Spelaeogammarus ginae, Bueno & Bichuette & Zepon & Penoni, 2022

Bueno, Alessandra Angélica de Pádua, Bichuette, Maria Elina, Zepon, Tamires & Penoni, Ludmila Rocha, 2022, A new species of the troglobitic genus Spelaeogammarus da Silva Brum, 1975 (Amphipoda: Artesiidae) from a cave in the Brazilian semi-arid region, with new records of its congener, Spelaeogammarus spinilacertus Koenemann and Holsinger, 2000, Nauplius (e 2022020) 30, pp. 1-17 : 3-10

publication ID	https://doi.org/ 10.1590/2358-2936e2022020
DOI	https://doi.org/10.5281/zenodo.10951448
persistent identifier	https://treatment.plazi.org/id/03828797-FFF8-5746-FC5C-FCE9E434FBB4
treatment provided by	Felipe
scientific name	Spelaeogammarus ginae
status	sp. nov.

Treatment

Spelaeogammarus ginae View in CoL sp. nov.

Bueno and Penoni

( Figs. 1–4 View Figure 1 View Figure 2 View Figure 3 View Figure 4 )

Zoobank: urn:lsid:zoobank.org:act:EE1300D7-465B-4E05-BD58-A06F26A407A1

Etymology. The epithet ginae is a tribute to Dr. Georgina Bond-Buckup , a devoted carcinologist that dedicated her life to the study of crustaceans.

Type material. Holotype: male, body length 12.24 mm, head length 0.84 mm, MNRJcarcino 030206, Brazil, state of Bahia, Gruna da Serra Verde cave, municipality of Coribe , (44°19’26.8”S 13°43’28.0”W), 05 Jul. 2021, M.E. Bichuette, J.S. Gallo, V. F.Sperandei, J.E. Gallão colls GoogleMaps . Paratypes (same collection data as holotype): 4 whole individuals, LES 00027746 About LES GoogleMaps ; 3 whole individuals, CCUFLA 447 ; 3 males and 1 female on slides, CCUFLA 448 .

Diagnosis. Antenna 1 less than half body length, flagellum with 18–20 articles, accessory flagellum 5-articulated. Antenna 2 subequal to antenna 1, f lagellum with 8–10 articles. Maxilla 1 outer plate bearing 7 multicuspidate setae and article 2 of palp with 6–7 long, simple setae. Pleopods 1–3 inner rami with 9–10, 10–11, and 10 long plumose setae on distal margin, respectively; uropod 2 outer ramus outer margin without seta; uropod 3 outer ramus internal margin with 0–1 simple seta, 8–19 long bifid setae and 3–7 cuspidate setae with accessory seta.

Description. Body slender ( Fig. 1 View Figure 1 ), completely depigmented, head without eyes ( Fig. 1 View Figure 1 ). Mean body length 10.39 ± 2.06 mm (N = 10) (7.44–12.24 mm); mean head length 0.71 ± 0.13 mm (N = 10) (0.50–0.84 mm). Epimeral plates 1–3 distoanterior margin rounded, distoposterior margin produced with a small spine.

Antenna 1 ( Fig. 2A View Figure 2 ) less than half body length, peduncle subequal to f lagellum, article lengths reducing gradually from 1 to 3, article 1 with 5 cuspidate setae with accessory setae on one side and 4–6 simple setae and 1–4 plumose setae on the other side, plumose and simple setae apically; flagellum with 18–20 articles, aesthetascs occurring distally on f lagellum from article 2 to 18; accessory f lagellum with 5 articles, reaching up to fifth article of flagellum.

Antenna 2 ( Fig. 2B View Figure 2 ) subequal in length to antenna 1, peduncle shorter than f lagellum, articles 4 and 5 elongated, subequal in size; flagellum with 8–10 articles.

Upper lip ( Fig. 2C View Figure 2 ) apically rounded with setules. Lower lip ( Fig. 2D View Figure 2 ) inner lobe with setules apically, rounded; outer lobe well developed, inner distal margin with some setules.

Maxilla 1 ( Fig. 2E View Figure 2 ) inner plate apical margin with 3 strong plumose setae, subequal to outer plate; outer plate apical margin with 7–8 multicuspidate setae; palp 2-articulate, article 2 inner margin with 6–7 simple setae in a row.

Maxilla 2 ( Fig. 2F View Figure 2 ) inner plate with about 11 plumose setae, 5–9 stout setae and 2 strong, longer plumose setae apically, setules laterally; outer plate slightly longer and slightly more slender than outer plate, apical margin with up to 14 slender setae and 7 plumose setae; slender setae and setules laterally.

