Liriopsis pygmaea ( Rathke, 1843 )

Peresan, Laura & Roccatagliata, Daniel, 2005, First record of the hyperparasite Liriopsis pygmaea (Cryptoniscidae, Isopoda) from a rhizocephalan parasite of the false king crab Paralomis granulosa from the Beagle Channel (Argentina), with a redescription, Journal of Natural History 39 (4), pp. 311-324 : 313-321

publication ID	https://doi.org/ 10.1080/0022293042000200103
persistent identifier	https://treatment.plazi.org/id/8F2C8796-FFB2-3E3A-FE2D-FDE59DBDEE80
treatment provided by	Felipe
scientific name	Liriopsis pygmaea ( Rathke, 1843 )
status

Treatment

Liriopsis pygmaea ( Rathke, 1843) View in CoL

( Figures 1–6 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )

Liriope pygmaea Rathke 1843: 60–63 , pl. 1, Figures 8–12; Steenstrup 1855: 25; Lilljeborg 1859: 6–14, pl. 1, Figures 1 View Figure 1 –23; Lilljeborg 1860: 73–74, pl. 6, Figures 1 View Figure 1 , 2 View Figure 2 .

Liriopsis View in CoL [ pygmaea ]: Schultze in Müller 1859: 310 (footnote).

Cryptothiria pygmaea: Bate and Westwood 1868: 261–266 [partim];? Czerniavsky 1868: 78– 79 (doubtful identification of a single male from the Black Sea).

Cryptoniscus pygmaeus: Müller 1871: 72; Fraisse 1878: 287.

Liriopsis pygmaea: Giard and Bonnier 1890: 389 View in CoL ; Sars 1899: 242–243, pl. 99, Figure 3 View Figure 3 , pl. 100, Figure 1 View Figure 1 ; Bonnier 1900: 195–197, Figure 31; Caullery 1908: 591; Nierstrasz and Brender à Brandis 1926: 14–15, Figures 9–17; Pérez 1929: 607–608; Pérez 1931: 509, 512; Shiino 1952: 334; Pike 1961: 237–239, Figure 7, Table 1; Bourdon 1963: 422; Nielsen and Strömberg 1965: 54; Bourdon 1967: 281, 284 (Table 1); George and Strömberg 1968: 251; Nielsen and Strömberg 1973: 77–92, Figures 1 View Figure 1 , 6 View Figure 6 , 7, 29, 36, 37; Altes 1981: 27; Grygier and Bowman 1990: 27–28; Grygier 1993: 186; Warrenchuk and Shirley 2000: 971–976, Figure 1 View Figure 1 .

Material examined

Beagle Channel (about 54 ° 54 9 S, 67 ° 12 9 W), 10– 50 m. Infesting the rhizocephalan Briarosaccus callosus . 24 July 1996: 14 Cr, 13 A ♀, 1 SA ♀ 2; 10 September 1996: 8 Cr; 2 October 1996: 80 Cr; 2 November 1996: 5 Cr; 20 December 1996: 14 Cr, 1 SA ♀ 2; 28

January 1997: 9 Cr, 6 SA ♀ 2; 23 March 1997: 45 Cr, 3 SA ♀ 1, 1 SA ♀ 2, 4 A ♀ (one of them carrying epicaridia); 10 June 1997: 28 Cr; 6 October 1997: 6 Cr.

Epicaridium larva

Total length. Approximately 0.26 mm.

Cephalon ( Figure 1a View Figure 1 ). Cephalon rounded anteriorly; body gradually narrowing posteriorly. Dorsal segmentation distinct. Pleotelson ( Figure 2d View Figure 2 ) projecting dorsally as rounded translucent lamella, extending somewhat beyond distal end of anal tube (hardly noticeable under light microscopy). Anal tube ( Figures 1c View Figure 1 , 2d View Figure 2 ) approximately as long as uropod peduncle, consisting of rolled laminae with margins in contact at dorsal mid-line, margins slightly fringed.

First antenna. Peduncle with two articles, basal article with three plumose setae. Rami with two and three distal setae, respectively (articulation with peduncle observed for one ramus only), two aesthetascs arising between rami.

