Redescription of the enigmatic myriapod Hanseniella chilensis (Hansen, 1903) (Symphyla, Scutigerellidae) based on scanning electron microscope images of Chilean specimens Author Parra-Gomez, Antonio https://orcid.org/0000-0002-4144-6610 Facultad de Ciencias, Universidad Austral de Chile, Av. Rector Eduardo Morales Miranda 23, Valdivia, Chile Author Perez-Schultheiss, Jorge https://orcid.org/0000-0003-4537-5677 Area Zoologia de Invertebrados, Museo Nacional de Historia Natural, Casilla 787, Correo Central, Santiago, Chile & Programa de Pos-Graduacao em Biologia Animal, Instituto de Biociencias, Universidade Federal do Rio Grande do Sul. Porto Alegre, Rio Grande do Sul, Brazil Author Fernandez, Leonardo D. https://orcid.org/0000-0001-9550-1921 Departamento de Zoologia (Laboratorio de Carcinologia), Instituto de Biociencias, Universidade Federal do Rio Grande do Sul. Porto Alegre, Rio Grande do Sul, Brazil & Facultad de Medicina Veterinaria y Agronomia, Universidad de Las Americas, Manuel Montt N ° 948, Providencia, Santiago, Chile limnoleo@gmail.com text ZooKeys 2024 2024-04-22 1198 1 15 http://dx.doi.org/10.3897/zookeys.1198.119723 journal article http://dx.doi.org/10.3897/zookeys.1198.119723 1313-2970-1198-1 BE4CB46906C14EA092B424C274DD617A 2E895B9E65DE5B69A5E2C4873C757A8B Hanseniella chilensis (Hansen, 1903) Figs 1 , 2 , 3 , 4 , 5 , 6 Scolopendrella immaculata Silvestri 1899 : 370 (Not Newport, 1845). Scutigerella chilensis Hansen, 1903: 27, 32, 46, 48, 51, plate 4, figs 4a-g; Silvestri 1905 : 746; Porter 1912 : 52; Dominguez 1992: 40; Vega-Roman et al. 2012 : 21, fig. 1. Hanseniella (Hanseniella) chilensis Bagnall 1913 : 198. Hanseniella chilensis Ringuelet 1955 : 110;? Aubry and Masson 1953 : 63;? Juberthie-Jupeau 1962 : 63, 75, fig. 5b; Scheller 1979 : 607; 1992 : 171; Soesbergen 2019 : 34. Type locality. Types not designated by Hansen (1903) , but the author described species based on specimens collected from San Vicente, Biobio region and Temuco, La Araucania region, central Chile. Material studied. 2 males , Chile : La Araucania region , Malleco province , Estero Lefuco , under rotting wood chips, -38.5153 , -71.7273 , 15-I-2022 , APG14 (field code) ; 1 male , same locality, leaf litter, -38.5135 , -71.7263 , 31-I-2022 , APG17-a (field code) ; 1 male , 2 female , same locality, under a rotting log ca. 944 m a.s.l. , -38.5132 , -71.7275 , 19-IX-2023 , PG-71-L/PG-71-L-a (field code) . Diagnosis. Adults specimens of Hanseniella chilensis can be separated from related species by the following combination of characters: Central rod follow by a triangular sulcus with a distinct small anterior seta, and two posterior setae (Figs 1A , 2A ); antennae usually with 29-37 (30-40 in Hansen (1903) specimens) antennomeres; first tergite rudimentary with one row of 9-11 setae (Fig. 1A ); dorsal cuticle scale-like and no pubescence or microsetae present (Fig. 2B ), macrochaetae present on most tergites as in Table 1 (Fig. 1B-D ); first podomere of first pair of legs bearing a posterolateral line of ca. 10 laminar needles; third podomere of 12th pair with one large dorsoposterior seta, 0.8 times the breadth of the podomere and fourth podomere bearing two distinct dorsoposterior larger setae, the largest being 1.2 times the breadth of the podomere [larger than in Hanseniella capensis (Hansen, 1903)]. Table 1. Chaetotaxy and posterior margin shape of the tergites, except the rudimentary first tergite.
