Baeticoniscus carmonaensis, Cifuentes & Peña Pérez & Luna, 2025

Cifuentes, Julio, Peña Pérez, Enrique & Luna, Álvaro, 2025, Baeticoniscus carmonaensis sp. nov. a new Isopod found in an underground aqueduct from the Roman period located in Southwest Spain (Crustacea, Isopoda, Trichoniscidae), Subterranean Biology 51, pp. 135-146 : 135-146

Baeticoniscus carmonaensis sp. nov.

Type material.

Holotype: • Seville, Carmona , 37.472, - 5.638, Mina de San Antón , 07/27/2022, male, A. Luna, A. Adame, D. León and E. Peña leg., MNCN 20.04/20569 .

Paratypes: Same locality and collectors as holotype: • 3 males, 03/12/2021, MNCN 20.04/20598 to 20.04/20600 ; • 1 female 06/11/2021, MNCN 20.04/20601 ; • 9 males, 07/27/2022, MNCN 20.04/20570 to 20.04/20578 ; 07/27/2022, • 2 males, 19 females (2 ovigerous) and 1 panga, MNCN 20.04/20579 to 20.04/20597 ; • 2 females, leg., JC 662 .

Etymology.

The new species name refers to the town where the species was collected, Carmona.

Type locality.

Carmona (Seville, Spain); system of underground galleries (37.471111, - 5.642222).

Diagnosis.

Cephalon with large tubercles, two elongated on the middle zone and four on posterior edge; pereonites 1 to 6 with 4 ribs and two on seventh; smooth pleon. Eyes of large, black ocellus. Pereopods 1 and 7 without sexual differentiation. Male pleopod 1, with endopod long, biarticulated and ending in hollow and striated conical point; exopod triangular, with protrusion near base. Male pleopod 2 with very long endopod ending in one silk; exopod with long rounded inner tip.

Description.

Maximum length: 2.5 mm male; 2.7 mm in a female. Coloration: Specimens examined are colorless, with dark pigmented ocellus Somatic characters: Cephalon (Figs 2 D, E , 3 A ) with triangular median lobe, large and rounded at end, lateral lobes and mediocre laterals slightly protruding from lateral edge and directed forwards. Pereon (Figs 2 D , 3 A ) with the pereonites epimera extended as well as the pleonites epimera in the pleon. Telson (Figs 2 D , 3 A ) trapezoidal, much shorter than posterior edge of uropod protopod, with concave sides and broadly rounded end.

Integumentary characters (Figs 2 D, E , 3 A ): cephalon with two small central tubercles, behind median lobe; two large elongated tubercles on middle area and four (2 + 2) on posterior margin, outer ones larger. Pereonites with four longitudinal ribs (2 + 2), gradually reducing, pereonite 6 with outer ribes smaller, and pereonite 7 two central ribs pleon. Ocular apparatus (Figs 2 D , 3 A ): formed by large ocellus. Appendages: Antennula (Fig. 3 B ) with three segments, basal one stout, second and third thinner and subequal in length; third segment with three long terminal aesthetascs. Antennas (Fig. 3 C ) with fourth segment stout and with some scaly tubercles on fourth and fifth segments; flagellum of three segments, second segment with a group of aesthetascs. Buccal pieces (Fig. 3 D – G ) similar to that of other species of the genus, with two free penicils on the left mandible (Fig. 3 D ) and one on the right (Fig. 3 E ). Maxillula and maxilliped as observed in Fig. 3 F, G .

Sexual characteristics of male: Pereopods 1 and 7 without sexual differentiation. Pleopod I (Fig. 3 H ): endopod long, biarticulated, with long setae at junction of both segments, and ending in hollow and fluted conical point; exopod triangular, elongated, with protruding outer edge near base. Pleopod II (Fig. 3 I ): endopod very long, sharp and ends in one silk; exopod with long and rounded inner tip; posterior border concave and inner one convex.

Habitat and ecology.

Our knowledge of the ecology of Baeticoniscus carmonaensis sp. nov. is limited due to the lack of specific studies on the species and the absence of other populations for comparison. Baeticoniscus carmonaensis sp. nov., along with others species, thrives in groundwater ecosystems. The only known population of this species has been found in elevated areas within the gallery system, beyond the reach of water floods. All specimens were discovered on or within pieces of rotten wood, likely fallen from wells connected to the underground galleries. When manipulating such wood, specimens were observed moving and hiding within the crevices of this decomposing material.

Conservation.

Baeticoniscus carmonaensis sp. nov. is known only from the type locality, where the total number of specimens observed by the authors during fieldwork does not exceed 150 – 200 individuals. The site remains well preserved, as it receives no tourist or other visits, except for those made for scientific purposes, typically between 0 and 5 per year. However, recent surveys have detected microplastics in the water and sediments, suggesting a potential interaction with this species (unpublished data). Any contamination event or alteration of the environmental conditions could severely affect the only known individuals of the species. Moreover, archaeological activities or other environmental transformations could have similar impacts. Thus, the major threats to the species include increased human presence and the associated impacts of habitat transformation and depletion.

Figures

Figure 2. Iberoniscus breuili Vandel, 1952, female, MNHN - IU- 2013-19986 A habitus. Baeticoniscus bullonorum Garcia, 2020, male, JC 400 B habitus C cephalon. Baeticoniscus carmonaensis sp. nov., male D habitus E cephalon. Scale bars: 0.5 mm (B – E); (A sin escala).

Figure 3. Baeticoniscus carmonaensis sp. nov., male, MNCN 20.04 / 20598 A habitus B antennula C antenna MNCN 20.04 / 20601 D left mandible E right mandible F maxillula G maxilliped. MNCN 20.04 / 20598 H Pleopod I I Pleopod II. Scale bars: 0.5 mm (A); 0.1 mm (C, H, I); 0.01 mm (B, D – G).