are deposited in the Icelandic Museum of Natural History in Reykjavik (IMNHR). Station 2011: one specimen, 20 July 1991, depth: 768 m, 65°41.43’N – 11°16.77’W; sediment type unknown (IINH 42251). Station 2414: three specimens, 20 July 1991, depth 978 m, 65°35.01’N – 10°59.98’W; bottom: brown sandy, silt mixed with foraminifera (IINH 42250). Station 2897: eight specimens, 24 August 1996, depth 672 m, 65°29.44’N – 27°32.55’W; sediment type unknown (IINH 42249). Station 2898: one specimen, 24 August 1996, depth 672 m, 65°29.30’N – 27°32.70’W; sediment type unknown (IINH 42248). Station 3140: one specimen, 25 August 1999, depth 768 m, 67°51.90’N – 22°14.89’W; sediment type unknown (IINH 42245). Station 3501: two specimens, 31 August 2002, depth 829 m, 62°59.84’N – 20°30.25’W; sediment type unknown (IINH 42246).

Male unknown.

Ethymology. The species name refers to the shape of the head (square) with the lateral lobe truncate.

Diagnosis. Pereon, Pleon and Urosome without long dorsal setae, Head square with anterior margin straight (lateral lobe truncate). One pair of superior corneal lenses. Antenna 1 length = 0.8 Antenna 2 length; Antenna 2 as long as body length (0.876). Coxa 4 external side bearing numerous short setae.

Description. Holotype. Female without oostegites. Length: 5.57 mm (Fig. 5). Body without long dorsal setae on the pereon, pleon and urosome.

Head (Fig. 6A): square with anterior margin straight, one pair of superior corneal lenses. Antenna 1 (Fig. 6B): shorter than antenna 2, peduncle of A1 with article 3 <article 1 <article 2 (6/13/17). Peduncle of A1 reaching article 5 of peduncle of A2; flagellum long, with 18 articles. Antenna 2 (Fig. 6C): longer than antenna 1 (A1/A2 = 0.81). Peduncle segment 5 longer than 4 (23/19). Flagellum with 23 articles. Antenna 2 near the body length. The two antennae bearing long numerous setae (Fig. 6B, C).

Upper lip and Lower lip bilobate (Fig. 6D, G). Mandible (Fig. 6H): molar strong; palp long, article 2 and 3 of same length; setae are present on the margin of each article, article 3 with very long apical setae. Maxilla 1 (Fig. 6E). the inner plate is conical shaped with two apical setae and some short hairs; outer plate with spine teeth distally; palp ended with strong teeth and spines. Maxilla 2 (Fig. 6F): dense apically setae on the two plates. Maxilliped (Fig. 6J): inner plate sub-rectangular, elongated, with few distal setae; internal margin of the outer plate with long setae and strong teeth; palp elongate, longer than outer plate, article 2 and 3 with long setae, article 3 triangular shaped, dactylus elongate and slender.

Pereon: without long dorsal setae (Fig. 5). Gnathopod 1 (Fig. 7A): coxa 1 roughly triangular, distal margin rounded and fringed with long setae; basis long, slightly curved, approximately rectangular with some setae on the two margins, length longer than ischium + merus + carpus, the merus, carpus and propodus bearing long setae; propodus oval; dactylus slender and curved with small setae, dactylus length = 0.51 propodus length. Gnathopod 2 (Fig. 7B): coxa 2 approximately rectangular and short (coxa length / basis length= 65/85), distal margin slightly rounded with few short setae; basis long with some setae, basis longer than ischium + merus +carpus; carpus longer than propodus (carpus length / propodus length = 53/30), approximately rectangular with long setae on the margins; propodus oval, long setae on the margins; dactylus slightly curved with short setae (Fig. 7C), dactylus length = 0.46 (17/37) propodus length. Pereopod 3 (Fig. 7D): coxa 3 triangular, distal margin rounded; basis rectangular, basis> ischium + merus + carpus. The margins of the different articles of pereopod 3, except dactylus, bearing few long setae; dactylus slender, curved and longer than propodus (dactylus length / propodus length = 1.35) (27/20). Pereopod 4 (Fig. 7E): coxa 4 square-shaped, external side bearing numerous short setae; anterior margin straight, length / width = 43/40, antero-ventral corner quadrate but not sharp, ventral margin straight with short setae, posterior concavity = 0.46 (17/37) length of the posterior length of the coxa 4, posterior hook broad, length = 17/42 width of coxa 4, posterior corner blunted; basis length> ischium + merus; the margins of the different articles of pereopod 4, except dactylus, bearing few long setae; dactylus slender, slightly curved and longer than propodus (dactylus length / propodus length = 1.125 (27/24). Pereopod 5 (Fig. 7F): coxa 5 rectangular, basis roughly rectangular with few setae on the anterior margin; carpus rectangular, anterior margin with few setae, posterior margin with two rows of little spines, distal margin with short spines and a long one; propodus rectangular, longer than carpus, with few short setae, and a long distal seta; dactylus short and curved, dactylus length / propodus length = 0.23 (12/51). Pereopod 6 (Fig. 8A): coxa 6 roughly trapezoidal shaped, posterior margin rounded; basis rounded with few short setae and spines on the anterior margin; carpus rectangular, anterior margin with few short setae, posterior margin with two rows of little spines, postero-distal lobe ornamented with short spines and a very long one; propodus a little longer than carpus, with few short setae, and a long distal seta; dactylus short and curved, dactylus length / propodus length = 11/40. Pereopod 7 (Fig. 8B): coxa 7 roughly rectangular; basis narrow (length without lobe / width = 80/35 = 2.28), anterior and posterior margin slightly concave, lobe slightly deflected, rounded with few long setae, reaching the merus; ischium quadrangular; merus rectangular with an antero-inferior lobe ending with a spine, posterior margin ornamented with few little spines; carpus pyriform (width / length = 17/20), with strong spines on the anterior and posterior margin (propodus length / carpus length = 15/20; propodus + dactylus / carpus = 23/20); propodus narrow, width / length = 5/15 (propodus width / carpus width = 5/17), with short apical setae; dactylus rectangular, short and narrow (length / width = 7/1) with two very small apical setae (dactylus length / propodus length = 8/15).

