Pentacletopsyllus montagni, Bang, Hyun Woo, Baguley, Jeffrey G. & Moon, Heejin, 2014
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Pentacletopsyllus montagni sp. n. Figs 1-6
Gulf of Mexico; 28°43.20'N, 88°20.68'W; depth 1590 m; mud.
Holotype: 1♀ (USNM No: 1231418) dissected on 8 slides, from the type locality. Paratypes: 2♀♀ and 1♂ (USNM No's listed in order presented in text: 1231419, 1231420, 1231421) each dissected on 8, 4 and 9 slides respectively, and 10♀♀ and 10♂♂ (USNM No's for specimens in vials (female, male): 1231422, 1231423) in 70% ethanol, vial. Additional samples were deposited in the first author’s collection. All from the type locality, collected by J. G. Baguley on May 2011.
Female. Body (Fig. 1A) elongated. Total body length 1121 µm (n=10; range: 1022-1242 µm, measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalic shield: 234 µm. Urosome narrower than prosome (Fig. 1A). Cephalothorax bell-shaped, with few tegumental sensilla; posterior and lateral margins irregularly serrated (Fig. 1D). Rostrum prominent, triangular; with a pair of sensilla near anterior margin, with bifid tip (Fig. 1E). Pedigerous somites with 1 pair of sensilla on dorsal surface, serrate posteriorly as cephalothorax; pleural areas well developed.
Urosome 5-segmented, comprising P5-bearing somite, genital double-somite and 3 free abdominal somites. All urosomites covered with small spinules dorsally and laterally. Urosomite with serrate posterior and posterolateral margin.
Genital double-somite (Fig. 4C), completely fused ventrally with original segmentation indicated by a transverse surface ridge dorsally and laterally. Genital field located near anterior margin with gonopore and copulatory pore located in median depression. P6 with 1 bare seta on a small protuberance. Anal somite with well-developed rounded operculum bearing row of setules (Fig. 4D).
Caudal rami cylindrical, about 7 times as long as wide, each ramus with 7 setae: setae I-II small, closely set, seta III subapical, setae IV-V bipinnate, seta V longest, seta VI bare and small, seta VII tri-articulate at base; tube pore presented dorsally near proximal inner margin (Fig. 1F).
Antennule (Fig. 2A) 5-segmented, with well-developed sclerite around base of segment 1. Segment 1 short, with 2 long spinule rows and 1 seta. Segment 2 with 2 outer processes, distal one longer than proximal one, each one bearing one seta distally. Segment 3 longest, with smooth posterior margin. Armature formula: 1-, 2-, 3-[8 + (1 + ae)], 4-, 5-[7 + acrothek]. Apical acrothek consisting of a small aesthetasc fused basally to 2 bare setae.
Antenna (Fig. 2B) 3-segmented, comprising coxa, allobasis and free 1-segmented endopod. Coxa small with spinule row. Allobasis elongated; original segmentation marked by incomplete surface sutures; 2 groups of strong spinules on abexopodal margin; with a long distal abexopodal seta. Exopod small, 1-segmented; with 1 apical and 1 lateral seta. Endopod elongated, with spinules along inner margin; lateral armature consisting of 2 pinnate spines and a minute seta; distal armature consisting of 1 apically curved pinnate spine, 1 bipinnate seta and 3 geniculate setae, the outer-most basally fused to an additional short seta.
Labrum with spinular ornamentation and covered with densely packed setules as in Fig. 2C.
Mandible (Fig. 2D) with large coxa bearing well-developed gnathobase, with 2 strong teeth, several multicuspidate teeth around distal margin and 1 pinnate spine at distal corner; spinules near base of palp. Palp biramous, basis with 3 pinnate setae; endopod with 1 lateral and 3 distal setae; exopod 1-segmented, with 1 apical seta.
Maxillule (Fig. 2E). Precoxa with few spinules near outer margin; arthrite strongly developed, with 2 surface setae and 9 apical spines and setae. Coxa with cylindrical endite bearing 1 naked seta, and 1 curved, pinnate spine. Basis with 2 setae and 1 bipinnate spine apically, and 1pinnate seta along outer margin; with several spinules around inner distal margin and base of endopod. Endopod incorporated in basis and presented by 1 seta. Exopod 1-segmented, with 1 pinnate and 1 naked setae.