Left mandible ( Fig. 2G View Figure 2 ) molar cylindrical and semi-triturative; setal row with 5plumose setae; lacinia mobilis present, oblong, apical margin with 5 crests; incisor multicuspidate; palp with 3 articles, article 2 the longest, article 3 subequal to 2, article 1 less than half the length of 2 and 3; article 1 almost as wide as long, article 2 slim, longer than wide, 3 slender setae with accessory seta on ventral margin either bifid or simple with accessory seta, article 3 with 1–2 stout long seta and 1–2 bifid long setae, apically.

Right mandible ( Fig. 2H View Figure 2 ) slightly longer than left mandible, setal row with 4 plumose setae, 2 of them longer and stronger than the others; palp 3-articulate, article 2 ventral margin with 4–5 slender setae with accessory seta,2 of them usually shorter, article 3 with 4 apical long setae with accessory setae.

Maxilliped ( Fig. 2I View Figure 2 )inner and outer plates subequal in size; inner plate with scattered long stout setae, apical margin rectangular bearing3 slim plumose setae and 2 Y-shaped stout setae; outer plate with scattered long bi- or trifid stout setae, apical margin rounded with 3–6 stout or plumose setae on the inner distal margin; palp 4-articulate; article 1 conical; article 2 twice as long as wide, inner margin with several long, trifid setae; article 3 inner margin with several long, trifid setae, inner face with row of plumose setae and some strong and short plumose setae apically; article 4 triangular, with long stout setae at inner margin, distal claw present.

Gnathopod 1 ( Fig. 3A View Figure 3 ) coxa rectangular; basis twice as long as wide, 4 small simple setae on anterior margin, up to 14–16 long, bifid setae on posterior margin, 1 simple small seta on posterodistal margin; ischium small, 1 bifid slender seta on posterodistal margin; merus quadrate, with long bifid setae and several setules along posterior margin; carpus subtriangular, posterodistal margin with setules, up to 7 plumose setae and 2 simple stout setae; propodus suboval, slightly longer than basis, palm oblique, about 2.5 × longer than posterior margin, 19–20 simple short setae, 10–11 short and strong cuspidate setae with accessory setae, 3–7 long slim simple setae and 3 long bifid setae; some scattered, long and thin trifid seta on inner margin; dactylus curved, congruent in length with palm, not reaching the palmar corner, some short simple setae dorsally.

Gnathopod 2 ( Fig. 3B View Figure 3 ) coxa subtriangular, wider than long, basis 3 × longer than wide, posterior margin with 14–18 stout long simple setae, anterior margin with 1 small simple seta, 0–1 simple seta on posterodistal margin; ischium and merus subrectangular, posterior margins with 1 and 2–4 small simple setae, respectively; carpus longer than wide, posterior margin with several short and long simple setae and some setules, anterior margin with 4–5simple short setae; propodus suboval, almost twice as long as wide, anterior margin with 9 groups of 1–5 simple short and long simple setae, posterior margin with 8 groups of 2–8 short and long simple setae and setules, palm oblique, subequal to posterior margin, with 14 short setae, 2 long, thin simple setae and 4–6 strong cuspidate setae with accessory seta; dactylus curved, claw-like, not reaching the palmar corner.

Pereopods 3–4 ( Fig. 3C–G View Figure 3 ) pereopods 3 and 4 alike, coxae 3 and 4 longer than wide; basis with 1 single small plumose seta on anterior margin, basis and ischium posterodistal margins with 1–2 simple short setae; merus with 2 simple or cuspidate short setae with accessory seta on anteroproximal margin, and up to 5 groups of 1–2 cuspidate short setae with accessory seta on posterior margin; propodus distal anterior margin with 3 simple setae, posterodistal margin with up to 7 groups of 1–3 cuspidate setae with accessory seta; dactylus short, with a plumose seta distally and 2 short setae coupled with the nail.

Pereopod 5 ( Fig. 3E View Figure 3 ) longer than pereopods 3 and 4, coxa slightly wider than long, anterior lobe with 7–8 simple setae, more developed than posterior, posterior lobe with1 long seta with accessory seta; basis almost twice as long as wide, anterior and posterior margins each with 7–10 groups of 1–2 simple or stout cuspidate setae with accessory seta; ischium with 2–3 simple long setae on anterodistal margin; merus 3 × longer than wide, anterior margin with 3–6 simple setae, posterior margin with 2–4 cuspidate setae with accessory seta, and 1 cuspidate seta with accessory seta on anteriodistal margin; carpus 5–6 × longer than wide, anterior margin with 4–6 groups of 1–2 cuspidate setae with accessory seta, posterodistal margin with 1 strong seta, long and slender setae occurring as fringe; propodus 7–8 × longer than wide, with 14–15 cuspidate setae with accessory seta on anterior margin, 1 simple thin seta on posterior margin, distally, 1cuspidate seta with accessory seta on posterodistal margin, long and slender setae occurring as fringe; merus, carpus and propodus subequal in length; dactylus short, with a plumose seta distally and 2 short setae coupled with nail.

