Halolaelaps hatfieldi, Krantz, 2016
Krantz, G. W., 2016, A new species of Halolaelapidae (Acari: Mesostigmata: Rhodacaroidea) from beach wrack in Yaquina Bay, Oregon, USA, with comments on opisthonotal plasticity and cribral development in the family, Journal of Natural History 50, pp. 1797-1812: 1799-1807
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Halolaelaps hatfieldi sp. nov.
( Figures 1A–F, 2A–H, 3A–D, 4A, 5)
With the general characteristics of the family as defined by Walter (2006), of the genus as defined by Halliday (2008), and of the celticus species group as defined in the introduction above.
Female ( Figures 1A–F, 2A, B, and 5)
Idiosomatic length averages 627 (548–685), width at level of coxae IV averages 382 (340– 426), podonotal shield width at level of coxae IV averages 304 (277–333) (n = 15). Dorsum ( Figure 1A) with strongly punctate and moderately reticulate podonotal and
opisthonotal shields bordered laterally by a broad band of striated integument; peritrematic shields expressed dorsally beyond coxae II and extending nearly to insertions of setae z 1, adjacent to but not fused to podonotal shield. Podonotal shield longer than opisthonotal shield [349 (329–370) versus 234 (211–249)], with 17 pairs of setae, j 1and z 1 minute, spinose, z 1 with offset insertions reminiscent of the T-shaped recumbent solenidia found on legs I–II of eupodoid Rhagidiidae ( Zacharda 1980) , setae j 3, j 6, z 4, z 5 and s 6 thick and spinose, varying in length, sometimes weakly pilose distally, other marginal and submarginal podonotal shield setae (z 2–3, 6; s 1–4, 6), along with j 2 ( Figure 1D), setiform, sometimes flagelliform, considerably longer (40–45) than median dorsal setae j 4–5 and z 5; adjacent integumental setae r 2–6 similar in length to marginal and submarginal podonotals, setiform or setiform/flagelliform. Opisthonotal shield roughly rectangular in shape and narrower posteriorly, with an anteromedian marginal indentation in which are located a pair of small scleritic platelets; shield setation subject to variation in the S series, typically with 10 pairs of setae, but often with as few as nine or with as many as 11 setae on one side of the shield or the other [i.e. S 4 may be inserted in the integument as in Figure 1A, left side, or on the lateral shield margin along with a supernumerary seta, S x, as in Figure 1A, right side, or, as in one specimen, seta S x may be joined by a supernumerary seta, J x, on the shield ( Figure 1A, left side)]; Z 4 thick and spinose, similar to podonotals j 6 and s 6 and occasionally pilose distally, Z 5 spinose but smaller, similar in length to J 3 and somewhat shorter than J 5, other opisthonotal setae (J 1, Z 1, Z 3, S series) longer, setiform; setae S 1–4 and four pairs of setiform R setae inserted in adjacent integument, with integumental lyrifissures and discernible shield pores as illustrated. Shield with a narrow, transversely oriented, posterior submarginal cribral process ( Figures 1A, 2A, 5) lying behind setae J 5 and extending laterally above and beyond insertions of setae Z 5, terminating at paired openings, which are considered here to represent glands gd Z5, cribral spicules pointing posteriorly.
Venter ( Figure 1B) with normally developed bilaciniate tritosternum bordered posteriorly by a pair of weakly defined presternal elements that are usually joined by a posteromedian bridge; with an elongate-rectangular sternal shield flanked by free endopodal platelets as is typical for the genus, shield with four lateral punctate areas as illustrated, sternal setae 2 more robust than st 1 or 3; metasternal setae free in integument, metasternal platelets small and more or less circular, each carrying a lyrifissure. Epigynal shield elongate and weakly convex posteriorly, epigynal setae (st 5) similar in shape and length to metasternals, shield bordered posteriorly by four narrow postgenital sclerites, with an additional pair of narrow sclerites between insertions of setae Jv 1–2, lyrifissures iv 5 free in integument and flanking posterior aspect of epigynal shield; opisthogaster typically with three or four pairs of setae between epigynal and ventrianal shields (Jv 1–3 and Zv 2; setae Zv 3 may be free in integument (see below), lyrifissures ivo 1–3 in striated opisthogastric integument between epigynal and ventrianal shields and forming a triangular pattern, with laterally placed ivo 2 lying posterior to small paired metapodal platelets. Ventrianal shield punctate and weakly reticulate, broad and rounded posteriorly and with slightly concave anterior margin, typically with three pairs of long setiform setae in addition to paired paranals and a terminal postanal seta that may be distally divided; one or both Zv 3 setae may be inserted in the integument so that the shield may have only two preanal setal pairs, Zv 4 may likewise be inserted on the shield ( Figure 1B); postanal seta flanked by a well-developed postanal cribrum that may appear deceptively narrow in ventral view, cribral spicules point anteriorly. Stigmata of peritremes ( Figure 1A) at level of insertions of coxae IV, peritremes extend anteriorly and anterodorsally along border of podonotal shield to insertions of setae z 1, peritrematic shields not fused to podonotal shield, each with a short curved extension posterior to stigmata.
