Byblisoides bellansantiniae, Peart, Rachael A., 2018

Peart, Rachael A., 2018, Ampeliscidae (Crustacea, Amphipoda) from the IceAGE expeditions, ZooKeys 731, pp. 145-173 : 149-153

Byblisoides bellansantiniae sp. n. Figs 2, 3, 4

Type material.

Holotype, female, 14 mm, ZMH K-47035, station IceAGE 1, 1054-1, Irmiger Basin, South Iceland, 031°22.60'W - 031°22.18'W, 61°36.19'N - 61°36.97'N, 2537.3 - 2538.1 m, ME85 - 3, supranet bucket of EBS, 07.09.2011.

Type locality.

Irminger Basin, South Iceland.

Etymology.

Named for Dr Denise Bellan-Santini, whose extensive research on the Ampeliscidae has greatly aided this study.

Diagnosis.

Anteroventral margin of head rounded and produced to length of anterior margin of head. Antenna 1 short, reaching to three-quarters of antenna 2 peduncle article 4. Pereopod 7 carpus anterior margin without plumose setae. Pereopod 7 basis posteroventral corner rounded. Uropod 2 inner ramus bearing marginal robust setae.Description. Based on holotype female 14 mm length. Head anteroventral corner produced forward, reaching almost level with the anterodorsal corner, anterior margin, excavate at antenna 2 insertion, antennal lobe concave, with two acute points, rostrum absent, head longer than deep, ventral margin slightly sinuous. Antenna 1 short, reaching to three-quarters length of antenna 2 peduncle article 4; peduncle article 1 subequal in length to article 2 (1.1 ×), article 2 longer than article 3 (3 ×), article 3 shorter than article 1 (0.3 ×); flagellum shorter than peduncle, comprising of three articles (article 1 longest), ventral margin of both peduncle and flagellum with long plumose, slender setae. Antenna 2 comparatively stout, reaching to just under half of the body length; peduncular article 4 subequal in length to article 5, article 5 ventral margin slightly serrate, with long slender setae; flagellum shorter than peduncle, with 4 articles.

Mandible molar well-developed and triturating, seven plumose robust setae in accessory setal row; incisor toothed; lacinia moblis with many teeth of different sizes; palp long, article 1 very short, article 2 longer than article 3 (2.2 ×) and curved with sparse setae, article 3 longer than article 1 (3.2 ×), moderately setose. Lower lip two lobed, inner plate half height of outer. Maxilla 1 inner plate rounded and small, covered in setules, no long setae; outer plate topped with toothed robust setae; palp with two articles, article 2 reaching to end of teeth on outer plate, tipped with five long plumose setae and five facial slender setae. Maxilla 2 inner and outer plates of equal height and width, both tipped with long plumose setae. Maxilliped inner plate very short, rounded, tipped with three long robust setae and two slender setae; outer plate twisted around palp, inner lateral margin lined with toothed robust setae becoming slender plumose setae distally; palp broad and subchelate in aspect, article 2 expanded and long bearing many strong slender plumose setae, article 3 narrow and folded over article 2, reaching only a third of the length, strongly setose, article 4 curved and acutely tipped, reaching half the length of article 3.

Gnathopod 1 coxa reaching to edge of anterior margin, coxa expanded distally, ventral margin narrowly curved lined with long plumose slender setae, plus a few medial plumose setae; basis narrow, lateral margins lined with long plumose, slender setae, medial setae long and plumose; merus slightly lobate and strongly setose particularly posteriorly; carpus longer than merus and longer than propodus (1.2 ×), strongly setose, particularly medially and posteriorly with long plumose setae, not lobate; propodus ovoid, weakly subchelate, palm not well defined, anterior and posterior margins lined with long plumose slender setae; dactylus short and curved, a third the length of the propodus, inner margin with a distal tooth and sparse slender setae. Gnathopod 2 coxa similar length to coxa 1, ventral margin curved (unevenly), fringed with medial and marginal sparse long plumose setae; basis long and narrow lateral margins with long slender plumose setae, merus with subacute posterior lobe, long plumose setae on both the anterior and posterior margins; carpus longer than merus and longer than propodus, narrow and not lobate, covered in long, plumose setae; propodus narrow, covered in long plumose setae; dactylus short, about a third the length of the propodus and slightly curved, inner margin setose.

Pereopod 3 coxa similar to coxa 2; basis long and narrow, anterior margin with short sparse setae, posterior margin without setae; merus narrow, shorter than basis, subequal to carpus and propodus together, both margins with sparse long plumose setae; carpus with long plumose setae on posterior margin; propodus longer than carpus, short sparse setae on posterior margin, posterior margin slightly concave; dactylus long and narrow, slightly curved, shorter than propodus. Pereopod 4 coxa subrectangular, posterior margin with extended rounded lobe, posterior margin below lobe concave, ventral margin almost straight and sparsely setose; basis same length as coxa with setose lateral margins; ischium setose along posterior margin; merus long and narrow, shorter than basis, longer than carpus and propodus together, setose with plumose setae along complete length of posterior margin and distal half of anterior margin; carpus shorter than propodus, setose along posterior margin; propodus long and narrow, setose on proximal posterior margin; dactylus long, narrow and straight, shorter than propodus.

