Redescription of Isotomiella alulu and I. delamarei (Collembola: Isotomidae) with notes on the systematics of the genus and new records from the Neotropics
Author
Kováč, Ľubomír
Author
Palacios-Vargas, José G.
text
Zootaxa
2008
1825
1
17
journal article
10.5281/zenodo.183085
2485506d-675c-4e5a-a306-53621ed4188b
1175-5326
183085
Isotomiella alulu
Christiansen & Bellinger, 1992
Figs 1–7
Diagnosis.
Body length 0.8–1.0 mm. Integument with distinct craters from Abd.IV to Abd.VI. Ant. IV with 34–42 thin subcylindrical sensilla in addition to 6 ovoid ones. Posterior margin of head with ciliated setae. Axial setae pattern 22,14 (16)/6,6,6,6 by half-tergum from Th. II to Abd. IV. Ventro-lateral area on Abd.II devoid of setae. Sensillar pattern 32/11212 by half-tergum from Th.II to Abd. V+VI; sensillum
spl
on Abd. V+VI 1.5 times of the length of unguis III. Ti.III with 2 strongly thickened apical spines. Subcoxae furcalis anterior/posterior with 10–12/7 setae; manubrium with two pairs of unequal ventro-distal setae; dens with 17– 19 ventral and 5 dorsal setae. Mucro bidentate.
Redescription.
Body length 0.8–1.0 mm (adult females). Colour white, habitus of
I. nummulifer
Deharveng & Oliveira, 1990
. Integument from Abd. IV to Abd. VI dorsally with many distinct craters (
Fig. 4
), 1.0– 1.5 times broader than diameter of macrosetae (1.5–5.5 Μm). Anterior abdominal segments with indistinct, or completely absent craters. Secondary granules and integumentary channels absent. Pseudopora distinct on Th. II.–Abd. IV.
Head. Labral setae pattern 4/554. Labrum with 4 anterior spinules, antero-lateral setae weakly thickened, setae in two distal rows (9) slightly thicker than those in proximal one (5). External lobe of maxilla with bifurcate palp, without ciliated setae and with 3 sublobal setae. Antennae (0.2 mm) 3.8–4.2 times shorter than body and apparently longer than head (0.16 mm). Length of Ant. I, II, III and IV as 26, 45, 45 and 85 μm. Ovoid sensilla
S1–S6
of Ant. IV subequal (8 μm); numerous supplementary thin sensilla present, 22–27 dorsal and 12–15 ventral (
Figs 1 and 2
). Ant. III organ with 2 small sensory rods, 3 short guard sensilla in position 1, 4 and 5 and additional sensillum
s´
. Ant. II with sensillum
s´
. Ant. I with 15–17 smooth ordinary setae, 2 basal microsetae and 2 unequal ventral sensilla:
S
(8 μm) and
s
(5 μm). Posterior margin of head with ciliated setae (
Fig. 3
), mesosetae
p1–p
3
in p-row always ciliated, additional 2–3 setae in
pp
-row eventually ciliated (usually
pp2, pp4
and
pp6
).
FIGURES 1–7.
Isotomiella alulu
Christiansen & Bellinger, 1992: 1
, Ant. IV and tip of Ant. III, dorsal view (full circle: position of long and narrow sensillum); 2, Ant. IV and tip of Ant. III, ventral view; 3, setal pattern of posterior part of head, dorsal view; 4, Abd. IV-VI, dorso-lateral view; 5, tibiotarsus, unguis and unguiculus of leg III; 6, subcoxae furcalis anterior and posterior; 7, furcula (left side in dorsal, right side in ventral view) and tip of dens with mucro in detail.
Terga. Axial setae pattern from Th. II to Abd. IV: 22,14(16)/6,6,6,6. Macrosetae long, ciliated, 1,2/2,3,4,4 by half-tergum from Th. II to Abd. IV. Both ciliated and smooth mesosetae present on terga: Th. II and III with 5–7 lateral setae ciliated, others smooth; Abd. I with most setae smooth; Abd. II and III with most dorsal setae ciliated, latero-ventral setae smooth; Abd. IV with most setae smooth, Abd. V+VI with dorsal setae smooth, some lateral setae ciliated. On Abd. II ventro-lateral area devoid of setae. Abd. V+VI with 7 microsetae („mesosetae
gl
“ after Deharveng & Oliveira 1990). Unpaired setae of Abd.V+VI:
a0
microseta (5 μm),
m0
and
p0
mesosetae (18 μm), all smooth. Mesoseta
p2
of Abd.VI slightly shorter than
p1
(23 and 26 μm respectively,
Fig. 4
), both smooth or indistinctly ciliated. Sensillar formula of the
nummulifer
-
type
: 32/11212 (
ms
: 12/00000;
s
: 20/11212) by half-tergum from Th.II to Abd. V+VI. Sensillum
sl3
on Th. II has migrated towards the anapleurum. Sensillum
spl
of Abd. V thick and long (18 μm). All posterior setae on anal valves smooth.