Second antenna ( Figure 2a View Figure 2 ). Peduncle with three articles; distal article longest, with three plumose and one small simple setae, distally. Flagellum with three articles gradually decreasing in length distally, third article with three long lamellae (only one drawn) and five setae (at least some of them plumose), largest seta as long as antenna.

Pereopods. First five pereopods alike, subchelate, becoming slightly longer posteriorly. Sixth pereopod ( Figure 2b View Figure 2 ) elongated, ending in bristle-like dactylus. Merus with one feeble seta proximally and two thicker ones distally. Carpus and propodus apparently coalesced, together fusiform. Dactylus slightly longer than basis.

Pleopods ( Figure 2c View Figure 2 ). All five alike, becoming slightly shorter posteriorly; exo- and endopod with three and two distal plumose setae, respectively.

Uropod ( Figures 1b View Figure 1 , 2d View Figure 2 ). Uropod widely covered dorsally by pleotelson lamella. Peduncle with one long plumose seta on outer distal angle. Exopod placed dorsally and anteriorly to endopod; distal end with two plumose setae. Endopod slightly shorter than exopod, with two large setae curved downwards and one small straight seta.

Cryptoniscus larva

Total length. 1.40–1.52 mm.

Body ( Figures 3a, b View Figure 3 , 4a View Figure 4 ). Body flattened dorsoventrally, gradually narrowing posteriorly, dorsal surface with faint (visible only under high magnification) transverse striations (not drawn). Cephalon slightly longer than half its width, frontal edge almost semicircular. Eyes very distinct, consisting of a single lens encircled by reddish pigment. All pereonites with a couple of minute setae dorsally; third and fourth pereonites slightly shorter than remaining ones. Pleon (including pleotelson) somewhat longer than the first five pereonites together; first to fourth pleonites with mid-ventral lobe between pleopods, becoming gradually less developed from first ( Figure 3e View Figure 3 ) to fourth and disappearing on fifth. Pleotelson with posterior margin rounded and entire, slightly exceeding peduncles of uropods.

First antenna ( Figure 4b View Figure 4 ). Peduncle with three articles. First article posteriorly expanded; caudal end rounded, with three setae (one plumose, two simple); anterior end projected medially into large spur-like tooth (either exposed, Figure 3d View Figure 3 , or partially covered by median plate, Figure 3c View Figure 3 ), and laterally with three setae (one plumose, two simple). Second peduncular article, ornamented with delicate ridges bounding polygonal areas ( Figure 3d View Figure 3 ); small tooth halfway along its anterior margin ( Figure 3d View Figure 3 ); distal end with row of four setae (two plumose, two simple) anteriorly and two setae (one plumose, one simple) posteriorly. Third peduncular article partly hidden by second one; anterior margin with long simple seta; distal margin with numerous aesthetascs (only most ventral ones drawn). Ventral flagellum with three long distal setae, dorsal flagellum with four long distal setae and two basal aesthetascs.

Second antenna ( Figure 4c View Figure 4 ). Second antenna scarcely extending beyond fourth pereonite (including distal setae). Peduncle with four articles, first two articles with fine striae. First article largest and unarmed, remaining ones gradually increasing in length and with setae, namely second article with one simple, third article with two plumose and one simple, and fourth article with four plumose (only ventral ones shown) and one simple setae. Flagellum with five articles, approximately 0.70 times as long as peduncle, with 2-1-2-1 short simple setae on first four articles (only ventral ones shown); fifth article with four unequal distal setae.

Oral cone. Oral cone directed anteriorly ( Figure 3c View Figure 3 ).

Pereopods. First pereopod ( Figure 4d View Figure 4 ): basis with strong distal condyle flanked by two transparent lamellae. Ischium 0.65–0.73 times as long as basis. Merus with seta-like projection anteriorly and two feeble simple setae posteriorly. Carpus, armed on posterior margin with distal tiny spine between two unequal setae, proximal one hardly noticeable. Propodus slightly shorter than basis, broadly articulated with carpus, postero-distal angle with a depressed area limited proximally by a blunt process bearing two unequal spines (see detail). Dactylus fitting into depressed area of propodus, anterior margin slightly serrated, with one stout spine and one delicate seta distally.

Second pereopod similar in shape to first, but slightly larger.

