Research Article |
Corresponding author: José Palacios Vargas ( troglolaphysa@hotmail.com ) Academic editor: Louis Deharveng
© 2016 Vladimír Papáč, José Palacios Vargas.
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:
Papáč V, Palacios-Vargas JG (2016) A new genus of Neelidae (Collembola) from Mexican caves. ZooKeys 569: 37-51. https://doi.org/10.3897/zookeys.569.5984
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The new genus Spinaethorax, whose proposal is based on specimens of Megalothorax spinotricosus Palacios-Vargas & Sánchez, 1999, is given a new name combination and a redescription. The type species comes from two caves in Campeche State, México. A new combination is also suggested for Megalothorax tonoius Palacios-Vargas & Sánchez, 1999. The new genus is similar to Megalothorax Willem, 1900 and Neelus Folsom, 1896, but it clearly differs from all genera within family Neelidae by a peculiar combination of characters and the presence of some new features, e.g. globular sensillum on Ant. III, sword-like macrosetae on oral fold. A comparative table and an identification key for all Neelidae genera as well as some summary tables of antennae chaetotaxy and legs setation for type species are provided.
Neelidae , Taxonomy, Mexico
The family Neelidae comprises five genera and 41 species in the world. However, only 9 species in 3 genera are known from Mexico (
Members of this family are cosmopolitan. Therefore, they have been found in various localities mainly associated with soil and litter at different altitudes from sea shore up to 3,000 m a.s.l. (
The most remarkable contribution on this family from Mexico is the work by
The present redescription of Megalothorax spinotricosus Palacios-Vargas & Sánchez, 1999, is based on original slides deposited in Facultad de Ciencias,
Body length was measured on slides excluding antennae and furcula. Lengths of unguis and unguiculus were measured between the most basal (proximal) point and the tip on their inner margins. Besides the common measurements, the ratio “unguis I, II, III (inner margin): Ti. I, II, III width (middle part)” that can be used as additional character, was also included.
We followed nomenclature used in last Neelus revision (
Abbreviations: Ant.—antennal segment; Th.—thoracic segment; Abd.—abdominal segment; Ti.—tibiotarsus; scx—subcoxae; s.f.—sensory field; wrc—free wax rod generating crypt; s1, s2, s3, s3´—swollen sensilla; dp—proximal part of dens; dd—distal part of dens;
A genus of the Neelidae Folsom, 1896 with the following diagnostic characters:
Habitus of Neelidae. Small size, about 0.6 mm. Color white. Tegumentary grain fine and uniform. Apex of head with sword-like spines, body with several such spines, mainly around sensorial fields. Ant. III and IV fused and Ant. III with small globular sensillum in proximal position. Anterior labral setae R1 and R2 thick, curved and smooth. Oral fold with 1+1 sword-like macrosetae. Basomedian field of labium furnished with 6+6 setae. Presence of 3 setae around abdominal sensory fields, no E3 spine/setae on dd. Mid abdomen with swollen sensilla s3 and s3´. Base of Abd. IV sternite with 1+1 neosminthuroid setae, smooth and with pointed tip.
Spinaethorax spinotricosus (Palacios-Vargas & Sánchez, 1999), comb. n.
Figs
Spinaethorax spinotricosus. 6 thoracic and abdominal chaetotaxy with abdominal sensory field enlarged 7 ventral tube in lateral view 8 tenaculum 9 male genital plate in lateral view, arrow shows anterior direction 10 female genital plate frontal view, av—anal valve setae, nch—neosminthuroid setae.
Holotype: female mounted on slide. Original label: 23/00/1991, Mexico, Campeche, Cueva Xtancumbilxunaan (cave), 29.xii.1996, A. Ruíz and S. Aguilar col., ext. soil. Paratypes: 1 female on slide, 23.viii. 1991, J. G. Palacios col., direct collection and 2 juveniles on slides, the same data as the holotype. Type material deposited at Facultad de Ciencias,
Mexico, Campeche, Cueva Actún Guachapil (cave), 1 male, 1 female and 2 juveniles on slides. Original label: 14/iv/2012, 22.iii.1997, A. Ruiz and S. Aguilar col., ext. guano; 1 female on slide, 29.v. 1997, J. G. Palacios col., ext. guano. Material deposited at Facultad de Ciencias,
Unpaired seta a0 between antennal basis. Labral chaetae R1 and R2 thick, curved and smooth. Oral fold with 1+1 sword-like macrosetae. Basomedian field of labium with 6+6 setae. Ant. III with small globular sensillum. Manubrium with 4+4 posterior setae. Mucro with both lamellae serrated and with rounded tip.
