Lepidocharon priapus 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 : 17-21

Taxon classification Animalia Isopoda Lepidocharontidae

Lepidocharon priapus Galassi & Bruce sp. n. Figures 1, 2, 3, 4, 5, 6, 7, 8, 15A

Material examined.

Holotype here designated. Adult ♂ (1.3 mm) completely dissected and mounted in polyvinyl lactophenol on one slide (MTQ W28329), 17 February 2009, coll. N.L. Bruce and M. Błażewicz-Paszkowycz.

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

Paratypes. 2 ♂♂ (0.9, 1.1 mm), 2 ♀♀ (1.1, 1.4 mm), Great Barrier Reef, Australia, completely dissected and mounted in polyvinyl lactophenol; 2 ♂♂, 1 ♀, same data as holotype preserved in alcohol; 1 ♂, 1 ♀ mounted on SEM stubs (all MTQ W30933).

Etymology.

The epithet is derived from the god Priapus (Πρίαπος) of the Greek mythology. He was considered the protector of livestock, fruit plants, gardens and male genitalia. He was famous for his largely phallic character and the specific names is here referring to the extraordinary length of the stylet of male pleopod 2.

Description of male.

Body length, measured from tip of cephalon to end of pleotelson, from 0.9 to 1.3 mm (n=6). Body 7.0-8.0 times longer than wide, dorsally flat. Cephalon (Fig. 1A) longer than wide (length/width ratio: ~1.3), as large as pereionites, lateral margins sub-parallel. Pereionites 1-3 with anterolateral margins of tergites protruding; pereionite 4 rectangular, without tergite protrusions, pereionites 5-7 with posterolateral margins of tergites protruded. Pereiopods inserted close to lateral closure of tergites (Figs 1A, 2 G–H) and extended outwards, coxal plates not discernible on dorsal and lateral views, small, totally incorporated to the border of the concavity housing the pereiopods (Fig. 2D, G–H).

Paragnaths (Fig. 3C) large, free distal margin with long slender simple setae and marginal and submarginal rows of scale setae. Labrum ovoid (Fig. 3D), ornamented with fine spines on free anterior margin.

Antennula (Fig. 1B) composed of 6 articles; article 1 1.5 as long as wide, directed anteriorly, with 2 simple setae; article 2 1.5 as long as wide, 0.8 as wide and 0.8 as long as article 1, with 4 setae inserted at distal third of article, 2 of which penicillate setae plus 1 long penicillate seta inserted on a lateral protrusion of article, accompanied by a short and thin naked seta on its basis; article 3 unarmed; article 4 with 1 lateral seta and 2 surface penicillate setae; article 5 shorter than article 4, bearing 1 long aesthetasc and 1 simple seta at basis of aesthetasc-bearing protrusion; article 6 short, 0.5 as long as article 5 and clearly articulated with article 5 (Fig. 2A), bearing 5 setae in total, two surface seta (one of which penicillate), one apical and one subapical simple setae; one long aesthetasc and a robust and long seta apically, both incorporated to article 6.

Antenna (Fig. 3 A–B) with 6 podomeres, 2 proximal articles short and stout, article 1 with 1 apical outer seta; article 2 naked; article 3 robust, length/width ratio: 1.25, with mesial apical seta and long exopod quite overreaching segment 4, knife-blade shaped and bearing 2 long and thin setae inserted on lateral margin at middle of exopod; article 4 stout and curved outward, 0.5 as long as article 3, with 2 apical mesial setae; articles 5 and 6 slender and long, article 6 longest, bearing 6 and 10 simple setae, respectively; flagellum composed of 9 articles in holotype; 11 articles in one male paratype; all flagellar articles with distal hyaline lamella partially covering insertion of following article, all armed with setae on distal margin, except article 9 ending with 3 simple and 1 penicillate setae.

