Paratachys aaa, Liebherr, 2021

Liebherr, James K., 2021, Hawaiian Paratachys Casey (Coleoptera, Carabidae): small beetles of sodden summits, stony streams, and stygian voids, ZooKeys 1044, pp. 229-268 : 229

Paratachys aaa sp. nov. Figures 3D-F , 4C , 9 , 10 , 11

Type material.

Holotype male (BPBM): HI: Hawaii Mountain View / Kazumura Cave 22-VII- / 1971 F. G. Howarth / 600' Inside lava tube cave / on slime on wall // BBM-00301 // HOLOTYPE ♂ / Paratachys / aaa / J. K. Liebherr 2020 (black-margined red label).

Allotypic paratype female (BPBM): HI: Hawaii Mountain View / Kazumura Cave 25-VII- / 1971 F. G. Howarth / 200' Inside lava tube cave // BBM-00302 // ALLOTYPE ♀ / Paratachys / aaa / J. K. Liebherr 2020 (black-margined red label).

Paratypes. Hawai‘i I.: Hamakua District: Pohakuloa Military Training Area, Bobcat Trail, Cave 10265DE, deep zone, 1650 m el., 30-xii-1994, Howarth (BPBM, 3). Kau District: Ocean View, Kipuka Kanohina System, Cordwinder Natural Bridge, upslope, 23-xi-2018, Hackell/ Porter/ Hudson/ Katz, lot HI00776 (UHIM, 1), Kona Mala Driveway Entr., 22-xi-2016, M. Slay/ C. Slay/ Porter, lot HI00094 (BPBM, 1; UHIM, 2), 21-xi-2017, M. Slay/ C. Slay/ Gracanin/ Hackell/ A. Engel/ S. Engel/ Porter, lot HI00179 (CUIC, 1), 25-xi-2017, C. Slay/ A. Engel/ Hackell, lot HI00301 (UHIM, 3), Kula Kai Caverns, Chocolate Factory, 22-xi-2017, Porter/ S. Engel/ A. Engel/ Bosted, lot HI00227 (UHIM, 1), Menehune Entrance, 11-xi-2018, Chong/ Hudson/ Porter/ Thomson, lot HI00508 (UHIM, 1), 20-xi-2018, M. Slay/ S. Engel/ Katz/ Taylor (UHIM, 3), Wilson’s Big Room, 20-xi-2018, C. Slay/ Engel/ Katz/ Taylor, HI00673, lot HI00619 (UHIM, 2), Xanadu XD 1, 23-xi-2016, M. Slay/ C. Slay/ Porter, lot HI00142 (UHIM, 1), Xanadu Extension 1, 23-xi-2018, M. Slay/ C. Slay/ Yelverton/ Gunter/ Gracanin, lot HI00755 (UHIM, 1). Puna District: Kaimu, Burn Cave, deep zone, site 4, 260 m el., 16-iii-1994, Howarth/ Miller (BPBM, 1), pitfall trap L-8, 260 m el., 16-19-iii-1994, Howarth/ Miller (BPBM, 1), pitfall trap M-5, 16-19-iii-1994, Howarth/ Miller (BPBM, 2); Mountain View, Cow’s Eye Entrance, 22-iii-2019, Hudson/ Gracanin/ Hackell/ C. Slay/ M. Slay, lot HI01050 (UHIM, 2), lot HI01061 (BPBM, 3), D Road Cave, 20-iii-2019, Porter/ Chong/ Engel/ Hudson/ Hackell, lot HI00973 (UHIM, 2), lot HI00988 (BPBM, 2), Epperson’s Cave, 20-iii-2019, C. Slay, M. Slay, Engel, Gracanin, lot HI 00949 (UHIM, 1), Keala Cave Entrance, 19-iii-2019, A. Engel, S. Engel, Hudson, Hackell, M. Slay, C. Slay, Porter, Gracanin, lot HI 00911 (UHIM, 1), Kazumura Cave, lava tube cave, 200' inside lava tube cave, 25-vii-1971, Howarth (BPBM, 1 [male genitalia missing]), Weldon Sheldon entrance, downslope, 21-xi-2018, A. Engel/ Hudson/ Taylor, HI00713 (CUIC, 2), upslope, 21-xi-2018, C. Slay/ Yelverton/ Gunter/ Gracanin/ Hackell, HI00722 (UHIM, 2), 21-iii-2019, Chong, Hudson, A. Engel, S. Engel, Gracanin, lot HI01017 (UHIM, 1); Pahoa, Pahoa Cave, deep zone, 180 m el., 15-iii-1994, Howarth/ Miller (BPBM, 1), on bait, 18-iii-1994, Howarth/ Miller (BPBM, 1). South Hilo District: Kaumana Cave, 10-xi-2018, Chong, Hudson, Porter, Thomson, Lot HI00499 (UHIM, 1), 19-iii-2019, Engel/ Hackell/ Gracanin, Lot HI00925 (UHIM, 1), Porter/ Engel/ Hudson, Lot 00942, (CUIC, 1; UHIM, 2).