Pereopod 6 ( Fig. 3F View Figure 3 ) coxa slightly wider than long, anterior lobe more developed than posterior, without setae, posterior lobe with 1 cuspidate seta with accessory seta; basis almost twice as long as wide, 9–10 cuspidate setae with accessory seta on both anterior and posterior margins, posterodistal margin with 1–2 small plumose setae or simple seta with accessory seta; ischium with 2 simple long setae on anterodistal margin; merus about 3×longer than wide, anterior margin with 3 simple setae, 1 simple seta and 1 cuspidate seta with accessory seta on anterodistal margin, posterior margin with 3 cuspidate setae with accessory seta, and 1 cuspidate seta with accessory seta on anteriodistal margin; carpus 5–6 ×longer than wide, anterior margin with4–5groups of1–3cuspidate setae with accessory seta, long and slender setae occurring as fringe, posterior margin with 2 simple slender setae, posterodistal margin with 2–3 cuspidate setae with accessory seta; propodus 8–9 × longer than wide, with 15 cuspidate setae with accessory seta on anterior margin, long and slender setae occurring as fringe, 4 cuspidate setae with accessory seta on distal margin; merus, carpus and propodus subequal in length; dactylus short, with a plumose seta distally and 2 short setae coupled with nail.

Pereopod 7 ( Fig. 3G View Figure 3 ) coxa almost as wide as long, 0–1 simple seta with accessory seta on anterior margin; basis longer than wide, anterior and posterior margins with 6–10 and 6–8 cuspidate setae with accessory seta, respectively; ischium with 2 cuspidate setae with an accessory seta and 1 simple, long seta on the anterodistal margin; merus 2–3 × longer than wide, anterior and posterior margins with 3 groups of 1–2 cuspidate setae with accessory seta, anterodistal margin with 2 cuspidate setae with an accessory seta, posterodistal margin with 2–3 cuspidate setae with an accessory seta; carpus 4–5 × longer than wide, anterior margin with 3 groups of 2–4 cuspidate setae with accessory seta, 8 cuspidate setae with accessory seta on the anterodistal margin, posterior margin with 2–3 groups of 1–5 cuspidate setae with accessory seta, 7–8 cuspidate setae with accessory seta on the posterodistal margin; propodus about 7 × longer than wide, anterior margin with a variable number of cuspidate setae with accessory seta and several long, slim bifid setae, posterior margin with 9 groups of variable numbers of bifid, simple and cuspidate setae with accessory seta, posterodistal margin with 1 simple and 4 cuspidate setae with accessory seta, 2 of them longer than the others; merus smaller than carpus and propodus; dactylus short, with a plumose seta distally and 2 short setae coupled with the nail.

Pleopods 1, 2 and 3 ( Fig. 4A–C View Figure 4 ) similar; peduncle elongated, respectively 3–5 × longer than wide, with 2 coupling spines each; inner rami 1-articulate, with 9–10, 10–11 and 10 plumose long setae on distal margin, respectively; outer ramus 3-articulate, third article the smallest; pleopod 1 outer ramus article 1 inner margin with 8–9 plumose setae, outer margin with 13–18 plumose setae, article 2 with 2 plumose setae, article 3 with 2 apical plumose setae; pleopod 2 outer ramus article 1 inner margin with 7–9 plumose setae, outer margin with 9–16 plumose setae, article 2 with 2 long plumose setae, article 3 with 2 long plumose setae; pleopod 3 outer ramus article 1 inner margin with 7–8 plumose setae, outer margin with 9–13 plumose setae, article 2 with 2 plumose setae, article 3 with 2 plumose setae.

Uropod 1 ( Fig. 4D View Figure 4 ) peduncle 3× longer than wide, with 4–5 stout, cuspidate setae with accessory seta on each side;inner ramus subequal in length to peduncle, with 3 dorsal stout simple setae with accessory seta and 5 apical setae, 2 out of 5 apical setae with accessory seta; outer ramus subequal in length to peduncle and to inner ramus, with 1–3 stout, cuspidate setae with accessory seta on inner margin and 4 apical setae, 1 longer than others.

Uropod 2 ( Fig. 4E View Figure 4 ) peduncle twice as long as wide, with 2 dorsal and2–3 distolateral stout, cuspidate setae with accessory seta; inner ramus subequal in length to peduncle, with 3 dorsal strong and 3 short cuspidate setae with accessory seta on internal margin, and 4 apical setae, 2 of them longer than others; outer ramus subequal in length to peduncle and to inner ramus, with 2 ventral cuspidate setae with accessory seta and 3–4 apical stout setae, 2 of them with accessory seta.

