Adaugammarus pilosus, Sidorov & Gontcharov & Sharina, 2015

Sidorov, Dmitry A., Gontcharov, Andrey A. & Sharina, Svetlana N., 2015, A new genus and two new species of cavernicolous amphipods (Crustacea: Typhlogammaridae) from the Western Caucasus, European Journal of Taxonomy 168, pp. 1-32 : 21-28

Adaugammarus pilosus gen. et sp. nov.

urn:lsid:zoobank.org:act:356488CF-429D-4F6D-AD07-2E04A8E659F1

Figs 2 , 4 I–K, 12–16

Diagnosis (both sexes)

As for the genus. A. pilosus gen. et sp. nov. is readily distinguished from the other cavernicolous typhlogammarids by the sexually dimorphic uropods. See the section ‘Discussion of affinities’ and the key below.

Etymology

The species epithet ( pilosus, Latin ), meaning “covered with hairs”, refers to the extremely setose uropods in males.

Material examined

Holotype

GEORGIA: sequenced ♀ (carrying 10 eggs), 13.5 mm, Sarma Cave (43°4158 N, 40°3633 E, approx.), 2346 m a.s.l., Transsib meander (sampling depth - 1270 m), Arabika massif, Gagra District , Western Caucasus, 15 Sep. 2011, coll. P.V. Rudko ( X44046 /Cr-1652- FEFU).

Paratypes

GEORGIA: ♂, 11.5 mm, ♀ (oostegites developed, setose), 12.5 mm, ♀ (carrying 21 eggs), 16.5 mm, same data as holotype; ♂, 17.5 mm, Sarma Cave, pit K25 Vodoprovod, (sampling depth - 1700 m), 21 Sep. 2011, coll. P. V. Rudko ( X44047 /Cr- 1653-55 - FEFU).

Description

Holotype

BODY LENGTH. 13.5 mm.

GENERAL BODY MORPHOLOGY ( Figs 2 , 4 I–J, 14C, G). Body smooth, with median and lateral thin setae, lacking dorsal cuticular elements (keel or tubercles). Head shorter than first pereon segment; rostrum indistinct; lateral cephalic lobe with recess; inferior antennal sinus shallow, sub-rounded. Eyes absent. Urosomites 1–3 on dorsal surface with lateral spines and setae; armed with notched spines in the following manner: 1 (0-0), 2 (1-1), 3 (1-0-1). Epimeral plate 1: postero-ventral corner prominent; posterior and ventral margins convex; 3 stiff setae along ventral margin, 5 setae along posterior margin. Epimeral plate 2: postero-ventral corner prominent; posterior margin straight; ventral margin convex; 3 stiff setae along ventral margin, 3 setae along posterior margin. Epimeral plate 3: postero-ventral corner prominent; posterior margin straight; ventral margin convex; 3 stiff setae along ventral margin, 1 seta along posterior margin. Telson: width:length ratio is 0.9:1; cleft 0.9 of length; 2 apical spines per lobe, each accompanied by 2 setae.

ANTENNAE ( Figs 2 , 12 A–B). Antenna 1 0.5× of body length; main flagellum with up to 34 articles; each article with 2–7 setae; peduncular articles in ratio 1:0.6:0.4; accessory flagellum 4-articulated. Length ratio of antenna 1 to antenna 2 is 1:0.5; flagellum of antenna 2 with 13 articles, each article densely setose; length ratio of peduncle articles 4 and 5 is 1:0.9; flagellum 0.2× longer than peduncle (articles 4+5); peduncular articles 4 and 5 densely setose, with tight bundles of long stiff setae on lateral and medial faces; gland cone very short.

