Asellus ismailsezarii Malek-Hosseini, Jugovic, Fatemi & Douady, 2022

Malek-Hosseini 1,2,3, Mohammad Javad, Jugovic 4, Jure, Fatemi 5, Yaser, Kuntner 1,2, Matjaz, Kostanjsek 3, Rok, Douady 6, Christophe J. & Malard 6, Florian, 2022, A new obligate groundwater species of Asellus (Isopoda, Asellidae) from Iran, Subterranean Biology 42, pp. 97-124 : 97

Asellus ismailsezarii Malek-Hosseini, Jugovic, Fatemi & Douady sp. nov.

Figs 2 , 3 , 4 , 5 , 6 , 7

Material examined.

Holotype: mature male, body length (BL) 8.2 mm (TU-SP.1), Ganow spring, Tuveh village, Andimeshk, Khuzestan Province, Iran, (32°48'31"N, 48°43'32"E, altitude 470 m above sea level). coll. Yaser Fatemi; 01. June. 2019 . Paratypes: 2 mature males, BL 8.2 mm (TU-SP.2), BL 6.5 mm (TU-SP.5), 1 juvenile male, BL 7.3 mm (TU-SP.7); 3 mature females, BL 8.1 mm (TU-SP.3), BL 8.1 mm (TU-SP.4), BL 6.7 mm (TU-SP.6); data same as holotype . Other material: 17 juvenile specimens (including specimens AS 2 and AS 3), data same as holotype. 1 mature female, BL 8.6 mm (specimen AS 1), 01. December.2018, Same locality as holotype. coll. Mohammad Javad Malek-Hosseini and Yaser Fatemi. All material was preserved in 70% ethanol and deposited at UCBLZ ( University Claude Bernard Lyon-Zoology , Lyon, http://cerese.univ-lyon1.fr/), under deposit numbers 2012.11.23.91-2012.11.23.99 and 2012.11.24.1-2012.11.24.47. We also deposited tubes containing stubs onto which pleopods I and II of holotype and paratype were mounted for producing SEM images .

Diagnosis of male.

Species of A. ismailsezarii sp. nov. with depigmented body and complete loss of eyes (Fig. 2 ). Body elongated oval, more than three times (3.2-3.5) as long as wide. Head up to 1.4 times as wide as long; frontal margin bisinuate, medially concave, lateral margins rounded, each with posterolateral prominence with few weak setae. Pereonites I-III with slightly convex lateral margins, and pereonites IV-VII with straight lateral margins, with only few small simple short setae of about the same length. Pleomere I-II width about 60% of pereonite VII width. Pleotelson subrectangular, lateral margins densely fringed with simple short setae of about the same length, terminal edge rounded, with only weak median prominence. Antennae I and II, lengths about 15% and 70% of body length and with 8 and 55 flagellar articles, respectively. Propodus I slender ovoid, with weak apophysa on palmar margin. Carpus and propodus IV only slightly curved, superior margin and submarginal surface of propodus IV with few (6) short and weak simple setae. Length of longest spiniform robust seta on propodus VII inferior margin only about 3% pereopod VII length. Pleopod I exopodite without symmetric concavity on lateral margin, lateral margin being rather straight to slightly convex. Pleopod II architecture following typical ‘‘ Asellus pattern’’ sensu Henry and Magniez (1995). Its endopodite with short (around 25% of protopodite length) horn-shaped basal spur (processus calcariformis). Pleopod IV and V with small respiratory areae, linea areae beginning and ending at the distal exopodite margin. Uropod short, up to about a quarter of body length.

Description of holotype and male type material

(values in parenthesis). Body (Fig. 3B ) 3.4 (♂♂: 3.3-3.5 ♀♀: 3.3-3.8) times as long as wide, elongated oval, without pigmentation. Head (Fig. 3B ) width 1.3 (♂♂: 1.1-1.4; ♀♀: 1.3-1.4) times of its length. Frontal margin bisinuate, medially concave, without rostral process, lateral margins rounded, each with small posterolateral protuberance, with few small, short stiff setae. No eye structures visible.

