Cristarmadillidium myrmecophilum, Recuero & Rodríguez-Flores & García-París, 2022

Recuero, Ernesto, Rodríguez-Flores, Paula C. & García-París, Mario, 2022, Homoplasy and morphological stasis revealed through multilocus phylogeny of new myrmecophilous species in Armadillidiidae (Isopoda: Oniscidea), Zoological Journal of the Linnean Society 194 (4), pp. 1312-1340 : 1323-1326

CRISTARMADILLIDIUM MYRMECOPHILUM SP. NOV.

( FIGS 1C , 5D , 6D , 7D , 8D , 9A–K )

Z o o b a n k r e g i s t r a t i o n: h t t p: / / z o o b a n k. o r g / urn:lsid:zoobank.org:act:872BCE5A-C6DC-4B51-9EF5-C36BE3C27BB7

Material examined: Holotype: male ( MNCN 20.04 /14300), Spain, Castilla-La Mancha, Ciudad Real Province, Guadalmez , 38°42′21.6″N, 4°57′01.5″W, 21 February 2013.

Paratypes: four males and five females ( MNCN 20.04 /14301- MNCN 20.04 /14309), same locality and date as holotype. – Two males and two females ( MNCN 20.04 /14310- MNCN 20.04 /14313), Spain, Extremadura, Badajoz Province, Capilla , 38°45′56″N, 5°01′54″W, 21 February 2013 . – One male and eight females ( MNCN 20.04 /14314- MNCN 20.04 /14322), Spain, Extremadura, Cáceres Province, Casas de Don Antonio , 39°11′59″N, 6°16′45″W, 28 December 2015 . – One male and One female ( MNCN 20.04 /14323- MNCN 20.04 /14324), Spain, Andalucía, Cádiz Province , Espera , 36°52′19.5″N, 5°51′49.5″W, 1 April 2012 .

Etymology: From the Greek μύρμηξ (myrmex), ant, and φίλος (philos), friend or lover, in reference to the observed association of this new species with ant nests.

D i a g n o s i s: A s p e c i e s o f C r i s t a r m a d i l l i d i u m differentiated from other species of the genus by the presence of a small schisma. Ornamentation of tegument without marked tubercles, although it presents slightly elevated granules reminiscent of tubercles, perceptible only at high magnification or in the largest specimens. Epimera vertical, not bent outwards in a bell-shaped transverse body section. Pleopod 1 exopod with rounded apexes and distal margin bent in an obtuse angle, resembling C. muricatum . Pleopod 2 exopod short, ~1.1 times as long as wide, also resembling C. muricatum .

Description: Maximum length: ♂ ~ 5 mm, ♀ 6.5 mm. Maximum width: ♂ ~ 2 mm, ♀ 3 mm. Colour in life brownish, lighter in epimera; antennae and pereopods whitish ( Fig. 1C ). Colour of specimens preserved in ethanol light brown to off-white. Body habitus ( Figs 1C , 5D ) strongly convex, able to roll up into a complete ball, with pereon and pleon presenting rows of shallow granules; epimera almost vertical.

Tegument with large areas of surface of pereon, pleon and epimera covered by rounded, concave papillae; anterior parts of epimera with rows of semicircular scales; with sparse but evenly distributed small scale-setae with broad base and short tip. Scalesetae stouter, triangular in parts of the head, such as scutellum, frontal line, antennae and clypeus. In pereopods, scale-setae large to very large, acutely triangular, resembling small spines; glandular fields in epimera of pereonites 2 and 3 with one or two pores, transversely elongated, located far from the lateral margin, medially in epimera 2, submedially in epimera 3.

Cephalon ( Fig. 8D ) of Eluma type, with frontal line continuing the scutellum upper margin and no trace of a postscutellar line. Scutellum triangular, wider than long, clearly separated from vertex but not protruding above it. Antennary lobes well developed, obliquely directed frontwards. Eyes small, with four to six pigmented ommatidia. Cephalic shield rugose, with obsolete granules, sometimes a little larger in the caudal margin, forming a diffuse transverse row.

Pereonite 1 covered with obsolete granules, poorly defined but arranged in two or three irregular transverse rows, the caudal one almost imperceptible in some specimens; posterior margin straight, clearly concave only at the start of the epimera; epimera 1 without granules, caudal angle with a small schisma ( Fig. 6D ), with inner lobe shorter than outer one, not forming a sulcus along the lateral margin. Pereonites 2–7 with one row of elongated, obsolete granules; a second, caudal row of granules is almost imperceptible; epimera without tubercles; lateral profiles squarish, but in epimera 4 narrow and rounded, and in epimera 5 rounded and broader than 4. Pleonites ( Fig. 7D ) with obsolete, barely perceptible granules, aligned in a single row along caudal margins; neopleura without tubercles. Telson ( Fig. 7D ) triangular, with broadly rounded apex; surface almost flat to slightly concave, without tubercles or at most with two poorly defined paramedian granules in large specimens.