Pereopod 5 basis almost rounded narrow distally, anterior margin broadly rounded, lined with long plumose setae, anterior margin bilobed without setae; ischium with acute posterior lobe; merus longer than ischium with only one long plumose seta on anterior margin, no setae on posterior margin; carpus longer than merus, longer than propodus, only setose along anterior margin (all plumose), not lobate; propodus narrow, setose along anterior margin, not lobate; dactylus short, strongly curved and smooth. Pereopod 6 basis nearly circular, subquadrate distally, anterior margin lined with short slender setae, and one long plumose seta, posterior margin without setae; ischium with acute posterior lobe; merus longer than ischium, not lobate, anterior margin with one long slender seta and one long robust seta, posterior margin without setae; carpus longer than merus and longer than propodus, anterior margin lined with eight long robust setae, anterior margin no setae, distal corner with two long robust setae; propodus long and narrow not produced into a distal lobe, anterior margin lined with four short plumose robust setae, distal corner bearing three long strong setae; dactylus short, curved and smooth. Pereopod 7 basis widest distally, ovoid, rounded, medial surface setose, anterior margin with sparse setae, ventral and partly posterior margin lined with long plumose setae all the way to the junction with the ischium, posterior corner slightly serrate; ischium short and not setose, except for anterodistal corner; merus longer than ischium, not lobate, anterior margin with two long robust setae, posterior with three long plumose setae and distally with one long plumose and one robust seta; carpus narrow, longer than merus, subequal to propodus, anterior margin with three robust setae and two distal robust setae, posterior margin without marginal setae, but with four long distal robust setae; propodus long and narrow, anterior margin without setae, posterior margin with two robust setae; dactylus long, straight and narrow, slightly shorter than propodus.

Pleon. Epimeron 1 posteroventrally broadly rounded, no tooth or setae. Epimeron 2 posteroventrally broadly rounded, no tooth or setae. Epimeron 3 posteroventrally produced to form a small subacute tooth, posterior margin straight, no ventral setae. Urosomite 1 produced into a straight dorsally, curved ventrally carina, unilobed when viewed from dorsal. Uropod 1, in situ, reaching to tip of uropod 2 rami; peduncle longer than rami, outer margin lined with three short robust setae, inner margin lined with three proximal, long plumose setae and five long robust setae, row of seven short, robust medial setae; rami subequal in length, outer ramus lined with six robust setae and three slender setae; inner ramus with hair-like setal fringe proximally and distally with four robust marginal setae. Uropod 2 peduncle same length as inner ramus but longer than outer ramus, inner margin with two robust lateral setae and six medial robust setae; outer ramus with four short medial robust setae, one long subterminal robust seta; inner ramus longer than outer ramus with proximal hair-like fringe and two long marginal distal robust setae. Uropod 3 peduncle much shorter than rami, with three distal, medial short robust setae, and two lateral robust setae; inner ramus slightly longer than outer, both rami leaf-shaped (broadest proximally); inner ramus lined with long slender plumose setae and four robust setae laterally (outer margin), five robust setae on inner margin; outer rami inner margin with long slender, plumose setae, outer margin with seven short robust setae laterally. Telson longer than wide (1.65 ×), 78 % cleft; each lobe concavely truncated distally, each lobe with three dorsal robust setae, two slender dorsal setae, one robust apical and one slender apical seta.

Remarks. Byblisoides is the smallest of the Ampeliscid genera with only seven species (including this species). However, the species fall into the same traps as the rest of the ampeliscids, in that they have relatively similar morphology needing a combination of characters to provide differences. Usually a species wouldn’t be described from a single specimen, but as this is a new record for the Icelandic region and distinctly a new species it has been done. Byblisoides bellansantiniae sp. n. fits the most recent diagnosis of the genus ( Barnard and Karaman 1991) in the flagella of antennae 1 - 2 with 4 or fewer articles. Article 3 of maxilliped palp unproduced. Article 2 of pereopod 7 with posterior margin oblique and article expanding ventrally, anterior margin of postero-ventral lobe near junction with article 2 usually setose. Telson much longer than broad, cleft much more than half its length.

This species also aligns to the description of the genus in the same publication, the only slight difference is with the lower part of posterior margin on coxa 4 being angled to the anterior margin (not parallel). Byblisoides bellansantiniae sp. n. has the closest affinities to B. profundi Mills, 1971 from the Gay Head - Bermuda transect from a depth of 4600-4900 m. The ventral shape of the coxa and general shape of pereopod 7 basis draw these species together. However, they are distinct because of the shape of the anteroventral corner of the head (produced and rounded in B. bellansantiniae sp. n. and not produced in B. profundi ), and setation of basis of pereopod 7 (medially setose in B. bellansantiniae , not setose in B. profundi ). Other differences include the setation of the carpus and propodus of pereopods 5 and 6 (without setae B. bellansantiniae , strong plumose setae B. profundi ).

A key to the species of Byblisoides is provided below. Built on that provided by J.L. Barnard, 1961.

Distribution.

Southern Iceland, North Atlantic. Depths 2500-2600 m.

Key to species of Byblisoides