Pereonites (Fig. 3B ) I-III with straight to slightly convex lateral margins and weakly rounded antero- and posterolateral angles, slightly protruding forwards. Last three pereonites with antero- and posterolateral angles slightly protruding backwards. Pereonite VI widest. Anterolateral, lateral and posterolateral margins of pereonites almost bare, with only sparse short simple setae. Coxopods well developed, margins of all epimerae dorsally visible, last three the most prominent.

Pleomere I-II short but wide (Fig. 3B ), their width about 62% of pereonite VII width, forming a stalk largely covered by posterior margin of pereonite VII. Pleotelson (Fig. 3B ) subrectangular, its width 1.02 (♂♂: 1.02-1.13; ♀♀: 0.96-1.01) times of its length, terminal edge rounded, with only weak median prominence between uropods. Lateral margins in their anterior quarters with few short setae, other three quarters with 30 (♂♂: 26-30; ♀♀: 26-36) (left side of pleotelson) and 32 (♂♂: 25-32; ♀♀: 29-35) (right side of pleotelson) dense but minute spiniform setae of about the same length. Terminal edge with a series of 12 (♂♂: 11-15; ♀♀: 11-19) short setae between the uropods. Dorsal surface almost bare, without setation.

Antenna I length (Fig. 3AI) 15% (♂♂: 15-16%; ♀♀: 16-17%) of body length, with 3 peduncular segments. First segment robust, with curved superior (longer) and inferior (shorter) margin, other two segments cylindrical. Second segment 1.3 (♂♂: 1.26-1.33; ♀♀: 0.98-1.30) times as long as first and 1.9 (♂♂: 1.28-1.88; ♀♀: 1.43-2.08) times as long as third. Longest setae on segment 1 approximately as along as width of second article, and length of longest setae on segment 2 about as long as article 3. Flagellum of 8 segments (♂♂: 6-8; ♀♀: 7-8), with 5 (♂♂: 3-5; ♀♀: 1-4) aestetascs on distal segments. Aesthetascs shorter as their parallel segments.

Antenna II length (Fig. 3AII) 62% (♂♂: 50-62%; ♀♀: 80-81%) of body length, with 6 peduncular and 55 (♂♂: 32-55; ♀♀: 47-55) flagellar segments. Sixth peduncular segment 1.6 (♂♂: 1.39-1.61; ♀♀: 1.39-1.43) times as long as fifth, both with only short setae, long setae present only on superior distal angles. Flagellum length 77% (♂♂: 66-77%; ♀♀: 76-77%) of antenna II length.

Mandibulae (Fig. 4MdbL) robust: Pars molaris (molar process) U-shaped, with toothed margin. Pars incisiva (incisor) formed by few blunt cusps arranged in semi-circle. Left lacinia mobilis with few cups and spine row of about 15 biserrate setae, the distal ones being longest. Palp of three segments. First palpal segment widest, with few simple setae distally. Second palpal segment 1.6 times longer than first, without setation along external margin, with two simple setae distalo-mesially, and few simple setae along internal margin. Third palpal segment around half as long as second, with row of about 20 robust biserrate setae along external margin. Maxilla I (maxillule; Fig. 4MxI) lateral lobe with few smooth (the outer spines cone-shaped) and few weakly serrate robust spines. Distal part of outer margin with 1 long slender seta. Mesial lobe with 4 robust long plumose setae. Maxilla II (Fig. 4MxII) lateral and middle lobe with 19 slender and simple, and 13 curved pectinate robust setae, respectively, mesial lobe with about 10 biserrate setae and parallel row of about 13 long simple setae along inner margin. Maxilliped (Fig. 4MxlpR) endite distal margin with about 11 biserrate robust setae, subapically with several rows of short simple setae. Mesial margin curved dorsally, with row of about 8 long biserrate setae, distomesial margin with setulose fringe and around 5 coupling hooks. Palp of five articles. First article with 2 short setae apically on outer margin; second about 2.5 times as long as first, subtrapezoidal, with 5 long stiff setae on outer margin and row of about 15 longer medially directed simple setae on inner margin. Third article a bit shorter as second, less broad, with 4 long stiff setae on outer margin and row of about 11 slender simple setae on inner margin. Fourth article approximately twice as long as third, slender, distally wider, with a row of 6 and about 20 long slender setae along outer and inner margin, respectively. Fifth article as long as first, ovoid, fringed with around 10 long slender setae and 2 longest stiff simple apical setae. Epipodite subrectangular, lateral margin almost bare, with only few (3) short simple setae.

