Balaustium hernandezi, Mąkol, Joanna, Arijs, Yves & Wäckers, Felix, 2012

Mąkol, Joanna, Arijs, Yves & Wäckers, Felix, 2012, A new species of Balaustium von Heyden, 1826 (Acari: Actinotrichida, Erythraeidae) from Spain, Zootaxa 3178, pp. 1-21 : 2-17

Balaustium hernandezi sp. nov.

Diagnosis. LARVA. Normal setae on palp tarsus smooth, except for the most proximally placed seta, which is barbed. NDV> 210. Tibia I with two solenidia.

DEUTONYMPH AND ADULT (FEMALE). A group of three setae AM in deutonymph and 11–13 in adult, located anterior of ASens. pDS: 45–75. Semipectinalae on palp genu absent. Length of palp genu in female> 120. Setae on palp tarsus smooth.

Description. LARVA ( Figs. 1–22 ). Metric and meristic data based on nine specimens. For metric data see table 1. Color in life red.

Idiosoma dorsum ( Figs. 1 , 10–11 , 16–18 ). Dorsum with 118–139 barbed setae, all dorsal setae uniform in shape, inserted in small platelets; eyes 19–20 µm in diameter; dorsal scutum relatively well marked, diamondshaped (in some specimens the anterior margin not clearly marked), punctate on the entire surface and foveate close to the posterior margin (the character visible under light microscope, in semi-transparent specimens); nonsensillary setae (AL, ML, PL) barbed; AL subequal to ML <PL (PL either incorporated in the shield, Fig. 10 , or located off the scutum, Fig. 11 ); two pairs of trichobothria (ASens <PSens), both with fine setules on entire length.

IL—idiosoma length, IW—idiosoma width, L—length of scutum, W—width of scutum, mDS—length of setae covering the middle part of idiosoma , pDS—length of postero-dorsal setae. For explanation of other symbols see Mąkol (2010).

Idiosoma venter ( Fig. 2 ). Ventral side of idiosoma with setae more slender than those on idiosoma dorsum; all setae barbed; two pairs of sternalae 1a and 2a between coxae I and II, 1a longer than the other ventral setae; 1b located at half length of coxal plate and shifted to its anterior margin, 2b and 3b placed in more central position on coxal plates II and III; 36–41 setae between coxae II and III; 55–66 setae posterior to coxae III; anus clogged up by the anal membrane.

Gnathosoma ( Figs. 9, 12 , 13–15 ). Chelicera composed of basal segment and movable claw; adoral setae (cs) with setules, located antero-laterally on gnathosoma dorsum, subcapitular setae (bs) similar to cs, located ventrally on gnathosoma, close to the spine-like setae (as); palpal supracoxal setae (ep) tiny and thumb-like, located posterolaterally on dorsal side of gnathosoma; pedipalp formula: B-B-BB-BBB-BNNNωζ; palp tibial claw simple with a distinct tooth located c. half of the odontus length, ventrally.

Legs ( Figs. 3–8 , 19–22 ). Leg segmentation formula 7–7–7; leg chaetotaxy: leg I: Cx 1B, Tr 3B, bFe 4B, tFe 7B, Ge 11B + 1σ+ 1ĸ, Ti 13B + 2φ + 1ĸ, Ta 30–31B + 2ζ + 1Cp + 1ω + 1ε; leg II: Cx 1B, Tr 3B, bFe 4B, tFe 6B, Ge 11B + 1ĸ, Ti 14B + 2φ, Ta 22B + 2ζ + 1Cp + 1ω; leg III: Cx 1B, Tr 2B, bFe 3B, tFe 6B, Ge 11B, Ti 13B + 1φ, Ta 21B + 1ζ; supracoxal setae of leg I (eI) tiny and thumb-like, slightly shorter than palpal supracoxalae (ep); normal setae on leg segments setulated or barbed; several setulated setae (c. 6) resembling the eupathidia ( Fig. 19 ), not sharpened terminally and nude in the apical part, arise along the ventro-lateral margin of tarsus I (the setae are barely visible under light microscope); dorsal eupathidia on tarsi I-II ciliated along the entire stem and subtended with short acicular companalae; tarsi I–III terminated with two claws and claw-like, ciliated empodium; anterior claw sickle-like, ciliated, posterior claw composed of two branches: one similar to anterior claw but shorter and another one terminated with discoid, pilose (pulvilliform in side view) structure ( Fig. 8 ).

