Lepidocharon lizardensis Galassi & Bruce

Galassi, Diana M. P., Bruce, Niel L., Fiasca, Barbara & Dole-Olivier, Marie-Jose, 2016, A new family Lepidocharontidae with description of Lepidocharon gen. n., from the Great Barrier Reef, Australia, and redefinition of the Microparasellidae (Isopoda, Asellota), ZooKeys 594, pp. 11-50 : 21-25

Taxon classification Animalia Isopoda Lepidocharontidae

Lepidocharon lizardensis Galassi & Bruce sp. n. Figures 9, 10, 11, 12, 13, 15B

Material examined.

Holotype here designated. Adult ♂ (1.1 mm), completely dissected and mounted in polyvinyl lactophenol on one slide, 17 February 2009; coll. N.L. Bruce and M. Błażewicz-Paszkowycz (MTQ W28330).

Type-locality: Australia, Lizard Island, off Coconut Beach, 14.68441°S, 145.47197°E, reef front, sand adjacent to bommies, 4 m, stn Liz 09-09A.

Paratypes. 1 ♂ (0.9 mm), 1 ♀ (1.2 mm) completely dissected and mounted in polyvinyl lactophenol, same data as holotype (all MTQ W28331).

Etymology.

The epithet lizardensis is after the type locality, Lizard Island, northern Great Barrier Reef, Queensland.

Description of male.

Body length measured from tip of cephalon to end of pleotelson 0.9-1.1 mm (n = 2). Body dorso-ventrally flattened, stocky, small-sized, about 6.5 times longer than wide (Figs 9A, 15B). Cephalon as long as wide (length/width ratio: ~1), as large as pereionites, lateral margins sub-parallel; anterior margin not projecting, rostrum absent. Dorsal surface of cephalon, pereionites and pleotelson (except free pleonite) ornamented with dorsal setules, arranged symmetrically and in pairs (Fig. 9A).

Pereionites 1-7 subequal in width (Fig. 9A); pereionites 1-3 with anterolateral margins of tergites only slightly protruding; pereionite 4 rectangular, without protrusions, pereionites 5-7 with posterolateral margins of tergites slightly protruded. Pereiopods inserted on lateral margins of tergites, visible in dorsal view (Fig. 9A); coxal plates rudimentary, incorporated to sternites.

Paragnaths (Fig. 9B) consisting of 2 large rounded lobes, deeply incised on medial side, ornamented with long setules on free mesial margins; thin simple setae are accompanied by small setules. Lateral margins with three short spinule rows. Labrum ovoid (Fig. 9C), with free anterior margin convex and medially thickened, with pair of thin scale-setae inserted symmetrically on the outermost sides of the free distal margin.

Antennula (Fig. 9D) composed of 6 articles; article 1 broadest, 1.6 as long as wide, directed anteriorly, with 2 simple and 2 penicillate setae; article 2 narrow, 1.6 as long as wide, 0.6 as wide and 0.7 as long as article 1, with 5 setae inserted at distal third of article, two of which penicillate; 1 long sensorial aesthetasc-like seta inserted on lateral protrusion, accompanied by a short and slender simple seta on its basis; article 3 unarmed; article 4 with 1 lateral simple seta and 2 penicillate setae inserted in apical position; article 5 slightly shorter (0.86) than article 4, bearing 1 long aesthetasc and 1 simple long slender seta at base of aesthetasc-bearing protrusion; 2 simple setae inserted at surface of article; article 6 very short, clearly articulated with article 5, bearing 2 subapical lateral setae, one of which aesthetasc-like penicillate seta, and 1 long apical seta close to 1 long aesthetasc and 1 subapical slender seta between them.

Antenna (Fig. 10 A–B): with 6 podomeres, articles 1 and 2 short, article 1 with mesial seta; article 2 with short lateral seta; article 3 robust, with mesial apical seta and long exopod overreaching segment 4, candle-flame shaped and bearing 2 short and slender setae inserted at middle of exopod; article 4 stout and curved with 2 apical mesial setae; articles 5 and 6 slender, article 6 longest, bearing respectively 7 and 12 armature elements, 5 of which transformed in penicillate setae with apical tuft; flagellum composed of 12 articles, all flagellar articles with setae on distal margins, most setae simple; some on flagellar articles 1 and 4 are penicillate setae.

