Trichorhina anophthalma Arcangeli, 1935

Figs 1–6

Material examined. Portugal: 2 females (LPS567), Évora, Alandroal, 38°42’13” N, 7°23’59” W, 02/XII/2022, leg. L.P. Da Silva; male (JC687 [ex. LPS570b]), same datum as preceding; female (LPS577), Évora, Vila Viçosa, 38°45’20” N, 7°24’38” W, 03/XII/2022, leg. L.P. Da Silva.

Remarks. Arcangeli (1935), in his work on the isopods of Portugal, provides a detailed description of this species, offering diagnostic elements for its differentiation. Later, Vandel (1946), in his work on the isopods of the same country, considered it necessary to make four observations on Arcangeli’s description. The observations concerning the ornamentation of the dorsal integument (observation 3) and the anatomy of the left mandible (observation 4) are important because they contradict Arcangeli’s description and may complicate the identification of this species. This species was also illustrated by Reboleira et al. (2015), but they did not address the discrepancies between the descriptions provided by the two earlier authors. Therefore, we considered it useful to provide a new description of T. anophthalma and the other studied species, as well as to highlight the differences among the species of this genus in the Iberian-Balearic region.

Description. Lacking pigmentation and ocular apparatus.

Integumentary characters (Figs 1A–B, 2A–C, 6): Dorsal integument without granulations, rounded scales, large fan-shaped scale-setae, along with smaller ones. N oduli laterales near posterior edge, closer to it from pereonite IV onward and slightly farther from lateral edge.

Somatic characters (Figs 1A–B, 2C): Cephalon slightly inserted into anterior concavity of pereonite I. Small triangular middle lobe with rounded tip, small rectangular lateral lobes. Posterior corner of pereonites I to III convex, in pereonites IV to VII angular. Pleon retracted in relation to pereon; small neopleura, posterior corners of pleonite V shorter than posterior edge of uropod protopods. Triangular telson, much shorter than wide, slightly curved sides and rounded tip, barely protruding beyond pleonite V corners.

Appendages (Figs 1C, 3A–E, 4A–C): Mandibles with 1+1 free penicils; left mandible molar penicil dichotomised into three branches with increasing sizes; right mandible molar penicil dichotomised into two unequal branches. Maxillula inner endite with two penicils and outer endite with seven teeth, two of them bifurcated. Maxilla and maxilliped as in Fig. 3D, E. Antennula with three segments, second barely noticeable, almost embedded on first; third with 5-6 short aesthetascs inserted at two levels and with lateral triangular spine. Short antennae, reaching posterior edge of pereonite II; fifth segment thickened; flagellum with two segments, first nearly one-third length of second. Uropod protopods much shorter than telson tip; endopods slightly shorter than exopods, both conical and small.

Sexual characters: Pereopods without sexual differentiation (Fig. 4D). Male pleopod I (Figs 1D, 5A–B) with long endopod slightly curved at tip; rectangular exopod, one and half times wider than long, rounded inner and outer sides, small teeth on posterior edge. Male pleopod II (Figs 1E, 5C–D) with very long endopod narrowing to thin tip; triangular exopod, with long distal tip, teeth on outer edge, and setae near tip. Male pleopod exopods III to V as in Fig. 5E–G, female exopods as in Fig. 5H–L.