Tegano tashanensis, Malek-Hosseini & Brad & Fatemi & Kuntner & Fišer, 2024

Malek-Hosseini, Mohammad Javad, Brad, Traian, Fatemi, Yaser, Kuntner, Matjaž & Fišer, Cene, 2024, A new cave-dwelling hadzioid amphipod (Senticaudata, Hadzioidea, Melitidae) from sulFIdic groundwaters in Iran, Contributions to Zoology 93 (2), pp. 107-126 : 113-117

Tegano tashanensis sp. nov.

https://zoobank.org/NomenclaturalActs/614E

536F-598E-4B12-8818-DEAF2F6026F7

Figs. 4 –10

Diagnosis. Small-sized stygobiontic amphipod, with robust appearance and clear troglomorphic features. Eyeless, unpigmented, least setose, long antennae and legs relative to body length, labium without inner lobes, mandibles without mandibular palps, exopodite of uropod III unsegmented. Pleonites 2 and 3 with 2 small setae on the postero-dorsal sides. One seta on each postero-dorsal side of the first two urosomites. Antenna I two thirds of the total body length. Outer lobe of maxilla I with 8 comb-like spines. Inner lobe of maxilliped with 3 stout, 3 serrated and 3 regular setae located apically and 3 serrated setae subapically. Gnathopods scarcely setose, highly dissimilar, propodite of gnathopod I less than half length of propodite of gnathopod II. Uropods I and II with slightly shorter exopodites than corresponding endopodites. Pereopods VI and VII of equal size, more than half of body length. Telson as long as wide, with 4 short apical setae on each lobe.

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Material examined. Holotype: ♂ (fig. 4A), Chah Kabootari Cave , Sarjowshar village , Tashan district , Behbahan county, Khuzestan Province, Zagros Mountains, southwestern Iran (30°52’10’‘N, 50°10’01’‘E, altitude 539 m a.s.l.), collected on 17.03.2018.

Paratypes: Locality as same as holotype, one dissected ♀ (fig. 4B), 1 ♂ and 2 ♀ undissected; collected on 08.12.2018.

Remark. The morphological description was performed on the body appendages belonging to the dissected holotype male. Sexual dimorphism was described by inspection of one paratype female.

Description (male): The total body length of the male is 4.7 mm ( fig. 5A). A chart containing detailed measurements on all diagnosis-relevant body appendages is presented in supplementary table S4.

Head. Head ( fig. 5A) with no rostrum; 10 % of the total body length (supplementary table S4).

Antennae. Antenna I (fig. 6A) about two thirds of the total body length, with main flagellum formed of 20 articles. Antenna I articles with short aestethascs, one third of the respective article. Antenna I peduncle 41 % of the total length of antenna I. Accessory flagellum formed of 1 article and does not exceed the length of the first article of the main flagellum (fig. 6C). Accessory flagellum with 6 apical setae and 1 serrate seta located subapically. A more frequent shape of the accessory flagellum is that present in the paratype male and females (fig. 6D). Here, accessory flagellum is longer, and it is formed of 2 articles.The distal article represents only 5 % of the total length of the accessory flagellum and it bears 2 long setae.

Antenna II (fig. 6A) with the flagellum formed of 10 articles; less than half of the total length of antenna I. The peduncle 60 % of the total length of antenna II.

Mouthparts. Labrum (fig. 6G) trapezoidal, with the width twice as much as its depth. Labium (fig. 6H) without inner lobes. The outer lobes each with one row of fine setae on the outer side. Maxilla I (fig. 6E) with 6 apical and 2 subapical setae on the distal article of the palp. The outer lobe with 8 comb-like spines apically. Inner lobe with 6 apical serrate setae and a row of lateral fine setae. Maxilla II (fig. 6F) with the outer lobe ¾ of the inner lobe length. Both lobes with a row of apical setae of various lengths. Outer lobe with a row of fine setae on the outer margin. The outer margin of inner lobe with one row of fine setae and one row of plumose setae. Mandibles lack palps. Left mandible (figs. 7I–7J) with the incisor process formed of two lamellas with 3 and 4 teeth. Lacinia mobilis with 4 teeth; 4 strong serrated setae between lacinia mobilis and molar process. Right mandible (fig. 6K) with 6 teeth on incisor process. Spiniform lacinia mobilis with 2 teeth. 4 larger serrated setae and a row of fine setae between lacinia mobilis and molar process. The molar process present 12 toothlike structures and an adjacent serrated seta. Maxilliped (fig. 7H) with the palp formed of 4 articles little setose. Article 1 with 1 seta on the inner margin. Article 2 with 13 setae (of which one serrated) aligned along the inner margin over the whole length of the article, and one seta located subapically on the outer margin. Article 3 with one group of 4 apical setae and two groups of 5 setae each on both inner and outer margins. Article 4 with a group of 4 fine setae on the ventral margin and 1 seta on the dorsal margin. The outer lobe of maxilliped (fig. 7I) with 4 serrated setae and 3 flattened spines located apically, a row of 7 setae and 7 denticles aligned over the inner margin. The inner lobe is provided apically with 4 serrated setae, 3 flattened spines and 3 more regular setae. 2 serrated setae located subapically on the inner margin of inner lobe.

