Trichoniscus panormidensis, Montesanto & Caruso & Lombardo, 2011

Montesanto, Giuseppe, Caruso, Domenico & Lombardo, Bianca Maria, 2011, A new species and new records of terrestrial isopods from Sicily (Isopoda: Oniscidea), Journal of Natural History 45 (31 - 32), pp. 1925-1935 : 1929-1934

Trichoniscus panormidensis sp. nov.

( Figures 4–7 )

Material examined

Holotype. One male, TP, Mount San Giuliano, Erice , 750 m above sea level (a.s.l.), under stones and leaves in a forest of Quercus ilex , 38 ◦ 2 ′ 12 ′′ N, 12 ◦ 35 ′ 33 ′′ E ( WGS84 ), 10 November 2009, leg. D. Caruso, G. Montesanto, E. Pezzino ( MZ –DBA 10010).

Paratypes. Thirteen males, 11 females, TP, Mount San Giuliano, Erice , 750 m a.s.l., under stones and leaves of Quercus ilex , 38 ◦ 2 ′ 12 ′′ N, 12 ◦ 35 ′ 33 ′′ E ( WGS84 ) , 10 November 2009; 23 males, 26 females, same locality , 15 December 2009; 14 males, 13 females, same locality , 12 February 2010; 8 males, 16 females, same locality , 17 March 2010, leg. D. Caruso, G. Montesanto, E. Pezzino ( MZ –DBA 10011) ; 16 males, 23 females, TP, Mount Inici, Castellammare del Golfo , 950 m a.s.l., under stones and leaves in a forest of Quercus ilex , 38 ◦ 0 ′ 19 ′′ N, 12 ◦ 51 ′ 37 ′′ E ( WGS84 ) , 11 November 2009, leg. D. Caruso, G. Montesanto, E. Pezzino, G. Sabella; 11 males, 43 females, same locality , 16 December 2009, leg. D. Caruso, G. Montesanto, E. Pezzino ( MZ-DBA 10012 ) .

Other specimens. Two males, TP, Mount Sparagio, P. Giacolamaro, 750 m a.s.l., under stones and leaves in a forest of Quercus ilex , 38 ◦ 3 ′ 25 ′′ N, 12 ◦ 45 ′ 08 ′′ E (WGS84), 2 March 1994, leg. G. Sabella; two males, TP, Mount Inici, Castellammare del Golfo, 950 m a.s.l., under stones and leaves in a forest of Quercus ilex , 38 ◦ 0 ′ 19 ′′ N, 12 ◦ 51 ′ 37 ′′ E (WGS84), 22 November 1996, leg. D. Caruso, G. Sabella (CC–DBA).

Diagnosis

A species of Trichoniscus characterized by the presence in the males of gland–piliferous organs (GPO) in the cephalon and in the first pereon tergite; surface of posterior portion of cephalon trapezoidal and concave, with posterior margin distinctly convex; dorsal surface of the body well pigmented, strongly pigmented eyes made by three ommatidia arranged as triangular vertices.

Description

Length: female up to 3.9 mm, male up to 3.4 mm. Body, narrow and elongated ( Figure 4A ), strongly pigmented with a smooth surface bearing a few short setae on the cephalon and on pereon and pleon tergites. Pigmented antenna. Legs and ventral body surface colourless; only a few scattered chromatophora are occasionally observed. In ethanol-preserved specimens, pigment almost completely disappears after a few years, with only the eyes remaining intensely pigmented. Strongly pigmented eyes made by three ommatidia arranged as triangular vertices. Antennal lobes convex with a protruding forward apex, with a few short and robust spines on the surface. Antennule long, made by three articles bearing apically six or seven aesthetascs ( Figure 4B ). The antenna, pulled backward, reaches the posterior margin of the second pereonite. Flagellum consists of six to eight articles, hardly distinguishable with a microscope. One row of sensorial sticks with four aesthetascs and one row of sensorial sticks with three aesthetascs are visible in the apical segments ( Figure 4C ). Telson trapezoidal, concave in the median portion, with two scale setae on each side ( Figure 4D ). Uropods large and long, with exopodite and endopodite apically, bearing tufts of hair.