DEUTONYMPH ( Figs. 23–25 ). Metric and meristic data based on 3 specimens. For metric data see table 2. Color in life red.

Idiosoma dorsum. Dorsal scutum elongate, with irregular sides, foveate, especially close to the posterior margin (the character visible under light microscope, in semi-transparent specimens), with c. 10 setae located between ASens and PSens; rod of crista metopica extended between insertions of ASens and PSens; scutum anteriorly with 3 setae AM, longer than ASens, but shorter than PSens; one eye and one urnula on each side of prodorsal scutum, setae around eye longer than eye diameter.

Female Deutonymph

1 2 3 Mean* 1 2 3 Mean*

IL 2250 2150 2210 2203 860 1010 810 893 IW 1700 1520 1550 1590 535 780 590 635 ASens 105 98 103 102 78 74 76 76 PSens 130 135 138 134 113 107 115 112 SBa 26 30 30 29 19 20 20 20 SBp 28 28 26 27 19 19 19 19 L 510 508 508 509 250 262 250 254 W 145 120 138 134 60 67 68 65 ISD 288 278 303 290 160 167 155 161 continued next page Female Deutonymph

1 2 3 Mean* 1 2 3 Mean* tFe IV 385 390 383 386 204 210 210 208 Ge IV 402 424 430 419 242 250 245 246 Ti IV 450 441 449 447 241 250 250 247 Ta IV(L) 185 182 181 183 95 105 102 101 Ta IV(W) 69 63 65 66 45 40 43 43 IL—idiosoma length, IW—idiosoma width. For explanation of other symbols see Mąkol (2010).

Idiosoma venter . Ventral setae with thinner shaft than in dorsal setae; the shaft covered with fewer setules, which are less distinct than in pDS; valves surrounding the anal opening covered with setae, which are similar to those covering the ventral side of opisthosoma, but shorter.

Gnathosoma. Palps with relatively sparse setation; palpal supracoxalae (ep) tiny and thumb-like, located postero-laterally on dorsal side of gnathosoma; palp femur and palp genu longer than wide (n = 1, PaFe L/W ratio = 2.26, PaGe L/W ratio = 2.29), palp tibia subtriangular in outline, with c. 7 setae; palp tarsus cylindrical, apically rounded with one normal seta and c. 10 solenidia (two of them slightly longer, located proximally); palp tibial claw with a median tooth.

Legs. Leg I slightly longer than leg IV, leg II the shortest; supracoxalae of legs I (eI) and II (eII) tiny and thumb-like, located in dorso-lateral part of coxal plates; all legs with barbed setae, specialized setae present on genua, tibiae and tarsi (leg I: Ge 2σ + 1ĸ, Ti 5φ + 1ĸ, Ta ∼ 15ω + 4ζ + 1ε; leg II: Ge 1σ + 1ĸ, Ti 3φ, Ta ∼ 3ω + 4ζ; leg III: Ge 1σ, Ti 2φ, Ta ∼ 1ω + 2ζ; leg IV: Ge 3σ, Ti 1φ, Ta 1ζ); additionally, along the ventral surface of tarsi, several (fewer than in female) setulated setae, not sharpened terminally and resembling the eupathidia (the setae are barely visible under light microscope); setae most numerous on tarsus I; tarsi terminated with paired claws, each claw covered with fimbriae.

FEMALE ( Figs. 26–40 ). Metric and meristic data based on 3 specimens. For metric data see table 2. Color in life red to red brown. Idiosoma oval, densely covered with setae.

Idiosoma dorsum ( Figs. 27–28 , 34–36 ). Dorsal setae set on small round sclerites; some setae on prodorsum are bent, with setules much longer at one side of the stem; dorsal scutum elongate, with distinct but irregular margins, foveate, esp. in the posterior part (the character visible under light microscope, in semi-transparent specimens); rod of crista metopica extended between ASens and PSens insertions; anterior part of scutum with c. 11–13 non-sensillary setae AM (103–125), longer than ASens, but shorter than PSens; ASens and PSens covered with short setules on entire length; c. 42 non-sensillary setae inserted in scutum, between ASens and PSens; one eye and one urnula on each side of prodorsal scutum; urnula located posterior to eye, setae around eye longer than eye diameter.

Idiosoma venter . Ventral setae more slender than setae covering the dorsal side of idiosoma ; genital opening surrounded by two pairs of valves, anal opening—by paired valves; setae arising at genital and anal openings similar to those covering the ventral side of opisthosoma, but shorter.