Mandible. Palp (Fig. 10C) on short cuticular projection. Palp article 1 naked, article 2 longest, about 2.5 times as long as wide, with 2 pinnate robust setae laterally, their insertion more or less coalescent with article; article 3 curved laterally, with 4 spinulose and 1 apicalmost unipinnate setae, distalmost longest and stout; 2 setule rows on lateral margin of article. Left mandible (Fig. 10D): incisor with 3 cusps; lacinia mobilis with 2 teeth; molar process with 2 long unipinnate spines and 1 short smooth seta. Between lacinia mobilis and molar process 2 transformed crested setae are present; 6 slender, long simple setae complement total pattern of 8 elements. Right mandible (Fig. 10E) incisor with 8 robust cusps; molar process with 3 apical spines, 2 of which unipinnate and robust, proximalmost naked and shorter; between incisor and molar process 6 spines are inserted, proximalmost curved, robust and uniserrate; remaining spines simple.

Maxillula (Fig. 11A) with slender mesial lobe tapering at distal part bearing 1 short apical seta accompanied by secondary subapical short seta and hair-like setules. Lateral lobe sub-rectangular in shape, bearing scale-setae on both lateral and mesial margins. Apical setation composed of 13 elements; 1 mesial slender seta, 1 mesialmost apical seta with bifid tip; 1 penicillate seta, 7 uniserrate setae, and 3 subapical surface simple setae.

Maxilla (Fig. 11B) mesial ramus with 8 setae, 2 naked setae on mesial margin, 6 apical setae, mesialmost naked, 1 uniserrate, third seta comb-teeth shaped, unipinnate, ornamented by fine setules regularly spaced and parallel to one another; remaining 3 setae simple. Lateral rami close-set, each bearing 4 setae of different lengths; lateralmost ramus with 3 spinulose and 1 short mesial setae.

Maxilliped (Fig. 11 C–D) palp robust and curved mesially; article 1 sub-rectangular in shape, bearing 1 lateral and 1 mesial short setae; article 2 robust, bearing 1 apical mesial seta; article 3 as long as article 2, with 1 lateral apical and 3 mesial setae inserted on mesial margin; article 4 curved inwards, slender, with 1 lateral and 4 apical setae inserted at boundary line between article 4 and 5; article 5 short and narrow, with 2 apical and 3 subapical setae, of which 3 are simple slender setae of different lengths and 2 are robust and large, stiff pectinate setae. Endite almost reaching end of palp article 2; mesial margin ending in pointed protrusion, with numerous hair-like setules and 2 coupling hooks mesially; apical free distal margin with 3 spine-like, serrate setae, 1 simple non-tapered seta, and 2 surface fan setae; epipod ovoidal, overreaching distal part of palp article 1, bearing 1 subapical short, minute seta (this seta not found in other specimens).

Pereiopod 1 (Fig. 11E) coxal plate hardly discernible; basis slightly enlarged, shorter than that of P2-P7, with 2 short setae on mesial surface and 1 short simple seta on distolateral margin, and 2 penicillate setae; 2 opposite setae on ischium, one of which longer, a tubular sensorial seta on surface; merus shorter than other articles, trapezoidal, bearing 3 long setae; carpus slender and longest, mesial margin with 2 thin setae; distolateral margin with 1 simple slender seta and 1 penicillate seta; propodus slender than carpus, ending with a small elongate sclerite, with 2 mesial slender setae and 1 bifid spiniform seta; spinule row on free distal mesial margin; 3 simple setae on anterior surface; a spinule row at insertion of bifid spine; dactylus with 4 thin sensorial setae, inserted in pairs at base of each claw. Pereiopods 2-7 (pereiopod 7 figured; Fig. 12A) with coxal plate rudimentary and incorporated to the sternite, basis slender than in pereiopod 1, bearing 5 setae, three of which penicillate and two slender simple setae; ischium slightly longer and slender than in pereiopod 1, rectangular in shape, bearing 3 setae, 1 of which transformed in penicillate seta; merus shorter than all other leg segments, trapezoidal, and slightly longer and slender than in pereiopod 1, bearing 2 setae on mesial margin, 1 robust seta on apical lateral margin and 1 slender simple seta on surface at boundary between merus and carpus; carpus almost as long as propodus; robust, bearing 1 simple thin seta and a bifid spine along mesial margin, and 2 short thin setae on lateral margin, a penicillate seta inserted close to apicalmost lateral seta; propodus slender than carpus, with small elongate sclerite, bearing 2 bifid stout spine-like setae on mesial margin, 2 surface simple setae of different lengths and a surface penicillate seta at distal third of article; dactylus ending with 2 strong claws with rounded tip, slightly subequal in length, lateral claw slender, mesial stouter and shorter; dactylus armed with 5 thin setae likely with sensorial function, 3 of which inserted at surface of article, at base of insertion of the longer claw, 2 surface setae inserted at basis of shorter and stouter claw.

