Iberiarmadillidium psammophilum, 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 : 1329-1332

IBERIARMADILLIDIUM PSAMMOPHILUM SP. NOV.

( FIGS 1B , 5A , 6A , 7A , 8A , 11A–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 / u r n: l s i d: z o o b a n k. o r g: a c t: 1 C E 3 0 D E E - B 5 F 1 - 46C3-9914-7B019312443C

Material examined: Holotype: male ( MNCN 20.04 /14325), Spain, Comunidad de Madrid, Madrid, El Pardo, 40°28′58″N, 3°45′03″W, 16 October 2015.

Paratypes: four males and five females ( MNCN 20.04 /14326- MNCN 20.04 /14334), same locality and date as holotype. – One male and one female ( MNCN 20.04 /14335- MNCN 20.04 /14336), same locality as holotype, 10 April 2012 . – Four males and three females ( MNCN 20.04 /14337- MNCN 20.04 /14343), same locality as holotype, 6 November 2012 . – Five males and four females ( MNCN 20.04 /14344- MNCN 20.04 /14352), same locality as holotype, 25 February 2015 . – Two males and two females ( MNCN 20.04 /14353- MNCN 20.04 /14356), same locality as holotype, 1 November 2015 . – Three males and three females ( MNCN 20.04 /14357- MNCN 20.04 /14362), Spain, Castilla y León, Ávila Province , Sotillo de la Adrada, 40°17′18″N, 4°33′07″W, 4 April 2011 .

Etymology: From Ancient Greek ψάμμος (psammos), sand, and φίλος (philos), friend or lover, referring to the preference for sandy soils where the species has been found. These sandy soils are formed by the erosion and deposit of granitic materials from the Sistema Central Mountains ( Vera, 2004).

Diagnosis: A species of Iberiarmadillidium characterized by the presence of elongated tubercles, usually not elevated in a keel-like shape or, if so, with roundish profile; those in posterior rows particularly elongated, surpassing the caudal margin of pereonites. Lateralmost pair of tubercles on pereonite 7 elongated, with the caudal one longer than the frontal one, at most subequal in size. Central pair of tubercles in pleonite 5 larger than lateral pairs. Pereonite 2 epimera with sinuous outer margin, in pereonite 3 epimera it might be sinuous or, more rarely, straight. Colour of epimera lighter than dorsal parts. Outer lobe of pleopod 1 endopod with almost straight margin. Pleopod 2 exopodite almost triangular, with moderately concave distal/outer margin; pleopod 2 endopod tapering progressively from base. Pleopod 4 exopod with almost straight distal margin.

Description: Maximum length: ♂ 5.5 mm, ♀ 6 mm. Maximum width: ♂ ~ 2.5 mm, ♀ 2.7 mm. Colour in life brownish, with epimera, antennae and pereopods whitish ( Fig. 1B ). Colour of preserved specimens, after ≤ 9 years in ethanol, light brown to off-white, with epimera usually lighter than dorsal parts. Body habitus ( Figs 1B , 5A ) strongly convex, able to roll up into a perfect ball, with pereon and pleon covered by rows of strong, elongated tubercles; specimens from Sotillo de la Adrada present much smaller tubercles than those from El Pardo, but they are still clearly visible even without magnification. Epimera vertical and slightly directed outwards, especially in the posterior half of the body.

Tegument with whole surface of pereon, pleon and epimera covered by round, convex, scale-like papillae with irregular margins, clearly visible in SEM images ( Figs 5A , 6A , 7A ), absent in tips of tubercles and some small areas between them; with sparse but evenly distributed small scale-setae with broad base and short tip, present also on tubercles. Scale-setae stouter in parts of the head, such as scutellum, frontal line and clypeum; in antennae, pereopods and uropods scale-setae triangular and stout, longer and thinner in antennal flagellum ( Fig. 11A–D ); Glandular fields with one or two pores, longitudinally elongated, elliptical, anteriorly located in epimera 1, submedially located in the lateral margin of other epimera, but not observed in every epimera.

Cephalon ( Fig. 8A ) of Eluma type, frontal line continuing scutellum upper margin and with no trace of a postscutellar line; scutellum triangular, broader than high, slightly concave in the middle, clearly separated and slightly elevated from vertex, but not protruding above it; antennary lobes well developed, obliquely directed frontwards; eyes small, with three to five pigmented ommatidia; cephalic shield covered by four rows of tubercles, irregularly arranged except caudal one, formed by ten to 12 tubercles, larger than the rest (in some specimens isolated, abnormally broad tubercles can be formed by the fusion of two regular ones).

