Halolaelaps euxinus, Trach, Viacheslav A., 2016

Trach, Viacheslav A., 2016, New and little known species of Halolaelaps (Acari: Mesostigmata: Halolaelapidae) from Ukraine, Zootaxa 4154 (4), pp. 436-452 : 437-444

Halolaelaps euxinus sp. nov.

( Figs 1–19 )

Diagnosis of adults. Epistome with anteromedian extension wider at the base and distally denticulate, flanked by a pair of shorter, denticulate anterolateral extensions; peritremes short; femur I with 12 setae; coxa II without anterior spur; genu III and IV with nine setae. Adult female with 17 pairs of setae on the podonotal shield and eight pairs of setae on the opisthonotal shield, Z2–Z4 located on the edge of the shield; endopodal plates between coxae I and II and between coxae II and III fused. The adult male with 21 pairs of setae on the podonotal shield and 14 pairs of setae on the opisthonotal shield; without chitinous clasps on the ventrianal shield; with one apophyses on genu IV; without apophyses on tibia IV.

Adult female ( Figs 1–9 ). Six specimens measured.

Gnathosoma. Second cheliceral segment 116 (111–120) long; fixed cheliceral digit with three larger proximal teeth and two smaller preapical teeth in addition to apical tooth and setiform pilus dentilis; movable cheliceral digit with three teeth in addition to apical tooth ( Fig. 1 ). Epistome with an anteromedian extension wider at the base and distally denticulate, flanked by a pair of shorter, denticulate anterolateral extensions ( Fig. 2 ). Palp 122 (118–124) long; number of setae (trocanter to tarsus): 2-5-6-14 -15; apotele 3-tined; seta al on femur, setae al1 and al2 on genu slightly thickened, setae d1 and d2 short, spine-like, one ventral seta on tibia modified, xiphoid. Subcapitulum 84 (80–88) wide at widest level ( Fig. 3 ). Deutosternum with seven transverse rows of deutosternal denticles (4–13 denticles per row). Internal malae short, outer branch of each internal mala and inner branch smooth. Corniculus horn-like. Measurements of setae: h1 23 (21–23), h2 17 (15–19), h3 21 (19–23), pc 17 (17–21).

Dorsal idiosoma ( Fig. 4 ). Idiosoma elongate. Podonotal shield 193 (193–202) long and 176 (172–185) wide at level of s4, strongly tapering anteriorly of s3; almost smooth; with 17 pairs of setae (j1–j6, z1–z6, s1–s4, s6; s5 absent) and seven pairs of distinguishable pores. Unsclerotised cuticle laterad of podonotal shield with six pairs of setae (r1–r6) and one pair of pores. Opisthonotal shield 181 (172–193) long and 130 (130–145) wide posteriorly from Z1; almost smooth; anterior margin with quadrangular central notch; posterior margin with cribrum; with eight pairs of setae (J1, J2, J4, J5, Z1–Z4; J3 absent) and four pairs of distinguishable pores, setae Z2–Z4 located on edge of shield. Unsclerotised cuticle laterad of opisthonotal shield with 12 pairs of setae (Z5, S1–S5, R1–R6) and eight pairs of pores. Measurements of setae: j1 13 (11–13), z1 8 (8–11), other setae on podonotal shield 13–21 (13–21), setae on opisthonotal shiels 19–21 (19–23), setae on unsclerotised cuticle 17–25 (17–27). All dorsal idiosomal setae aciculate and smooth.

