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 Author Bueno, Alessandra Angélica de Pádua Laboratório de Carcinologia, Departamento de Ecologia e Conservação, Programa de Pós-Graduação em Ecologia Aplicada, Universidade Federal de Lavras. 37200 - 900, Lavras, Minas Gerais, Brazil. & Ab 02 D Author Bichuette, Maria Elina Laboratório de Estudos Subterrâneos, Departamento de Ecologia e Biologia Author Zepon, Tamires Laboratório de Estudos Subterrâneos, Departamento de Ecologia e Biologia Author Penoni, Ludmila Rocha Laboratório de Carcinologia, Departamento de Ecologia e Conservação, Programa de Pós-Graduação em Ecologia Aplicada, Universidade Federal de Lavras. 37200 - 900, Lavras, Minas Gerais, Brazil. & Ab 02 D text Nauplius 2022 e 2022020 2022-06-17 30 1 17 http://dx.doi.org/10.1590/2358-2936e2022020 journal article 10.1590/2358-2936e2022020 2358-2936 10904910 DC66DAC4-5AAA-461F-AEF7-847FB1AB02D7 Spelaeogammarus spinilacertus Koenemann and Holsinger, 2000 ( Fig. 6 ). Material examined (all from Brazil , state of Bahia ). 1 adult , LES 0016806, municipality of Iraquara, Buraco do Cão cave, 12°23’37.5”S 41°36’08.2”W , 20Jun. 2009 , M . E . Bichuette , L . Senna-Horta colls .; 3 adults , LES 0000230 , municipality of Palmeiras , Canoa Quebrada cave , 12°25’29.6”S 41°33’28.1”W , 12 Jul. 2004 , M . E . Bichuette coll.; 1 adult , LES 0000231 , municipality of Palmeiras , Canoa Quebrada cave , 12°25’29.6”S 41°33’28.1”W , 13 Nov. 2004 , M . E . Bichuette coll.; 3 adults , LES 0004906 , municipality of Iraquara , Gruta da Lagoa Seca cave , 12°18’42.7”S 41°34’03.6”W , 23 Jan.2007 , M . E . Bichuette coll.; 2 adults , LES0022569 , municipality of Iraquara , Gruta da Lagoa Seca cave , 12°18’42.7”S 41°34’3.6”W , 23 Jan. 2007 , M . E . Bichuette coll.; 1 adult , LES 0016823 , municipality of Iraquara , Gruta Umburana cave , 12°20’25.4”S 41°36’32.0”W , 19 Jun. 2009 , M . E . Bichuette coll.; 2 adults , LES 0000225 , municipality of Iraquara , Lapa Doce System , 12°20’01.7’’S 41°36’16.5”W , 30 Mar. 2005 , M.E. Bichuette , D.R. Pedroso colls.; 3 adults , LES 0022568 , municipality of Iraquara, Lapa Doce System; 12°20’01.7’’S 41°36’16.5”W , 30 Oct. 2016 , M.E. Bichuette , M. Rosendo , J.E. Gallão colls.; 3 adults , LES 0001804 , municipality of Iraquara, Lapa Doce System, 12°20’01.7’’S 41°36’16.5”W , 25 Mar. 2000 , D. Allegrini coll.; 2 adults , LES 0027745 , municipality of Iraquara, Lapa Doce System, 12°20’01.7’’S 41°36’16.5”W , M.E. Bichuette , J.P.M. Araujo , G.H.N. Basílio , M.A. Rasteiro colls . Table 1. Morphological characteristics of the species of the genus Spelaeogammarus from Brazil. Legend: “—” not specified or unidentified.