Mandible palp (Fig. 3E) on short cuticular projection; palp article 1 without setae, article 2 longest, about 2.5 times longer than wide, with 2 pinnate robust setae laterally, their insertion more or less coalescent with article; article 3 curved laterally, with 5 pinnate robust setae, distalmost seta longest; 2 cuticular comb rows on lateral margin of article. Left mandible (Fig. 3E): incisor with two strong and large cusps; lacinia mobilis as in the genus; molar process with two long unipinnate setae accompanied by 1 short simple spine. Between lacinia mobilis and molar process 3 thin, long and simple spines and 3 unipinnate spines are present, 1 modified seta, cockscomb-shaped, close to lacinia mobilis, with total of 7 elements. Right mandible (Fig. 3F) incisor with 6 robust cusps; 2 long unipinnate and 1 short simple seta. Between incisor and molar process 6 spines are inserted, apicalmost robust, curved and unipinnate, 3 naked and 2 unipinnate spines.

Maxillula (Fig. 4A): mesial lobe slender and tapering at distal part bearing 1 short apical seta accompanied by 2 subapical shorter setae and two lateral thin and short setae. Lateral lobe sub-rectangular in shape, bearing scale-like elements on both lateral and mesial margins. Apical setation composed by 11 elements; 3 simple setae in subapical position (surface apical setae); 2 mesial setae with apical tuft; remaining 6 distal setae unipinnate.

Maxilla (Fig. 4B): mesial ramus with 9 setae, 3 naked and slender setae on mesial margin, 1 surface seta short; 5 apical setae, mesialmost and 3 lateralmost apical setae simple and slender; second apical setae (starting from mesial margin) comb-like, strong, unipinnate and ornamented with fine regularly-spaced setules parallel to one another. Lateral rami close-set, each bearing 4 slender and simple setae, respectively.

Maxilliped (Figs 4C, D, 2B, C): palp robust and curved inwards; article 1 sub-rectangular in shape, bearing 1 mesial and 1 lateral setae; article 2 longest, robust, rounded on mesial margin, with 2 setae at distomesial angle; article 3 shorter than article 2 with 1 distolateral and 3 mesial setae; article 4 angled mesially, with 1 seta on distolateral margin, 1 seta on mesial margin and 3 setae on distal margin; article 5 about 0.5 as long as article 4, with 8 apical setae, of which 6 are simple slender setae and 2 are stiff pectinate setae. Endite almost reaching end of palp article 2; mesial margin ending in a pointed protrusion, with numerous hair-like setules and 2 coupling hooks medially; apical free distal margin with 4 bipinnate, spine-like, stout setae and 1 simple non-tapered seta; 3 subapical fan setae are present; epipod ovoidal, reaching distal part of palp article 1.

Pereiopod 1 (Figs 2E, 4E): coxal plate hardly discernible, basis slightly enlarged, relatively short in comparison to length of same segment of pereiopods 2-7, with 3 short setae, one of which is a penicillate seta; 2 opposite setae on ischium, transformed in sensorial penicillate setae; merus trapezoidal, shorter than all other articles, bearing 4 long and large setae on mesial and lateral apical margins; carpus longer than merus bearing 2 opposite long slender setae; mesiodistal margin with spinule row; propodus longer and slender than merus, ending with a small sclerite (Fig. 2E), with mesial hyaline lamella, bearing 1 bifid robust seta and 5 slender setae; dactylus with 6 slender sensorial setae, 3 of which inserted on surface of dactylus at base of insertion of longer claw, 2 surface setae inserted at basis of shorter claw, 1 seta on mesial distal margin of dactylus. Pereiopods 2-7 with strong dactylar claws with rounded tip. Morphology, relative length of pereiopodal segments and their armature apparently identical. Pereiopods 2-7 (pereiopod 7 figured; Fig. 5A) with coxal plate hardly discernible, basis slender than in pereiopod 1, bearing 4 setae, 2 of which penicillate, and 2 not transformed slender setae; ischium longer than in pereiopod 1, rectangular in shape, bearing 3 setae, 2 of which penicillate; merus shorter than articles, trapezoidal, and stouter than in pereiopod 1, bearing 1 sensorial seta on mesial margin, and 2 robust spiniform setae on apical mesial and lateral margins, respectively; a pointed protrusion discernible on mesial margin in subapical position accompanied by 1 thin seta; carpus longest; longer than both merus and propodus, bearing 4 elements; 1 proximal mesial simple seta and 1 bifid spine; 2 lateral setae located on apical lateral margin, 1 of which thin and long, the latter transformed in a penicillate seta; propodus long and slender than carpus, ending with elongate sclerite (Fig. 2F), bearing 2 bifid stout spines on mesial margin and 4 simple thin setae of different lengths; dactylus ending with two stout claws subequal in length, armed with 5 thin setae likely with sensorial function, 3 of which inserted on surface of dactylus at base of the insertion of longer claw, 2 surface setae inserted at basis of shorter claw.

