Research Article |
Corresponding author: Sopark Jantarit ( fugthong_dajj@yahoo.com ) Academic editor: Wanda M. Weiner
© 2020 Sopark Jantarit, Katthaleeya Surakhamhaeng, Louis Deharveng.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Jantarit S, Surakhamhaeng K, Deharveng L (2020) The multiformity of antennal chaetae in Troglopedetes Absolon, 1907 (Collembola, Paronellidae, Troglopedetinae), with description of two new species from Thailand. ZooKeys 987: 1-40. https://doi.org/10.3897/zookeys.987.54234
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Two new species of the genus Troglopedetes Joseph, 1872 (T. meridionalis sp. nov. and T. kae sp. nov.) are described from caves of the Thai peninsula. This is the first report of the genus south of the Kra Isthmus. The two new species have two rows of dental spines shared by all Thai Troglopedetes. They differ from other members of the genus mainly in the arrangement of dorsal chaetotaxy on head. The antennal chaetotaxy of the two species is analysed in detail in the second part of the paper. All types of antennal chaetae of both new species and their distribution patterns are described for each antennal segment: scales, ordinary chaetae, S-chaetae and subapical organite of Ant. IV. Twenty different types of chaetae are recognised and all except one are present in both species. The total numbers of ordinary chaetae and S-chaetae and their patterns of distribution on antenna are very similar between the two species (483 vs. 518 ordinary chaetae; 207 vs. 208 S-chaetae). Each type of chaetae has its own distribution pattern, markedly contrasted between dorsal and ventral side of antennae, and between antennal segments. This diversity of morphologies and distribution patterns and their similarity between the two species, as well as differences with other species of the same family, suggest that antennal chaetotaxy could provide powerful new characters for the taxonomy of Troglopedetes and related genera.
Antennae, chaetotaxy, Entomobryoidea, Isthmus of Kra, phaneres, S-chaetae, subterranean habitat
The genus Troglopedetes Joseph, 1872 is present in both edaphic and subterranean environments (
The genus Troglopedetes was erected in 1872 by Joseph for T. albus Joseph, 1872 from caves in Slovenia. Later,
The genus was subsequently recorded from Thailand by
Troglopedetes is one of the best-defined genera of Paronellidae by the subdivision of its 4th antennal segment, a feature unique in the family. However, other important taxonomic characters have not been described in detail in many species, like the dorsal chaetotaxy of head and body, S-chaetal pattern on antennae and tergites, trichobothria complex, arrangement of pseudopores, and furcal structure. Regarding the antennae, like for other Entomobryoidea, only a few chaetae have been considered in published descriptions, mostly those of the sensorial organ of the third antennal segment. The complexity of antennal chaetotaxy in Entomobryoidea, with its large number of chaetal types and strong polychaetosis, may explain why authors have been so reluctant to analyse these organs in great detail. Recent works, however, by
In this study, we describe two new species, T. meridionalis sp. nov. and T. kae sp. nov., from caves of peninsular Thailand. These records are the first report of the genus south of the Kra Isthmus, considered so far as a probable biogeographical transition zone between the genus Troglopedetes and the closely related genus Cyphoderopsis (
The specimens of the two Troglopedetes species described here were found in the dark zone of two caves, Tham Don Non, Lang Suan district, Chumphon Province and Tham Kae, La-ngu district, Satun Province (Fig.
Distribution of Troglopedetes in Thailand (empty blue circles) with distributed limestone (orange colour) of the country 1 T. maffrei Deharveng & Gers, 1993 2 T. longicornis Deharveng & Gers, 1993 3 T. centralis Deharveng & Gers, 1993 4 T. fredstonei Deharveng, 1988 5 T. leclerci Deharveng, 1990 6 T. microps Deharveng & Gers, 1993 7 T. multispinosus Deharveng & Gers, 1993 8 T. maungonensis Deharveng & Gers, 1993 9 T. calvus Deharveng & Gers, 1993 10 T. dispersus Deharveng & Gers, 1993 11 T. convergens Deharveng & Gers, 1993 12 T. paucisetosus Deharveng & Gers, 1993 13 T. meridionalis sp. nov. 14 T. kae sp. nov. and its habitus (small colour picture). Small dark dots indicate province capitals; scale 1:250,000.