For lengths of different character see Table
Lengths (µm, mean in parenthesis) of different morphological characters of Spinaethorax spinotricosus comb. n. (male, females and juvenile separately).
Body part | Spinaethorax spinotricosus comb. n. male | Spinaethorax spinotricosus comb. n., females | Spinaethorax spinotricosus comb. n., juvenile |
---|---|---|---|
Body total | 520 | 530–720 (605) | 350–500 (445) |
Head width | 135 | 133–215 (162) | 100–130 (121.2) |
Head length | 170 | 183–237 (209) | 130–167 (154.8) |
R1 labrum | 8 | 9–12 (10) | 7–8 (7.6) |
R2 labrum | 10 | 10–14 (11.5) | 8–10 (9.3) |
Antenna | 120 | 125–145 (132.6) | 94–112 (106.3) |
Ant. I | 10 | 11–13 (11.4) | 9 |
Ant. II | 23 | 25–30 (26.4) | 18–23 (21.6) |
Ant. III–IV | 87 | 90–104 (97.5) | 67–81 (76) |
Ant. IV sensillum Sy | 16 | 16–18 (16.6) | 10–12 (11.3) |
Ant IV macrosensilla S | 23–29 | 20–32 (23–31) | 14–24 (14.8–22.6) |
Tibiotarsus I width | 17 | 17–18 (17.5) | 15–17 (16.4) |
Tibiotarsus II width | 17 | 16–19 (16.8) | 14–17 (16) |
Tibiotarsus III width | 17 | 16–19 (17.4) | 16–18 (16.5) |
Unguis I | 27 | 26–33 (28.7) | 18–23 (21.2) |
Unguis II | 25 | 24–30 (26.3) | 16–21 (19) |
Unguis III | 23 | 23–30 (25) | 15–21 (18.8) |
Unguiculus I | 14 | 13–16 (14.1) | 10–12 (11.2) |
Unguiculus II | 14 | 14–18 (15.5) | 10–12 (11) |
Unguiculus III | 15 | 14–18 (16.1) | 9–13 (11.5) |
Manubrium | 54 | 56–66 (60.3) | 35–45 (42.5) |
Dens (proximal part, dp) | 32 | 29–36 (32.3) | 20–26 (23.3) |
Dens (distal part, dd) | 56 | 66–83 (71.2) | 41–57 (55.6) |
Mucro | 67 | 65–87 (73.6) | 42–58 (53.4) |
Mucro width (middle part) | 6 | 7–9 (7.7) | 5–7 (6.1) |
Macroseta on oral fold | 25 | 25–30 (28) | 18–23 (21) |
Spines IL1 on head | 37 | 35–42 (37.3) | 28–30 (28.8) |
Spines IL2 on head | 33 | 28–36 (31.1) | 21–26 (23.9) |
Spines IL3 on head | 30 | 28–33 (29.8) | 17–25 (22.5) |
Spines IL4 on head | 20 | 17–21 (18.1) | 12–15 (14) |
Head. Head length and width 215 and 145 µm, respectively. No eyes. Head with smooth, pointed ordinary setae and spines of different width and length (Fig.
Thorax and abdomen (Fig.
Appendages. Ant. III and IV not separated (Fig.
Spinaethorax spinotricosus comb. n. | ||||
---|---|---|---|---|
Chaetae | S | Sg | Misc | |
Ant. I | 3 | 0 | 0 | |
Ant. II | 6 | 0 | 0 | |
Ant. III | 15 | 0 | 0 | 2 Sensory organs, 1 spine-like chaeta, 1 globular sensillum Sg, 1 leaf-like sensillum Sg |
Ant. IV | 13 | 13 | 0 | 1 Sx; 1 Sy; 1 Or; 1a; 1sa |
Spinaethorax spinotricosus comb. n. | |||
---|---|---|---|
Leg I | Leg II | Leg III | |
Subcoxae I | 1 | 1 | 3 |
Subcoxae II | 1 | 1 | 1 |
Coxae | 1 | 1 | 2 |
Trochanter | 4 | 3 | 3 |
Femur | 8 | 8 | 8 |
Tibiotarsus | 13 | 14 | 13 |
Sensory fields (Figs
Both sexes known.
The genus is named after the spine-like setae on thorax and abdomen.
Spinaethorax spinotricosus is currently known from two caves and is putatively spread in the cave systems of Yucatán Peninsula, mainly in places with accumulation of bat guano or other type of rich organic material.