MOUTH PARTS (typical gammarid, Figs 4K , 13 ). Labrum rounded, clypeus unfused, longer than broad. Inner lobes of labium absent, outer lobes broad, with stiff curved setae marginally, mandibular process distinct (narrow). Left mandible: incisor with 5 teeth, lacinia mobilis with 4 teeth; between lacinia and molar a row of 11 serrate spines. Right mandible: incisor process with 4 teeth, lacinia mobilis bifurcate, with several small denticles, between lacinia and molar a row of 9 serrate spines; triturative molar process with long plumose seta. Mandibular palp article 2 longer than article 3 (distal); proximal palp article without setae; second article with 21 setae; distal article narrowed, with 2 A groups of 2 and 7 setae, respectively, 2 B groups of 3 and 4 setae, respectively, 13 D setae and 4 E setae. Maxilla 1 palp long, distal article with 1 or 3 apical spines accompanied with setae (both palps asymmetric, right palp broader, with 1 seta on outer margin); outer plate with 14 multi-toothed spines; inner plate trapezoidal, with 10 plumose setae. Maxilla 2 with both plates narrowed, inner plate with oblique row of 8 plumose setae; both of them apically with numerous setae in two rows. Maxilliped palp article 2 broad, with about 75 setae (some of them in 8 oblique clusters) along inner margin; article 3 narrow, densely setose, with long setae on inner face; article 4 (distal) with dorsal seta, bearing 5 setae at nail base, nail half as long as pedestal; outer plate with 18 flattened, naked spines, 2 long serrate spines and 3 long plumose setae on apex; inner plate with 3 strong spines (1 supplemental spine on medial face) and 13 stiff, naked setae apically and sub-apically, 24 plumose setae on ventral face, 5 stiff denticulate setae on dorsal face. Foregut lateralia with 17 strong pectinate spines, with densely setose row of stiff setae.

COXAL PLATES, GILLS AND OOSTEGITES ( Figs 12 C–D, 14A–B, 15A–C). Coxal plate 1 of rectangular shape, antero-ventral margin extended, with sparse setae. Coxal plate 2 of sub-rectangular shape, antero-ventral margin narrowed with, sparse setae. Coxal plate 3 width:depth is 0.5:1, antero-ventral margin narrowed, with 3 setae. Coxal plate 4 of sub-quadrate shape, as long as broad; posteriorly with broad excavation; along ventral margin sparse setae. Coxal plates 5–7 progressively smaller towards the posterior; coxal plates 5–6 with anterior lobe well-developed; posterior margin pointed, with 4 or 5 setae. Coxal plate 7 sub-rectangular, along posterior margin 3 setae in shallow serration. Coxal gills 2–7 stalked, large but progressively smaller towards the posterior; gills 2–4 sub-triangular, gills 5–7 saccular or irregularly ovoid. Oostegites 2–5 on gnathopod 2 and pereopods 3–5, very broad, with long marginal setae.

GNATHOPODS 1–2 ( Figs 12 C–F). Gnathopod 1: ischium broadly setose, with stiff setae on distal and lateral margins. Carpus 0.36× length of basis and 0.4× length of propodus; anterior margin of carpus with 1 group of setae; carpus posteriorly with transverse row of lateral and marginal setae. Propodus almondshaped, palm convex, with cutting margin smooth and longer than posterior margin; along posterior margin a row of simple setae; anterior margin with 3 sets of setae, antero-distal group with 10 setae; palmar margin with short, notched setae along outer and inner faces, palmar angle undefined, a group of 10 distally-notched, strong spines on both faces (with 2 strong mid-palmar spines in the place where tip of nail close); nail long, 0.4× total length of dactylus, 1 seta along anterior margin, without setules at hinge. Gnathopod 2: basis width:length is 0.3:1. Ischium broadly setose, with stiff setae on distal and lateral margins. Carpus 0.27× length of basis and 0.4× length of propodus; anterior margin of carpus with 1 distal set of setae; carpus posteriorly with 5 lateral sets of setae and transverse row of marginal setae. Propodus small (compared to the body) and same length as propodus of gnathopod 1; propodus pyriform, palm convex with cutting margin smooth and shorter than posterior margin; posterior margin with 8 sets of stiff setae; anterior margin with 5 sets of setae; antero-distal group with 10 setae; palmar margin with short, notched setae along outer and inner faces, palmar angle undefined, a group of 5–6 distally-notched, strong spines on both faces in the place where tip of nail close (with 1 strong midpalmar spine); dactylus similar to that of gnathopod 1.

PEREOPODS 3–7 ( Figs 14 A–B, 15A–C). Lengths of pereopods 3–4 is 0.95:1. Dactylus 4 0.5× propodus 4; nail length 0.5× total dactylus length. Dactyli 3–4 with dorsal plumose seta; inner margin with 1 stiff seta and 1 thin seta at hinge. Lengths of pereopods 5:6:7 is 0.9:1:0.9. Pereopod 7 length 0.5× body length. Bases 5–7 narrowed distally; length:width is 1:0.5–0.6; posterior margin curved (distinctly in basis 7), without postero-distal lobes; marginal serrations with short setae posteriorly (expressed in basis 5); 3–4 notched spines anteriorly. Dactylus 7 length 0.28× of propodus 7 length. Dactyli 5–7 with dorsal plumose seta; inner margin with 1 stiff seta and 1 thin seta at hinge.