Abbreviations
Ant. antennal segment
Abd. abdominal segment
AIIIO apical organ of Ant. III
Th. thoracic segment
Tita tibiotarsus
mac macrochaetae
mes mesochaeta(e)
mic microchaeta(e)
psp pseudopore
tric trichobothria
ms S-microchaeta(e)
s or sens S-chaeta(e)
VT ventral tube
Pseudopore arrangement follows
In the concept of Soto-Adames et al. (2014), the tribe Troglopedetini is considered a synonym of Paronellini. This is plausible, but not supported by the last detailed redescription of Paronella fusca Schött, 1893, type species of the genus Paronella, by
Troglopedetes albus Joseph, 1872
Medium sized Paronellidae. Body colour white, sometimes with light orange to red pigment dots. Eyes per side 0–3. Scales present on antenna, head, body and ventral side of furca, absent on ventral tube and legs. Pseudopores on tergites arranged as 1, 1/1, 1, 1, 1 by half tergite from Th. II to Abd. IV, with a row of 4+4 pseudopores behind the posterior row of chaetae of Abd. IV. Labial basis chaetotaxy as M1M2R(r)E(e)L1(l1)L2(l2). Presence of one or two sublobal hairs on maxillary outer lobe. Antennae of various length, composed of four segments, with Ant. IV always divided into two equal or subequal sub-segments and devoid of apical bulb. Suture zone of head when visible follows divergent lines. Trichobothrial pattern 0, 0/0, 2, 3, 3. Dorsal macrochaetotaxy oligochaetotic, polychaetotic on the collar. Macrochaetae on head present as 0–7+0–7 in area dorsalis (central mac). Th. II with a compact group of 6+6 mac accompanied by 0–4+0–4 mac anteriorly. Th. III with a group of 3+3 mac accompanied by 0–1+0–1 mac anterior-externally. Claw with 0–2 inner teeth, a pair of lateral ones and a dorsal tooth. Dens elongated with one or two rows of spines, those on external row larger, more serrated than those on internal row. Mucro of various length, 2–16 × shorter than dens, with 3–5(6) main teeth, proximal tooth sometimes with 1–5 basal toothlets.
The number and arrangement of trichobothria on Abd. IV allows clear separation of Troglopedetinae (3+3 trichobothria) from other Paronellidae (2+2 trichobothria). Many characters are unknown for several species of Troglopedetes, including its type species. Two characters complementary to those listed by Soto-Adames et al. (2014) are discussed below. A new set of characters present in Troglopedetes are presented below as a result of this work.
Pseudopores are arranged on tergites as in other Entomobryoidea: 1, 1/1, 1, 1, 1 from Th. II to Abd. IV. Additionally, a row of 4+4 pseudopores is constant behind the posterior row of chaetae of Abd. IV (
Dorsal clothing of macrochaetae is clearly oligochaetotic in the Troglopedetes species where it has been described. Pattern on Th. II includes a compact group of six chaetae (P3 complex of Soto-Adames et al. 2014) which is very obvious and constant. The same group, including 3–6 mac, is present in Trogolaphysa (
Dens of Troglopedetes is elongated with either one or two rows of spines, those of the external row larger and more serrated than those of the internal one that are rather short and smooth. Soto-Adames et al. (2014) mistakenly stated that Troglopedetes has a single row of dental spines. In fact, species of the Mediterranean region, Africa, south-west and central Asia known so far have only one row of 8–45 dental spines, but all Thai species have two rows of dental spines (internal row with 9–45 spines, external one with fewer spines).
Holotype male and seven paratypes on slides (one male, four females and two subadults). Thailand: Satun Province: La-Ngu district, Tham Kae, 6°53'41"N, 99°46'44"E, 24 m a.s.l., 25 Jul 2017, S. Jantarit, A. Nilsai and K. Surakhamhaeng leg., dark zone of cave, by aspirator (sample # THA_SJ_STN04). Holotype and five paratypes deposited in
Head | Body | Appendages | |||
Ant. I | 90 | Th. II | 137 | Man | 305 |
Ant. II | 215 | Th. III | 133 | Dens | 283 |
Ant. III | 148 | Abd. I | 101 | Mucro | 30 |
Ant. IVa | 136 | Abd. II | 130 | Furca | 618 |
Ant. IVb | 138 | Abd. III | 144 | Claw I | 37 |
Ant. | 727 | Abd. IV | 515 | Claw II | 35 |
Head | 286 | Abd. V | 75 | Claw III | 36 |
Abd. VI | 71 | ||||
Body | 1,592 |
Habitus. Slightly troglomorphic, slender, with elongate legs, furca and antennae. Body length 1.3–1.6 mm. Fourth abdominal segment 3.5–6 × (n = 9, all adults) as long as the third one along dorsal axis. Furca well developed, ca. 1.6–2.2 (n = 8) × shorter than body length. Body colour white with spots of orange pigment. Eyes absent, no ocular patch.
Chaetal types. Four types of chaetae on somites, appendages (except antennae) and mouthparts: scales, present on antennae I and II, head, body and furca, absent on legs and ventral tube; ordinary chaetae on all body parts; S-chaetae and trichobothria on tergites; hairs devoid of sockets on outer maxillary lobe and labial papilla. Chaetal types on antennae are much more diverse and described further separately.
Pseudopores
(Figs
Troglopedetes kae sp. nov. A head chaetotaxy (left = A to G mac nomenclature; right = AMS nomenclature) B outer maxillary lobe C labial palp of papillae D maxillary head of ventral sides E maxillary head of dorsal sides F ventro-distal complex of labrum G labrum H mandible I labial basis and ventral chaetotaxy of head, right side.
Mouthparts. Labral formula 4/5,5,4 (Fig.