Gnathopods. Gnathopod I (fig. 7A) with the coxal plate in the shape of a rectangular trapezoid. The depth of coxal plate I larger than its width (ratio depth:width 1.0:0.5). Basipodite length:width ratio 1.0:0.3. Ischiopodite with one posteroventral group of 4 setae. Basipodite length:carpopodite length ratio 1.0:0.6. Meropodite with a row of fine setae along the whole ventral margin and 4 longer apical setae. Carpopodite with a row of 8 setae located posteroventral, a group of 4 setae located apically and 1 anterodorsal seta. Propodite (fig. 7C) with the length: width ratio 1.0:0.6. Propodite least setose, 2 setae on the ventral margin, a group of 4 setae on the dorsal margin and one group of 6 setae located antero-apically. 2 setae on the lateral surface and 2 small setae in the vicinity of the palmar corner. Palmar spines absent. Dactylopodite with the nail one quarter of the total dactylopodite length. 1 seta on the outer margin of dactylopodite.

Gnathopod II (fig. 7B) highly different compared to gnathopod I. Ovoid coxal plate with the depth: width ratio 1.0:0.6. Basipodite length:width ratio 1.0:0.35. Ischiopodite with on posteroventral group of 3 small setae. Basipodite: carpopodite length ratio 1.0:0.55. Carpopodite with 5 groups of 2‒4 setae along its ventral margin, 1 and 2 setae located apically on each side, 1 small seta on the dorsal margin. Long propodite (fig. 7D), length:width ratio1.0:0.7.Propodite gnathopod II:propodite gnathopod I length ratio 1.0:0.25. Propodite with eight groups of 1–2 setae in its ventral margin, four groups of 2‒3 setae on the dorsal margin and one group of 4 setae located antero-apical. On its surface, the propodite has two median groups of 2 setae, and one group of 2 setae close to the palmar corner. Palmar spines missing. Short dactylopodite nail, representing 15% of the total dactylopodite length. One seta on the outer margin of dactylopodite. Pereopods. Pereopod III (fig. 7E) with a relative rectangular coxal plate, ratio depth:width 1.0:0.55. Dactylopodite with the nail measuring one third of the total length of the dactylopodite, one dorsal seta with plumose tip and one fine seta at the nail insertion. Propodite: dactylopodite length ratio 1.0:0.35. Pereopod III nearly equal in length to pereopod IV (ratio 1.0:0.97).

Pereopod IV (fig. 7F). Coxal plate with depth:width ratio 1.0:0.87. Gill ovoid, almost as large as the coxal plate. Dactylopodite (fig. 7G) with nail measuring one third of the total dactylopodite length, with one dorsal seta with plumose tip and one seta at nail insertion. Propodite:dactylopodite length ratio 1.0:0.35.

Pereopod V (fig. 8A). Coxal plate bilobed. Basipodite ovoid, length:width ratio 1.0:0.83. Short and thick setae present along the anterior and posterior margins of basipodite. Dactylopodite (fig. 8B) with one seta with plumose end on the outer margin and one seta al the insertion of the nail, which represents one quarter of the total dactylopodite length. Propodite:dactylopodite length ratio 1.0:0.38.

Pereopod VI (fig. 8C). Coxal plate of a relatively triangular shape, with a deep concavity in its dorsal margin. Basipodite (length:width ratio 1.0:0.82) with an ovoid shape, 7 groups of 2 setae on the anterior margin and 17 setae on the posterior margin. Dactylopodite (fig. 8D) with 1 plumose seta on the outer margin. The nail length represents one quarter of the total dactylopodite length. Ratio propodite:dactylopodite length 1.0:0.35.

Pereopod VII (fig. 8E). The coxal plate is trapezoidal. Basipodite with an ovoid to trapezoidal shape, ratio length:width 1.0:0.75. Basipodite with nine groups of 2 setae each on the anterior margin, and 21 small setae over the entire length of posterior margin.