The young have only one proximal seta on dens.
This species, described from a cave in State of Guerrero, shares with new type species of the genus similar generic characters like presence of sword-like macrosetae on oral fold, globular sensillum on Ant. III., stouter spines on Th., fusion of Ant. III and IV, 3+3 setae around Abd. s.f., 2+2 setae on proximal part of dens and absence of E3 spine on distal part of dens. The main differences consist in setation of hind Abd. (numerous thickened macrosetae in S. tonoius comb. n. vs. numerous spine-like microsetae in S. spinotricosus comb. n.), in chaetotaxy of the apex of head (only one spine IL 1 in S. tonoius comb. n. vs. three spines IL 1–IL 3 in S. spinotricosus comb. n.), in the structure of tenent hairs on Ti. (more developed in S. tonoius comb. n. vs. shorter in S. spinotricosus comb. n.) and in setation around Abds.f. (absence of axial spine in S. tonoius comb. n. vs. presence of spine in S. spinotricosus comb. n.). Species description is based only on one adult specimen (holotype) and does not allow us to describe it in an appropriate way, along with drawings and measurements.
The family Neelidae was for a long time an overlooked group of Collembola, mainly due to its small size and lack of diagnostic characters. In spite of the foregoing facts recent years molecular phylogenetic analysis have revealed unexpected diversity within this family (
Character | Megalothorax Willem, 1900 | Neelides Caroli, 1912 | Neelus Folsom,1896 | Zelandothorax Delamare Deboutteville & Massoud, 1963 | Acanthoneelidus Bretfeld & Griegel 2006 | Spinaethorax gen. n. |
---|---|---|---|---|---|---|
Sensory fields | yes | no | yes | yes | yes | yes |
Ant. III/IV fused | yes | no | no | yes | no | yes |
Retinaculum teeth | 3+3 or 4+4 | 2+2 | 3+3 | 4+4 | 4+4 | 3+3 |
Neosminthuroid chaetae at the base of Abd. IV sternite | 2+2 | 4+4 or 5+5 | 1+1 | 2+2 | 1+1 | 1+1 |
Dental proximal setae (dp) | 1 | 1 | 2 | 1 | 1 | 2 |
Nr. of setae on basomedian field of labium | 3+3 or 4+4 | 2+2 | 4+4 | - | - | 6+6 |
E3 spine/chaeta on distal part of dens (dd) | no | yes | yes | no | no | no |
Nr. of setae around Abd. sf | 5 | absent sf | 2 | - | 5 | 3 |
The identification key is based on that of
1 | Head and body with well developed sensory fields; R1 labrum setae shorter than R2; labrum without apical fringes and split structures; retinaculum with 3+3 or 4+4 teeth | 2 |
– | Large sensory fields absent; R1 labrum setae longer than R2; labrum with apical fringes and split structures; retinaculum with 2+2 teeth | Neelides Caroli, 1912, type species Neelides folsomi Caroli, 1912; Italy |
2 | Dens with short conical spines posteriorly; median labral setae present; a-row of labrum with 4 or 6 setae | 3 |
– | Dens with broad triangular spines posteriorly; median labral setae missing; a-row of labrum with 5 setae | Zelandothorax Delamare Deboutteville & Massoud, 1963, type species Megalothorax novozealandiae Salmon, 1944 (New Zealand) |
3 | Ant. III and IV not separated | 4 |
– | Ant. III and IV separated with suture | 5 |
4 | Sensory fields of abdomen with 5 marginal setae; 2+2 neosminthuroid setae; basomedian field of labium with 3+3 or 4+4 setae; proximal part of dens with one seta | Megalothorax Willem, 1900, type species Megalothorax minimus Willem, 1900; Belgium |
– | Sensory fields of abdomen with 3 marginal setae; 1+1 neosminthuroid setae; basomedian field of labium with 6+6 setae; proximal part of dens with two setae | Spinaethorax gen. n., type species Spinaethorax spinotricosus comb. n. (Mexico) |
5 | Sensory fields of abdomen with 2 marginal setae; apex of head without spines; proximal part of dens with two setae (only N. fimriatus with one seta) | Neelus Folsom, 1896, type species Neelus murinus Folsom, 1896; United States of America |
– | Sensory fields of abdomen with 5 marginal setae; apex of head with blunt spines; proximal part of dens with one seta | Acanthoneelidus Bretfeld & Griegel, 2006, type species Acanthothorax pratensis Bretfeld & Griegel, 1999 (Poland) |
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