Ventral chaetotaxy of head
(Fig.
Antennae
(Figs
Body dorsal chaetotaxy
(Figs
Head with 12–13 peri-antennal mac in line on each side, with 4+4 central mac (chaetae A, B, E, F of
Th. II with a collar consisting of a few rows of mac along its anterior and antero-lateral margins, a compact group of six central mac on each side (“P3 complex” of Soto-Adames et al. (2014) and two antero-lateral mac; one antero-lateral ms; one antero-lateral sens; two or three short mic laterally, and a few others not counted centrally (Fig.
Th. III with four mac by side (a group of three central and one anterior to them), one sens at antero-lateral margins, and ca. eight or nine mac or long mes at lateral margins (Fig.
Abd. I without central mac, with one ms laterally on each side, and three mes laterally, mic not counted (Fig.
Abd. II with two tric on each side and six or seven modified mes around them (three or four around the internal tric and three near external tric), two mac (one near internal tric and one near external tric), one sens near internal tric (Fig.
Abd. III with three tric on each side (one internal, two external) and eight or nine modified mes around tric (two near internal tric, six or seven near the two external tric); four mac (one near internal tric and three near external tric); one sens anterior to internal tric and one ms posterior to the two external tric; several mes at lateral margins, not counted (Fig.
Abd. IV with three tric on each side (two antero-lateral, one postero-lateral) and ca. 7–9 modified mes around the two antero-lateral tric; postero-lateral tric without modified mes. Mac distributed as three central on each side (one antero-external to pseudopore, two anterior to posterior tergite margin), one near postero-lateral tric, and at least four external, mixed with many mes or smaller mac on lateral to posterior margins (not counted); probably three sens anteriorly; at least six S-like chaetae sensu
Abd. V with only one sens detected on each side, and several ordinary chaetae from mes to mac, not counted (Fig.
Legs
(Fig.
Troglopedetes kae sp. nov. continued A distal part of tibiotarsus III and claw complex with pointed tenent hair B distal part of tibiotarsus III and claw complex with clavate tenent hair C trochanteral organ D anterior side of ventral tube E lateral flap of ventral tube F posterior side of ventral tube.
Ventral tube
(Fig.
Furcal complex
(Fig.
Genital plate
(Fig.
Troglopedetes kae sp. nov. is only known from a small chamber in the dark zone of a cave, accessible by a very low and narrow passage. Specimens were found as small populations in an oligotrophic habitat, i.e., on wall and ground with very humid and wet environment, without any trace of organic matter.
The species name is taken from the type locality (Tham Kae).
Troglopedetes kae sp. nov. has four medial head macrochaetae, three medial Abd. IV macrochaetae, one inner teeth of claw and mucro with five teeth. It is near T. centralis Deharveng & Gers, 1993 from a cave in Doi Chiang Dao, Chiang Mai province in the absence of eyes, chaetotaxy of labial basis and of outer maxillary lobe, dorsal macrochaetotaxy from head to Abd. IV, chaetotaxy of anterior side of ventral tube and claw morphology. However, T. kae sp. nov. differs from T. centralis by its smaller size (1.3–1.6 vs. 1.7–2.1 mm), body colour with spots of orange pigment (vs. white), longer antennae (0.5–0.6 × as long as body vs. 0.4), thinner claw with an internal tooth at 30 vs. 50–65% from the basis, chaetae on lateral flap of the ventral tube (6+6 vs. 7+7), higher ratio dens:mucro (9.3–13.7 vs. 8.8), and mucro with five teeth (vs. four).
In the same cave and same habitat, we found another morphotype with very different claw complex; thick and clavate tenent hair, two strong inner teeth on claw at 74% and 91% of inner edge, and external edge of unguiculus with two or three minute outer basal teeth, sometimes inconspicuous (Fig.
The locality where T. kae sp. nov. was collected is located 400 km south of the Isthmus of Kra, i.e., more south than other described Troglopedetes from Thailand. The Isthmus of Kra is well-known to be a biogeographical transition zone between Indochinese and Sundaic fauna (Fig.
Holotype male and four paratypes (one female, three subadults) on slides. Thailand: Chumphon Province: Lang Suan district, Tham Don Non (Tapan), 9°54'14"N, 99°02'41"E, ca 60 m a.s.l., 25 Jul. 2015, S. Jantarit leg., dark zone of cave, by aspirator (sample # THA_SJ_CPN01). Holotype and two paratypes deposited in
Troglopedetes meridionalis sp. nov., measurements in µm (from holotype).
