Gabunillo thomensis, 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 : 643-646

Gabunillo thomensis n. sp.

( Figs 2E ; 7 ; 8 )

urn:lsid:zoobank.org:act:9A0C45FD-4370-4BDB-B8B2-AFCA390EF93F

TYPE MATERIAL. — Holotype. Democratic Republic of São Tomé and Príncipe • 1 ♀; Trilho dos Tuneis ; 0°18’03.7”N, 6°33’07.4”E; 11.V.2022; L.P. da Silva leg.; MNCN 20.04/20604 .

ETYMOLOGY. — The specific name refers to the fact that it lives on the island of São Tomé.

ECOLOGY. — Gabunillo thomensis n. sp. is an epigean species. It was found between litter in a secondary forest.

DESCRIPTION

Body

Body size 1.5× 0.8 mm. White colour when captured, likely lacking pigmentation.

Integumentary characters ( Figs 2E ; 7A, B ; 8A, B )

Integument without granulations, with a dense covering of large rounded scale-setae with notched margins ( Figs 7C ; 8E ).

Somatic characters ( Figs 2E ; 7A, B ; 8 A-D)

Strongly convex body, pleuroepimers and neopleurons almost vertical to the ventral side. No ocular apparatus.

Cephalon. Vertex separated from the profrons by a thin line that fades in the central part; profrons with a triangular convexity in the center.

Pereon. Almost straight posterior edge of tergites I to IV, tergites V to VII with a very small rounded tip. Thickened lateral edge of pleuroepimer I, with a wide and deep schism separating the two lobes; widely rounded anterior lobe; triangular posterior lobe with a rounded apex, protruding laterally in relation to the anterior. Epimers of pereonites II and III with a triangular lateral edge; conical anterior edge of pereonite II epimer that points towards the posterior edge without reaching it. Pleuroepimers IV to VII quandragular.

Pleon. Highly curved epimers of pleonite V, surrounding the uropod protopods.

Telson. Almost as long as wide, with a broad, triangular tip and a rounded apex, with concave lateral edges.

Appendages ( Fig. 8 F-Q)

Mouth apparatus with right mandible with a molar penicil and one + one free penicils and the left mandible with one+ one free penicils; maxillule with the outer branch with four + four simple teeth and the inner branch with two penicils; maxilliped endite with a large seta; biarticulated palp with two large setae on the basal segment. Antennula with three segments, second segment much smaller than the other two, third segment with a group of long aesthetascs at the tip. Antenna short and stout; first flagellum segment with a third of the length of the second; second flagellum with a group of short aesthetascs. Uropods with the endopod longer than the telson; protopod grooved on the posterior margin, with a small exopod inserted. Pleopods without respiratory structures in the exopods.

REMARKS

The genus Gabunillo was established by Schmalfuss & Ferrara (1983) and currently includes two species, Gabunillo coecus Schmalfuss & Ferrara, 1983 described from Gabon and Gabunillo aridicola Souza, Senna & Kury, 2010 described from Brazil.

Schmalfuss & Ferrara (1983) in their generic description indicate the “pereon segment 1 with a tiny groove along its margin” and in their description of G. coecus point out “inner and outer lobes of schisma equal in length”. They also indicate that it lacks pigment and ocular apparatus, the scale-setae present a large elongated scale, the posterior border of the first pereonite is straight and the exopod of the uropod is inserted into an incision at the end of the protopod.

Souza et al. (2010) in the description of G. aridicola indicate among other characters that it is pigmented, presents an ocular apparatus formed by 13 ommatidia, the scale-setae are triangular and Y-shaped; the posterior edge of the first pereonite is sinuous and the uropod exopod inserts dorsally into protopod. These characters that do not match those indicated for the generic description of Gabunillo nor are similar to those of G. coecus . Fernandes et al. (2019) consider as doubtful the inclusion of G. aridicola in this genus, pointing out some differences between G. aridicola and G. coecus as for example the protopods of the uropods ( Fernandes et al. 2019: 1119-1120) and the possible presence of monospiracular lungs in pleopods. Considering all these, we also believe it would be appropriate to review the systematic status of G. aridicola to confirm if it belongs to the genus Gabunillo .