Antennula three-segmented: first article broadest, second article shortest, and third article as long as first one and with subapical aesthetascs. Antenna ( Fig. 9C ) with small but robust, triangular scale-setae, more numerous in articles 4 and 5, thinner and longer in the flagellum; fifth article longer than flagellum, bearing distally a long, spiniform seta; second flagellar article 2.5–2.8 times as long as first, bearing two rows of aesthetascs. Pleopod 1 and 2 exopods with monospiracular covered lungs. Uropod ( Fig. 9D ) with scarce triangular scale-setae, with protopod 0.8 times as long as endopod and 2.5 times as long as exopod; exopod about two times as wide as long.

Male: Pereopod 1 ( Fig. 9A ) merus and carpus armed with two irregular lines of strong, spiniform setae along sternal margin, longer in carpus; sternal margin of propodus with long spiniform setae in distal half; isolated long, strong, spiniform setae present also in basis, ischium and tergal margin of merus. Pereopod 7 ( Fig. 9B ) with no distinct sexual modifications, ischium with straight sternal margin; with long, strong, spiniform setae along sternal margin of carpus and propodus, and isolated in basis, ischium and merus. Pleopod 1 exopod ( Fig. 9E ) with internal half rounded, about two times as long as external half, with concave proximal margin, and distal margin bent in an obtuse angle; endopod ( Fig. 9F ) 2.2 times as long as exopod, distal portion acute, with no differentiated structures. Pleopod 2 exopod ( Fig. 9G ) subtriangular, with acute distal end and deeply concave outer/distal margin; endopod ( Fig. 9H ) narrow, about twice as long as exopod. Pleopod 3 exopod ( Fig. 9I ) with concave distal margin; pleopod 4 exopod ( Fig. 9J ) almost quadrangular; pleopod 5 exopod with distal margin slightly concave ( Fig. 9K ).

Remarks: We found this species in Mediterranean scrublands and meadows, on sandy soils, always under stones hosting ant nests. The population from Guadalmez, Ciudad Real, was found in the company of Tapinoma nigerrimum (Nylander, 1856) or Pheidole pallidula (Nylander, 1849) .

Figures

Figure 1. Map showing the sampling localities of Iberiarmadillidium pinicola (black stars), I. psammophilum (purple stars), I. sakura (white star), Cristarmadillidium breuili (black circle), Cristarmadillidium muricatum (red circles) and C. myrmecophilum (yellow circles). Habitus in vivo: A, I. pinicola from Valdemaqueda, Madrid; B, I. psammophilum from El Pardo, Madrid; C, C. myrmecophilum from Casas de Don Antonio, Cáceres; D, C. muricatum from Punta de Benimaquia Cave, Alicante; and E, C. breuili from Bolumini Cave, Alicante.

Figure 5. Scanning electron photomicrographs showing the general habitus of Iberiarmadillidium psammophilum (A), Iberiarmadillidium pinicola (B), Iberiarmadillidium sakura (C), Cristarmadillidium myrmecophilum (D) and Cristarmadillidium muricatum (E).

Figure 6. Scanning electron photomicrographs showing details of pereonite 1 and 2 epimera of Iberiarmadillidium psammophilum (A), Iberiarmadillidium pinicola (B), Iberiarmadillidium sakura (C), Cristarmadillidium myrmecophilum (D) and Cristarmadillidium muricatum (E) (only epimera 1 is shown).

Figure 7. Scanning electron photomicrographs showing details of the telson of Iberiarmadillidium psammophilum (A), Iberiarmadillidium pinicola (B), Iberiarmadillidium sakura (C), Cristarmadillidium myrmecophilum (D) and Cristarmadillidium breuili (E).

Figure 8. Scanning electron photomicrographs showing details of the head of Iberiarmadillidium psammophilum (A), Iberiarmadillidium pinicola (B), Iberiarmadillidium sakura (C) and Cristarmadillidium myrmecophilum (D).

Figure 9. Cristarmadillidium myrmecophilum from ~8 km north-east of Hoyo de Pinares, male paratype: A, pereopod 1; B, pereopod 7; C, antenna; D, uropod; E, pleopod 1 exopod; F, pleopod 1 endopod; G, pleopod 2 exopod; H, pleopod 2 endopod; I, pleopod 3 exopod; J, pleopod 4 exopod; and K, pleopod 5 exopod.