With the exception of the first and the fourth pair, seven pairs of pereopods similar in construction and ambulatory, increasing in length towards posterior pairs. Pereopod I (Fig. 5PpI) grasping, subchelate. Propodus I (article 6) slender ovoid, 2.2 (♂♂: 2.2-2.5; ♀♀: 2.6-2.8) times as long as wide, with weakly expressed proximal apophysa with few stronger spiniform setae (♂♂: 3-4; ♀♀: 2-4) and other sparsely set row of shorter simple setae (about 10 in total). Dactylus I (article 7) length about 70% (♂♂: 70-82%; ♀♀: 70-78%) of propodus length, with 5 (♂♂: 4-6; ♀♀: 5) sparsely placed slender stiff robust setae along inferior margin (their length increasing towards unguis). Pereopod I length 31% (♂♂: 31-38%; ♀♀: 31-40%) of body length, length relations of articles from ischium (article 2) to dactylus (article 7): 1: 0.9 (♂♂: 0.7-0.9; ♀♀: 0.7-1.0): 0.5 (♂♂: 0.3-0.5; ♀♀: 0.4-0.5): 0.2 (♂♂: 0.15-0.20; ♀♀: 0.20-0.24): 0.9 (♂♂: 0.7-0.9; ♀♀: 0.8-1.0): 0.7 (♂♂: 0.7-0.8; ♀♀: 0.7-0.8), unguis length 18% (♂♂: 18-25%; ♀♀: 19-24%) of dactylus length.

Pereopod IV (Fig. 5PpIV) grasping, with parallel, but only slightly curved superior and inferior margins of propodus. Pereopod IV length 36% (♂♂: 36-47%; ♀♀: 42-47%) of body length, length relations of articles from ischium (article 2) to dactylus (article 7): 1: 0.6 (♂♂: 0.6-0.8; ♀♀: 0.6-0.7): 0.4 (♂♂: 0.4-0.5; ♀♀: 0.4-0.5): 0.7 (♂♂: 0.7-0.9; ♀♀: 0.7-0.8): 0.8 (♂♂: 0.8-0.9; ♀♀: 0.8-1.0): 0.4 (♂♂: 0.3-0.4; ♀♀: 0.3-0.4), unguis length 32% (♂♂: 32-39%; ♀♀: 29-41%) of dactylus length. Carpus IV superiodistal angle with 5 (♂♂: 5-6; ♀♀: 5-6) spiniform setae, longest one 26% (♂♂: 18-26%; ♀♀: 17-26%) of carpus length. Propodus IV inferior margin and mesial surface with 6 (♂♂: 3-6; ♀♀: 3-4) acute stiff robust setae, longest robust seta 7% (♂♂: 7-10%; ♀♀: 8-11%) of propodus length, inferodistal surface with 3 (♂♂: 2-4; ♀♀: 0-5) short simple and penicilate setae, superior margin and submarginal surface with 6 (♂♂: 6-13; ♀♀: 12-13) short simple and penicilate setae, superior distal angle with 4 (♂♂: 4-6; ♀♀: 5-6) long simple setae and 1 penicilate seta. Dactylus IV inferior margin with 2 (♂♂: 2; ♀♀: 1-2) robust stiff setae, superior margin distally with 2-5 simple setae.

