Howaia alba, Ballarin & Eguchi, 2023

Ballarin, Francesco & Eguchi, Katsuyuki, 2023, Integrative taxonomic revision of the genera Nesticella and Howaia in Japan with the description of five new species (Araneae, Nesticidae, Nesticellini), ZooKeys 1174, pp. 219-272 : 219

publication ID	https://dx.doi.org/10.3897/zookeys.1174.101251
publication LSID	lsid:zoobank.org:pub:608FAD80-206A-428E-9743-F8ED4F3139BB
persistent identifier	https://treatment.plazi.org/id/140385CD-7B9B-421C-9752-7182907C5369
taxon LSID	lsid:zoobank.org:act:140385CD-7B9B-421C-9752-7182907C5369
treatment provided by	ZooKeys by Pensoft
scientific name	Howaia alba
status	sp. nov.

Treatment

Howaia alba sp. nov.

Figs 2A-J View Figure 2 , 4E-H View Figure 4 , 15C View Figure 15 , 16B (Japanese name: tsuzupisuki-horahimegumo ツヅピスキホラヒメグモ) View Figure 16

Nesticella mogera Shimojana 1977: 353, fig. 6 (♂, misidentification).

Type material.

♂ Holotype (NMST-Ar. 25251): Japan: Okinawa Pref.: Miyako-jima Is.: Shimozato Hirara, Oharaminami Park, Tsuzupisuki-abu cave (ツヅピスキアブ), 32 m, long and humid cave, in the dark zone of the cave, 24.79468°N, 125.28192°E, 12.Nov.2020, F. Ballarin leg.

Paratypes: Japan: Miyako-jima Is.: 3♀, same data as the holotype (NSMT-Ar 25252); 1♀, same locality 14.Nov.2020, F. Ballarin leg. (RMUF); 5♀, same locality, 16.Sep.2022, F. Ballarin leg. (2♀ MNHAH, 3♀ FBPC); 4♀, Nobaru Ueno, Pinza-abu cave (ピンザアブ洞穴), 57 m, long and muddy cave, in the dark zone of the cave, 24.74853°N, 125.33443°E, 13.Nov.2020, F. Ballarin leg. (RMUF); 3♀, same locality, 17.Sep.2022, F. Ballarin leg. (FBPC).

Other material examined.

Japan: Miyako-jima Is.: 1 juv., Nakabari, Nakabari Limestone Cave (仲原鍾乳洞), 24.73384°N, 125.37610°E, 29.Dec.2021, R. Miyata leg. (FBPC) GoogleMaps .

Etymology.

The specific name is derived from the Latin word for the color white (albus, adjective) referring to the whitish coloration of the species.

Diagnosis.

The new species is similar to H. mogera and to the troglobitic species H. rongtangensis (Lin, Ballarin & Li, 2016) from Hainan Island, H. subterranea sp. nov., and N. occulta sp. nov. Male of H. alba sp. nov. can be distinguished from male of H. mogera and H. rongtangensis by the different shape of the larger paracymbium (P) bearing a longer, slimmer, and sharper distal process (Di) (vs slimmer P with a shorter, larger, and blunter Di in H. mogera and H. rongtangensis ) (Figs 2A-D View Figure 2 , 4E-G View Figure 4 cf. Figs 1A-D View Figure 1 , 4A-C View Figure 4 and Lin et al. 2016: fig. 44A, B, D). Female of the new species are distinguished from female of H. mogera , H. subterranea sp. nov., and N. occulta sp. nov. by the larger and stockier scapus (Sc) with a slightly rounded posterior margin (vs slimmer Sc with a flat posterior margin in H. mogera , a longer Sc with a wider lobated tip in H. subterranea sp. nov., and a slimmer, tongue-like Sc ending with a strongly concave tip in N. occulta sp. nov.) (Figs 2E-G View Figure 2 , 4H View Figure 4 cf. Figs 1E-G View Figure 1 , 3D, E View Figure 3 , 4D View Figure 4 , 11C, D View Figure 11 , 13E, F View Figure 13 ).

Description of male

(holotype). Habitus as in Fig. 2H View Figure 2 . Total length 1.88. Prosoma 0.94 long, 0.83 wide. Carapace uniformly pale yellowish. Eyes completely degenerated and reduced to white maculae. Cervical groove and fovea indistinct. Chelicerae brownish. Labium, maxillae, and sternum of the same pale color as carapace. Legs uniformly pale yellowish. Leg formula: I, IV, II, III. Legs measurements as follows: I 6.17 (1.61, 0.47, 1.60, 1.72, 0.77), II 4.71 (1.32, 0.39, 1.20, 1.18, 0.62), III 3.89 (1.11, 0.31, 0.95, 1.02, 0.50), IV 5.17 (1.50, 0.37, 1.34, 1.31, 0.65). Opisthosoma uniformly greyish-yellow, covered with long, sparse hairs.