Head | Body | Appendages | |||
---|---|---|---|---|---|
Ant. I | 78 | Th. II | 137 | Man | 345 |
Ant. II | 150 | Th. III | 114 | Dens | 340 |
Ant. III | 125 | Abd. I | 62 | Mucro | 30 |
Ant. IVa | 125 | Abd. II | 76 | Furca | 715 |
Ant. IVb | 125 | Abd. III | 110 | Claw I | 27 |
Ant. | 603 | Abd. IV | 400 | Claw II | 27 |
Head | 300 | Abd. V | 62 | Claw III | 27 |
Abd. VI | 40 | ||||
Body | 1,301 |
Habitus. Slightly troglomorphic, slender, with elongate legs, furca and antennae (Figs
Troglopedetes meridionalis sp. nov. A habitus B labial palp of papillae E C outer maxillary lobe, right side D chaetotaxy of basal area of labium, right side E mandible F maxilla G ventral chaetotaxy of head, left side H antenna, right side I distal organ of Ant. III, right side J dorsal chaetotaxy of head.
Chaetal types. Four types of chaetae on somites, appendages (except antennae) and mouthparts: scales, present on antennae I and II, head, body and furca, absent on legs and ventral tube; ordinary chaetae on all body parts; S-chaetae and trichobothria on tergites; hairs devoid of sockets on outer maxillary lobe. Chaetal types on antennae are much more diverse and described separately further.
Pseudopores
(Figs
Troglopedetes meridionalis sp. nov. continued A dorsal side of Ant. I with scale and S-chaetae, right side B dorsal side of Ant. I with all chaetal types, right side C ventral side of Ant. I with scale and S-chaetae, right side D ventral side of Ant. I with all chaetal types, right side E type of scale F type of antennal ordinary chaetae G type of antennal S-chaetae H subapical organite of Ant. IV.
Troglopedetes meridionalis sp. nov. continued A ventral side of Ant. III with S-chaetae, right side B dorsal side of Ant. III with S-chaetae, right side C dorsal side of Ant. III with all chaetal types, right side D ventral side of Ant. II with scale and S-chaetae, right side E dorsal side of Ant. II with scale and S-chaetae, right side F dorsal side of Ant. II with all chaetal types, right side.
Mouthparts. Labral formula 4/5,5,4; prelabral chaetae short, bent and ciliated, labral chaetae thinner, smooth and acuminate, those of the distal row slightly shorter than those of the median row. Ventro-distal complex of labrum well differentiated, asymmetrical, with two distal combs (a larger one with 6–8 teeth on the left side, a smaller one with more than ten minute teeth on the right side) and an axial pair of sinuous tubules. Distal part of labrum not adorned with spines dorso-distally. Labial palp similar to that of T. kae sp. nov. (Fig.
Ventral chaetotaxy of head
(Fig.
Antennae
(Figs
Dorsal chaetotaxy
(Figs
Th. II collar consisting of a few rows of mac along its anterior and antero-lateral margins, a compact group of six central mac on each side (“P3 complex”) and two antero-lateral mac; one antero-lateral ms; one antero-lateral sens; two or three short mic laterally, and a few others not counted centrally (Fig.
Th. III with four mac on each side (a group of three central and one anterior to them); one sens at antero-lateral margins; one mic laterally; and ca. 11+11 mac or long mes at lateral margins (Fig.
Abd. I without central mac, with one ms laterally on each side; two or three mic arranged in line externally to pseudopore and two larger lateral mic; three mes laterally (Fig.
Abd. II with two tric on each side and six or seven modified mes around them (two around the internal tric and four or five near external tric), two mac (one near internal tric and one near external tric), one sens near internal tric; three mic (one close to internal tric and two close to external tric), others mes sockets internally visible, not counted (Fig.
Abd. III with three tric on each side (one internal, two external) and nine or ten modified mes around tric (two near internal tric and seven or eight near the two external tric); four mac (one near internal tric and three near external tric); one sens anterior to internal tric and one ms posterior to the two external tric; two mic/mes external to the external mac; several mes at lateral margins, not counted (Fig.
Abd. IV with three tric on each side (two antero-lateral, one postero-lateral); and ca. 6–9 modified mes around the two antero-lateral tric; postero-lateral tric without modified mes. Mac distributed as three central on each side (one antero-external to pseudopore, two anterior to posterior tergite margin), one near postero-lateral tric, and four or five external, mixed with many mes or smaller mac on lateral to posterior margins (not counted); probably three sens anteriorly; at least seven S-like chaetae sensu
Abd. V with only two sens detected on each side, and several ordinary chaetae from mes to mac in size (Fig.
Legs
(Fig.
Ventral tube
(Fig.
Furcal complex
(Fig.
Dens straight, elongate, hairy, slightly and progressively tapering, dorsally with two rows of spines, mixed with ciliated mes of various length, thickness and shape. Dorso-external row with 17–20 subequal spines, dorso-internal row with 30–37 subequal spines (asymmetries between dentes); external spines larger and less sclerotised than internal ones. Short ciliated mes interspersed with spines in the external row; dorsally between the two rows of spines a mix of short and long ciliated mes, irregularly arranged in one row distally turning to 3–4 rows proximally; laterally, many short ciliated mes; dorso-distally, 3–(4) stronger ciliated mes; 2+2 psp on dorso-basally between the two rows of spine, sometimes inconspicuous. Dens ventrally entirely and densely scaled, scales elongate (20–38 µm), arranged in short lines from 3–5 (distally) to 6–8 scales (proximally) (Fig.
