Ctenorillo atlanticus, Cifuentes & Da & Silva, 2023

Cifuentes, Julio & DA SILVA, Luis P., 2023, Terrestrial isopods (Isopoda, Oniscidea) of São Tomé Island, with the description of two new Armadillidae Brandt, 1831 species, Zoosystema 45 (21), pp. 635-652 : 638-641

Ctenorillo atlanticus n. sp.

( Figs 2C ; 3-6 )

urn:lsid:zoobank.org:act:D725674D-4695-468C-9ED2-71CA18622FAD

TYPE MATERIAL. — Holotype. Democratic Republic of São Tomé and Príncipe • 1♂; São Tomé; 0°20’30.1”N, 6°44’12.6”E; 9.V.2022; L.P. da Silva leg.; MNCN 20.04/20603 .

Paratype. Democratic Republic of São Tomé and Príncipe • 1 ♂; Praia dos Governadores ; 0°24’44.1”N, 6°39’41.7”E; 17.V.2022; L.P. da Silva leg.; Coll. JC673 • 1 ♀; Praia dos Governadores ; 0°24’44.1”N, 6°39’41.7”E; 17.V.2022; L.P. da Silva leg.; OST045b ; IBI • 1 ♂; São Tomé; 0°20’29.9”N, 6°44’12.5”E; L.P. da Silva leg.; OST010a ; IBI • 1 ♀; São Tomé; 0°20’29.9”N, 6°44’12.5”E; L.P. da Silva leg.; OST010b ; MNHN-IU-2022-1620 • 1 juvenile; São Tomé; 0°20’29.9”N, 6°44’12.5”E; L.P. da Silva leg.; OST010c ; IBI .

ETYMOLOGY. — The specific name refers to the fact that it lives on an island bathed by this ocean.

ECOLOGY. — Ctenorillo atlanticus n. sp. is an epigean species. The specimens from São Tomé were found beneath dead wood in a city park, while those from Praia dos Governadores were found underneath the bark of a fallen tree on the beach.

DESCRIPTION

Body

Maximum body length 3 mm in a female and 3.5 mm in a male. General coloration dark purplish brown, with lighter muscle insertions and pleuroepimers ( Fig. 2C ).

Integumentary characters ( Figs 2C ; 3A, C ; 4 A-D)

Integument with circular depressions and with large ribs and tubercles. Cephalon with six rows of tubercles, more notorious towards the posterior and central region. First pereonite with three rows, formed respectively by four, six and seven tubercules that form more or less developed ribs, in addition to two other large tubercles partially fused at the limit of the pleuroepimer; from tergites II to VI with two alternate rows of tubercles, also forming ribs more or less developed, numbering three+three in the anterior row and three +one+three in the posterior row, plus another large rib at the limit of the pleuroepimer which moves towards the posterior edge of the tergite in the successive segments; in tergite VII with two alternate rows of tubercles, formed by two+two in the anterior row and two+one+two in the posterior, in addition to the ribs in the pleuroepimer edge. Pleonites III and IV with two+two strong tubercles. Pleonite V and the base of the telson with two large paramedian tubercles. Scale-setae very small and with a more or less semi-circular scale ( Fig. 4E ).

Somatic characters ( Figs 2C ; 3 A-C; 4B-F)

Strongly convex body, pleuroepimers almost vertical towards the ventral side, neopleurons and telson with a slight lateral expansion. Ocular apparatus with eight ommatidia. Cephalon. Frontal shield with a protuberance slightly above the vertex, slightly convex at its edge and curved up.

Pereon. Lateral edge of pleuroepimer I very little raised, and separated from the rest of the tergite by a depression; very acute anterior angle; posterior angle with a schisma with two differentiated lobes, the anterior lobe with a truncated posterior margin, the posterior lobe with a rounded shape and protruding in relation to the anterior lobe in a lateral view. Epimera from pereonite II with a triangular inner lobe, much shorter than the outer lobe. Pleuroepimers II to VII quadrangular.

Pleon. Neopleurons slightly extended.

Telson. Hourglass shaped, with the distal part narrower than the basal, the rear edge slightly convex and extended, and with marked angles.

Appendages ( Fig. 5 A-G)

Mouth apparatus with mandibles with molar penicil formed by several feathered setae; left mandible with two + one free penicils and right mandible with one+ one; maxillule with four+ six teeth; maxilliped endite with a large subapical seta and two short triangular setae. Antennula with three segments, the second much smaller than the other two, and the third with a group of aesthetascs at the tip. Antenna short and stout; the first flagellum segment with half of the length of the second, the second flagellum with a group of short aesthetascs. Uropod with the endopod reaching half the length of the protopod; protopod with a trapezoidal shape and a concave internal edge; exopod greatly reduced, on the dorsal side of the protopod and near the inner margin ( Fig. 4D ). Pereopod I with several hyaline scales in the ventral side in both sexes. Monospiracular respiratory structure is present in all of the pleopods, and opening near the base of the outer edge.

Male sexual characters ( Figs 3D, E ; 6 A-I)

Pereopods I and VII without sexual differentiation. Pleopod I with the endopod curved in its distal third and a dilation at the tip; triangular exopod, with a very long internal side and with a pointed termination. Pleopod II with a very long endopod and with a broad tip at the end; triangular exopod, with a very large internal side. Pleopods III to V as shown in Figure 6 G-I.