Gnathosoma ( Figs. 26 , 29–33 ). Setation on palps more dense than in deutonymphs; palpal supracoxalae (ep) tiny and thumb-like, located postero-laterally on dorsal side of gnathosoma; palp femur (n = 1, 212.5) and palp genu (n = 1, 150) distinctly longer than wide (n = 1, PaFe L/W ratio = 2.62, PaGe L/W ratio = 2.70), without setae of semipectinalae type; palp tibia (n = 1, 62.5) subtriangular in outline, with 11 setae; palp tibial claw (n = 1, 35) with a median tooth; palp tarsus (n = 1, 52.5) cylindrical, apically rounded with one nude basal seta and 11 solenidia (ω), of which 3 are slightly longer, located proximally, the remaining ones short and robust; the area at the base of gnathosoma, anterior to dorsal scutum, covered with distinct star-shaped tubercles.

Legs ( Figs. 37–40 ). Leg I> leg IV> leg III> leg II; supracoxalae of legs I (eI) and II (eII) tiny and thumb-like, located in dorso-lateral part of coxal plates; all legs with barbed setae, specialized setae arise at genua, tibiae and tarsi (leg I: Ge 6σ + 1ĸ, Ti 11φ + 1ĸ, Ta 4ζ + ∼ 15ω + 1ε; leg II: Ge 2σ + 1ĸ, Ti 3φ, Ta 4ζ + ∼ 8ω; leg III: Ge 2σ, Ti 3φ, Ta 4ζ + ∼ 3ω; leg IV: Ge 4σ, Ti 2φ, Ta 4ζ + ∼ 2ω); additionally, along the ventral surface of tarsi, several setulated setae, not sharpened terminally and resembling the eupathidia (the setae are barely visible under light microscope); setae most numerous on tarsus I; tarsi terminated with paired claws, each claw covered with fimbriae.

Distribution. Spain.

Etymology. The species is named after Jorge Hernandez of Biobest Spain who collected the species and has since studied its occurrence in the Almeria region.

Type material. Holotype female, ID no. MNCN 20.02/17157 ( NMNS). Paratypes: two deutonymphs (ID no. MNCN 20.02/17158, MNCN 20.02/17159) and two larvae (ID no. MNCN 20.02/17160, MNCN 20.02/17161) ( NMNS); one female (ID no. RMNH. ARARI.P.8760), one deutonymph (ID no. RMNH. ARARI.P.8761) and two larvae (ID No. RMNH. ARARI.P.8762, RMNH. ARARI.P.8763) ( RMNH). All specimens obtained from a rearing culture established based on mites collected by Jorge Hernandez in a sweet pepper ( Capsicum annuum ) greenhouse in El Ejido, Province of Almeria, Spain, November 2009.

Remarks. Four species of Balaustium , i.e. B. barloventensis , B. biscutalae Mayoral et Barranco, 2009 , B. floralae Grandjean, 1947 and B. malpaisesensis , all known exclusively from larvae, but also B. neominiatum Mihelčič, 1958 , B. papillatum Mihelčič, 1958 and B. veletense Mihelčič, 1958 , known exclusively from active post-larval forms, have been hitherto reported from Spain ( Haitlinger 2004; Mayoral & Barranco 2009; Mihelčič 1958a, b). The main difference between B. hernandezi sp. nov. and species known from Spain, as well as other members of Balaustium for which larvae have been described, pertains to the NDV formula (the number of setae present on dorsal (ƒ D formula) and ventral side of idiosoma (ƒ V formula), excl. intercoxalae I and II). For the time being the highest value of NDV was recorded in B. hernandezi sp. nov. (215–247 vs 177 in B. barloventensis , 174 in B. biscutalae , c. 134 in B. brunoni Haitlinger, 2005 , c. 172 in B. florale , c. 137 in B. innocentae Haitlinger, 2006 , c. 141 in B. kacperi , 200 in B. kendalli , 125 in B. malpaisesensis , 138–142 in B. medardi ( Haitlinger 2000a) , c. 178 in B. minodorae Haitlinger, 2000 ( Haitlinger 2000b) , c. 128 in B. murorum , c. 106 in B. nikae , c. 133 in B. rajmundi , c. 128 in B. soydani Haitlinger, 2000 , c. 151 in B. wratislaviensis , 144 in B. zhangi . From B. cristatum (NDV value not provided in the original description, ƒ D formula calculated from the drawing) the newly described species differs in the number of dorsal setae (118–139 in B. hernandezi sp. nov., c. 49 in B. cristatum ).