PLEOPODS ( Fig. 15 D–G). Pleopods 1–3 sub-equal, each with 2 coupling setae accompanied by 1 stiff seta; peduncular articles fringed with long, thin setae; proximal article of inner rami fringed with 5 simple setae. Pleopods 1–3 rami with 19–21 articles each.

UROPODS ( Figs 2 , 14 D–F). Uropod 1 protopodite with 1 basofacial spine, 2 dorso-lateral spines and 3 dorso-medial spines; exopodite:endopodite length is 1:0.8; rami straight, with single spines along outer margins; both with 5 spines apically and sub-apically (two of them strong). Uropod 2 exopodite 0.2× shorter than endopodite. Uropod 3 protopodite with 2 groups of spines on apex; endopodite 0.7× of protopodite length, with 2 spines and 6 long setae apically; exopodite 1.3× longer than protopodite, with 3 groups of lateral spines, long simple setae along inner margin, 3 spines and about 13 setae apically.

Male (paratype X44049 /Cr-1655-FEFU)

Body length 17.5 mm, with sexually dimorphic characters ( Fig. 16 ). Larger than female, with more stout body. Antenna 2 densely setose. Gnathopods 1 and 2 propodi sub-similar, almond-shaped, but propodus of gnathopod 2 larger than propodus of gnathopod 1; palmar margins beveled, palm straight, with cutting margin acanthaceous; nail short, 0.3x total length of dactylus. Uropods 1–3 extremely setose. Uropod 1 protopodite with 3 sets of long setae along inner margin; exopodite broad and curved, longer than endopodite; rami setose, with dense bundles of long, swirling setae. Uropod 2 protopodite with 5 sets of long setae along inner margin; exopodite as long as endopodite; rami setose, with dense bundles of long, swirling setae. Uropod 3 protopodite with 5 sets of long setae along inner margin; endopodite 1.3× longer than protopodite, with 2 spines along inner margin and 2 spines on apex; exopodite broad, 1.6× longer than protopodite, with 3 groups of lateral spines, 3 spines on apex; rami setose, with dense bundles of long, swirling setae.

Variability

Not observed.

Distribution and ecology

Adaugammarus pilosus gen. et sp. nov. inhabits aquatic biotopes in the Sarma Cave ( Figs 1–2 ) in the eastern Arabika massif (species was observed at depths of - 1270 m and - 1700 m) and revealed an ability to move in a hygropetric zone.

Phylogenetic analysis

To access the affinities of the newly described taxa and confirm their genetic distinctness, we sequenced a partial mt- cox1 gene from Z. sandroruffoi sp. nov. (6 accessions, Table 1 ) and Adaugammarus gen. nov. (4 accessions) and assembled a data set including their putative relatives, Accubogammarus , Metohia , Typhlogammarus , and Zenkevitchia spp. ( Table 1 ). Specimens of Zenkevitchia sandroruffoi sp. nov. from the Trojka (- 30 m depth) and Sarma caves (- 350 m) produced identical sequences ( KT427522 and KT427521 , respectively), as did two further specimens from the Orlinoe Gnezdo cave (- 75 m; KT427523 and KT427524 ); the intraspecific distance is 0.34 ± 0.17 SE ( Table 2 ). All four specimens of Adaugammarus pilosus gen. et sp. nov. from the deepest part of the Sarma Cave (-1270 to - 1700 m; KT427516 – KT427519 ) were also almost identical in sequence; the intraspecific distance is 0.09 ± 0.09 SE ( Table 2 ). Redundant sequences were excluded from the analyses. The resulting topology ( Fig. 3 ) was generally in agreement with that previously obtained for a smaller data set ( Sidorov et al. 2015). Species of Zenkevitchia were members of a clade (81% BP) that also included Accubogammarus and Adaugammarus gen. nov. Topologically, Z. revazi was a basal divergence in this lineage. Adaugammarus gen. nov. was resolved as a sister (96%) to a cluster composed of Z. sandroruffoi sp. nov., Z. admirabilis , and Z. yakovi . The branching pattern among these species remained unresolved. Four highly similar (p -distances 0.002–0.01) Z. sandroruffoi formed a robust (100%) clade characterized by a relatively long branch. Accessions from the Sarma and Trojka caves shared two synapomorphic substitutions and were clustered together to the exclusion of specimens from Orlinoe Gnezdo.

Figures

Fig. 2. Vertical distribution of amphipod species in the Sarma Cave. Map adapted from Sidorov et al. (2014), compiled by V.V. Sukhachev.