Pleon (Fig. 5): the postero-dorsal segments of the pleon without setae. Epimeral plate 1 (Fig. 8C): anterior margin oblique and straight, ventral margin rounded, posterior margin slightly convex. Epimeral plate 2 (Fig. 8C): square shaped, anterior and posterior margin straight, inferior one slightly convex, postero-inferior corner rounded. Epimeral plate 3 (Fig. 8C): square shaped, anterior and posterior margin straight, inferior one slightly convex, corners rounded.

Urosome (Fig. 5): the urosome segment 1 has a dorsal carina straight, moderately hight, with the apex rounded. Uropod 1 (Fig. 8D): long, rami slender, curved, and equal length; inner ramus with two little spines; peduncle longer than the ramus, with one spine on the distal margin. length rami / length peduncle = 54–56 / 64. Uropod 2 (Fig. 8E): shorter than Uropod 1; rami triangular and short, inner ramus shorter than the outer one, with a row of spines on each ramus, outer ramus length / peduncle length = 78 /102; peduncle rectangular, robust with a strong spines on the distal margin. Uropod 3 (Fig. 8F): peduncle short and strong (length / width = 58/35); rami of unequal length, roughly rectangular, longer than peduncle (rami length / peduncle length = 90–100/58); inner ramus with three spines and some apical setae, outer ramus with apical long setae and also some long setae on the outer margin.

Telson (Fig. 8G): triangular, apically rounded, cleft on 25/35 of the length; one seta present on the apical part of each lobe.

Distribution: North Atlantic Ocean; this species was collected between 672 m and 978 m. The nature of the bottom is indicated for only one sample: brown sandy silt mixed with foraminifera.

Taxonomic remarks. H. truncata is probably a non mature female, but the original characters in the sub-group with superior corneal lenses justify its description as a new species. H. truncata belongs to the sub-group with the superior pair of corneal lenses clearly visible; the inferior pair is absent; a narrow Pereopod 7 basis, and the absence of dorsal tuft, this sub-group includes six other species: H. tubicola, H. spinosa, H. descansa, H. fundiensis, H. oonah, and H. antennata. H. truncata differs from the other neighbouring species by the following characters:

— Head square with anterior margin straight (oblique in H. tubicola; H. spinosa; H. fundiensis; H. antennata).

— Antennae subequal, Antenna 2 near the body length; in H. tubicola, the antennae are subequal and reach 2/3 of the body length; they reach 1/3 of the body length for H. fundiensis; in H. spinosa the Antenna 2 length is include between 1/3 and 1/2 of body length. For the two other species, H. descansa and H. oonah, the Antenna 1 is half the length of Antenna 2; whereas in H. antennata, the Antenna 1 is longer than Antenna 2.

— Coxa 4 square-shaped, external side bearing numerous short setae.

— Epimeral plate 3 square shaped; the posterior margin is oblique or slightly curved in the other species (except for H. descansa).

— Uropod 1 long, with rami slender, curved, and of equal length; they are of unequal length for H. tubicola, H. descansa, H. fundiensis, H. oonah and H. antennata (except H. spinosa with rami of equal length, and especially as Uropod 2 rami are strongly armed).

In the introduction we indicate that it is necessary to supplement the description of two species described by Stephensen in 1925: Haploops vallifera and Haploops similis. This is the object of the following section.