Diagnosis.

This is a small-bodied, pallid Paratachys with thin, translucent cuticle, and an iridescent sheen to the elytra due to the elongate transverse microsculpture; standardized body length 1.9-2.2 mm. The eyes are small but somewhat variable, with from 3-5 ommatidia crossed by a horizontal diameter of the eye, and from 4-6 ommatidia crossed by a vertical diameter (Fig. 9C-F ); OR = 1.14-1.19. The elytra are broad, with broadly rounded humeri and broad, nearly truncate apices. The elytral apical recurrent groove is broadly, shallowly impressed. Sutural interneur 1 (i1) of each elytron is well impressed, with the two interneurs bracketing an elevated, callous-like elytral suture, whereas interneurs 2 and 3 are broadly, shallowly impressed to obsolete on the disc, with the outer interneurs absent except for the configuration of interneur 8 (i8) characteristic of Paratachys ( Boyd and Erwin 2016: fig. 1A).

Description.

Head narrow, ocular lobes nearly flattened anterad the genae in dorsal view (Fig. 9A ); frontal grooves narrow mesad anterior supraorbital seta, broadest between anterior eye margins, and extended to lateral reaches of frontoclypeal suture; antennae moderately elongate, antennomere 9 length twice diameter; mandibles of moderate length, mandibles elongate, distance from dorsal condyle to apex 1.6 × distance from condyle to anterolateral labral margin; labrum transverse, anterior margin evenly emarginate across width, six-setose; penultimate maxillary palpomere broadly spindle-shaped, apical palpomere a narrow spindle (Fig. 9A ). Prothorax variably transverse, MPW/PL = 1.33-1.46, with lateral margins distinctly sinuate anterad the acute, projected hind angles, MPW/BPW = 1.18-1.27, the sinuosity of the lateral margins accentuating the cordate appearance more than that represented by measuring pronotal width over the hind angles; pronotal median base depressed, its juncture with disc smooth, basal margin extended medially to form a collar that extends posterad the concave margins posterad the laterobasal depressions; laterobasal depression deepest as a lateral extension of the discal-median base juncture that is directed to the concave basal margin mesad hind angles; pronotal median impression finely depressed, narrow, pronotal disc flattened each side of midline; anterior transverse impression obsolete medially, broadly, shallowly extended laterally to narrowly rounded, moderately projected front angles. Elytra subquadrate, short, humeri broad, EL/MEW = 1.38-1.47; basal groove present laterad position of third interneur on interval distance laterad the parascutellar seta Ed1, groove convexly joined to lateral marginal depression; lateral marginal depression moderately reflexed, of equal breadth from seta Eo3 to subapical sinuation; broader Eo elytral setae elongate, e.g., seta Eo2 length = 0.7 mm, Eo9 length = 0.8 mm (Pahoa Cave, 15-iii-1994, ♂, BPBM). Pterothorax moderately elongate; mesepisternal depression smooth posterad juncture with mesosternum; metepisternum elongate, lateral length 1.6 × maximal width; metathoracic flight wings vestigial, the alae reduced to broad-based stenopterous flaps that extend nearly to posterior margin of first abdominal tergite (Fig. 9G ) or to position of seta Eo4 when viewed through elytron, vestiges of radial, medial and cubital veins visible in the wing membrane. Abdomen with one seta each side of apical ventrite in males, two seta each side of ventrite in females. Microsculpture evident on all somites; frons covered with shallow transverse mesh, sculpticells isodiametric and cuticular surface rougher in broad frontal grooves; pronotal disc glossy with elongate transverse sculpticells producing silvery sheen, median base with distinct transverse lines medially, and irregular isodiametric sculpticells laterally; elytra iridescent due to mix of elongate transverse-mesh and transverse-line microsculpture, the transverse lines denser laterally; abdominal ventrites glossy laterally with shallow, swirling elongate-mesh microsculpture. Pelage present on head, prothorax, elytra, pterothorax, abdominal ventrites and legs; pelage on head, pronotal disc, and elytra comprising microsetae separated by distances subequal to setal length (Fig. 9C-F ), the microsetae linearly arrayed along elytral interneurs as well as along ommatidial margins of the eyes (Fig. 9B ); prosternum and mesosternum covered with sparse pelage medially; pelage of short microsetae present on abdomen in middle of ventrite 2 between metalegs, and progressively more broadly on ventrites 3-6 (absent dorsad arc of metaleg movement); anterior and posterior surface of prothoracic femora sparsely covered with microsetae, anterior (ventral) surfaces of meso- and metathoracic legs more densely covered with elongate microsetae, the setal bases situated more closely than microsetal lengths, trochanters and coxae similarly covered with microsetae. Coloration pale; vertex rufous to rufo-flavous, clypeus rufo-flavous, labrum flavous; antennomeres flavous, outer antennomeres 4-11 with slight smoky cast; maxillary and labial palps flavous; pronotum rufo-flavous; elytra rufo-flavous, elytral lateral marginal depression narrowly flavous medially; elytral epipleuron rufo-flavous, concolorous with thoracic and abdominal ventrites; legs flavous from trochanters outward; pro- and mesocoxae concolorous with outer leg segments, metacoxae rufo-flavous to match thoracic ventrites. Legs with only basal male protarsomere bearing a blunt, antero-apical process.