Appendages. Setae numbers from leg I to III (ciliated setae in parenthesis): anapleura 1(1), 2(1), 4(3); katapleura 1(1), 6(3), 7(3); coxae 2, 10(2), 12(2); trochantera 10, 10, 10; femora 20, 24, 26(0–3) and tibiotarsi 28, 28, 31–32. Ti. I with 7 setae in the proximal whorl. Ti. III with 2 strongly thickened apical spines (
Fig. 5
). No spine-like setae on femora, trochantera or pleura. Unguis and unguiculus (18 and 12 µm) of normal shape (not elongated), untoothed. Tubus ventralis with 4+4 distal, 3+3 anterior and 2+2 posterior setae. Retinaculum with 4+4 teeth and 1 seta on the rami. Subcoxae furcalis anterior with 10–12 setae (6–9 ciliated), subcoxae furcalis posterior with 7 setae (5–7 ciliated,
Fig. 6
). All setae on manubrium and dentes smooth. Manubrium (45 µm) with 2+2 unequal ventro-distal setae placed in transversal row, 2+2 lateral and 19–22 + 19–22 dorsal setae. Ventro-proximal setae on manubrium absent. Dens (125 µm) with 17–19 ventral (distal one distinctly longer) and 5 thin dorsal setae. Mucro (8 µm) bidentate (
Fig. 7
). Basal hooks of dens normal.
Only females known.
Variability.
At the posterior margin of head
p1–p3
mesosetae of
p
-row are always ciliated (sometimes also
p5, p6
and
p7
). In
pp
-row 2 or 3 setae are ciliated (
pp2
,
pp4
or also
pp6
). One specimen from
Ecuador
with dorso-external sensillum in the middle of the Ant.IV clearly thicker than other ordinary dorsal sensilla.
Type
material.
Holotype
(female) on slide Nr. 6738, Hawaii, Oahu Island, Manoa Falls Trail, ohia fern scrub forest, soil,
3.viii.1986
, K. Christiansen lgt., 3
paratypes
on slides (2 ex. Nr.6743, 1 ex. Nr. 6745) with the same collecting data.
Type
material kept in the Bishop Museum, Honolulu, Hawaii,
U.S.A.
Other material.
HAWAII. Oahu island: Aiea Loop Trail, forest in soil and under bark,
4.viii.1986
, K. Christiansen lgt. (Nr. 6749a–3 ex., Nr. 6749b–3 ex., Nr. 6754–3 ex.); Haiku Stairs; scrub and grass,
5.viii.1996
, K. Christiansen. lgt. (Nr. 6764–4 ex.); Manoa Falls Trail, litter, P. Bellinger lgt.,
23.ix.1996
(Nr. 4766–4 ex.); Waahila Ridge Recreational Area (Honolulu),
Casuarina
grove, soil,
6.viii.1986
, K. Christiansen.lgt. (Nr. 6770–4 ex.); Waianae Kai,
7.viii.1996
, kukui grove, soil, K. Christiansen lgt. (Nr. 6784–3 ex.).
Kauai island: Hanalei Walley State Conservation Area, dry forest, under bark,
25.vii.1986
, K. Christiansen lgt. (Nr. 6728–2 ex.); Kapaa, forest reserve,
26.ix.1980
, litter under paper bark tree and moss on hau tree,
26.ix.1980
, L.M. Goff lgt. (Nr. 5202–4 ex., Nr. 5207–6 ex.); Kapaa, cane field area, moss on paper bark tree,
26.ix.1980
, L.M. Goff lgt. (Nr. 5203–1 ex.).
All specimens from Hawaii are kept on slides and deposited in the Bishop Museum, Honolulu,
U.S.A.
, except slides Nr. 6728 and Nr. 6784 deposited at the Grinnell College, Grinnell, Iowa,
U.S.A.
MEXICO
. Chiapas, Biological Station Chajul, litter,
20.x.1993
. G. Ríos and R. Villavicencio lgt. (1 ex.) Campeche: Actún Guachapil, seeds, guano and fruits,
22.3.1997
, A. Ruiz lgt. (2 ex.) Veracruz: Grutas de Atoyac, soil,
6.xii.1981
, V. Granados lgt. (1 ex.); Palma Sola, rotten trunk,
5.vi.1976
, J. G. Palacios lgt. (1 ex.).
GUATEMALA
. Alta Verapaz, tropical rain forest, soil, 1976, G. Kramer lgt. (1 ex.).
NICARAGUA
. León, Izapa, soil and leaf litter,
16.vi.1986
. J. G. Palacios lgt. (7 ex.).
ECUADOR
. Los Tayos (Eastern foothills of S. Andes), seed deposit from oil bird faeces (
Steatornis caripensis
),
1.vii.1976
. P. Ashmole lgt. (1 ex.).
Discussion.
By the presence of 2+2 ventral manubrial setae and 2 mucronal teeth
Isotomiella alulu
Christiansen & Bellinger, 1992
is related to
I. spinifer
Deharveng & Oliveira, 1990
,
I. nummulifer
Deharveng & Oliveira, 1990
,
I. fellina
Mendonça & Fernandes, 2003
and
I. delamarei
Barra, 1968
. Differential characters of the redescribed species and the closely related ones are listed in
Table 1
.