As far as species known from post-larval forms are concerned the differences are expressed mainly in the metric and meristic data. Adults of B. hernandezi sp. nov. differ from some other members of the genus in the length of dorsal opisthosomal setae (45–75 in B. hernandezi vs 35–45 in B. afghanicum Cooreman, 1960 , 37– 44 in B. kendalli , 36–55 in B. medicagoense Meyer et Ryke, 1959 , 40– 52 in B. putmani , 32–47 in B. southcotti Feider et Chioreanu, 1977 , 18– 34 in B. xerothermicum GabryŠ, 2000, 30 in B. veletense Mihelčič, 1958 , 28 in B. vignae Meyer et Ryke 1959 , 24– 44 in B. zhangi ); similar differences apply to species known from deutonymph instar (45–73 in B.

hernandezi vs 22 in B. graminum Meyer et Ryke, 1959 ). The newly described species differs from B. unidentatum ( Trägårdh, 1904) in the lack of semipectinalae on palp genu (semipectinalae present in B. murorum and in B. unidentatum ), and from B. murorum in the chaetotaxy of palp tarsus (in B. murorum setulated setae prevail). The differences between B. hernandezi sp. nov. and B. araneoides ( Berlese, 1910) are expressed in the shape of dorsal opisthosomal setae (setae almost nude in B. araneoides ). B. hernandezi sp. nov. is also distinguishable by the presence of a relatively long palp genu (female: n = 1, L/W ratio = 2.70, deutonymph: n = 1, L/W ratio = 2.29), whereas the corresponding value calculated from the original drawings for post-larval forms of B. neomurorum Schweizer, 1951 equals at 1.58 and of B. submurorum Schweizer et Bader, 1963 at 1.00–1.56. Additionally, the distinction between B. hernandezi sp. nov. and B. medicagoense is possible based on the papillae-like structures on legs (absent in B. hernandezi , present in B. medicagoense ).

A group of 3 (in deutonymphs) and 11–13 setae AM (in adults), located anterior of ASens, is present in B. hernandezi sp. nov. (vs two setae in active post-larval form of B. araneipes Cooreman, 1956 , B. obtusum Trägårdh, 1931 and B. papillatum , and also in females of B. bipilum Meyer et Ryke, 1959 and B. dowelli ( Smiley 1966) , vs one seta in deutonymph of B. cristatum ). Two setae are located at the level of sensillae in active post-larval forms of B. madeirense Willmann, 1939 . Mihelčič (1958b) reported the presence of 1–3 (4 in the drawing) setae AM in representatives of B. neominiatum ; the specimens studied by latter author most likely represent the adult stage, which can be inferred from the basic body measurements.

Several other species originally placed in Balaustium are based on superficial descriptions. Consequently, even their generic classification is unclear. However, they are not conspecific with B. hernandezi sp. nov. The aforementioned group comprises B. affine Willmann, 1954 (dorsal opisthosomal setae reported as nude), B. angustum Evans, 1953 (posterior process of crista sharpened terminally, pDS = 24), B. aonidiphagus Ebeling, 1934 (body red in color, but with greenish or bluish iridescence).

The comparison with two other species, i.e. B. antarcticum ( Trägårdh, 1907) described based on post-larval forms and hitherto known exclusively from Falkland Islands and B. bulgariense Oudemans, 1926 , recorded from Austria, Bulgaria and Czech Republic, will remain impossible unless a redescription is provided. The ambiguous generic affiliation of Erythraeus antarcticus (which should be placed either in Balaustium s.s. or in Abrolophus Berlese, 1891 ) was depicted by Southcott (1961).

Biology. The life cycle of B. hernandezi sp. nov., similar to other terrestrial Parasitengona mites, comprises seven instars: egg, deutovum (prelarva), larva, three nymphal instars and adult. There is a regression in the first (protonymph) and third (tritonymph) nymphal instars, which results in an alternation of motile and quiescent stages.

In greenhouses, the mites were observed throughout the year, with the highest abundance in spring and summer, but a second peak occurring in November and December. Its appearance, which is possibly dependent on several climatological factors, does not necessarily reflect the actual phenology of mites. The seasonal abundance of B. medicagoense in winter grain crops and pastures was associated with summer and winter temperature and winter precipitation, with a likely diapause period in summer ( Arthur et al. 2011). Further studies on the phenology of B. hernandezi sp. nov., as well as on voltinism of the species, will be carried out in future.