Male palp as in Figs 2A-D View Figure 2 , 4E-G View Figure 4 . Cymbium relatively elongated, covered with thin sparse setae, bearing some thicker setae on the distal-prolateral margin (Fig. 2D View Figure 2 ). Paracymbium with a single distinctly sclerotized, stocky distal process (Di), slightly elongated near the tip and a single sharp, spine-like ventral process (Ve) (Figs 2A-D View Figure 2 , 4E-G View Figure 4 ). Embolus (E) long and filiform, origin of embolus positioned at ~ 6:00 o’clock on radix (Rx). Radical apophysis (Ra) broad, with a granulate surface. Conductor with 3 distinct processes (Cp, Cr, Cm) and a half-transparent distal lobe (Cl). Prolateral process of the conductor (Cp) flat, ribbon-like and headed counterclockwise, wrapped around embolus. Retrolateral process of conductor (Cr) wide and thick, curved internally, with a broadened, flat central part. Median process of conductor (Cm) stout, horn-like, strongly sclerotized bearing a smaller, stout ventral process. (Figs 2A-C View Figure 2 , 4E, F View Figure 4 ).

Description of female

(one of the paratypes). Habitus as in Figs 2I View Figure 2 , 15C View Figure 15 . Total length 2.3. Prosoma 1.09 long, 0.92 wide. Cephalic area as in Fig. 2J View Figure 2 . Coloration and other details as in male. Legs measurements as follows: I 6.56 (1.83, 0.50, 1.74, 1.67, 0.82), II 5.09 (1.46, 0.42, 1.27, 1.22, 0.72), III 4.09 (1.31, 0.36, 0.90, 0.92, 0.60), IV 5.46 (1.65, 0.45, 1.42, 1.27, 0.67).

Epigyne and vulva as in Figs 2E-G View Figure 2 , 4H View Figure 4 . Scapus (Sc) short and stumpy, approximately as long as wide, ending with a slightly rounded posterior margin (Figs 2E, F View Figure 2 , 4H View Figure 4 ). Copulatory opening (Co) at the inner-lateral sides of scapus. Internal ducts slightly visible through the transparent tegument, shaped as a narrow V. Copulatory ducts (Cd) short and thick, slightly divergent to each other, slightly twisted in the inner trait with 1 coil, curving outward and then inward before reaching the spermathecae. Insemination ducts (Id) thin, coiled around the Cd). Spermathecae (S) small and rounded, separated from each other by ~ 2 × their diameter (Fig. 2G View Figure 2 ).

Size variation.

Female (based on 5 specimens): total length: 2.00-2.67, prosoma length: 1.05-1.12, prosoma width: 0.92-0.97.

Distribution.

Endemic to Miyako-jima Is., Ryukyus, Japan (Fig. 16B View Figure 16 ).

Habitat and ecology.

Howaia alba sp. nov. is found in the natural caves in Miyako-jima Is. This species builds simple scaffold webs between rocks and in crevices at the base of the walls or on the floor of the caves. It dwells exclusively in the dark zone of the caves, in areas characterized by relatively high and uniform temperature and humidity (e.g., Tsuzupisuki-abi cave: temp: 25.2 °C, hum: 94.1%; Pinza-Abu cave: temp: 25.1 °C, hum: 92.6%) (Fig. 15G View Figure 15 ). Adults of Howaia alba sp. nov. were observed preying on Schizomida ( Bamazomus siamensis (Hansen, 1905) which roam the floor of the caves in Miyako-jima Is. Females carrying the eggs cocoon attached to their spinnerets were also observed (but not collected) sitting on webs or wandering under rocks. Despite extensive surveying, no specimens were found in the numerous artificial tunnels or underground water reserves dug in the limestone rocks of the island. The complete absence of eyes and pigmentation, the lack of external records and the finding of the species only in the deepest areas of the caves identify H. alba sp. nov. as a true troglobiont.

Remarks on misidentifications.

This species was recorded and illustrated for the first time by Shimojana (1977: fig. 6A-C). Due to the general similarities in the shape of genitalia, it was identified as H. mogera although the author highlighted the lack of eyes in these specimens ( Shimojana 1977: 353). Our analysis, based on both morphology and molecular data, supports H. alba sp. nov. as a closely related species but clearly distinct from H. mogera .