Arcangeli (1950) in his publication on the isopods captured during the exploration carried out by H. Damas in the Albert National Park ( Democratic Republic of the Congo), renamed in 1969 as Virunga, described the species Eubelum squamatum Arcangeli, 1950 , from specimens captured in Mogembe.Among other characters, Arcangeli (1950: 25) wrote: “Questa specie si distingue facilmente per la forte pruinosità della superficie dorsale del corpo dovuta a squamosetole a ventaglio (del tipo Trichorhina ): nello spazio interposto a tali squamosetole il tegumento presenta squame semicircolari (see fig. 74)”. The Italian author gives great importance to the characteristic scale-setae from a E. squamatum , that allows its easy separation from the rest of the species of the genus Eubelum Budde-Lund, 1885 , that currently has 30 species found mainly in equatorial Africa. Arcangeli (1950) also indicates “Il cephalon presenta un margine frontale un poco ribattuto all'indietro nella parte mediana dove è molto sottile”, and “L’inspessimento al margine laterale degli epimeri del 1° pereionite non è molto pronunziato: tuttavia esso présenta un distinto, per quanto tenue, solco longitudinale che posteriormente si risolve nello schisma che sépara due lobi dei quali l'inferiore o coxopodale, più strettamente arrotondato, sorpassa distintamente all’indietro quello superiore”. This is, the junction of the vertex and the profrons is very poorly marked in the middle and the groove on the lateral edge of the first pereonite is also poorly marked. Characters that match the description of the genus Gabunillo and not the genus Eubelum . It should be noted that Arcangeli (1950) also points to E. squamatum that “Il sistema tracheale, discretamente sviluppato negli exopoditi del 1° e 2° paio di pleopodi va riducendosi assai nei successivi”. If indeed this species presents a respiratory system in the exopods of the pleopods, it could not be included in the genus Gabunillo . Considering that E. squamatum presents some characteristics similar to the species of the genus Gabunillo , it seems necessary to establish the differences between genera, to include or not the species in this genus, after verifying the presence or absence of the respiratory system. Arcangeli (1950) indicates that E. squamatum ocular apparatus is made up of 15 ommatidia, the fifth segment of the antenna have a sharp tooth, the epimer of the fifth pleonite is slightly divergent and the telson terminates in a subrectangular shape with the end point nearly straight. While also confirming the systematic status of G. aridicola , the other two species of the genus Gabunillo , G. coecus and G. thomensis n. sp., differed from E. squamatum by the lack of pigmentation, ocular apparatus, the tooth on the fifth segment of the antenna, the lungs in pleopods, the epimer of the fifth pleonite is convergent and the telson ends in a triangular point with a rounded apex.

The new species described in this work, G. thomensis n. sp., presents as G. coecus , according to Schmalfuss & Ferrara (1983) description, small size, without pigmentation nor ocular apparatus, cephalon with frontal margin interrupted in the middle, pereon segments II and III with a transversal crest on the ventral side, triangular telson, exopods pleopods without respiratory structures, uropod with a rectangular protopod and a small subterminal exopod. However, it differs from G. coecus that has an elongated scale-setae, a small groove along the edge of the first pereon segment, and the inner and outer lobes of the schisma have equal length. Gabunillo thomensis n. sp. has a very wide scale-setae, a wide groove along the edge of the first pereon segment, and inner lobe of the schisma is longer than the outer lobe, allowing these characters to easily separated both species.

Gregory (2014) named as Gabunillo Schmalfuss & Ferrara, 1983 , 53 female specimens found in the Rainforest Biome of the Eden Project, an extensive glasshouse complex in Cornwall, United Kingdom. A brief description and some drawings were provided, but no formal description or name were given. The overall appearance of this species is similar to the one described in this work, but the scarce information provided does not allow us to ensure that they are the same species. Moreover, Gregory (2014) indicates that it presents an ocular apparatus formed by a reddish ommatidium and “The entire body surface, including the short stout antennae, is covered in blunt-tipped scale-spines”, while G. thomensis n. sp. lacks an ommatidium and its scale-setae have a very large fan-shaped scale with a crenated edge.

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. 7. — Gabunillo thomensis n.sp.:A, pereonites I and II, lateral view;B, telson and uropods; C, scale-setae. Scale bars: A, B, 0.1 mm; C, 0.01 mm.

FIG. 8. — Gabunillo thomensis n. sp.: A, cephalon and pereonite I, frontal view; B, pleon, telson and uropods; C, pleuroepimer I, dorsal view; D, pleuroepimer II, ventral view; E, scale-setae; F, left mandible; G, right mandible; H, maxillule; I, maxilliped; J, antennula; K, antenna; L, uropod, ventral view; M, female exopod I; N, female exopod II; O, female exopod III; P, female exopod IV; Q, female exopod V. Scale bars: 0.1 mm.