Tergite number Number of setae on tergal surface and margins (ca.) Number of rows (counting hind setae as so) Anterolateral macrochaeta (per side) Posterolateral macrochaeta (per side) Hind macrochaeta pointing outwards and/or forwards (per side) Posterior margin
2 33-38 3 1 1 1 Almost straight
3 41-55 3 1 1 1 Almost straight
4 42-52 3 0 1 1 Almost straight
5 37-47 3 0 1 1 Almost straight
6 61-82 5 1 1 1 Almost straight
7 56-65 3 0 1 1 Slightly concave
8 38-55 3 0 1 1 Slightly concave
9 67-82 5 1 1 1 Almost straight
10 57-65 3 0 1 1 Slightly concave
11 44-59 3 0 1 1 Slightly concave
12 66-84 5 1 1 1 Almost straight
13 54-65 3 0 1 1 Slightly concave
14 61-71 5 0 1 1 Slightly concave
15 33-46 2-3 0 0 1 Convex between cerci
Figure 1. APG-17-a Male, dorsal view A head, first tergite and part of the second tergite (dfs-distinct frontal seta, ms-macroseta) B tergites 2-5 (am-anterolateral macrochaeta, hm-hind macrochaeta, pm-posterolateral macrochaeta) C tergites 11-13 D last tergite and cerci (hm-hind macrochaeta (abraded), hs-hind seta). Scale bars: 200.0 µm ( A-C ); 100.0 µm ( D ). Figure 2. Details of some relevant structures of APG-17-a Male ( A, B ) and PG-71-L-a Female ( C, D ) A central rod and triangular sulcus from the top of the head (hs-hind seta, oe-ovoid end, ss-short seta, ts-triangular sulcus) B tergal surface of tergite 3 (cr-cuticular rim) C Toemoesvary organ and proximal surface (km-knob with microseta, lp-linguiform protuberance) D apical zone of the last antennomere (sb-sensilla basiconica, so-sensory organ). Scale bars: 50.0 µm ( A, B ); 10.0 µm ( C, D ). Description. Length of body (measured dorsally) without cerci and antennae: female ca. 3.5-4.3 mm, males ca. 4.7-5.2 mm. Head . 1.4 times broader than long, frontal margin slightly convex with 1+1 distinct setae, lateral margins convex with a sharp anterolateral angle, posterior margin concave with rounded posterolateral angles (Fig. 1A ). Central rod well defined, posterior end slightly ovoid, followed by a triangular sulcus with a short seta near the anterior end, and 1+1 hind setae, both directed inwards and forwards (Figs 1A , 2A ). Frontal and top of head sparsely covered with setae, 3+3 macrosetae near the antennal base and 1+1 anterolateral macrosetae, ca. 2.1 as long as common head setae (Fig. 1A ). Toemoesvary organ circular, proximal surface covered by linguiform protuberances and small knobs bearing microsetae (Fig. 2C ). First maxillae simple, with a single subtriangular palp, ca. 1.6-2.0 longer than wider, around the same length of the most proximal setae. Second maxillae distal margin with 3+3 papilla-bearing lobes, anterior part with several protuberances, each one supporting a single seta, anterolateral margin with 3+3 (some males with 4+4) two-forked organs with a small medial process subtruncated at the tip. Both maxillae bearing setae across the surface. Antennae . Long, ca. 0.4-0.5 times the body length, with 29-37 antennomeres. Surface covered by pubescence, 1st antennomere with only one distal whorl of setae, 2nd-10th antennomeres with two poorly defined whorls very close to each other, middle whorl composed by larger setae and the distal by shorter setae, a 3rd whorl begins around 8th-14th antennomere below middle whorl. Small tri-forked organ on the distal margin starting from 4-9th antennomere and on, appears to be four-forked on later antennomeres. Sensilla basiconica present on distal margin from 8-10th antennomere and on, increasing in number and more acuminated in shape towards distal antennomeres (Fig. 4A ). Distal margin of antennomeres with granular surface. First antennomeres ca. 1.7-1.8 times broader than long (Figs 1A , 3A ), 2-4 antennomeres ca. 2.7-2.8 times broader than long, middle antennomeres ca. 1.1-1.5 times broader than long, distal antennomeres elongated and ca. 0.8 times broader than long. Apical antennomere spherical, sensilla basiconica present, apex of the segment bearing a large sensory organ borne from a small protuberance, composed of a central stalk which yields 5 slightly longer spiniform processes with curved-inwards tips; two additional similar organs, a large and a smaller one, composed of 4 spiniform processes in total besides the central stalk, basal protuberance absent or remarkably reduced (Figs 2D , 4B ). Tergites . Cuticle scale-like, surface smooth except for seta and macrochaeta (Figs 1B-D , 2B ). Rows and number of setae as in Table 1 . First tergite rudimentary, with one row of 9-11 setae, a pair longer than the rest (however it seems to be a variable character) (Fig. 1A ). Anterior surface portion from the second tergite and on with a set of circular cuticular rims (Fig. 2B ). Hind setae rather large, increasing gradually but considerable in length towards the posterior body portion, on last segments almost equal in length to macrochaetae (Fig. 1C ). First, third, sixth, tenth, and fourteenth tergite semicircular, fourth, fifth, seventh, eleventh, and twelfth subtrapeziform, eighth and thirteen subrectangular, fifteenth subquadrate. Third, sixth, ninth, twelfth and fourteenth tergites longitudinally broader than preceding ones. Posterior margin as in Table 1 . Tergal surface with poorly defined rows of setae as in Table 1 (Figs 1B, C , 2B ). Second and third tergite bearing on each side one anterolateral macrochaeta directed slightly forwards, one posterolateral macrochaeta directed outwards and forwards, and a posterior macrochaeta borne from the hind margin also directed outwards and forwards (Fig. 1B ). Fourth and fifth tergite bearing only one posterolateral and hind-borne macrochaetae on each side (Fig. 1B ). Sixth with macrochaetae same as second and third tergite. Seventh and eighth with macrochaetae same as fourth and fifth tergite. Ninth macrochaetae same as sixth tergite. Tenth and eleventh macrochaetae same as seventh and eighth. Twelfth macrochaetae same as ninth. Thirteenth and fourteenth macrochaetae same as tenth and eleventh. Posterior margin of last tergite with two short hind setae between cerci and two macrochaetae pointed outwards near the cerci base, U-shaped incision absent (Fig. 1D ). Ventral surface . Covered by microsetae (Fig. 3B ), last segment surface with laminar needles borne at the posterior end of scale-like layers. Coxal sacs . Mostly heart-shaped, fully developed at the bases on legs 3-9, margins with short setae and around 8-13 larger setae (Fig. 3C ). Male organs . Two very simple ventral contiguous semicircular plates held closely together and covered by pubescence. Legs . First pair of legs composed of 4 segments, from proximal to distal: First podomere short, bearing 3-4 setae, lateral cuticle scale-like, bearing a posterolateral line of ca. 10 laminar needles (similar to Fig. 3B ). Second podomere 2.0 times longer than wider, dorsal and lateral cuticle scale-like (similar to Fig. 3B ), one large distinct seta held proximolaterally and ca. 12 lateral setae, anteroventrally with 2 setae, largest seta held medioventrally and 0.8 times the breadth of the podomere, followed by a short spine held on a small bump, and two ventrodistal large setae, a line of several laminar needles near the laterodistal margin and most distal "scales" also bearing laminar needles (similar to Fig. 3B ). Third podomere subequal in length and width, surface pubescent, bearing 3 dorsal setae and 4 lateral setae. First to third podomere distal margins glabrous and microgranulated, scale-like surface also glabrous. Fourth podomere 3.9 times longer than wider, surface pubescent, with ca. 11 dorsal, 6 lateral and ca. 9 ventral setae; dorsal and ventral setae increasing gradually in length towards the apex. Two claws, posterior more curve and around 3/5 the length of the anterior claw, frontal seta around 1/2 the length of the anterior claw (Figs 3A , 4C ). 12th pair of legs composed of 5 segments: First podomere short, with ca. 12-13 ventral setae, surface scale-like, distal "scales" bearing laminar needles. Second podomere 1.7 times longer than wider, dorsal surface scale-like, 1-3 distodorsal setae, ca. 31 lateral setae, dorsolateral surface also scale-like, lateroventrally with "scales" bearing laminar needles (similar to Fig. 3B ), and a short spine near the margin held on a small bump, ventral surface pubescent and bearing ca. 14 setae, 2 large distinct setae and one medial short spine. Third podomere subequal in length and width, bearing ca. 13 dorsal setae and one large dorsoposterior seta, 0.8 times the breadth of the podomere (Fig. 3D ), laterally with ca. 9 setae, posterior margin with a line of several needles and "scales" also with laminar needles. Fourth podomere 1.6 times longer than wider, surface pubescent, bearing several setae and two distinct dorsoposterior larger setae, the largest being 1.2 times the breadth of the podomere (Fig. 3D ). First to fourth podomere distal margins glabrous and microgranulated, scale-like surface also glabrous. Fifth podomere 3.1 times longer than wider, surface pubescent with several setae. Dorsal setae of podomeres generally longer than the ventral ones (Fig. 3D ). Two claws, both curve, anterior claw basally thicker and slightly longer, frontal setae around 7/10 the length of anterior claw (Fig. 4D ). Styli . Short and straight, densely covered by pubescence, bearing two distinct large setae on distal