G nathosoma ( Figure 2B) with elongate base, hypostomatic and subcapitular setae setiform, more or less equal in length (~50), hypostomatics h 1 similar in length to h 2–3 but distinctly more robust than either, with a membranous, evansescent swelling proximal to a setiform terminus; subcapitular groove with nine rows of unevenly spaced denticles that vary in size, internal malae membranous and smooth, corniculi short, extending only to insertions of palpfemoral seta al; gnathotectum ( Figure 1F) similar to that of other celticus group members, with a broad base carrying an anterior process that is strongly bipectinate for over half its length and that terminates anteriorly in a nearly smooth, narrow stalk; basal and middle articles of chelicerae extremely long, with basal article ~ 260 and middle article ~ 170, fixed digit ( Figure 1E) with two distally placed teeth and a short, needle-like pilus dentilis inserted behind the more proximal tooth, dorsal cheliceral seta short, smooth; movable digit with three distal teeth, median tooth more strongly produced than the others.
Legs of moderate length, dorsally rugose, legs I and IV considerably longer than II–III (~ 500 versus ~ 375–450), tarsal ambulacra each with two large pulvillar lobes between paired tarsal claws and a pair of smaller lobes that flank the basilar sclerite, ambulacra II– IV with long (~ 10), paired, spiniform operculi projecting anteriorly from lateral ambulacral walls, operculi obscure or absent on ambulacra I. Leg chaetotaxy as described for H. posidonis Halliday ( Halliday 2008), but with some differences; e.g. as illustrated earlier for H. celticus ( Blaszak and Ehrnsberger 1998a) and as seen in female specimens of H. orientalis Ishikawa, tibia II has 10 setae (pl 2 present: 2 2/1 2/1 2) rather than eight as in H. posidonis ( Figure 1C), and femur II has 11 rather than 10 setae (2 3/1 2/2 1); many dorsal leg setae short, distally or laterally divided, other leg setae may be spinose ( Figure 1C).
Sperm access system generally similar to that of H. posidonis Halliday ( Halliday 2008), consisting of a pair of long (~ 145) double-walled tubili originating at paired sperm induction pores (solenostomes) originating at coxae IV, or possibly between coxae III and IV, and extending to a median bulbous obovate sacculus; tubuli broad at their origins (~ 14) and narrowing beyond to ~ 8, but then expanded and produced into a series of folds near their junction with the sacculus.
Male ( Figures 2C–H, 3A)
Somewhat smaller than female; overall length averages 523 (493–562), width at level of coxae IV averages 320 (290–370), podonotal/opisthonotal shield lengths average 302/ 221 (n = 10). Podonotal and opisthonotal shields of dorsum ( Figure 2C) similar to those of female in ornamentation, but are expanded laterally to include 13 pairs of marginal setae which, in female, are inserted in the adjacent integument; dorsal peritrematic elements narrow, confined anteriorly to podonotal shield margins. Podonotal shield with 22 pairs of setae (r 2–6 inserted on shield), setae j 2, z 6 and s 1 distinctly shorter than in female, other marginal and submarginal setae (z, s and r series) mostly longer as in female, j 3, z 4 and s6 pilose distally, j6 pilose or smooth, lateromarginal setal insertion patterns may vary from one side to the other; e.g. setae s 2, r 2 and r 3 in Figure 2C are either marginal or submarginal on the shield; side-to-side asymmetry in shield configuration also may lead to incongruous placement of some setal insertions (e.g. s 2). Opisthonotal shield broad, rounded laterally, and carrying 21 pairs of setae (S 1–4, R 1 and R 3–5 inserted on shield); J series simple, relatively short, J 4 distinctly shorter than in female ( Figure 1A); marginal and submarginal setae (Z, S and R series) mostly elongate and setiform, including Z4 ( Figure 2F, top), which in the female is short and spinose, seta Z 5 ( Figure 2F, bottom) short and distally pilose (Z 5 smooth and spinose in female), Z 1, S 1 and R 1 simple, more posterior setae mostly pilose distally; with a narrow, submarginal cribral process as in female, located between insertions of J 5 and Z 5.