Dactylopodite Downloaded (fig. from 8F) Brill with.com one07/10/ plumose 2024 01:59 seta on outer margin. Nail one fifth of the total dactylopodite length. Ratio propodite:dactylopodite length 1.0:0.37. Pereopods V:VI:VII length ratio as 1.0:1.2:1.2

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Pereopods VI and VII of equal size, the longest legs of Tegano tashanensis sp. nov., measuring 2.5 mm.

Pleopods. Pleopods I, II and III highly similar (fig. 8G), with unequal rami and 2 retinacula (fig. 8H).

Uropods. Urosomites I and II with 1 dorso-lateral seta on each side; dorsal margin of urosomites III with no seta. One spiniform seta on the posteroventral angle of the first urosomite near the insertion of uropod I. Uropod I (fig. 9A) little setose. Endopodite slightly longer than the exopodite; ratio endopodite:exopodite 1.0:0.87. Uropod II (fig. 9B) little setose, endopodite longer than the exopodite; ratio endopodite:exopodite 1.0:0.81. Uropod III (fig. 9c) short, approximately 20% of the total body length. Basipodite with 2 apical stout setae on posterior margin and 2 smaller setae on anterior margin. Short endopodite, half the length of basipodite, with 1 short apical seta. Single-segmented exopodite, with 3 groups of 3 setae on the posterior margin, 5 groups of 2‒3 setae on the anterior margin, six robust apical setae (fig. 9E).

Epimeral plates. Epimeral plates ( fig. 5B) of different shape and size. Depth ratio of epimeral plates I, II and III is 1.0:1.3:1.2. Epimeral plates with right postero-ventral angle and convex ventral margin. Epimeral plates II and III with 4 setae on the posterior margin. Pleonites II and III with 1 dorsolateral seta on each side.

Telson (fig. 9F) as long as wide. 4 short apical spines on each lobe. The longest spine ¼ of total telson length. One mesial spine on each lobe, 1‒2 lateral spines on each lobe.

Sexual dimorphism

Sexual dimorphism in Tegano tashanensis sp. nov. is negligible. While the male via Open seems stouter and with slightly longer antennae and pereopods, the diagnostic characters are invariable in the inspected male and female. To test for differences in quantitative traits, like body length (female of 3.86 mm vs. male of. 4.77 mm), we would need more individuals.

Etymology

The species is named after the name of Tashan-Chah Kabootari aquifer which Tashan and Chah Kabootari caves are parts of this unique ecosystem. The species epithet is an adjective meaning “of the Tashan cave”.

Taxonomic remarks

The genus Tegano was erected by Barnard and Karaman (1982), on the basis of a single species, Melita seticornis , primarily due to the reduced mandibular palp. Nowadays, the genus Tegano comprises 12 described species distributed from Australia, Sri Lanka (Indian Ocean), and Palau, the Philippine Islands, and the Solomon Islands (all in the tropical western Pacific Ocean ), Norfolk Coast of United Kingdom and Curaçao Island (both Atlantic Ocean). Tegano includes some obligate cave-dwelling representatives (Sawicki et al., 2005).

The newly described species belongs to a group of Tegano species with completely reduced mandibular palps. There are three species in this group, Tegano vagabundus from Sri Lanka, where mandibular palp is replaced by a long seta (Karaman, 1984), and Tegano tashanensis sp. nov. in Chah Kabootari Cave ( Iran) and Tegano panglaoensis from Philippines, where the mandibular palp is completely absent. The latter species differs from herein described T. tashanensis sp. nov. by presence of eyes and labial lobes, narrow bases of pereopods V-VII (much broader in T. tashanensis sp. nov.), single basiofacial spine on uropod I (two in T. tashanensis sp. nov.), longer distal Downloaded article from on Brill.com exopodite 07/10/of 2024 01 uro-:59:59PM. pod This III is (an short open in access T. article tashanensis distributed sp. nov.) under, and the terms more pointed telson lobes (subrounded in T. tashanensis sp. nov.) ( Sawicki et al., 2005).

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There is an unclear relationship to hadzioid genus Fiha , which we could not analyze phylogenetically, with reduced mandibular palp and inner labial lobes. However, Fiha differs from Tegano tashanensis sp. nov. in slenderer body (more stout in T. tashanensis sp. nov.), accessory flagellum of antenna I (3‒4 articles in Fiha , 1‒2 in T. tashanensis sp. nov.), longer propodus in gnathopod I (relatively shorter in T. tashanensis sp. nov.), coxal plate IV shallow (deeply incised in T. tashanensis sp. nov.), and shallower and more open telson (longer lobes close together in T. tashanensis sp. nov.) ( Stock, 1988).