end, largest one around 1.8-2.2 times the length of the shorter one, last one difficult to see sometimes, held posterolaterally (Fig. 4E ). Sense calicles . Pit margin covered by simple short setae and what appears to be bi- and tri-branched setae. Two distinct larger setae posteromedial to pit, 5.3 times the length of the short pit margin setae. Sensory seta inserted in the middle of the cavity, very long. Cerci . Surface covered by medium-size setae, which increase in length towards the apex, distal end without setae, apical seta 0.9 times the wider part of cerci, accompanied by a smaller outer seta around 0.25 times the length of the apical seta (Figs 1D , 3D ). Figure 3. PG-71-L-a Female, ventral view A head and first pair of legs B ventral surface details proximal to left leg of pair 8 and its 2 first podomeres, podomere 4 and 5 of pair 7 partially show (lm-laminar needles, sc-scale-like cuticle, slm- "scales" with laminar needles) C coxal sac near leg pair 4 D last pair of legs and cerci (ap-apical seta, ls-large seta, os-outer seta). Scale bars: 100.0 µm ( A, D ); 50.0 µm ( B ); 20.0 µm ( C ). Figure 4. Illustrations showing some relevant structures of the species A antennomere 20 of a male B apical antennomere (sensory organs not as detailed as described due to their small size, smallest one not visible on this angle) C distal end of the first pair of legs D distal end of the last pair of legs (frontal seta abraded) E styli. Scale bar: 50 µm . Distribution. Africa:?Madagascar: Banks of Betaly River, near Bezavona (see Remarks); South America: Argentina: Neuquen Province: Lago Curruhue (Currhue mendum Juberthie-Jupeau 1962 ); Lago Los Cantaros . Neuquen-Rio Negro Provinces: Nahuel Huapi Reserve. Rio Negro Province: Lago Frias ; Puerto Blest. Chile: Biobio Region: San Vicente. Araucania Region: Lefuco; Temuco;?Villarrica (see Remarks). ( Silvestri 1899 ; Hansen 1903 ; Aubry and Masson 1953 ; Juberthie-Jupeau 1962 ) (Fig. 5 ). Figure 5. All known records of Hanseniella chilensis (Hansen, 1903). Diamond = uncertain records from the literature, Star = new record herein, Circle = literature records. Remarks. Direction of macrochaetae can be variable due to specimen conservation and preparation on slides, but on live specimens in the field, the macrochaetae seem to point forwards in most, if not all, tergites (Fig. 6A-C ); it is important to note that some setae and macrochaetae were abraded on the SEM specimens. An additional record of H. chilensis is reported in Madagascar by Aubry and Masson (1953) , however, it is very likely that it is a morphologically similar species or accidentally introduced on the island; the authors likewise point out that the presence of this species on the island is strange (Fig. 5 ). Silvestri (1899) also mentions Villarrica as an additional record where he observed H. chilensis (at the time misidentified as S. immaculata ), nevertheless, this locality is never mentioned again by Hansen (1903) nor Bagnall (1913) (Fig. 5 ). Figure 6. A , B habitus of the species C general habitat where the species can be found. Affinities. Investigation of complete specimens of H. chilensis collected in central Chile allowed us to conclude that this species shares important morphological similarities with only one other congeneric species. Particularly, we noted that H. chilensis exhibits macrochaetae on all tergites (excluding the rudimentary first), a trait shared only with H. capensis ( Hansen 1903 ; Soesbergen 2019 ). Although it can be easily distinguished from H. capensis by the shape of the claws of the last pair of legs, as in this last species, the claws are distinctively thicker basally ( Hansen 1903 ). Also, the overall number of macrochaeta per tergite is higher in H. chilensis than in H. capensis . Additionally, Soesbergen (2019) described in his appendix that H. arborea Scheller, 1979 possesses macrochaeta on all tergites; however, in the original description, Scheller (1979) explicitly describes that the species exhibit macrochaeta on tergites 2-4, 6, 7, 9, 10, 12, 13 and 14. This last author also mentions that the distribution of macroseta or "large setae" on the fourth and fifth podomeres of the last pair of legs is closely similar to H. chilensis , but we noted that they are remarkedly shorter in length. Unfortunately, we were unable to compare H. chilensis with H. hardyi (Chamberlin, 1920), H. neozelandica (Chamberlin, 1920) and H. paolettii Scheller, 1993 because the number of macrochaetae present in their tergites remains unknown ( Soesbergen 2019 ). Therefore, the morphological affinity between H. chilensis and these last three species remains mostly unresolved.