Third ( Figure 5a View Figure 5 ) to fifth pereopods alike, but slightly increasing in length posteriorly. Basis length roughly equal to that of propodus. Ischium 0.76–0.81 times as long as propodus, biceps-like, distally with two transparent lamellae flanking merus. Merus with one thick and one feeble setae, distally. Carpus with strong spine on distal-posterior angle. Propodus with three spines in distal depressed area, posterior margin with fringe of minute setae. Dactylus apparently fused with distal spine (no articulation discernible at high magnification), both together approximately half as long as propodus, posterior margin with fringe of minute setae, distal end bifid.

Sixth pereopod ( Figures 3e View Figure 3 , 5b View Figure 5 ): ischium approximately half as long as basis. Merus with one thick and one feeble setae, distally. Carpus approximately as long as merus. Propodus almost globular, approximately 0.75 times as long as ischium. Dactylus (probably the dactylus itself plus a completely fused distal spine) extremely large and styliform, almost twice as long as basis. Seventh pereopod ( Figures 3e View Figure 3 , 5c View Figure 5 ) as sixth except for: shorter thick seta on merus (only the thicker basal part of this seta remains).

Coxal plates. Coxal plates (epimeres) with fine cuticular striations and without marginal teeth ( Figure 3e View Figure 3 ).

Pleopods. All five pleopods alike ( Figure 5d View Figure 5 ). Basal segment with two coupling setae on inner margin, these slightly longer than endopod. In first four pleopods both rami with five plumose setae distally, outermost setae of exopods clearly shorter than remaining ones. Fifth pleopod as previous ones, except endopod with only three distal setae.

Uropod ( Figure 5e View Figure 5 ). Peduncle and endopod combined approximately as long as pleotelson. Peduncle widely covered by pleotelson, outer margin with two unequal simple setae distally, longer one reaching end of exopod. Exopod approximately 0.80 times as long as endopod. Endopod with six delicate plumose setae proximally on dorsal surface, inner margin with fringe of minute setae, distal end with five plumose and three simple setae, two of latter longer than others, 1.5 and twice as long as article, respectively. Exopod, with five simple setae at distal end, longest seta approximately three times as long as article.

Early subadult female

Total length. 6.0– 8.2 mm.

Whole isopod inside mantle cavity of rhizocephalan externa. Body ( Figure 6a, b View Figure 6 ) orangereddish (same colour as rhizocephalan ovary), consisting of large sac with small flat disc tilted over it. Appendages absent. Sac with five or six lateral lobes and pyriform vesicle (heart?) visible through cuticle. Disc with irregular concentric folds, detached from sac on one side but continuous with it on the other. Apparently, sac develops as internal anchor and disc becomes external brood sac in latter stages.

Advanced subadult female

Total length. 8.0– 9.7 mm.

Anterior part of isopod protruding from mantle cavity of rhizocephalan externa. Body ( Figure 6c View Figure 6 ) divided by constriction into two parts: rhomboidal caudal anchor, immersed in mantle cavity, and a freely exposed anterior subspherical sac. In some specimens developing adult visible beneath subadult cuticle. These developing adults with incipient brood pouch on ventral surface, visible as elongated area bounded by two folds and with rudiments of anterior finger-like processes and caudal digitations at its extremities.

Adult female

Total length. 3.3–9.3 mm.

Anchor with definitive form and sac exhibiting long ventral slit, through which the epicaridium larvae are expelled. Body ( Figure 6d, e View Figure 6 ) divided by narrow neck into anchor deeply embedded in host’s body and subspherical part (brood pouch) protruding from host’s mantle wall. Anchor part: dorsal surface convex, with three parallel hollow bars; ventral surface concave, with tiny central papilla (called ‘vésicule rectale’ by Caullery, 1908, in his description of Liriopsis monophthalma ). Heart visible through translucent cuticle as rounded sac below this papilla. Brood pouch: dorsal surface circumvallated by four lines, with five bunches of longitudinal muscles between them (muscles only evident in spent females). Ventral surface with longitudinal mid-line groove in ovigerous females (visible as slit in spent females). Mid-line furrow (slit): anterior end with finger-shaped process fitting between thick margins ( Figure 6f View Figure 6 ); posterior end with six internal digitations, only visible by stretching pouch and peering through slit ( Figure 6g View Figure 6 ).