Mucro rather stout, short, 12–15 × shorter than dens (Fig.
Genital plate. Genital plate not seen.
Troglopedetes meridionalis sp. nov. was found in small populations in the dark zone of a cave, foraging on a small patch of old and humid bat guano.
The name of the species, meridionalis, means southern in Latin, referring to the location of the species in the southern part of peninsular Thailand.
Troglopedetes meridionalis sp. nov. is the only species of the genus with one medial head macrochaeta. It is similar to T. convergens Deharveng & Gers, 1993 from a cave of Ratchaburi province in the absence of eyes, two rows of dental spines, labial basis chaetotaxy, similar dorsal chaetotaxy from head to Abd. IV, anterior ventral tube chaetotaxy, and claw morphology. It can be distinguished by the combination of characters listed in Tables
The pair of mac immediately ahead A and that ahead the uneven anterior mac on head are not figured in
Summary of main general and head characters of Thai Troglopedetes (N = northern Thailand, W = western Thailand, S = southern Thailand).
Species/Characters | Length (mm) | Eyes | Colour | Ant.: Body | Labial basis | Sublobal hairs | Central mac on head | Mac on head | Locality (province) |
---|---|---|---|---|---|---|---|---|---|
T. calvus | 0.90–1.37 | 0 | white | 0.6 | M1M2REL1l2 | 2 | 0 | – | Kanchanaburi (W) |
T. centralis | 1.7–2.1 | 0 | white | 0.4 | M1M2REL1l2 | 2 | 4+4 | A, B, E, F | Chiang Mai (N) |
T. convergens | 0.95–1.3 | 0 | white | 0.45–0.5 | M1M2REL1l2 | 2 | 2+2 | A, E | Ratchaburi (W) |
T. dispersus | 1.3–1.4 | 0 | white with red pigment | 0.6 | M1M2Re(E)L1l2 | 2 | 3+3 | A, C, E | Kanchanaburi (W) |
T. fredstonei | 1.4–2.1 | 0 | white with red pigment | 0.5 | M1M2REL1l2 | 2 | 5+5 | A, B, C, E, F | Chiang Mai (N) |
T. kae sp. nov. | 1.3–1.6 | 0 | white with orange pigment | 0.46 | M1M2REL1l2 | 2 | 4+4 | A, B, E, F | Satun (S) |
T. leclerci | 0.7–1.0 | 3+3 | white | 0.44 | M1M2REL1l2 | 2 | 7+7 | A, B, C, D, E, F, G | Chiang Mai (N) |
T. longicornis | 1.8–2.2 | 0 | white | 0.8 | M1M2ReL1l2 | 2 | 5–6+5–6 | A, B, C, D, E, (F) | Mae Hong Son (N) |
T. maffrei | 1.3–1.75 | 0 | white | 0.4 | M1M2ReL1l2 | 1 | 7+7 | A, B, C, D, E, F, G | Mae Hong Son (N) |
T. maungonensis | 1.1–1.2 | 0 | white | 0.5 | M1M2REL1l2 | 1 | 7+7 | A, B, C, D, E, F, G | Chiang Mai (N) |
T. meridionalis sp. nov. | 1.3–1.5 | 0 | white with orange pigment | 0.46 | M1M2REL1l2 | 2 | 1+1 | A | Chumphon (S) |
T. microps | 1.5–2.0 | 1–2+1–2 | white | 0.6 | M1M2REL1l2 | 1 | 4–5+4–5 | A, B, C, E, (F) | Chiang Mai (N) |
T. multispinosus | 1.8–2.2 | 0 | white, red eye patch | 0.9 | M1M2ReL1l2 | 2 | 3+3 | A, B, E | Chiang Rai (N) |
T. paucisetosus | 0.85–1.06 | 0 | white with some red pigment | 0.6 | M1M2REL1l2 | 2 | 1–2+1–2 | A, (E) | Prachuap Khiri Khan (W) |
Summary of main characters of body and appendages of Thai Troglopedetes (N = northern Thailand, W = western Thailand, S = southern Thailand, ? = no information).
