Ischnomesus hirsutus, Souza-Filho, 2017

Souza-Filho, Jesser F., 2017, Three new species of the genus Ischnomesus (Isopoda: Asellota: Ischnomesidae) from Brazilian deep sea, Zootaxa 4312 (2), pp. 259-276 : 262-265

publication ID	https://doi.org/ 10.11646/zootaxa.4312.2.3
publication LSID	lsid:zoobank.org:pub:F07Dc169-C969-48B0-B74F-Eb853539Ce86
DOI	https://doi.org/10.5281/zenodo.5698533
persistent identifier	https://treatment.plazi.org/id/03D0566A-FFB8-FFE5-FF19-FBACFC78C50E
treatment provided by	Plazi
scientific name	Ischnomesus hirsutus
status	sp. nov.

Treatment

Ischnomesus hirsutus View in CoL sp. nov.

( Figures 2–4 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. Holotype: 1 adult female, 11 mm, ( MOUFPE 15.542 View Materials ), station SLN #2 R3, 0–2 cm, campaign Seillean , Espírito Santo Basin, 20°03’37.8”S, 39°30’12.3”W, 1450 m depth, November 2006. GoogleMaps

Paratypes: 1 adult female (dissected and drawn, mouthparts and pereopod1 on two slides), ( MOUFPE 15.543 View Materials ), station SLN #8, R3, 2– 5 cm, campaign Seillean , Espírito Santo Basin, 20°03’55”S, 39°60.8”W, 1445 m depth, November 2006 . 1 adult female, (UFS-CRU-0216), station FN6R2, 2– 5 cm, campaign Marseal, Alagoas-Sergipe Basin , 11°15’27.3”S, 36°52”13.2”W, 2–5 cm, 1000 m depth, March 2013 . 1 adult female, (UFS-CRU-0217), station CN9R1, 5– 10 cm, campaign Marseal, Alagoas-Sergipe Basin , 11°05’14.3”S, 35°53’53.6”W, 5–10 cm, 3000 m depth, March 2013 GoogleMaps .

Etymology. Hirsutus from the Latin adjective meaning shaggy, this name alludes to the setose body.

Diagnosis. Head dorsal surface with small setae. Maxilliped epipodite smooth. Pereonite I with 1 pair of anterolateral small pedestal spines. Pereonites I–IV with pair anterodorsal pedestal setae. Pereonite V length 2.5 width, without spines, but covered with short simple setae. Pereonites VI–VII without pedestal setae, but covered with short simple setae. Pleotelson without spines, but covered with simple short setae. Pleotelson with lateral fields bulge.

Description (based on female holotype, MOUFPE 15.542). Dorsal cuticle covered with simple setae. Head length 1.3 width, dorsal surface with small setae. Delicate suture visible between head and pereonite I.

Antennula ( Fig. 2 View FIGURE 2 D) with 6 articles. Article 1 squat and globular, with 7 short setae on anterior margin; article 2 biggest, length 3.9 article 1 length, covered with 9 ventromedial setae and 10 lateral setae; article 3 tubular and elongate, 1.3 longer than 4–6 together, with 4 lateral and 5 ventromedial simple setae, 1 distal long simple seta; article 4 with 1 ventromedial seta and 4 distal; article 5 with 1 distal seta; article 6 with 3 distal setae.

Antenna ( Fig. 2 View FIGURE 2 E) article 1 with 1 robust seta, 1 robust seta with accessory seta and 2 simple setae; article 2 longest, with 5 robust setae, 3 distal and 2 lateral and 8 simple setae, 4 ventromedial, 2 distal and 2 lateral; article 3 with 5 distal setae. Flagellum missing.

Remarks. Ischnomesus hirsutus sp. nov. has a pattern of ornamentation similar to I. tasmanensis Merrin & Poore, 2003 . The positioning of anterolateral spine, on pereonite I, and dorsal spines, on pereonites I–IV, observed in I. tasmanensis is the same position of the pedestal spine and pedestal setae observed in Ischnomesus hirsutus sp. nov., respectively. However, this species differs from I. tasmanensis by pleotelson: spines, format and lateral fields bulge in pleotelson, never reported before.

Bathymetric range. 1000–3000 m depth.

Distribution. Alagoas-Sergipe Basin and Espírito Santo Basin.