Variation.

A series of five individuals from Kaumana Cave, South Hilo District, include the largest individuals observed for this species. Their standardized body lengths range 2.1-2.2 mm, whereas all other individuals from caves in Hamakua, Puna, and Kau District range 1.9-2.1 mm standardized body length. The Kaumana specimens are also more heavily melanized, though their rufo-brunneous coloration is concolorous with the darkest individuals from the other localities. As neither of these attributes are diagnostic, and variation in male genitalia (below) does not support recognition of the Kaumana Cave individuals as representatives of a distinct species, all individuals described here are considered conspecific.

Male genitalia.

Aedeagal median lobe straight to slightly expanded near midlength, dorsal surface straight near midlength, evenly narrowed to rounded tip that is densely covered with sensilla (Fig. 3D-F ); flagellar complex broadly hemi-ovoid, with parallel cuticular ridges emanating from densely sclerotized ventrobasal margin; narrow, strap-like right paramere with three setae on narrowly rounded apex; basally broad left paramere elongate, the parallel-sided apical portion with broadly rounded, three-setose apex. There is some variability observable among aedeagal dissections with the dissection of a beetle from Kazumura Cave (Fig. 3D ) somewhat broader at midlength, and the aedeagus of a male from Kaumana Cave (Fig. 3F ) more gracile than the male from Kau (Fig. 3E ). The Kaumana male is larger than the other two (2.2 mm vs. 2.0 mm) consistent with the slightly longer aedeagus observed in that dissection (Fig. 3F vs. Fig. 3D, E ). The position of the flagellar complex within the aedeagal shaft is to be discounted, as the entire internal sac is eversible, and its position in repose would vary depending on the level of saccal inversion.

Female reproductive tract.

Bursa copulatrix short, broad, with spermathecal duct entering near base of common oviduct (Fig. 10 ); spermathecal duct very long, by measurement of drawing with mapping opisometer, 1.7 mm (!); spermathecal reservoir indistinctly annulated, at right angle to basal atrium and duct, spermathecal gland duct entering spermatheca near bend; spermathecal gland with narrow duct leading to broader reservoir, the reservoir bearing a small apical assemblage of ductule-bearing secretory cells on a narrow duct; gonocoxa bipartite (Fig. 4C ); basal gonocoxite 1 narrow, elongate, a single apical fringe seta near apex of lateral apodeme; apical gonocoxite 2 broadened basally, with lateral extension directed dorsad to ventral surface of coxite bearing two lateral ensiform setae; one dorsal ensiform seta just apicad position of apical lateral ensiform seta; two apical nematiform setae situated in elongate fossa situated halfway between position of dorsal ensiform seta and tightly rounded apex of gonocoxite 2.

Etymology.

The species name Paratachys aaa incorporates the Hawaiian word ' a‘a.‘ā, meaning lava cave ( Nā Puke Wehewehe 'Ōlelo Hawai‘i 2020). Being a Hawaiian word, the epithet is to be treated as a noun in apposition.

Distribution and habitat.