Ventral idiosoma ( Fig. 5 ). Tritosternum with elongate trapezoidal base and very fine lightly pilose laciniae; base of tritosternum length 27 (23–27), laciniae length 53 (50–57). Presternal area lightly sclerotised, not clearly separated of sternal shield. Sternal shield rectangular; smooth and with anterior margin indistinct; region anterior to the first pair of sternal setae (st1) lightly sclerotised; approximately 99 (97–103) long (with presternal area) and 55 (53–57) wide at widest level; with three pairs of setae and two pairs of lyrifissures. Setae st4 and lyrifissures iv3 on metasternal plates. Genital shield smooth; with seta st5; longer than wide; weakly narrowed anterior to st5 and 55 (50–55) wide at level of setae st5. Two pairs of pores on unsclerotised cuticle, posterolaterad of st5. Endopodal plates between coxae I and II, and coxae II and III fused; endopodal plates between coxae III and IV free. Anal shield obovate; 82 (76–82) long and 76 (76–82) wide at widest level; anus located in center of shield; with circumanal setae and a pair of pores; cribrum well developed. Unsclerotised cuticle around of anal shield with a pair of elongate metapodal plates (25 (23–27) long and 5 (4–6) wide), a pair of transverse platelets between Jv1 and Zv1, nine pairs of setae (Jv1–Jv5, Zv1–Zv4) and four pairs of pores. Peritreme 44 (42–48) long, extending anteriorly to level of median region of coxa III (region between r4 and r5). Peritrematal shield extending anteriorly to level of coxa I (region between z1 and s1) and posteriorly as a narrow and diagonal strip to level of posterior margin of coxa IV; not fused to podonotal shield and fused anteriorly to large accessory platelet. Two free smaller accessory plates and a pair of pores located between peritrematal shields and podonotal shield; two free exopodal plates, an elongate platelet between coxae II and III and a triangular platelet between coxae III and IV located between peritrematal shields and coxae II–IV. Spermathecal apparatus not distinguishable. Measurements of setae: st1–st 5 15–17 (15–19), setae on unsclerotised cuticle 15–25 (15–27), para-anal 19 (19–21), post-anal 27 (27–29). All ventral idiosoma setae aciculate and smooth, except st2 thicker and blunt.

Legs ( Figs 6–9 ). Lengths: I 368 (353–391), II 265 (251–279), III 228 (223–242), IV 307 (298–326). Chaetotaxy: Leg I: coxa 2, trochanter 6 (1 0/1 1/2 1), femur 12 (2 3/1 2/2 2), genu 12 (2 3/2 2/1 2), tibia 12 (2 3/2 2/ 1 2); Leg II: coxa 2, trochanter 5 (1 0/1 0/2 1), femur 11 (2 3/1 2/2 1), genu 11 (2 3/1 2/1 2), tibia 10 (2 2/1 2/1 2), tarsus 18 (3 3/3 1/1 2/2 3); Leg III: coxa 2, trochanter 5 (1 0/1 0/2 1), femur 6 (1 2/1 1/0 1), genu 9 (2 2/1 2/1 1), tibia 8 (2 1/1 2/1 1), tarsus 18 (3 3/3 1/1 2/2 3); Leg IV: coxa 1, trochanter 5 (1 0/1 0/2 1), femur 6 (1 2/1 1/0 1), genu 9 (2 2/1 3/0 1), tibia 8 (2 1/1 2/1 1), tarsus 18 (3 3/3 1/1 2/2 3). All setae aciculate and smooth, except ad1 of femur II, ad1 and pd of femur III, pd2 of genu III, ad1 and ad2 of femur IV, pd3 of genu IV, short, thickened and spur-like. Coxa II without anterior spine. Pretarsi I-IV similar in shape; consisting of an ambulacral stalk, a pair of sclerotised claws, four rounded pulvillar lobes and two acuminate ventro-lateral processes (obscure on tarsi I).

Adult male ( Figs 10–15 ). Five specimens measured.

Gnathosoma. Second cheliceral segment 90–92 long; fixed cheliceral digit with one tooth in addition to apical tooth and setiform pilus dentilis; movable cheliceral digit with one tooth in addition to apical tooth; dorsal cheliceral seta obscure ( Fig. 10 ). Spermatodactyl 27–32 long, sinuous, shorter than movable digit. Arthrodial process of chelicera, palp chaetotaxy, apotele, epistome, deutosternum and shape of hypostomal setae as in adult female, except xiphoid seta on palp tibia absent. Subcapitulum 71–78 wide at widest level. Measurements of setae: h 1 23–25, h 2 13–15, h 3 17–19, pc 15–17.