Male. Pereopods 1 and 7 show no sex differentiation ( Figure 4E, F ). Pleopods 1 and 2 similar to Trichoniscus provisorius Racovitza, 1908 . Pleopod 1 with triangular exopodite bearing lobes with a few thin setae on external margin ( Figure 5A ). Endopodite with thin sharp apex with several transverse streaks or stripes. Pleopod 2 with oval-shaped exopodite with a short rounded apex ( Figure 5B ). Endopodite long and thin in its apical section. Cephalon and first pereonite showing GPO. Cephalon has a characteristic shape that permits immediate identification: in the posterior portion it has a long and deep transverse furrow that takes up nearly half of the cephalon width. Posterior margin of this furrow lower than the vertex. Characteristic setae present inside the furrow, some showing channelling possibly linked to glands underneath, as demonstrated in Trichoniscus alexandrae Caruso, 1978 ( Lombardo et al. 2006). Surface of the posterior portion of the cephalon is trapezoidal and concave, with posterior margin distinctly convex ( Figure 6 ). Pereon 1 tergite with a light but wide dip in the median portion, with nearly rectangular shape. Other characteristic setae also present inside this dip.

Etymology

The name panormidensis derives from the geographic location of the three peaks from which the species has been collected. These mountains were part of the ancient carbonatic Panormide platform (Upper Triassic–Upper Miocene).

Remarks

The genus Trichoniscus includes approximately 100 species, some characterized by GPOs, typical male secondary sexual characters ( Vandel 1951). These GPOs are generally formed by concavities, holes, or openings, and have setae, scales or hair inside. These structures are well known in Trichoniscus ( Vandel 1960; Caruso 1978), although they are not exclusive to this genus; they are also present in the males of some species of the genera Cyphonethes , Hyloniscus , Oritoniscus , Titanethes , Bethalus and Colombophiloscia ( Tabacaru 1996) . Vandel (1951) hypothesized that GPOs may be odoriferous organs, similar to those of Lepidoptera, functioning to entice the opposite sex. Recently, Lombardo et al. (2006) studied the ultrastructure of GPOs in T. alexandrae , observing that they are linked to large glands. Secretions (pheromones?) are associated with the setae of these organs inside the dip. Among the 13 species of Trichoniscus with GPOs, only four species exhibit this organ on the cephalon and the first pereon tergite: T. circuliger Veroheff , found in Switzerland and northern Italy; T. dancaui Tabacaru , found on Mount Mehedinti of Romania; T. karawankianus Verhoeff , found in southern Austria; and T. alexandrae Caruso , found in Sicilian caves.

Trichoniscus panormidensis sp. nov. possesses GPOs on the cephalon and on the first pereon tergite; nevertheless, the morphology and position of these structures are exclusive to this new species. However, the species shows remarkable morphological affinities with T. alexandrae , differing in two regards. First, the shape and position of the cephalic furrow differs, because in T. panormidensis sp. nov. it is in the posterior portion of the cephalon; it is more extended but the margins are closer in the median section. Second, the general morphology of the dip in the first pereon tergite differs between the two species. In T. panormidensis sp. nov. the GPO is hardly visible because of its less concave shape. Moreover, this new species differs from T. alexandrae , a troglobian species of two Sicilian caves, both in the general shape of the cephalon and in the presence of well-developed eyes. Trichoniscus panormidensis sp. nov. is strongly pigmented and lives in humicol habitats, whereas in T. alexandrae the eyes and pigment are always absent. Populations of Trichoniscus panormidensis sp. nov. have been found in Sicily on top of mountains, above 700 m a.s.l., in undergrowth litter and decaying plant matter ( Figure 7 ).

Figures

Figure 4. Trichoniscus panormidensis sp. nov. (male, paratype from Mount San Giuliano, Erice). (A) Animal in dorsal view, scale bar: 0.5 mm; (B) antennula; (C) antenna; (D) telson and uropods; (E) pereopod 1; (F) pereopod 7.

Figure 5. Trichoniscus panormidensis sp. nov. (male, paratype from Mount San Giuliano, Erice). (A) Pleopod 1 and genital papilla; (B) pleopod 2.

Figure 6. Trichoniscus panormidensis sp. nov. (male, paratype from Mount San Giuliano, Erice). Cephalon and pereonite 1, dorsal. The arrows indicate the position of gland–piliferous organs.

Figure 7. Distribution map of Trichoniscus panormidensis sp. nov. in Sicily.