Pereopod VII (Fig. 5PpVII) with long slender articles, its length 70% (♂♂: 67-81%; ♀♀: 65-72%) of body length, length relations of articles along pereopod VII (given as in pereopod IV): 1: 0.9 (♂♂: 0.9-1.0; ♀♀: 0.8-0.9): 0.7 (♂♂: 0.6-0.7; ♀♀: 0.6-0.7): 1 (♂♂: 1.0-1.1; ♀♀: 0.9-1.1): 1.4 (♂♂: 1.2-1.4; ♀♀: 1.1-1.4): 0.3 (♂♂: 0.3-0.4; ♀♀: 0.3), unguis length 30% (♂♂: 30-39%; ♀♀: 33-43%) of dactylus length. Ischium VII with 8 (♂♂: 6-8; ♀♀: 6-6) spiniform setae along its margins, with around 7 spiniform setae along inferodistal margins of merus, and a group of around 4 spiniform setae on superiodistal angle of merus VII, longest one 42% (♂♂: 42-58%; ♀♀: 44-53%) of merus length. Carpus VII with around 6 strong spiniform setae along inferior and inferodistal margins, few (around 2) weaker spiniform setae along superior margin, and a group of (around two strong and two weak) spiniform setae at superior-distal angle. Propodus VII inferior margin with row of 6 (♂♂: 6; ♀♀: 6) acute stiff robust setae, longest robust seta 10% (♂♂: 9-11%; ♀♀: 11-15%) of propodus length, mesial surface and inferodistal angle with 6 (♂♂: 2-6; ♀♀: 3-5) submarginal simple setae, with few weak simple setae at inferodstal angle. Superior margin and submarginal surface with 10 (♂♂: 7-10; ♀♀: 3-12) short simple and penicilate setae, superior distal angle with 1 (♂♂: 1-2; ♀♀: 1-2) simple setae and around 5 penicilate seta. Dactylus VII inferior margin with 2 (♂♂: 2; ♀♀: 1-2) robust stiff setae, longest 30% (♂♂: 30-39%; ♀♀: 33-43%) of dactylus length, superior margin distally with around 5 (♂♂: 4-6; ♀♀: 4-5) simple setae.

Male pleopod I (Fig. 6PlpI, Fig. 7 ) protopodite 0.92 (0.88-0.96) times as wide as long, retinacle on medial margin of 5 (4-5, exceptionally less) hooks. Exopodite elongated ovoid, its width 77% (57-77%) of its length, with 19 (6-23) simple setae along lateral and distal margins, and 7 (7) plumose terminal marginal setae. Without concavity on lateral margin, lateral margin being rather straight to slightly convex. In juvenile males (Fig. 6PlpI (juv)), pleopod I exopodit external margin proximally elongated in a finger-like projection, with one plumose seta on it, and around 8 plumose setae along lateral and distal margins.

Male pleopod II (gonopod; Fig. 6PlpII, Fig. 7 ) protopodite subtrapezoidal, with rounded angles, its width 77% (76-83%) of its length. Lateral and medial margins without setae. Exopodite oval, almost twice (1.76-1.96) as long as wide, its proximal segment with around 2 simple setae on it its lateral margin; lateral and medial margins of distal segment fringed with 11 (6-11) simple and 6 (0-6) long plumose setae, respectively. A well-developed and rounded catch lobe on the dorsal side and medial margin of the distal segment of exopodite. This catch lobe partly overlaps the proximal segment of exopodite. Endopodite elongated ovoid, its length 60% (60-71%) of protopodite length, with a short horn-shaped basal spur (processus calcariformis): 43% (37-55%) of endopodite length. Dorsal side of endopodite entirely smooth. Ventral side with a finger-like labial spur (processus cylindriformis), an anterior lobe densely covered with serrated scales, and a spoon-shaped Capitulum. Surface of Capitulum is smooth and without spines. A short but large-diameter Cannula is clearly visible with scanning electron microscopy between the anterior lobe and Capitulum . In juvenile males, pleopod II (Fig. 6PlpII (juv)) without endopodite, exopodite almost without setation.