Paratachys aaa has attained a very broad subterranean distribution that includes lava tube caves within Mauna Loa and Kilauea volcanic flows. The species prefers the deep zone of lava tube caves ( Howarth 1982), and can thus be considered troglobitic. The type locality, Kazumura Cave northeast of Kilauea (Fig. 11 ), was formed approximately AD 1445 ( Clague et al. 1999), during an eruption of Mauna Loa that lasted approximately 50 years. Pauoa Cave and Burn Cave near the eastern tip of Hawai‘i Island were formed from Puna volcanics derived from Kilauea eruptions that occurred less than 1000 years ago. Similarly, the caves in Kau accessed from sites in Ocean View Estates near South Point (Fig. 11 ) were all formed during eruptive episodes of Mauna Loa involving k3 flows that range in age from 750-1500 years old ( Trusdell et al. 2005). The northwesterly Bobcat Cave north of the Mauna Loa caldera (Fig. 11 ) is situated at the margin of a k3 flow overlying an older k2 flow, giving an age of origin for that cave of at most 1500 years ago. And most recently, Kaumana Cave just WSW of Hilo, formed during the 1880-1881 eruption of Mauna Loa. Thus P. aaa occupies a disparate array of recently formed lava tube caves derived from several eruptive episodes. That these tiny beetles have attained such a broad distributional range among caves of different flows supports Howarth’s (1972) proposal that Hawaiian cave animals occupy both the larger lava tube caves accessible to humans (and collectors), but also the fractal network of mesocaverns ranging from 0.1-20 cm in diameter that connect those tubes. Add lignified organic layers sandwiched between older and newer flows ( Moore et al. 1989) to the mix, and one obtains a complex web of interconnected subterranean voids that supports a variety of microorganisms and the food web built upon them. Paratachys beetles serve as an apex predator in this system ( Howarth 1973), with their active foraging necessarily leading to dispersal among variously available and connected tubes and mesocaverns ( Howarth 1983, 1987). Whereas above-ground elevational variation in habitats coupled with geographical variation in rainfall and temperature serve to define geographic distributions, the relatively more homogeneous subterranean voids would allow beetle dispersal among variously connected mesocaverns. Given that their bodies are only 2 mm long, requiring only occasional meals and encounters with conspecifics of the opposite sex to support persistent populations among the variously connected cave systems, P. aaa have dispersed underground to colonize a broad swath of recently built Hawai‘i Island.

Figures

Figure 3. Paratachys spp., male aedeagus, i. e., median lobe and associated smaller right paramere and larger left paramere (right lateral view) A P. terryli; Kauai: Namolokama Mtn., 23 - v- 2005 (CUIC) B P. arcanicola lectotype slide; " Tachys arcanicola Blackburn Type ♂ E. C. Z. (permanent slide, Euparal?, left paramere missing; NHMUK). " C P. haleakalae; East Maui: Haleakala N. P., Kipahulu Vy., 30 - iv- 1991 (CUIC) D-F P. aaa; Hawai'i I D Puna, Mountain View, Kazumura Cave, 21 - xi- 2018, lot HI 00713 (CUIC) E Kau, Ocean View, Kipuka Kanohina System, 21 - xi- 2017, lot HI 00179 (CUIC) F South Hilo, Kaumana Cave, 19 - iii- 2019, lot HI 00942 (CUIC); disassociated left paramere below, ectal view.

Figure 4. Paratachys spp., left female gonocoxa, ventral view A P. terryli; Kauai: Namolokama Mtn., 23 - v- 2005 (CUIC) B P. haleakalae; East Maui: Haleakala N. P., Kipahulu Vy., 30 - iv- 1991 (CUIC) C P. aaa; Hawai'i I.; Mountain View, Kazumura Cave, 21 - xi- 2018, lot HI 00713 (CUIC). Abbreviations: afs, apical fringe seta; ans, apical nematiform setae; des, dorsal ensiform seta; gc 1, basal gonocoxite; gc 2, apical gonocoxite; les, lateral ensiform setae.

Figure 9. Paratachys aaa A male, dorsal habitus view; Kau, Kona Mala, 21 - xi- 2017, lot HI 00179 B mentum and associated mouthparts, ventral view, of above male specimen C larger ovoid compound eye of female, lateral view; Mountain View, Kazumura Cave, 21 - xi- 2018, lot HI 00722 D moderately sized ovoid compound eye of male, lateral view; also lot HI 00722 E smaller rounded compound eye of male, lateral view; Kaimu, Burn Cave, 16 - 19 - iii- 1994 F small compound eye of male, lateral view; Kaimu, Burn Cave, 16 - iii- 1994 G stenopterous left metathoracic flight wing of male (elytron removed), dorsal view; Kau, Kona Mala, 21 - xi- 2017, lot HI 00179.

Figure 10. Paratachys aaa female reproductive tract, ventral view; Mountain View, Kazumura Cave, 21 - xi- 2018, lot HI 00713 (CUIC). Abbreviations: bc, bursa copulatrix; co, common oviduct; sd, spermathecal duct; sg, spermathecal gland; sp, spermatheca. Schematic drawing breaks spermathecal duct at " A " to accommodate drawing to page size. Estimated length of spermathecal duct 1.7 mm.

Figure 11. Distributional records of Paratachys aaa. Abbreviations: H, Hilo; K, caldera of Kilauea Volcano; ML, summit caldera of Mauna Loa Volcano.