REMARKS

The genus Ctenorillo Verhoeff, 1942 currently comprises 15 species: C. ausseli ( Dollfus, 1893) from Spain (Canary Islands); C. bananae ( Van Name, 1920) from Angola, Cameroon and Congo; C. dazai Carpio-Díaz, López-Orozco & Campos-Filho, 2018 from Colombia; C. fagei ( Paulian de Félice, 1941) from Ivory Coast; C. ferrarai Campos-Filho, Araujo & Taiti, 2014 from Brazil; C. gabunensis Schmalfuss & Ferrara, 1983 from Gabon; C. guinensis ( Schmalfuss & Ferrara, 1983) from Guinea; C. kenyensis Schmölzer, 1974 from Tanzania and Uganda; C. legai (Arcangeli, 1941) from Ethiopia; C. meyeri Taiti, 2018 from South Africa; C. mineri ( Van Name, 1936) from Guyana and Venezuela; C. parituberculatus ( Taiti & Ferrara, 1987) from Malawi; C. regulus ( Van Name, 1920) from Somalia and Zaire; C. strinatii ( Schmalfuss & Ferrara, 1983) from Congo; and C. tuberosus ( Budde-Lund, 1904) from Brazil ( Dollfus 1893; Van Name 1920, 1936; Paulian de Félice 1941; Verhoeff 1942; Schmölzer 1974; Schmalfuss & Ferrara 1983; Taiti & Ferrara 1987; Schmalfuss 2003; Campos-Filho et al. 2014, 2017; Taiti 2018; Carpio-Díaz et al. 2018). It is therefore a genus mainly with an African tropical distribution.

The characters present in Ctenorillo atlanticus n. sp. place it in this genus of the family Armadillidiidae , characters such as tubercles and elongated bumps in the cephalon, pereon and pleon, the frontal shield of the cephalon protruding above the vertex, the telson in the shape of an hourglass and a very reduced exopod. In this genus, the best character of specific differentiation is the number and arrangement of the tubercles and dorsal protuberances ( Campos-Filho et al. 2014; Taiti 2018). The presence of large tubercles that form elongated protuberances differentiates Ctenorillo atlanticus n. sp. from C. bananae and C. kenyensis with weak tubercles, and from C. ausseli with conical tubercles. Out of the remaining twelve species, only C. fagei , C. gabunensis , C. legai and C. tuberosus have the same number of tubercles in the pleon (four in the III; four in the IV and two in the V) and in the telson (two) as Ctenorillo atlanticus n. sp. However, C. legai and C. tuberosus have a large number of tubercles on the pereon compared to the smaller number in Ctenorillo atlanticus n. sp. Additionally, Ctenorillo atlanticus n. sp. differs from C. fagei and C. gabunensis in the number of rows and tubercles on the cephalon and pereon.

Figures

FIG. 2. — A, Agnara madagascariensis (Budde-Lund, 1885), habitus; B, Ctenorillo bananae (Van Name, 1920), habitus; C, Ctenorillo atlanticus n. sp., habitus; D, Cubaris murina Brandt, 1833, habitus; E, Gabunillo thomensis n. sp., habitus; F, Venezillo crassus (Budde-Lund, 1904), habitus; G, Elumoides atlanticus Ferrara & Schmalfuss,1983,habitus; H, Eubelum asperius Van Name, 1920, habitus;I, Burmoniscus kohleri (Schmalfuss & Ferrara,1978), habitus;J, Congophiloscia saothomensis Schmalfuss & Ferrara, 1978, habitus; K, Niambia atracheata (Schmalfuss & Ferrara, 1978), habitus; L-N, Trichorhina hospes Silvestri, 1918, habitus (L), antennula (M), scale-setae (N); O-Q, Trichorhina kribensis Ferrara & Schmalfuss, 1983, habitus (O), antennula (P), scale-setae (Q); R, Nagurus cristatus (Dollfus, 1889), habitus. Scale bars: A-C, I, J, L, O, 0.5 mm; D, F, H, K, R, 1 mm; E, G, 0.1 mm; M, N, P, Q, 0.01 mm.

FIG. 3. — Ctenorillo atlanticus n. sp.: A, vertex and first pereonite; B, cephalon, first and second pereonites; C, pleon, telson and uropods; D, first male pleopod; E, second male pleopod. Scale bars: A, B, D, E, 0.1 mm; C, 0.5 mm.

FIG. 4. — Ctenorillo atlanticus n. sp.: A, disposition of tubercles; B, habitus, lateral view; C, cephalon and first perionite; D, pleon and telson; E, scale-setae; F, cephalon, pereonites I and II, ventral view. Scale bars: B-D, F, 0.5 mm; E, 0.01 mm.

FIG. 5. — Ctenorillo atlanticus n. sp.: A, left mandible; B, right mandible; C, maxillule; D, maxilliped; E, antennula; F, antenna with detail of scales; G, uropod, ventral view. Scale bars: A-D, F, G, 0.1 mm; E, 0.01 mm.

FIG. 6. — Ctenorillo atlanticus n. sp.: A, male pereopod I; B, male pereopod VII; C, male pleopod I, endopod; D, male pleopod I, exopod; E, male pleopod II, endopod; F, male pleopod II, exopod; G, male pleopod III, exopod; H, male pleopod IV, exopod; I, male pleopod V, exopod. Scale bars: 0.1 mm.