Pleopod III (Fig. 6PlpIII) exopodite rounded triangular, about 1.6 times as long as wide, with almost straight medial margin. Medio-distal, terminal and latero-distal margins with around 8 long plumose setae. No setation along medial and lateral margins. Endopodite length about 0.7 of exopodite length.

Pleopod IV (Fig. 6PlpIV) exopodite broadly ovoid, about 1.6 times as long as wide, its area equally shaped as in pleopod V. Without setation along margins. Endopodite subrectangular, its length about 0.8 of exopodite length.

Pleopod V (Fig. 6PlpV) exopodite ovoid, 1.6 (♂♂: 1.6-1.7; ♀♀: 1.5-1.6) times as long as wide, its margins without setation. Respiratory area small, its surface 21% (♂♂: 21-28%; ♀♀: 22-28%) of exopodite surface, linea areae beginning and ending on the distal exopodite margin. Endopodite suboval, its length almost as long (holotype: 97%) as exopodite.

Uropod (Fig. 6U ) length 24% (♂♂: 24-25%; ♀♀: 17-24%) of body length. Proto-, endo- and exopodite length relations: 1:1.52 (♂♂: 1.40-1.52; ♀♀: 1.53-1.77):1.49 (♂♂: 1.25-1.49; ♀♀: 1.30-1.56). Endopodite with 9 (♂♂: 9; ♀♀: 8-9) spiniform simple setae and 7 (♂♂: 7-9; ♀♀: 8-9) penicilate setae, longest simple seta length 14% (♂♂: 14-15%; ♀♀: 10-13%) of endopodite length.

Female type material.

Body length 6.7-8.1 mm (3.3-3.8 times of body width), almost identical to male except, antenna II seems longer than in males, around 4/5 of body length, but with similar number of flagellar segments (47-55). Pereopod I (Fig. 5PpI(F)) propodus with less expressed proximal apophysa, slender and longer propodus, 2.6-2.8 times as long as wide (♂♂: 2.2-2.5). Pereopod IV (Fig. 5PpIV(f)) not for grasping, ambulatory, little longer than the preceding pairs. Without pleopod I. Pleopod II (Fig. 6PlpII(f)) suboval, about 1.3 (1.3-1.4) times as long as wide, with 12-13 long marginal plumose setae. Uropods seem a bit shorter than in males (♂♂: 24-25%; ♀♀: 17-24%), with relatively longer endopodite compared to protopodite (♂♂: 1.40-1.52 versus ♀♀: 1.53-1.77 times as long as protopodite).

Morphological comparison with other Asellus species.

Among the 18 species of Asellus presently described, A. ismailsezarii sp. nov. resembles morphologically A. monticola Birstein, 1932 (Suppl. material 6: Table S6). Pleopods I and II appear to be almost identical between the two species, although Henry and Magniez (1996) did not provide SEM photos of these pleopods for A. monticola . In both species, the endopodite of pleopod II has a spoon-shaped Capitulum with no spines. However, A. ismailsezarii sp. nov. differs from A. monticola in that it is eyeless and fully depigmented, has a slightly curved pereopod IV and bears no setae on proximal margins of exopodite of pleopods IV and V. These morphological differences are sufficient to consider the studied specimens as belonging to a distinct species. We also provided in Suppl. material 6: Table S6, a morphological comparison with A. kosswigi , A. aquaticus aquaticus , A. aquaticus infernus and A. aquaticus cavernicolus showing that A. ismailsezarii sp. nov. shows many morphological differences with both surface and subterranean aquatic species and subspecies of the A. aquaticus complex. Contrary to A. ismailsezarii sp. nov., all members of the A. aquaticus complex show a helical Capitulum , suggesting the new species does not belong to that complex.

Molecular species delimitation.