Uropod 3 ( Fig. 4F View Figure 4 ) peduncle short, slightly longer than wide and less than half length of rami, with 1–3 small cuspidate setae with accessory seta dorsally and 0–1longer cuspidate seta with accessory seta dorsally on the distolateral margin; inner ramus with 7 groups of 1–2 cuspidate setae with accessory seta dorsally, 4 groups of 1–2 cuspidate setae with accessory seta distally on internal margin, and 2 short cuspidate setae with accessory seta apically; outer ramus with row of 0–1 simple long seta plus 8–19 bifid long setae plus 3–7 stout, cuspidate setae with accessory seta distally on internal margin, 4–5 groups of 1–4 stout, cuspidate setae with accessory seta dorsally, and 3 strong and 1–2 thin setae apically.

Telson ( Fig. 4G View Figure 4 ) almost as long as wide, apical margin with concave excavation, with 2 apical, 2 subapical stout, cuspidate setae with accessory seta and 3 plumose setae on one side, and 1 apical stout, cuspidate seta with accessory seta and2subapical stout, cuspidate setae with accessory seta and 1 plumose seta on the other side.Variations:symmetrical distribution of setae, with 1 apical and 2 subapical stout, cuspidate setae with accessory seta plus 3 subapical plumose setae on each side.

Sternal gills occurring on segments 2–7. Coxal gills sac-like on segments 3–6.

Female: no apparent sexual dimorphism. Oostegites slim, observed on pereonites 2–6, with curly pointed setae.

Taxonomic remarks. A thorough morphological comparison between the known Spelaeogammarus species is provided ( Tab. 1 View Table 1 ), including the new one here described. We highlight the following differences: Spelaeogammarus ginae sp.nov. differs from S.bahiensis , S. spinilacertus , and S. titan in the number of articles on the accessory flagellum of antenna 1; the basis of pereopod 5 of S. ginae sp. nov. is quite setose (12–14 cuspidate setae with accessory seta on the posterior margin), while S. sanctus has no observed seta in this structure; the gnathopod 2 posterior margin of the basis of S. ginae sp. nov. (with 14–18 setae) differs from those of S. santanensis (21–23 setae) and of S. trajanoae (8–9 setae); and the palp of the maxilla 1 of S. ginae bears 6–7 setae, while S. uai palp has only 4.

Distribution, habitat, ecology and behavior. Freshwater, hypogean. Specimens of S. ginae sp. nov. were found in a single pool formed by the upper phreatic aquifer at Gruna da Serra Verde cave ( Fig. 5A–D View Figure 5 ). The cave is located at Bambuí Group, a geomorphological unit, in a region called Serra do Ramalho, with typical dry-forest vegetation. The region has dozens of caves, all of carbonate rock (limestone caves), some with several kilometers of passages ( Rubbioli et al., 2019). The pool has a soft bottom of silt, with little organic matter (some vegetation and drops of guano) and limestone riff les ( Fig. 5B View Figure 5 ). In the wet season, the extension of the pool reaches 150 m in length and approximately 1.5–2.0 m in width ( Fig. 5D View Figure 5 ); in the dry season (May–October) the pool showed a smaller dimension ( Fig.5B View Figure 5 ) of 1.38 m in length, 0.52 m in width, and approximately 0.18 m in depth (0.72 m 2 of area and 0.13 m 3 of volume), with a high abundance (48) of individuals trapped in the pool. The temperature was relatively high (24.1 ºC) and the pH followed the values for karstic waters (pH = 7.2). The individuals were found only in the dry season, when the population densities per area and per volume were particularly high for troglobitic species (66.6 inds. m-2 and 369 inds. m-3, respectively). All individuals (approximately 48) observed in the pool showed a fast swimming-behavior (observation from 12:15 PM until 13:40 PM), mainly on the soft-bottom (Video S1), with a few stops to forage on particulate vegetal debris and drops of guano. The individuals did not show photophobic behavior, i.e., did not react to the light of the flash-lamps, with an intensity of about 600 lumens. Despite the large concentration of individuals in a small pool, the species did not appear to have a gregarious habit.

Conservation. We propose that S. ginae sp. nov. should be classified as Critically Endangered (CR) according to the IUCN criteria B1ab(iii), i.e., the extent of occurrence ( EOO) estimated less than 100 km 2 (criteria B1); one location (criteria a); continuing decline in the quality of habitat (criteria b). The species is possibly endemic to its type locality and the surroundings of the cave have several anthropogenic impacts including cattle grazing and deforestation. These impacts contribute to decline in the quality of habitat. Another impact could be related to climate change or due to cyclical events of drought and f lood. The single pool where the species occurs has been suffering a decrease in the water level during the last three yearly dry-seasons ( MEB., pers. obs.).