Dorsal idiosoma ( Fig. 11 ). Idiosoma elongate. Podonotal shield 164–189 long and 168–189 wide at level of r5, tapering anteriorly of r2; almost smooth; with 21 pairs of setae (j1–j6, z1–z6, s1–s4, s6, r1, r2, r5, r6; s5 absent) and six pairs of distinguishable pores. Unsclerotised cuticle laterad of podonotal shield with two pairs of setae (r3 and r4) and one pair of pores. Opisthonotal shield 160–168 long and 143–160 wide at level of S1; almost smooth; with two narrow incisions between anterior margin of shield and Z4; posterior margin with cribrum; with 14 pairs of setae (J1, J2, J4, J5, Z1–Z5, S1–S5; J3 absent) and four pairs of distinguishable pores. Unsclerotised cuticle laterad of opisthonotal shield with six pairs of setae (R1–R6). Measurements of setae: j 1 11–13, z 1 8–11, other setae on podonotal shield 13–19, J 5 11–13, Z5 32–36, other setae on opisthonotal shield 15–21, setae on unsclerotised cuticle 15–21. All dorsal idiosomal setae aciculate and smooth.

Ventral idiosoma ( Fig. 12 ). Tritosternum with wide trapezoidal base and fine lightly pilose laciniae; base of tritosternum length 15–17, laciniae length 32–38. Presternal area lightly sclerotised, not clearly separate from sternogenital shield. Sternogenital shield smooth and with anterior margin indistinct; region anterior to the first pair of sternal setae (st 1) lightly sclerotised; approximately 153–174 long (with presternal area); with elongate anterolateral projections; with five pairs of setae and three pairs of lyrifissures; with an oval contoured area near posterior margin of shield. Endopodal plates fused with sternal shield, except for a plate posterolaterad of coxa IV. Unsclerotised cuticle between sternogenital and ventrianal shields with an elongate plate (7–9 long and 23–34 wide). Ventrianal shield semi-circular, with irregular anterior margin; 111–137 long and 113–137 wide at widest level; with nine pairs of setae (Jv1–Jv5, Zv1–Zv4) in addition to circum-anal setae and one pair of distinguishable pores; without chitinous clasps; cribrum well developed. Peritrematal shields, peritremes and adjacent plates as in female; peritreme 38–46 long. Measurements of setae: st1–st 5 11–17, para-anal 15–17, post-anal 25–33, other setae on ventrianal shield 13–23. All ventral idiosoma setae aciculate and smooth.

Legs ( Figs 13–15 ). Lengths: I 316–344, II 251–279, III 205–233, IV 260–307. Chaetotaxy similar to those of adult females. Shape of setae as in adult female, except for hook-like apophyses (av on femur II, mv and av2 on tarsus II ( Fig. 13 ), av on femur III ( Fig. 14 ), av on femur IV, pv2 on tarsus IV ( Fig. 15 )) and normal apophyses (“knots” in Błaszak & Ehrnsberger, 1999) on trochanter, femur and genu II ( Fig. 13 ), femur III ( Fig. 14 ), femur and genu IV ( Fig. 15 ). Tips of hook-like apophyses blunt, rarely acuminate. Apex of tarsi II–IV with ventral spine. Pretarsi similar to those of adult female.

Deutonymph ( Figs 16–19 ). Five specimens measured.

Gnathosoma. Mostly as in adult female. Second cheliceral segment 88–95 long. Palp 95–99 long; xiphoid seta on palp tibia absent. Subcapitulum 59–67 wide at widest level. Measurements of setae: h 1 17–19, h 2 12–14, h 3 15– 17, pc 13–15.