Species/ Characters | Central Mac on Th. II | Central Mac on Abd. IV | Claw (inner teeth) | Position of inner teeth | Tenent hair | Lateral flaps of VT | Internal row of spine | Dens: mucro | Locality (province) |
---|---|---|---|---|---|---|---|---|---|
T. calvus | 8+8 | 3+3 | 2 | 65%, 85% | capitate | 7+7 | 14–32 | 8.5 | Kanchanaburi (W) |
T. centralis | 8+8 | 3+3 | 1 | 50–65% | pointed | 7+7 | 37–42 | 8.8 | Chiang Mai (N) |
T. convergens | 8+8 | 3+3 | 1 | 55% | capitate | 7+7 | 19–23 | 9 | Ratchaburi (W) |
T. dispersus | 8+8 | 3+3 | 1(2) | 50%–(80%) | pointed or capitate | 7+7 | 25–29 | 8.5 | Kanchanaburi (W) |
T. fredstonei | 8+8 | 3+3 | 1 | 58–60% | pointed or capitate | 7+7 | ? | 15 | Chiang Mai (N) |
T. kae sp. nov. | 8+8 | 3+3 | 1 | 30–35% | pointed | 6+6 | 26–33 | 9.3–13.7 | Satun (S) |
T. leclerci | 8+8 | 2+2 | 1 | 50% | pointed or feebly capitate | 6+6 | 18 | 5–6 | Chiang Mai (N) |
T. longicornis | 8+8 | 3+3 | 1 | 30–45% | pointed | 7+7 | 29–36 | 13.1 | Mae Hong Son (N) |
T. maffrei | 9+9 | 3+3 | 2 | 65, 75–85% | pointed or capitate | 6+6 | 21–28 | 9.4 | Mae Hong Son (N) |
T. maungonensis | 9+9 | 3+3 | 2 | 65, 85% | capitate | ? | 27–30 | 9.7 | Chiang Mai (N) |
T. meridionalis sp. nov. | 8+8 | 3+3 | 1 | 50–55% | pointed | 6+6 | 30–37 | 12–15 | Chumphon (S) |
T. microps | 8+8 | 3+3 | 1 | 65% | capitate | 7+7 | 36–42 | 13.6 | Chiang Mai (N) |
T. multispinosus | 8+8 | 3+3 | 1 | 35% | pointed | 7+7 | 34–41 | 12.7 | Chiang Rai (N) |
T. paucisetosus | 8+8 | 2+2 | 2 | 65, 80% | capitate | 7+7 | 18–24 | 9.6 | Prachuap Khiri Khan (W) |
The work presented below is an attempt to build a comprehensive list of phanere types found on the antennae of an Entomobryoidea, to describe them morphologically, and to explore their distribution on antennal surface. Antennae bears many useful taxonomic and phylogenetic characters in Poduromorpha and has been the object of many studies (
There are five main types of phaneres (sensu
Three types of scales were recognised in Thai Troglopedetes, but only one type was found on antennae of T. kae sp. nov. All scales are roundish, oval, variable in size on different organs, devoid of ridges but adorned by a dense and homogeneous cover of minute spicules (Fig.
Type 1 – round shape (20–30 µm long) on body and furca (Fig.
Type 2 – oval shape (15–50 µm × 7–30 µm) on antennae, body and furca (Fig.
Type 3 – thin, elongated (20–40 µm × 5–8 µm) on ventral side of dens (Fig.
Antennal scales are of type 2 (25–35 µm long), oval, present dorsally only on Ant. I and II and ventrally on Ant. II, absent ventrally on Ant. I, and absent on Ant. III and IV (Figs
Ordinary chaetae are the most numerous chaetae on the body and appendages of Troglopedetes. They are well-diversified on antennae (Fig.
S-chaetae (sensu
Type 1–minute mic, thin, pointed and dark (3–4 µm) (Fig.
Type 2–short mic, thin, usually bent and dark mic (5–6 µm) (Fig.
Type 3–short mic, thin, rather curved apically and hyaline (5–6 µm) (Fig.
Type 4–short, hyaline and swollen mic (foliaceous sens) (5–6 µm) (Fig.
Type 5–short, thin, bent, hyaline mic (sometimes looks dark) (7–8 µm) (Fig.
Type 6–short, thin, erected and dark mic (6–12 µm) (Fig.
Type 7–rather long, bent, hyaline mic, thinner distally and broad basally (7–12 µm) (Fig.
Type 8–rather long, thin, erected and hyaline mic (sometimes looking dark) (10–15 µm) (Fig.
Type 9–long, subcylindrical, bent, hyaline mic (12–14 µm) (similar to type 10 but smaller and thinner) (Fig.
Type 10–long, subcylindrical, bent, hyaline and rather broad mic (10–15 µm) (Fig. 12G10); corresponding to antennal S-chaetae type l sensu
Type 11–long, thin, erected and dark mic (10–20 µm) (Fig. 12G11); corresponding to antennal S-chaetae type sensu
Type 12–long, thin and hyaline mic (24–30 µm) (Fig. 12G12); possibly corresponding to antennal S-chaetae type e sensu
Type 13– minute, pointed and dark mic (2 µm) (Fig.
Type 14–rather short, subcylindrical, bent, hyaline (6–8 µm) (Fig. 12G14).
Short, thick, dark, swollen at tip (4 µm) phanere with protecting chaeta, inserted dorso-internally ca. 20–50 µm from the apex (Fig.