Pleonite 0.29 as long as and 0.84 as wide as pereionite 7 (Figs 1A, 6A), small, narrower and shorter than pereionites and pleotelson; well discernible on dorsal and ventral views, partially covered by pereionite 7 on ventral view (Fig. 6A).

Penial papillae, as for the genus, coalescent and located at the middle of the free posterodistal margin of pereionite 7, with undulated free outer margins and a medial channel (Fig. 6 A–B).

Pleotelson 1.37 as long as maximal width (Figs 8D, 15A), longer than wide (length/width ratio: from 1.75 to 2.00, n = 5). Dorsal side with semicircular thickening, as dorsal and ventral body surfaces; with 4 dorsal setae, arranged in two pairs; lateral margins each bearing 3 slender setae. Pleotelson distal margin with 12 marginal setae, inserted in apical or subapical position; 2 of them are penicillate setae.

Male pleopods 1 elongate and slender, fused proximally, with sperm tube medially with an anterior opening ornamented by small spines (Figs 5B, 6A, C), approximately 3.3 as long as maximum width (measured at widest section of proximal part of pleopod). Proximal part of pleopod large and gradually tapering at distal part, bordered by paired rows of 10 imbricate scale-like elements on posterior surface. Middle part of pleopod with free lateral margins smooth, parallel, and slender, ending with convex rounded margins, tapering apically, with paired well-developed distal protrusions, each ending with rounded apex, a hyaline membrane, crenulated on lateral margin, and smooth on mesial margin. Stylet-guiding groove parallel to lateral margins of pleopod, and folded by hyaline lamella, sclerotized in terminal part on both lateral and mesial sides of distal part of pleopod. Distal part of pleopod with 7 setae.

Male pleopod 2 (Fig. 7A): protopod elongate, sub-rectangular at its proximal part, and with rounded mediodistal corner; surface of protopod with semicircular thickening (Fig. 7B), exopod extruding partially from distal part of protopod, appendix masculina (endopod) extraordinarily long, more than 3 times (3.0-3.3; n = 4) the protopod length, ending with a long stylet with a sclerotized rib that runs along its entire length; terminal part with inflated lateral margins tapering to an acute tip. Stylet quite overreaching distal part of protopod, and reaching in length distal part of uropods.

Pleopod 3 (Fig. 7C, D) with endopod bearing 1 apical, 1 mesial subapical and 1 lateral plumose setae; exopod 2-segmented, with setulose hyaline lamella on lateral margin; exopod 1 elongate, 2.8 times longer than exopod 2, the latter ending with short simple seta.

Pleopod 4 (Fig. 8A) rudimentary, ellipsoidal, uniramous.

Uropods long and slender (Fig. 8B), approximately two times longer than pleotelson. Protopod long, two times longer than endopod. Exopod and endopod long and slender; endopod longer than exopod, the latter inserted in subapical position on protopod. Mesial margin of protopod armed with 5 setae; lateral margin with 8 setae, 8 surface setae, 4 of which are slender and located on ventral surface, remaining setae on dorsal surface large. Endopod with long setae on distal third, 6 of which are penicillate setae, remaining 7 setae slender, simple, with rounded tip. Exopod armed with 9 setae on distal third, all of which slender; apicalmost setae longest.

Female.

Body length generally similar to male (Fig. 15A). Body length measured from tip of cephalon to end of pleotelson from 0.9 to 1.4 mm. (n = 3). Length/width ratio: ~8.5. Female operculum elongate (Figs 6D, 8C), sub-rectangular in shape, with parallel lateral margins, proximal margin straight; distal part medially incised, bearing 2 close-set short medial setae and 2 setae in apical lateral position. Operculum surface with semicircular thickening (Fig. 6D).

Remarks.

Detailed comparison between the two species is given in the remarks for Lepidocharon lizardensis sp. n.