Dorsal idiosoma ( Fig. 16 ). Idiosoma elongate. Podonotal shield 151–172 long and 143–155 wide at level of r3, tapering anteriorly to r3; weakly reticulated; with 22 pairs of setae (j1–j6, z1–z6, s1–s4, s6, r1–r3, r5, r6; s5 absent) (in some specimens r3 on unsclerotised cuticle) and five pairs of distinguishable pores. Unsclerotised cuticle laterad of podonotal shield with a pair of setae (r4). Opisthonotal shield 134–147 long and 105–126 wide at level of setae S1; weakly reticulated; anterior margin with wide shallow notch; with 14 pairs of setae (J1, J2, J4, J5, Z1–Z5, S1–S5; J3 absent) and with seven pairs of distinguishable pores. Unsclerotised cuticle laterad of opisthonotal shield with six pairs of setae (R1–R6). Measurements of setae: j 1 8–11, z1 6–8, other setae on podonotal shield 11–21, J5 6–8, Z 5 29–44, other setae on opisthonotal shield 15–23, setae on unsclerotised cuticle 13–17. All dorsal idiosomal setae aciculate and smooth.

Ventral idiosoma ( Fig. 17 ). Tritosternum with elongate trapezoidal base and very fine lightly pilose laciniae; base of tritosternum length 21–25, laciniae length 42–50. Presternal area lightly sclerotised, not clearly separate from sternal shield. Sternal shield smooth and with anterior margin indistinct; region anterior to the first pair of sternal setae (st1) lightly sclerotised; approximately 147–158 long (with presternal area); with five pairs of setae and three pairs of lyrifissures. Endopodal plates between coxae I and II, coxae II and III, and coxae III and IV free. Anal shield obovate; 59–63 long and 36–44 wide at widest level; anus located in center of shield; with circum-anal setae and a pair of pores; cribrum well developed. Unsclerotised cuticle around of anal shield with nine pairs of setae (Jv1–Jv5, Zv1–Zv4), a pair of small metapodal plates and a pair of liryfissures posterolaterad of st5. Peritreme 170–185 long; extending anteriorly to level of coxa I (region of s1). Peritrematal shield reduced. Exopodal plates free. Measurements of setae: st1–st 5 13–15, setae on unsclerotised cuticle 13–23, para-anal 15–17, post-anal 25– 27. All ventral idiosoma setae aciculate and smooth.

Legs ( Figs 18–19 ). Lengths: I 251–288, II 205–223, III 167–195, IV 233–260. Mostly as in adult female, but acuminate ventro-lateral processes on pretarsi obscure. Setae av, pv and pd1 on genu III, av and pv on tibia III ( Fig. 18 ), av on genu IV, av and pv on tibia IV ( Fig. 19 ) thickened, relatively thicker than in adult female.

Material examined. Holotype female: Ukraine, Odessa oblast, Belgorod-Dnestrovsky district, vicinity of Zatoka (46°01' N, 30°24' E), Black Sea Coast , in seaweed, 7 October 2012 . Paratypes: 23 females, 6 males, 1 deutonymph, same data as holotype ; 1 male, 17 deutonymphs, same locality and date, from Talorchestia deshayesii (Audouin, 1826) ( Amphipoda : Talitridae ); 7 deutonymphs, Ukraine, Odessa oblast, Odessa, beach city (46°27' N, 30°46' E), seaweed, 10 February 2008 ; 2 females, 3 males, Ukraine, Odessa oblast, Kominternovsky district, vicinity of Chernomorskoe (46°35' N, 30°57' E), Black Sea Coast , sand with shells and seaweed, 8 March 2008 ; 2 females, 1 male, same locality, sand with seaweed, 7 May 2008 ; 2 females, 4 males, 1 deutonymph, Ukraine, Odessa oblast, Kominternovsky district, vicinity of Lubopol (46°43' N, 31°09' E), coast of Tiligul estuary (liman), seaweed, 11 May 2008 ; 6 females, 4 males, 7 deutonymphs, Ukraine, Odessa oblast, Kominternovsky district, vicinity of Grigorovka (46°35' N, 31°00' E), Black Sea Coast , seaweed, 7–8 June 2014 ; 5 deutonymphs, same locality and date, from T. deshayesii ; 1 female, Ukraine, Odessa oblast, Kominternovsky district, vicinity of Kryzhanovka (46°33' N, 30°47' E), beach, seaweed, 29 July 2014. All types material were collected by the author.