Morphological characteristic	S. ginae sp. nov.	S. bahiensis	S. sanctus	S. santanensis	S. spinilacertus	S. titan	S. trajanoae	S. uai
A1 length in relation to body length	<0.5	—	0,4	0.4-0.5	0.5	~0.5	—	~0.5
A1 flagellum number of articles	18–20	16	22	20-21	17-20	26	—	17-20
A1 accessory flagellum number of articles	5	3-4	5	5	4	6	—	5
A2 flagellum number of articles	8–10	7	10	8-10	7	10	—	7-8
M1 outer plate number of multi-cuspidate setae	7–8	7	7	7	6-7	6	—	7
M1 palp article 2 number of apical setae	6–7	0	~7	—	5-6	~7	—	4
G1 basis posterior margin number of setae	14–18	7-9	15-17	20	6-8	20	9-10	15
G2 basis posterior margin number of setae	14–18	0	20	21-23	9-10	23	8-9	18
P5 basis posterior margin number of setae	12-14	—	0	12	10-11	~20	10-12	8
P7 basis posterior margin number of setae	6–8	—	~9	—	7-9	~11	10	~9
Pleopod 1 inner ramus distal margin number of plumose setae	9–10	—	11	—	—	10	—	9
Pleopod 2 inner ramus distal margin number of plumose setae	10–11	—	12	—	—	11	—	9
Pleopod 3 inner ramus distal margin number of plumose setae	10	—	10	—	—	13	—	9
U1 outer ramus number of setae on outer margin	0	0	0	—	0	7	—	0
U1 outer ramus number of setae on inner margin	1–3	2	3	—	3	21	—	5
U2 outer ramus number of setae on outer margin	0	—	1	—	2-3	3	—	1
U2 outer ramus number of setae on inner margin	2	—	2	—	0	2	—	2
U3 outer ramus number of setae on outer margin	11–13 cuspidate with accessory seta	—	15	—	12-18	12	4-18	18 cuspidate with accessory seta
U3 outer ramus number of setae on inner margin	0–1 simple + 8–19 bifid long + 3–7 cuspidate with accessory seta	—	21 bifid long + 4 cuspidate with accessory seta	—	~20 bifid	21 simple	—	16 bifid + 5 cuspidate with accessory seta
Nauplius, 30: e2022020	11

Figure 5. Outcrops and pastures close to the Gruna da Serra Verde cave ( A ); cave gallery in the dry season ( B ) and detail of the small pool formed by the upper phreatic aquifer, where specimens of Spelaeogammarus ginae sp. nov. were found ( C ); map indicating the state of Bahia, the Gruna da Serra Verde cave, and the land use and land cover of the area ( D ). Photographs: M.E. Bichuette. Identification. Taxonomic treatment followed the original description of S. spinilacertus (see Koenemann and Holsinger, 2000 ) and the key to Spelaeogammarus species ( Rogers et al. , 2020 ). Spelaeogammarus spinilacertus is characterized by 4 articles on antenna 1 accessory flagellum; antenna 2 is 25 % shorter than antenna 1, flagellum with 7 segments; 6 multicuspidate setae on maxilla 1 outer plate; and 4 plumose setae on maxilliped inner plate ( Koenemann and Holsinger, 2000 ; Rogers et al. , 2020 ). The original description of the species was based on one holotype and one allotype ( Koenemann and Holsinger, 2000 ), hampering the observation of variation. All but one diagnostic characteristic were observed on the analyzed material, i.e ., instead of 6 multicuspidate setae on maxilla 1 outer plate, we found 7 setae, which could represent variability in this character. Figure 6. Preserved specimen of Spelaeogammarus spinilacertus Koenemann and Holsinger, 2000 from Buraco do Cão cave, Iraquara municipality, state of Bahia, Brazil ( A ) and live specimen of S. spinilacertus from Canoa Quebrada cave, municipality of Iraquara, state of Bahia, Brazil ( B ). Photograph: ( A ) Luciana B.R. Fernandes, ( B ) Adriano Gambarini. Geographic distribution and ecological data . The distributional range of Spelaeogammarus spinilacertus increased from two (Baixa do Salitre and Jaburu caves) to seven caves (new records: Lapa Doce System, Gruta da Umburana, Gruta da Lagoa Seca, Buraco do Cão, and Canoa Quebrada caves) that define a polygon of approximately 101 km 2 ( Fig. 7C ). All caves are located in the Chapada Diamantina region, central portion of the state of Bahia , northeastern Brazil , upper Paraguaçu River basin. The limestone rocks from Chapada Diamantina region are dated to the Neoproterozoic age, and belong to the Una Geological Group, Salitre Formation ( Schobbenhaus et al. , 1984 ). These caves present lentic water bodies of the upper phreatic zone. Spelaeogammarus spinilacertus occurs in shallow, soft-bottom pools (observations of individuals were to 2 m depth), with slow water current ( Fig. 7A, B ). Populations show a preference for swimming close to the substrate, formed mainly of silt, limestone riffles, and guano piles and, less frequently, in the mid-water and surface ( MEB ., pers. obs.). The abundance is relatively high in two caves, Canoa Quebrada (observed in June/2005) and Lapa Doce System (observed in October/2016), with 40 and 20 individuals respectively.Physical and chemical variables showed little variation between the cave waters and three of them are typical of karst waters (alkaline pH and high conductivity): pH from 7.7 to 7.9; conductivity from 0.474 to 0.639 µS. cm-1 ; temperature from 22.5 to 26.3 ° C ; and salinity from 0.1 up to 0.2 %. We propose that Spelaeogammarus spinilacertus should be classified as Endangered ( EN ) according to the IUCN criteria B 1ab(iii). The species has an extent of occurrence ( EOO ) estimated less than 5,000 km 2 (criteria B 1); one location (defined as a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present) (criteria a); and continuing decline in the quality of habitat (criteria b). The species is associated with phreatic water and, therefore, a single threatening event can rapidly affect the individuals of different caves. The region is influenced by several anthropogenic impacts including cattle grazing, agriculture, but the main impact could be pollution of the phreatic waters by pesticides, as the caves are located outside protected areas such as the Chapada Diamantina National Park ( Gallão and Bichuette, 2018 ). These impacts contribute to decline in the quality of habitat. Spelaogammarus spinilacertus co-occurs with the troglobitic catfish Rhamdiopsis krugi Bockmann and Castro, 2010 , also endemic to limestone caves of the Chapada Diamantina ( Bichuette et al. , 2015 ) and considered one of the predators of the amphipod species.