Fig. 4. — A–D. Anopogammarus birsteini Derzhavin, 1945. ♀, 9.0 mm, X44039/Cr-1645-FEFU: A. Habitus from left side. B. Urosome. C. Head. D. Metasomal and urosomal segments with telson. — E–G. Zenkevitchia sandroruffoi sp. nov. Paratype, ♀, 6.3 mm, X44045/Cr-1651-FEFU. E. Lateralia. F. Head. G. Urosome. — H–K. Adaugammarus pilosus sp. nov. Holotype, ♀, 13.5 mm, X44046/Cr- 1652-FEFU. H. Lateralia. I. Head. J. Urosome. K. Lateralia.

Fig. 12. Adaugammarus pilosus gen. et sp. nov. Holotype, ♀, 13.5 mm, X44046/Cr-1652-FEFU. A. Antenna 1. B. Antenna 2. C. Gnathopod 1. D. Gnathopod 2. E–F. Palmar margins of gnathopods 1 and 2 propodi (setation omitted).

Fig. 13. Adaugammarus pilosus gen. et sp. nov. Holotype, ♀, 13.5 mm, X44046/Cr-1652-FEFU. A. Left mandible. B. Right mandible. C. Article 3 of mandibular palp, ventral setation. D. Upper lip. E. Lower lip. F. Maxilla I. G. Outer plate of maxilla 1. H. Palp of right maxilla 1. I. Maxilla 2. J. Maxilliped. K. Inner plate of maxilliped, inner face. L. Inner plate of maxilliped, outer face. M. Outer plate of maxilliped.

Fig. 14. Adaugammarus pilosus gen. et sp. nov. Holotype, ♀, 13.5 mm, X44046/Cr-1652-FEFU. A. Pereopod 3. B. Pereopod 4. C. Epimeral plates 1–3. D. Uropod I. E. Uropod 2. F. Uropod 3. G. Telson.

Fig. 15. Adaugammarus pilosus gen. et sp. nov. Holotype, ♀, 13.5 mm, X44046/Cr-1652-FEFU. A. Pereopod 5. B. Pereopod 6, part. C. Pereopod 7. D. Pleopod 1. E–G. Coupling setae of pleopods 1–3.

Fig. 16. Adaugammarus pilosus gen. et sp. nov. Paratype X44049/Cr-1655-FEFU, ♂, 17.5 mm. A. Gnathopod 1, part. B. Gnathopod 2, part. C. Uropod 1. D. Uropod 2. E. Uropod 3. F. Telson.

Fig. 1. Distribution map of Typhlogammaridae species and Anopogammarus in the Transcaucasia. 1. Zenkevitchia sandroruffoi sp. nov. 2. Adaugammarus pilosus gen. et sp. nov. 3. Zenkevitchia sp. sensu Jaume in Sendra & Reboleira (2012). 4. Zenkevitchia admirabilis (complex of species). 5. Zenkevitchia yakovi Sidorov, 2015. 6. Zenkevitchia revazi Birstein & Ljovuschkin, 1970, comb. resurr. 7. Anopogammarus birsteini Derzhavin, 1945.

Fig. 3. Unrooted ML-tree with bootstrap support values based on the mt-cox1 sequences (values less than 50% not shown). Specimen labels refer to information given in Table S1. Scale bar indicates the number of substitutions per site.

Tables

Table 2. Estimates of pairwise sequence divergence (uncorrected p-distances) of partial mitochondrial COI gene among and within species (bold type) of the Balkan and Caucasian Typhlogammaridae. Numbers in brackets correspond to geographic locality on Fig. 1; n/a = not applicable.

Species	Number of sequences	1	2	3	4	5	6	7	8
1. Zenkevitchia sandroruffoi [1]	6	0.0034
2. Adaugammarus pilosus [2]	4	0.159	0.0009
3. Zenkevitchia yakovi [5]	3	0.142	0.141	0.0024
4. Metohia carinata	1	0.245	0.235	0.237	n/a
5. Typhlogammarus mrazeki	1	0.241	0.246	0.243	0.217	n/a
6. Typhlogammarus sp.	1	0.247	0.234	0.248	0.217	0.138	n/a
7. Zenkevitchia admirabilis [4]	2	0.138	0.150	0.128	0.239	0.233	0.247	0.0783
8. Zenkevitchia revazi [6]	1	0.206	0.210	0.210	0.255	0.246	0.251	0.207	n/a