In this study, ordinary chaetae on a single antenna numbered 483 for T. meridionalis sp. nov. and 518 for T. kae sp. nov. and were assigned to the 5 categories described above; 208 S-chaetae were numbered for T. meridionalis sp. nov. and 207 for T. kae sp. nov. and were assigned to the 14 morphological categories described above. (Tables
Detailed distribution of antennal chaetae. Presence in Verhoeffiella and Alloscopus by comparison with chaetal morphologies described by
Type of chaetae | Distribution on antenna | Location | Position on antennal segment | Number of chaetae | Presence in Verhoeffiella | Presence in Alloscopus | |
---|---|---|---|---|---|---|---|
T. meridionalis sp. nov. | T. kae sp. nov. | ||||||
Type 1 | Ant. III | dorsal | latero-proximal | 1 | 1 | × | × |
Type 2 | Ant. I | ventral | basal | 4 | 4 | – | – |
Ant. II | dorsal | basal | 2 | 2 | – | – | |
Type 3 | Ant. I | ventral | proximal | 2 | 2 | – | – |
Ant. II | ventral | proximal | 1 | 1 | – | – | |
Type 4 | Ant. III | dorsal | AIIIO | 2 | 2 | × | × |
Type 5 | Ant. I | ventral | all segment | 7 | 6 | × | × |
Ant. III | dorsal | AIIIO | 2 | 2 | – | – | |
Type 6 | Ant. I | dorsal | basal | 3 | 3 | × | × |
Type 7 | Ant. II | ventral | all segment | 3 | 7 | – | – |
Ant. III | dorsal | lateral | 0 | 2 | – | – | |
Ant. III | ventral | middle to proximal | 3 | 4 | – | – | |
Ant. IVa | dorsal | middle to proximal | 4 | 4 | – | – | |
Type 8 | Ant. I | ventral | all segment | 6 | 10 | – | – |
Ant. II | dorsal | middle to proximal | 9 | 8 | – | – | |
Ant. II | ventral | all segment | 9 | 9 | – | – | |
Ant. III | dorsal | all segment | 10 | 15 | – | – | |
Ant. III | ventral | middle to proximal | 11 | 6 | – | – | |
Ant. IVa | dorsal | all segment | 9 | 10 | – | – | |
Ant. IVa | ventral | all segment | 13 | 5 | – | – | |
Ant. IVb | dorsal | all segment | 9 | 9 | – | – | |
Ant. IVb | ventral | all segment | 11 | 0 | – | – | |
Type 9 | Ant. I | ventral | latero-proximal | 2 | 1 | – | – |
Ant. II | ventral | proximal | 2 | 4 | – | – | |
Type 10 | Ant. I | ventral | latero-proximal | 14 | 5 | × | × |
Ant. II | ventral | proximal | 2 | 5 | – | × | |
Ant. III | dorsal | upper middle | 0 | 1 | – | × | |
Ant. III | ventral | proximal | 1 | 4 | – | × | |
Ant. IVa | dorsal | middle to proximal | 1 | 3 | – | × | |
Ant. IVb | dorsal | middle | 2 | 3 | – | × | |
Type 11 | Ant. IVa | dorsal | latero-proximal | 0 | 1 | × | × |
Ant. IVb | dorsal | all segment | 19 | 22 | × | × | |
Ant. IVb | ventral | all segment | 35 | 36 | × | × | |
Type 12 | Ant. I | ventral | all segment | 8 | 6 | × | × |
Type 13 | Ant. IVa | dorsal | middle of Ant. IVa | 0 | 3 | – | – |
Type 14 | Ant. II | dorsal | proximal | 1 | 1 | – | – |
Subapical organite | Ant. IVb | dorsal | proximal near the tip | 1 | 1 | × | × |
Ordinary chaetae | Ant. I | dorsal | all segment | 13 | 28 | × | × |
Ant. I | ventral | all segment | 27 | 38 | × | × | |
Ant. II | dorsal | all segment | 63 | 67 | × | × | |
Ant. II | ventral | all segment | 68 | 77 | × | × | |
Ant. III | dorsal | all segment | 45 | 38 | × | × | |
Ant. III | ventral | all segment | 36 | 45 | × | × | |
Ant. IVa | dorsal | all segment | 62 | 59 | × | × | |
Ant. IVa | ventral | all segment | 53 | 60 | × | × | |
Ant. IVb | dorsal | all segment | 49 | 48 | × | × | |
Ant. IVb | ventral | all segment | 67 | 58 | × | × | |
Overall | 692 | 726 | ? | 945 |
Type of S-chaetae/antennal segment | Troglopedetes meridionalis sp. nov. | Troglopedetes kae sp. nov. | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Ant. I | Ant. II | Ant. III | Ant. IV | Total | Ant. I | Ant. II | Ant. III | Ant. IV | Total | |||
Ant. IVa | Ant. IVb | Ant. IVa | Ant. IVb | |||||||||
Type 1 | – | – | 1 | – | – | 1 | – | – | 1 | – | – | 1 |
Type 2 | 4 | 2 | – | – | – | 6 | 4 | 2 | – | – | – | 6 |
Type 3 | 2 | 1 | – | – | – | 3 | 2 | 1 | – | – | – | 3 |
Type 4 | – | – | 2 | – | – | 2 | – | – | 2 | – | – | 2 |
Type 5 | 7 | – | 2 | – | – | 9 | 6 | – | 2 | – | – | 8 |
Type 6 | 3 | – | – | – | – | 3 | 3 | – | – | – | – | 3 |
Type 7 | – | 3 | 3 | 4 | – | 10 | – | 7 | 6 | 4 | – | 17 |
Type 8 | 6 | 18 | 21 | 22 | 20 | 87 | 10 | 17 | 21 | 15 | 9 | 72 |
Type 9 | 2 | 2 | – | – | – | 4 | 1 | 4 | – | – | – | 5 |
Type 10 | 14 | 2 | 1 | 1 | 2 | 20 | 5 | 5 | 5 | 3 | 3 | 21 |
Type 11 | – | – | – | – | 54 | 54 | – | – | – | 1 | 58 | 59 |
Type 12 | 8 | – | – | – | – | 8 | 6 | – | – | – | – | 6 |