We found eleven MOTUs within the " Asellus pattern", including one MOTU corresponding to A. ismailsezarii sp. nov. (Fig. 8A ). Maximal patristic distances among COI sequences within the same MOTU (i.e., within-MOTU distances) ranged from 0 to 0.19 (0.01 for A. ismailsezarii sp. nov.) (Suppl. material 7: Table S7). Minimal patristic distances among sequences belonging to A. ismailsezarii sp. nov. and sequences belonging to the other MOTUs (i.e., between-MOTU distances) ranged from 0.76 to 1.00 (Suppl. material 7: Table S7). The considerable gap between within- and between-MOTU patristic distances supports our taxonomic assessment that A. ismailsezarii sp. nov. is a distinct species.

Phylogenetic relationships as inferred from the COI gene indicated that A. ismailsezarii sp. nov. does not belong to the A. aquaticus complex, which itself contained six MOTUs, including A. kosswigi (Fig. 8A ). Within that complex, only MOTU E corresponding to A. aquaticus Linnaeus, 1758 sensu stricto was widely distributed across Europe (Fig. 9 ). The resulting tree of the nuclear 28S rDNA sequences agreed well with the COI phylogeny, again indicating that A. ismailsezarii sp. nov. was a sister species of the A. aquaticus complex (Fig. 8B ). Patristic distances derived from the 28S loci also corroborated COI results by revealing a strong divergence between A. ismailsezarii sp. nov. and the other MOTUs.

Etymology.

The name of the new species is a patronym for ‘’ Mohammad Ismail Sezari’’, the legendary guard of the train tracks from the area of the type locality. In year 1986, he sacrificed his life to save 750 others that were on a collision course train.

Figures

Figure 2. Habitus of Asellus ismailsezarii sp. nov. (Female AS 1). The photo shows a specimen exposed to air after the stone it was under had been turned over. Body length is 8.6 mm.

Figure 3. Asellus ismailsezarii sp. nov., Ganow spring, Western Iran. Holotype male, 8.2 mm: A I, II antennae I and II B body dorsal view.

Figure 4. Asellus ismailsezarii sp. nov., Ganow spring, Western Iran. Paratype male, 8.1 mm (TU-SP. 2), mouthparts: MdL, left mandible; Mx I, maxilla I; Mx II, maxilla II, MxlpR (v), right maxilliped (ventrally).

Figure 5. Asellus ismailsezarii sp. nov., Ganow spring, Western Iran. Holotype male, 8.2 mm: Pp I, IV, VII - pereopods I (distal articles), IV, VII. Female, 8.1 mm: Pp I, IV (f) - distal articles of pereopods I, IV.

Figure 6. Asellus ismailsezarii sp. nov., Ganow spring, Western Iran. Holotype male, 8.2 mm: Plp I, II; II, IV, V - pleopods I, II, III, IV, IV; U - uropod (pleopod VI). Female, 8.1 mm: Plp II (f) - pleopod II. Juvenile male, 7.3 mm: Plp I, II (juv) - pleopods I, II.

Figure 7. Asellus ismailsezarii sp. nov., male; SEM micrographs of (A) pleopod I (paratype male BL 8.2 mm: TU-SP. 2). Photo also shows one genital papilla inserted on ventral side of pereionite VIII B, C, D pleopod II endopod (holotype male BL 8.2 mm: TU-SP. 1) B, C ventral view and D lateral view.

Figure 8. Phylogenetic relationships among taxa belonging to the Asellus pattern derived from Maximum likelihood analysis of (A) 585 COI mtDNA sequences, (B) thirty 28 S rDNA sequences. The clade comprised of M. dybowskii and L. poberezhnii was used as outgroup. In A, branches to molecular operational taxonomic units (MOTU) as delimited with the fixed threshold method implemented by Lefebure et al. (2006) were collapsed. In B, branches to the main clades were collapsed. Colors and symbols as in Fig. 9. Branch supports are approximate likelihood ratio test (aLRT) values (black) and bootstrap values (red).

Figure 9. Map showing the distribution of molecular operational taxonomic units (MOTU) within the " Asellus pattern ". Site locations for Asellus hilgendorfii (Japan) and Mesoasellus dybowskii and Limnoasellus poberezhnii (Lake Baikal, Russia) are not shown. Colors and symbols as in Fig. 8.