The laboratory culture of mites allowed for completion of the life cycle and the population was maintained for several generations. The duration of the developmental stages is given in Fig. 41 . If fed on pollen alone, the duration of the larval instar (n = 10, F = 2.185; df = 11; P = 0.017) and deutonymph instar (n = 10, F = 6.475; df = 11; P = 0.043) was prolonged with 2.6 days and 6.1 days respectively, when compared to mites which were kept on pollen and prey. However, the developmental time of the inactive protonymphal stage was not affected (n = 10, F = 1.209; df = 11; P = 0.724).

Adding pollen to the prey diet had no positive effect on the development rate of particular instars (larva, n = 10: F = 0.621; df = 11; P = 0.738; protonymph, n = 10: F = 0.941; df = 11; P = 0.6768; deutonymph, n = 10: F = 0.313; df = 11; P = 0.473; tritonymph, n = 10: F = 0.583; df = 11; P = 0.184), nor on the total developmental time (n = 10; F = 2.210; df = 11; P = 0.712). Time required for development from larva to adult stage was 20.4 (n = 10) and 20.8 (n = 10) days, when offered prey and prey and pollen respectively.

The diet had no influence on the survival of immature stages when prey was included in the diet. 100% of the mites in both treatments completed development to adulthood.

In the rearing spermatophores were observed, in which the mobile filaments of the sperm could be observed under the microscope after mounting.

Usually, females deposited batches containing up to 150 eggs per oviposition bout. Eggs were reddish immediately after deposition, but turned black after 3–5 hours. At the beginning of deutovum instar, the chorion breaks in two and part of the embryo surrounded by an orange membrane becomes visible. The observed morphology of this instar was identical to one described by Cadogan and Laing (1977) for B. putmani .

Occasional cannibalistic behavior was observed in both immature mites and adults. Active mites were found to have two defense mechanisms while handling: (1) faking death and (2) the secretion of an urnulae-derived red fluid just posterior to the eyes.

Figures

FIGURE 41. Development of Balaustium hernandezi sp. nov. fed on different diets.

FIGURES 1 – 2. Balaustium hernandezi sp. nov. (larva): 1. Dorsal side of the body; 2. Ventral side of the body.

FIGURES 3 – 5. Balaustium hernandezi sp. nov. (larva): 3. Leg I; 4. Leg II; 5. Leg III.

FIGURES 6 – 8. Balaustium hernandezi sp. nov. (larva): 6. Tarsus I, lateral aspect; 7. Tarsus I, medial aspect; 8. Tarsus III termination (not to the scale).

FIGURES 9 – 12. Balaustium hernandezi sp. nov. (larva): 9. Palp, medial aspect; 10. Dorsal scutum with setae PL on the shield; 11. Dorsal scutum with setae PL off the shield; 12. Anterior part of gnathosoma, ventral aspect.

FIGURES 13 – 18. Balaustium hernandezi sp. nov. (larva), SEM micrographs: 13. Terminal segments of palps; 14. Palp tibia and palp tarsus, lateral aspect; 15. Palp tibia and palp tarsus, antero-lateral aspect; 16. Scutum; 17. Eye; 18. Dorsal opisthosomal setae.

FIGURES 19 – 22. Balaustium hernandezi sp. nov. (larva), SEM micrographs: 19. Tarsus I (eupathidium-like setae indicated with arrows); 20. Eupathidium and companala (Cp) on tarsus I; 21. Tibia I; 22. Tarsus III.

FIGURES 23 – 25. Balaustium hernandezi sp. nov. (deutonymph): 23. Palp, lateral aspect; 24. Eye (E) and urnula (Ur); 25. Dorsal scutum.

FIGURES 26 – 28. Balaustium hernandezi sp. nov. (female): 26. Palp, lateral aspect; 27. Eye (E) and urnula (Ur); 28. Dorsal scutum.

FIGURES 29 – 34. Balaustium hernandezi sp. nov. (adult, female), SEM micrographs: 29. Terminal segments (Ge – Ta) of palps; 30. Palp, antero-lateral aspect; 31. Palp tibia and palp tarsus, lateral aspect; 32. Palp tibia and palp tarsus, medial aspect; 33. Integument at the base of gnathosoma, dorsal side of the body; 34. Scutum.

FIGURES 35 – 40. Balaustium hernandezi sp. nov. (adult, female), SEM micrographs: 35. Eye (on the right) and urnula (on the left); 36. Dorsal opisthosomal setae; 37. Tarsus I termination; 38. Tarsus II termination; 39. Tarsus III termination; 40. Tarsus IV termination.