Type 13 | – | – | – | – | – | 0 | – | – | – | 3 | – | 3 |
Type 14 | – | 1 | – | – | – | 1 | – | 1 | – | – | – | 1 |
Overall S-chaetae | 46 | 29 | 30 | 27 | 76 | 208 | 37 | 37 | 37 | 26 | 70 | 207 |
Subapical organite | – | – | – | – | 1 | 1 | – | – | – | – | 1 | 1 |
Overall ordinary chaetae | 40 | 131 | 81 | 115 | 116 | 483 | 66 | 144 | 83 | 119 | 106 | 518 |
Total | 86 | 160 | 111 | 142 | 193 | 692 | 103 | 181 | 119 | 145 | 177 | 726 |
First antennal segment: eight types of S-chaetae are recognised (Figs
Second antennal segment: seven types of S-chaetae are recognised (Figs
Third antennal segment: six types of S-chaetae are recognised (Figs
Fourth antennal segment: five types of S-chaetae are recognised (Figs
Fourth antennal segment I (a): five types of S-chaetae are recognised: type 7, type 8, type 10, type 11 and type 13 (T. meridionalis sp. nov. has only three types while T. kae sp. nov. has all types), all present on the dorsal side.
Fourth antennal segment II (b): three types of S-chaetae are recognised: type 8, type 10, and type 11, all present on the dorsal side. Two types are present on the ventral side (type 8 and type 11).
The most frequent S-chaetae are type 8 and type 10 that are present all along antennal segments, followed by type 7 that was found on three antennal segments (Ant. II, III, IVa), but not on Ant. I. Type 2, type 3, and type 9 were found on only two segments (Ant. I and Ant. II). Type 5 was found on only two segments (Ant. I and Ant. III). Other types are all limited to a single antennal segment: Ant. I (type 6 and type 12), Ant. II (type 14), Ant. III (type 1, type 4) or Ant. IV (type 11, and type 13 in T. kae sp. nov.) (see Tables
With regard to the abundance of S-chaetae along antennal segments, type 8 is the most common followed by type 11 (Tables
The diversity of chaetal types was very similar in the two studied species, and between-species differences in the relative numbers of each chaetal type were limited, probably only reflecting individual variability. Similarities with Verhoeffiella and Alloscopus have been noted, but there was also many differences regarding the types of chaetae. It is not clear whether chaetal morphologies which seem special to one of the three genera are really taxon-specific receptors, or the result of undetected homologies due to different morphological evolution of some chaetae in the two genera. The only way to test these hypotheses will be to investigate thoroughly Entomobryoidea of other lineages.
The antennal phaneres of T. meridionalis sp. nov. and T. kae sp. nov. are arranged in a complex pattern. On the 20 morphological types of chaetae that we recognised (five types for ordinary chaetae, 14 types for S-chaetae and subapical organite of Ant. IV), 12 types were located at a fixed position on antennal segments (four types of ordinary mes; S-chaetae type 1, type 4, type 6, type 11, type 12, type 13, and type 14; subapical organite of Ant. IV) (Tables
It is rather common that Ant. II and III fuse together (Fig.
S-chaetae on antennal segments vary in number and probably type diversity, depending on size, age, and sex of Collembola, but this remains to be documented. They are also related to species ecology. Cave adapted species in particular are said to have more developed sensory structures than surface species (
Antennal chaetotaxic characters are widely used for the supraspecific taxonomy of Poduromorpha (
In a broader context, the complexity of chaetal types and distribution patterns described illustrate the functional complexity of arthropod antennae. Though information is lacking, chaetal pattern of distribution on antennae is probably mostly related to their function and the abiotic environment (light, soil, water, food) and interaction within communities. Antennal sensilla ultrastructure and functions in Collembola were studied by Altner’ team in several papers (e.g.,
We would like to thank Anne Bedos and two anonymous reviewers for many useful suggestions. We also thank Rueangrit Promdam, Areeruk Nilsai, and Kanchana Jantapaso for offering help in the field. This work is supported by Division of Biological Science, Faculty of Science, Prince of Songkla University, the National Science and Technology Development Agency (FDA-CO-2563-11031-TH), and the Thailand Research Fund (RSA6280063).