Pleonite length 0.27 pereionite 7 length, width 0.86 pereionite 7 width (Figs 9A, 14A, 15B).

Pleotelson longer than wide (Fig. 14A, 15B) (length/width ratio: from 1.33 to 2.00, n = 2). Dorsal side with 6 setae, a pair located on proximal part of pleotelson, other 2 pairs of setae arranged in close-set two pairs, both pairs located on distal third of pleotelson. Lateral margins bearing 3 slender setae at each side; 16 setae bordering free distal margin of pleotelson, inserted in apical or subapical position; 4 of them are penicillate setae.

Male pleopods 1 (Fig. 12B) elongate, coalescent in proximal part, with sperm tube medially, length about 4.5 times longer than maximum width (measured at widest section of proximal part of pleopod). Proximal part of pleopod large and gradually tapering at its distal part, bordered by paired rows of 4 scale–like elements. Middle part of pleopod with free distal margins smooth, parallel and slender, ending with slightly inflated sub-distal rims, tapering in apical part with paired well-developed sub-rounded bilobate tips. Stylet-guiding groove folded by hyaline lamella, running parallel to lateral margins of pleopod, only slightly sclerotized and ending with a transversal straight margin. Set of distal setae composed by 6 elements only.

Male pleopod 2 (Fig. 13A): protopod elongate, sub-rectangular at proximal part, with rounded mediodistal corner; exopod protruding from protopod at middle of mesial margin, appendix masculina (endopod) stylet ending with skewed apex, opening oblique; stylet short, shorter than and not reaching distal part of protopod.

Pleopod 3 (Fig. 13 B–C) exopod bearing 1 apical plumose seta, 1 lateral subapical medial long plumose seta and 1 subapical mesial plumose seta. Between mesial and apical setae exopod is protruded in rounded or bilobate lobes (Fig. 13 B–C); endopod with setulose hyaline lamella on mesial margin bordered by fine setule row; endopod 1 elongate, about 2.2 longer than endopod 2, the latter ending with short simple subapical seta.

Pleopod 4 (Fig. 13D) rudimentary, ellipsoidal, uniramous.

Uropods unknown.

Female.

Body length approximately as in male. Body length measured from tip of cephalon to end of pleotelson 1.2 mm. No sexual dimorphism observed in body morphology, cephalic appendages and pereiopods. Female operculum (pleopod 2) elongate (Fig. 14B), sub-ovoid, with rounded lateral margins, proximal margin straight; distal margin with medial incision, with 2 close-set short medial setae very close to medial incision and 2 longer apical setae in lateral position. Operculum surface smooth. Uropods unknown.

Remarks.

Lepidocharon priapus and Lepidocharon lizardensis differ from each other in several characters: 1) the morphology of the antennal scale (blade-knife shaped in Lepidocharon priapus vs. candle-flame shaped in Lepidocharon lizardensis ); 2) the slender body with different degree of protrusion of the pereionites 1-3 and 5-7 (markedly protruded in Lepidocharon priapus vs. stouter and less protruded in Lepidocharon lizardensis ); 3) the different shape of the male pleopod 1 (with strongly protruded and pointed apical lobes and sclerotized hyaline lamella in Lepidocharon priapus vs. sub-rounded and undulated apical lobes and a tiny hyaline lamella in Lepidocharon lizardensis ); 4) the setal complement of the male pleopod 1 (7 in Lepidocharon priapus vs. 6 in Lepidocharon lizardensis ); 5) the morphology of the male pleopod 2 (sub-rectangular and long protopod with endopodal stylet extraordinarily long, reaching the tips of the uropods in Lepidocharon priapus vs. ovoidal protopod with a short stylet, not reaching the distal part of the protopod in Lepidocharon lizardensis ); 6) female operculum sub-rectangular in shape, with straight lateral margins in Lepidocharon priapus vs. oval, with convex lateral margins in Lepidocharon lizardensis ); 7) a rounded pleotelson in Lepidocharon priapus (sub-truncate in Lepidocharon lizardensis ), and 8) body surface with visible semicircular thickening in Lepidocharon priapus (smooth in Lepidocharon lizardensis ).