Pereonites ( Fig. 5A ) with elongated tubercles, low with rounded transverse section or high with rounded profile; particularly elongated in caudal rows, surpassing the caudal margin of pereonites. Pereonite 1 with three or four rows of tubercles, irregularly arranged, but caudal one that is formed by 14 tubercles; posterior margin straight, concave at the beginning of epimera ( Fig. 5A ); epimera 1 with three or four irregularly arranged, small to large tubercles; caudal angle with a small schisma ( Fig. 6A ), with inner lobe poorly differentiated and shorter than outer one, not forming a sulcus along the lateral margin. Pereonite 2 with two rows of elongated, subequal tubercles, with some small, isolated tubercles between them, the caudal one with 14 or 15 tubercles; epimera 2 with sinuous outer margin, showing one or two small- to medium-sized tubercles, absent in specimens from Sotillo de la Adrada. Pereonite 3 with two rows of elongated, subequal tubercles, often with some small isolated tubercles among them, the caudal one with 14 tubercles; epimera 3 with sinuous outer margin (straight in some specimens from Sotillo de la Adrada) and showing one or two small- to mediumsized tubercles, absent in specimens from Sotillo de la Adrada. Pereonite 4 with two rows of tubercles, with some small isolated tubercles among them, the caudal one with 14 tubercles; epimera 4 without tubercles (Sotillo de la Adrada) or with a barely marked tubercle (El Pardo), lateral profile broadly rounded to squarish. Pereonite 5 with two rows of tubercles, with some small isolated tubercles among them, the caudal one with 13 or 14 elongated tubercles; lateralmost tubercles usually elongated, the caudal one longer or subequal; epimera 5 without tubercles (Sotillo de la Adrada) or with a barely marked tubercle (El Pardo), lateral profile squarish, with anterior corner rounded. Pereonite 6 with two rows of tubercles, with some small isolated tubercles among them, the caudal one with 12–14 tubercles; lateralmost tubercles usually elongated, the caudal one longer or subequal; epimera 6 without tubercles (Sotillo de la Adrada) or with one or two small tubercles (El Pardo), lateral profile squarish, sometimes with rounded corners. Pereonite 7 with two rows of elongated tubercles, the caudal one with 12 tubercles, longer than the frontal ones, surpassing the caudal margin of pereonite; lateralmost tubercles elongated, caudal ones longer than frontal; epimera 7 without tubercles (Sotillo de la Adrada) or with one or two small tubercles (El Pardo), lateral profile squarish. Pleonites with a single row of rounded, medium to large tubercles: six to nine in pleonite 1, seven to nine in pleonite 2, eight to ten in pleonite 3, eight or nine in pleonite 4 and six in pleonite 5. Central, paramedian pair of tubercles in pleonite 5 always larger than lateral ones ( Fig. 7A ). Neopleura 3 and 4 with one barely marked tubercles in specimens from El Pardo, without tubercles in specimens from Sotillo de la Adrada; neopleura 5 with no apparent tubercles. Telson ( Fig. 7A ) triangular, with broadly rounded apex; surface with two paramedian, medium-sized, elongated tubercles; apex slightly curved outwards, giving a concave appearance. Antennula three-segmented: first article broadest, second article shortest, and third article with subapical aesthetascs. Antenna ( Fig. 11C ) densely covered with small but robust, triangular scale-setae, thinner in the flagellum; with fifth article of peduncle slightly longer than flagellum; flagellum with second article 2.3–2.5 times as long as first article. Pleopod 1 and 2 exopods with covered lungs. Uropod ( Fig. 11D ) with abundant small, triangular scale-setae; protopod about as long as endopod and twice as long as exopod; exopod about two times as broad as long.

Male: Pereopod 1 ( Fig. 11A ) merus and carpus armed with two lines of long, strong, spiniform setae along sternal margin. Long spiniform setae present in sternal margin of propodus only in distal third. Pereopod 7 ( Fig. 11B ) with no distinct sexual modifications; ischium with slightly concave sternal margin. Sternal margin of merus, carpus and propodus armed with long, strong, spiniform setae. Pleopod 1 exopod ( Fig. 11E ) with internal half ~2.5 times as long as external half, with concave proximal and distal margins; distal and proximal ends of inner half broadly rounded, bearing a single seta in distal margin. Endopod ( Fig. 11F ) 2.4 times as long as exopod; outer lobe with almost straight margin; distal portion ending in a narrow apex, with no particular structures. Pleopod 2 exopod ( Fig. 11G ) almost triangular, with concave outer/distal margin bearing long setae and slightly convex proximal margin; endopod ( Fig. 11H ) ~1.5 times as long as exopod; narrow, tapering progressively from the base to the apex. Pleopod 3 exopod ( Fig. 11I ) with concave distal margin, more straight in 4 and 5 ( Fig. 11J, K ), all of them bearing setae; a marked convexity is present in the proximal margin of pleopod 4 exopod.

Remarks: There is considerable interpopulational variation in the degree of development of the tubercles covering the cephalic shield, pereonites and pleonites, with tubercles larger and much more conspicuous in specimens from El Pardo (Madrid) than in those from Sotillo de la Adrada (Ávila). All populations have been found during wet months, under stones in the company of ants in sandy siliceous soils in typically Mediterranean landscapes dominated by Quercus ilex L. (El Pardo) or Pinus pinea (Sotillo de la Adrada) . Populations from El Pardo (Madrid) have been found in nests of Camponotus cruentatus (Latreille, 1802) , Pheidole pallidula and Aphaenogaster dulcineae Emery, 1924 .

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 11. Iberiarmadillidium psammophilum from El Pardo, 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.