The holotype (female) and 9 paratypes (2 females, 3 males, 4 deutonymphs) (slides No 7-10-2012 /01, 7-10- 2012 /02) are deposited in the collections of the Museum of Zoology, I. I. Mechnikov Odessa National University; other specimens in the collections of the Department of Zoology I. I. Mechnikov Odessa National University.

Etymology. The specific name euxinus refers to “Pontus euxinus ”, the Latin name of the Black Sea, where type specimens were collected.

Remarks. According to epistome with an anteromedian extension wider at the base and distally denticulate, flanked by a pair of shorter, denticulate anterolateral extensions, femur I with 12 setae, and the absence of an anterior spur on coxa II, Halolaelaps euxinus belongs to the group of species referred as Halolaelaps (Saprogamasellus) by Błaszak & Ehrnsberger (1993).

The adult female of Halolaelaps euxinus is most similar to Halolaelaps caesariensis Athias-Henriot, 1961 . Both species are characterised by 17 pairs of setae on the podonotal shield and eight pairs of setae on the opisthonotal shield. But H. caesariensis has endopodal plates between coxae I and II and between coxae II and III not fused, and setae Z2–Z4 located at some distance from the edge of opisthonotal shield (in H. euxinus endopodal plates between coxae I and II and between coxae II and III fused, and setae Z2–Z4 located on the edge of the opisthonotal shield). The adult male of H. euxinus differs from H. caesariensis by the absence of chitinous clasps on the ventrianal shield, the number of setae on the podonotal shield (21 pairs in H. euxinus , 22 pairs in H. caesariensis ), and the absence of apophyses on tibia IV.

Adult males of Halolaelaps euxinus is also similar to Halolaelaps similis Blaszak & Ehrnsberger, 1993 and Halolaelaps giganteus Blaszak & Ehrnsberger, 1998 (by absence of chitinous clasps on ventrianal shield) but the latter have 18 pairs and 22 pairs of setae on podonotal shield, respectively; 20 and 13 pairs of setae on opisthonotal shield, respectively, absence of apophysis on genu IV ( H. similis ), presence of apophysis on tibia IV ( H. giganteus ). Adult females of H. similis and H. giganteus have endopodal plates between coxae I and II and between coxae II and III not fused; and 16 and 17 pairs of setae podonotal shield, respectively.

The new species was collected mainly on sandy beaches, in the same habitat as Talorchestia deshayesii (Audouin, 1826) ( Amphipoda : Talitridae ). This supralittoral species is distributed on the Black Sea Coast, and acts as an indicator of anthropogenic loadings on beaches ( Son & Koshelev 2013).

Figures

FIGURE 1 – 5. Halolaelaps euxinus sp. nov. Adult female. 1. Lateral (antiaxial) view of chelicera; 2. Epistome; 3. Hypostome; 4. Dorsal idiosoma; 5. Ventral idiosoma. Scale bar = 50 µm.

FIGURES 6 – 9. Halolaelaps euxinus sp. nov. Adult female. 6. Leg I (coxa to tibia); 7. Leg II; 8. Leg III; 9. Leg IV. Scale bar = 100 µm.

FIGURE 10 – 15. Halolaelaps euxinus sp. nov. Adult male. 10. Lateral (antiaxial) view of chelicerae; 11. Dorsal idiosoma; 12. Ventral idiosoma; 13. Leg II; 14. Femur of leg III; 15. Leg IV (femur to tarsus). Scale bar = 50 µm.

FIGURE 16 – 19. Halolaelaps euxinus sp. nov. Deutonymph. 16. Dorsal idiosoma; 17. Ventral idiosoma; 18. Leg III (femur to tibia); 19. Leg IV (femur to tibia). Scale bar = 50 µm.