Maxilla (Fig. 2F). Syncoxa with 3 endites, each with a short row of spinules. Proximal endite small and with 1 strong pinnate spine. Middle endite produced into pectinate spine and with 2 setae. Distal endite with 3 pinnate setae. Allobasis drawn out into strong, slightly curved, distally pinnate claw, accessory armature consisting of 2 bare and 1 pinnate seta. Endopod small, with 3 naked setae.
Maxilliped (Fig. 2G) comprising syncoxa, basis, and 1-segmented endopod. Syncoxa with 3 plumose setae and several short rows of spinules. Basis with 1 longitudinal row of spinules along palmar margin. Endopodal segment produced into strong and distally pinnate curved claw; accessory armature consisting of 1 long naked seta and 1 small seta at base.
Swimming legs 1-4 (Fig. 3A, 3B, 3C, 4A) with wide intercoxal sclerite, biramous, endopods 2-segmented, exopods 3-segmented. Coxae and bases with row of spinules along outer margins as illustrated.
P1 (Fig. 3A). Coxa large, with inner and outer spinular rows. Basis with strong bipinnate seta on outer margin and bipinnate spine on inner distal surface; inner portion produced as a cylindrical pedestal for endopod. Endopod 2-segmented, prehensile; enp-1 as long as enp-2; enp-1 with one small seta on middle third of inner margin; enp-2 with 2 pinnate inner setae, and 1 pinnate spine and 1 geniculate seta distally. Exopod 3-segmented. Exp-1 and exp-2 with 1 pinnate spine; exp-2 with 1 inner seta; exp-3 with 2 geniculate distal setae and 2 strong spinulose outer spines.
P2-P4 (Figs 3B, 3C, 4A). Coxae and bases with spinular rows along outer margin and anterior surface. Basis wider than long, with pinnate spine (P2-P3) or bare seta (P4), each seta arising from a setophore. Each ramus consisting of 3-segmented exopod and 2-segmented endopod. Armature formula as in generic diagnosis.
P5 (Fig. 4B) with separate exopod and baseoendopod. Baseoendopod longer than wide, forming long biarticulate (not triarticulate) outer setophore bearing the basal seta. Endopodal lobe triangular, with 5 bipinnate setae. Exopod about three times as long as wide, with 1 inner, 1 distal and 3 outer pinnate setae.
Male. Body (Fig. 5A). Male slightly smaller and more slender than in female. Body length 1075 µm (N=10; range: 1007-1132 µm, measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at P2-bearing thoracic somite: 196 µm. Sexual dimorphism in antennule, P2 endopod, P5 and P6.
Prosome (Fig. 5A) 4-segmented, comprising cephalothorax (bearing first pedigerous somite) and 3 free pedigerous somites. Posterior margin of cephalothorax and pedigerous somites with serrated process, with integumental sensilla. Rostrum as in female (Fig. 5B).
Urosome (Fig. 5C) 6-segmented, comprised of P5-bearing somite, genital somite, and 4 free abdominal somites. Urosomite with crenulate posterior margin dorsally and ventrally.
Antennule (Fig. 6A) 7-segmented; subchirocer with geniculation between segments 5 and 6. Segment 1 with 1 row of long spinules along outer distal margin. Segment 2 with 1 cylindrical process along posterior margin, with 1 seta apically. Segment 4 represented by a small sclerite along anterior margin. Segment 5 swollen with large bump along posterior margin. Segment 7 with triangular distal half. Armature formula: 1-, 2-, 3-, 4-, 5-[7 + 4 pinnate + 1 modified + (1 + ae)], 6-, 7-[7 + acrothek]. Apical acrothek consisting of 2 small naked setae.
P2 (Fig. 6E). Exopod as in female. Endopod modified, 2-segmented; enp-2 with 4 plumose inner setae; inner apical seta fused to segment forming short apophysis; outer apical seta shorter than female; outer seta reduced and presented by minute naked seta (Fig. 6F).
Fifth pair of legs (P5) (Fig. 6G) fused medially. Baseoendopod with outer setophore bearing the basal seta. Endopodal lobe with 1 inner and 2 distal bipinnate setae. Exopod shorter than in female, about three times as long as wide, with 1 inner, 1 distal and 2 outer pinnate setae.
P6 (Fig. 5C) asymmetrical, bearing 1 naked seta on a cylindrical process.
The species is named in honor of Dr. Paul Montagna, Endowed Chair for Ecosystem Studies and Modeling at the Harte Research Institute, Texas A&M University Corpus Christi. Dr. Montagna has had a long and distinguished career studying meiofauna, hapacticoid systematics, and marine ecosystem dynamics, particularly in the Gulf of Mexico.
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