TABLE 1.
Differential diagnosis of the
Isotomiella
species with 2+2 ventral manubrial setae and 2 mucronal teeth (Me,
Ma––ciliated meso-, macrochaeta; mi, me, ma––smooth micro-, meso-, macrochaeta)
Character
I. spinifer
I. nummulifer
I. alulu
I. fellina
I. delamarei
Deharveng & Deharveng & Christiansen & Mendonça &
Barra, 1968
Oliveira, 1990 Oliveira, 1990 Bellinger, Fernandes, 1992 2003
Body length (mm) 0.7–0.75 0.5–0.9 0.8–1.0 0.4–0.5 0.9–1.0
I. alulu
is closely related to
I. nummulifer
, differing by the following characters: longer body: 0.9–1.0 mm (0.5–0.9 mm in
I. nummulifer
), high number of fine supplementary sensilla on Ant. IV: 34–42 (around
10 in
I. nummulifer
), axial setae pattern formula 22,14/6,6,6,6 by half-tergum from Th. II to Abd. IV (22,14/4,4,4,6 in
I. nummulifer
), macrosetae formula 1,2/2,3,4,4 by half-tergum from Th. II to Abd. IV (1,1/1,2,4,4 in
I. nummulifer
), the ratio of sensillum
spl
(Abd. V+VI) to
GIII
: 1.5 (1.0 in
I. nummulifer
), 19–22 dorsal setae on manubrium by half side (
12–15 in
I. nummulifer
), and 17–19 ventral setae on dens (
19–24 in
I. nummulifer
).
| Labrum - antero-external spines |
+ |
- |
- |
- |
+ |
| Ant.I - ordinary setae |
15–16 |
16–18 |
15–17 |
16 |
16–17 |
| Ant.IV - supplementary sensilla |
3–4 |
10 |
34–42 |
9 |
8 |
| Head - ciliated setae |
- |
+ |
+ |
? |
- |
| Th.II–Abd.IV - axial chaetotaxy |
20-22,14/6,6,6,6 |
22,14/4,4,4,6 |
22,14/6,6,6,6 |
20,14/4,4,4,6 |
18,12/6,6(8),8,8 |
| Th.II–Abd.IV – macrochaetae |
? |
1,1/1,2,4,4 |
1,2/2,3,4,4 |
1,1/1,3,3,4 |
1,1/3,3,3,4 |
| Th.II–Abd.V - sensilla |
3,2/1,1,2,1,2 |
3,2/1,1,2,1,2 |
3,2/1,1,2,1,2 |
3,2/1,1,2,1,2 |
3,2/0,0,1,3,5 |
| Abd.VI - setae a0, m0, p0 |
me, ma (Ma), me |
mi, me, me |
mi, me, me |
mi, me, me |
Me, Ma, Me |
| Ratio sensillum spl (Abd.V–VI) / GIII |
1.1 -1.2 |
1.0 |
1.5 |
0.4 |
1.3 |
| TiIII - thick tenent setae |
+ |
+ |
+ |
- |
- |
| Tubus ventralis - posterior/anterior/distal setae |
2+2/3+3/ 4–6+4–6 |
2+2/3+3/4+4 |
2+2/3+3/4+4 |
5/3+3/4+4 |
5+5/3+3/2+2 |
| Retinaculum - setae |
1 |
1–3 |
1 |
1 |
1 |
| Manubrium - ventral/lateral setae |
1–2 /? |
2 / 2 |
2 / 2 |
2 / 2 |
2 / 0 |
| Subcoxa furcalis anterior/poste- rior setae |
7–9/6–7 |
10–15/7–10 |
10–12/7 |
12/7 |
5–9/6–8 |
| Dens - ventral/dorsal setae |
10–14/2 |
19–24/5 |
17–19/5 |
19–21/5 |
10–12/4 |
| Ratio: dens/GIII |
4.5 |
8.0–8.5 |
6.9 |
5.5–7.1 |
3.6 |
| Cuticle ornamentation (Abd.IV– VI) |
craters |
craters |
craters |
- |
- |
| Abd.II - setae in lateral field |
? |
? |
absent |
? |
reduced |
Geographic distribution.
From the list of
I. alulu
localities provided in this paper indicates that the species is not endemic to the Hawaii Islands. Its distributional range is much greater, covering also Central and at least northern part of South
America
, most-probably majority of the Neotropical biogeographic region. Such an example of affinity of Hawaiian
Collembola
to the Neotropics is interesting, since
Christiansen and Bellinger (1994)
pointed out that Hawaiian fauna of
Collembola
appears to have been recruited primarily from North
America
and temperate Asia. However, it is also possible that
I. alulu
has pantropical distribution range similarly as closely related
I. nummulifer
. The species was cited previously as
Isotomiella minor
from
Nicaragua
(
Maes & Palacios-Vargas 1988
).