Venter ( Figure 3A) with tritosternal laciniae weakly pilose, presternal elements weakly developed, separate, lying laterad a large, anteromarginal genital operculum; sternal, metasternal, genital and endopodal elements fused into a single sternitigenital shield, anterior punctate areas of shield distinct, posterior punctate areas weakly defined, represented by few puncta; sternal setae 1–4 short, smooth, st 5 short, broad and conical. Ventrianal shield punctate-reticulate throughout, broader than long and rounded posteriorly; median portion of anteromedian shield margin in the form of a discrete truncate extension that mirrors the truncate posterior margin of the adjacent sternogenital shield (extension occasionally a free platelet), remaining anterior ventrianal shield margin irregularly excavated as illustrated, metapodal elements subsumed into anterolateral shield corners, with a pair of poroids (probably iv 5) between ventrianal and sternitigenital borders; with seven pairs of simple setae, the more anterior pairs (Jv 1–2) being the shortest, Jv 4–5 long, setiform, paranal setae similar to Jv 2 in length, postanal seta terminally inserted, long and distally pilose, bordered by narrow postanal cribral remnants as in female, lyrifissures ivo 1–3 on shield rather than in opisthogastric integument, their placement on each side forming a triangle as in female. Peritremes similar to those of female, but peritrematic shields narrower, confined anteriorly to margin of expanded podonotal shield.
Gnathosoma similar to that of female ( Figure 2B) except for the following: gnathogastric setae h 1 with membranous subterminal expansion more developed than seen in available female specimens, occasionally appearing leaf-like ( Figure 2G). Fixed digit of chelicera ( Figure 2H) with a broad subterminal tooth and a short pilus dentilis inserted proximal to it, dorsal seta simple; movable digit with a conical subterminal tooth and a broader indented tooth proximal to it; with a sinuous, basally inserted spermatodactyl that extends slightly beyond the digit itself.
Legs generally similar to those of female, but often with reduced setal numbers (e.g. femur and genu II with 9 and 10 setae rather than 11 as in female); conical lateroventral spines of femur, genu and tibia I ( Figure 2D) stronger than in female, dorsal spinose setae of femur, genu and tibia II mostly divided distally ( Figure 2E), seta pv 2 of femur II a large rounded spur.
Deutonymph ( Figure 3B, C)
Length of idiosoma averages 480 (444–537), width at level of coxae IV averages 298 (259–340), podonotal longer than opisthonotal shield as in adults (averages = 298/191)
(n = 8). Dorsum ( Figure 3B) with general setal and ornamentation characteristics of the female, but podonotal shield with 18 pairs of setae rather than 17 (r 6 on shield), setae j 1 and z 1 as in female, j 3, j 6, z 4 and s 5 more robust than remaining dorsals, z 6 shorter than j 6. Opisthonotal shield with 12 or 13 pairs of setae (S 2 and accompanying poroid either on or off shield), shorter than podonotal shield and without anteromedian indentation and scleritic platelets; Z 4 robust, other lateral shield setae mostly setiform or setiform/ flagelliform; with a narrow posterodorsal cribral process as in adults. Peritrematic shield as in female, but somewhat narrower and with shorter post-stigmatic extension.
Venter ( Figure 3C) with tritosternum and presternal elements as in female; with a narrow, weakly punctate intercoxal shield, short smooth st 1–5 inserted on the shield margins, endopodal elements free; with three or four narrow sclerites posterior to the intercoxal shield and with a pair of sclerites between Jv 1–2. Ventrianal shield weakly punctate/reticulate, with two or three pairs of preanal setae (Zv 3 may be inserted in the integument adjacent to shield); postanal seta spinose, longer than paranals, flanked by a well-developed cribrum and a pair of marginal gland pores (gd Z5?), cribral spicules point anteriorly.
Gnathosoma and setal development of legs similar to those of female; subterminal membranous expansion of hypostomatic setae h 1 similar to that of female, tibia II with 10 setae as in adults.
Protonymph ( Figures 3D, 4A)
Length of idiosoma averages 357 (333–380), width at level of coxae IV averages 250 (241–259) (n = 2). Dorsum ( Figure 3D) with large podonotal and considerably smaller opisthonotal shield; length/width of podonotal average 231/203, and of opisthonotal shield 203/89, both shields strongly punctate. Podonotal shield with 10 pairs of setae, of which j 3 and s 5 are short and spinose, and remaining setae are simple and of moderate length, setae j1 inserted in the integument anterior to shield, z1 absent; posterior border of shield with only two pairs of setae (j 6, s 5), with four pairs of setae inserted in integument adjacent to shield (r 5–6, along with two more anterior pairs); shield bordered laterally by a pair of narrow platelets (ps) that represent rudimentary peritrematic shields. Podonotal and opisthonotal shields separated by a broad, striated integumental area in which seven pairs of setae (J 1–2, Z 2–3, S 2–3, R 1), six pairs of lyrifissures, and a pair of small sclerites (probably homologues of the scleritic platelets on the female dorsum) are located. Opisthonotal shield elliptical in shape, posterior shield border folded ventrally so that J 5 are posteromarginal, and Z 5 and the normally posterodorsal cribrum are ventral (see below); shield with six pairs of setae, of which J 4, S 4 and S 5 are long and setiform, Z 4 short and spinose, similar to J 5 in length, Z 5 longer and pilose distally.
Venter ( Figure 4A) with weakly defined ovate sternal shield that carries st 1–3 and two pairs of poroids, iv 5 mediad from coxae IV, endopodals absent; with three pairs of opisthogastric setae (Jv 1–2, Zv 2) inserted anterior to anal shield, lyrifissures ivo1–3 present, opening between coxae IV and lateral angles of anal shield, metapodal platelets absent. Anal shield weakly punctate, paranal and postanal setae short, smooth, equal in length to opisthogastric setae, with a well-developed cribrum lying behind postanal seta, with a pair of putative gland pores lateral of cribrum and mediad from integumentally inserted setae Jv 5, cribral spicules point anteriorly. Peritremes short, with stigmata opening at level of coxae IV and peritrematic elements extending only to mid-level of coxae III. Posteromarginal aspect of venter covered by folded posterior margin of dorsal opisthonotal shield, carrying distally pilose dorsal setae Z 5 in median portion and a short, narrow, ventrally expressed dorsal cribrum directly behind their insertions, spicules point anteriorly because of its ventral orientation.
Gnathosoma with gnathotectum as in later stages, but lateral pectinations weakly developed except at the base, hypostomatic setae 1 robust but apparently without subterminal expansions, h 1–3 and capitular setae shorter than in later stages, deutosternal denticles undeveloped; chelicerae obscure in both available specimens.
Legs with many segments displaying rudimentary setal numbers; e.g. the femoral/ genual/tibial setal count on leg I is 10/8/8 rather than 13/12/12 as in adult, the femur/ genu/tibia count on leg IV is 4/5/7 rather than 6/9/8, and that of tibia II is seven (1 1/1 2/ 1 1) rather than 10 as found in earlier stages (2 2/1 2/1 2).
Fifteen females, ten males, eight deutonymphs and two protonymphs ex Ulva / Zostera beachwrack in a backwater of Yaquina Bay, Hatfield Marine Science Center, Newport, Oregon, USA, collected on the following dates: 19 August 2013, 24 March 2014, 18 June 2014, 13 August 2014. Holotype female and allotype male (collected 19 August 2013) to National Museum of Natural History, Washington, D.C.; paratypes to Oregon State Arthropod Collection, Corvallis; Acarology Laboratory, The Ohio State University, Columbus; Canadian National Collection, Ottawa; Australian National Insect Collection, Canberra.
The specific name hat fi eldi honours the distinguished US Senator Mark O. Hatfield (1922–2011), for whom Oregon State University’ s Hatfield Marine Science Center is named.
Differential diagnoses of most of the known celticus group species of Halolaelaps have been based primarily on the number of setae inserted on the opisthonotal and podonotal shields of adult females ( Blaszak and Ehrnsberger 1998a). Based on shield chaetotaxy alone, H. hat fi eldi sp. nov. is unique among the 10 described species in having 17 pairs of podonotal shield setae and (typically) 10 pairs of opisthonotal shield setae. Halolaelaps decemsetosus B.& E. also has 10 opisthonotal setal pairs, but differs from H. hat fi eldi in having 16 rather than 17 pairs of podonotal shield setae (setae s2 are inserted in the adjacent integument). Four additional celticus group species share the characteristic of 17 pairs of podonotal shield setae ( H. celticus Halbert , weberi B.& E., orientalis Ishikawa, and posidonis Halliday ), but all have fewer than 10 opisthonotal setae ( Ishikawa 1979; Blaszak and Ehrnsberger 1998a; Halliday 2008). Many of the marginal setae seen in H. hat fi eldi (s/S and r/ R series) are setiform or setiform/flagelliform ( Figure 1A, D) and are considerably longer (40–45 μm) than those illustrated for other celticus group species ( Blaszak and Ehrnsberger 1998a; Halliday 2008). A known exception is H. orientalis , in which many of the marginal setae are similar to those of H. hat fi eldi and clearly longer than shown in existing diagnoses of the species ( Ishikawa 1979; Blaszak and Ehrnsberger 1998a). Ventrally, the sternal shield of H. hat fi eldi displays a distinct quadriareolate pattern of ornamentation ( Figure 1B) that may be unique for the species, although sternal shield ornamentation is not mentioned in earlier celticus group diagnoses.
University of Stellenbosch
Departamento de Geologia, Universidad de Chile
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