A new subgenus and new species of Orthocladius van der Wulp, with a phylogenetic evaluation of the validity of the subgenera of the genus (Diptera: Chironomidae)
Author
Saether, Ole A.
text
Zootaxa
2005
974
1
56
journal article
10.5281/zenodo.171314
9fcc3e54-c294-42b8-8f12-75919ae4f461
11755326
171314
Orthocladius
(
Mesorthocladius
)
lamellatus
sp. n.
(
Figs. 8–12
,
13–17
,
23, 24
,
31, 32
,
35, 36
)
Type
material
Holotype
ɗ reared from larva,
USA
: Ohio, Delaware Co., Olentangy R., N. of Winter Road,
5 ii
emerged
14 iii 1987
, M. J. Bolton (
ZMBN
Type
No. 406).
Paratypes
:
USA
: Ohio, Franklin Co., Sciota park, springstream, mature ɗ pupa reared from larva, mature Ψ pupa reared from larva,
26 iv 1987
, M. J. Bolton (
ZMBN
); Ohio, Franklin Co., springstream tributary to Sciota R.,
4 larvae
,
1 v 1986
, M. J. Bolton (
ZMBN
); Ohio, Delaware Co., Highbanks Metro Park, small stream, 1ɗ, mature ɗ pupa reared from larva,
3 larvae
,
4 iv 1987
,
26 iii 1989
. M. J. Bolton (
ZMBN
).
|
Etymology
|
|
From Latin,
lamella
, small
|
plate |
and |
atus
,
|
equipped |
with, |
referring |
to |
the |
presence |
of |
| labral lamellae in the larva. |
Diagnostic characters
The male imago is separable from the other species of the subgenus by having a well developed virga consisting of a cluster of spines combined with unibiserial scutellars, robust anal point and sensilla chaetica on both mid and hind leg. The pearshaped seminal capsule with apical rugulosity separates the female from other species. The pupa differs from other members of the subgenus by lacking pedes spurii B, from other members of the genus except
O. chuzesextus
by having median point band on tergites III and IV fused with posterior band and lacking apical spurs or lateral threads on the anal lobe. From
O. chuzesextus
it differs only by its larger size (
4.1–5.4 mm
versus 3.0–
3.6 mm
). The larva can be separated from other members of the genus by the presence of labral lamellae combined with a bifid premandible.
FIGURES 8–12.
Orthocladius
(
Mesorthocladius
)
lamellatus
sp. n.
, male imago, 8: head, 9: thorax, 10: wing, 11: hypopygium, 12: gonostylus, different view.
Male imago
(
n
= 2–3 except when otherwise stated)
Total length
4.49–4.57 mm
. Wing length
2.24–2.41 mm
. Total length/wing length 1.90–2.00. Wing length/length of profemur 2.60–2.76. Coloration dark brown with blackish brown vittae.
Head (
Fig. 8
). AR 1.95–2.28. Ultimate flagellomere 775–841 µm long. Temporal
setae
12–15, including 3–6 inner verticals, 6 outer verticals, and 3 postorbitals. Clypeus with 10– 12
setae
. Cibarial pump, tentorium and stipes as in
Fig. 8
. Tentorium 195–199 µm long, 56 µm wide. Stipes 165–184 µm long, 68 µm wide. Palpomere lengths (in µm): 41–47, 53– 64, 86–109, 75–90, 105–135.
Thorax (
Fig. 9
,
n
= 4). Antepronotum with 6–8, 7
setae
. Dorsocentrals 10–14, 12; anterior dorsocentral 15–79, 45 µm long, second 26–98, 71 µm long, third 86–106, 97 µm long; acrostichals 13–18(3); prealars 7–9, 8. Scutellum with 13–21, 17
setae
, unibiserial.
Wing (
Fig. 10
). Anal lobe moderately produced. VR 1.03 (1). Costal extension 15–17 µm long. Brachiolum with 1 seta, R with 9–10
setae
, other veins bare. Squama with 25–31
setae
.
Legs. Spur of front tibia 71–79 µm long, spurs of middle tibia 30 and 23–26 µm long, of hind tibia 75 and 23–24 µm long. Width at apex of front and middle tibia each 56 µm, of hind tibia
68 m
.
Pseudospurs present on ta1 of mid and hind leg, 23–34 µm long; one specimen with additional pseudospur on ta2 of mid leg. Sensilla chaetica 3 at 0.10–0.13 to 0.22–0.24 of ta1 of mid leg, 6–8 at 0.10–0.16 to 0.25–0.33 on ta1 of hind leg. Lengths (in µm) and proportions of legs:
| fe |
ti |
ta1 |
ta2 |
ta3 |
| p1 813–926 |
888–1153 |
614–756 |
357–482 |
293–331 |
| p2 756–954 |
888–1049 |
425–482 |
274–302 |
217–222 |
| p3 857–1068 |
1134–1276 |
605–671 |
394–416 |
284–302 |
| ta4 |
ta5 |
LR |
BV |
SV |
BR |
| p1 |
148–203 |
132–142 |
0.66–0.69 |
2.27–2.45 |
2.75–2.77 |
1.6–2. |
| p2 |
151 |
113–132 |
0.46–0.49 |
3.30 |
4.49–4.53 |
2.6–2.8 |
| p3 |
175–189 |
132–142 |
0.53 |
2.96–3.10 |
3.14–3.49 |
2.9–3.0 |
Hypopygium (
Figs. 11, 12
). Anal point 86–120, 109 µm long including triangular base; robust, tapering with rounded apex; with 10–14, 13
setae
including on base; laterosternite IX with 10–11, 11
setae
. Phallapodeme 53–86, 74 µm long; transverse sternapodeme 83–99, 95 µm long, oral projections moderately to well developed. Gonocoxite 308– 364, 342 µm long; superior volsella collarlike; inferior volsella with ventral part not extended beyond dorsal part.. Gonostylus 135–167, 152 µm long; crista dorsalis apical, rounded; megaseta 10–19 µm (3) long. Virga 26–36, 32 µm long; consisting of cluster of 7 spines. HR 2.18–2.37, 2.26; HV 2.74–3.12 (2).
Female imago
(
n
= 1 mature pupa)
Total length about
4.10 mm
. Coloration apparently not as dark as in male.
Head. AR 0.75. Flagellomere lengths (in µm): 56, 38, 38, 49, 154. Coronal suture 56 µm long. Temporal
setae
not measurable. Clypeus with 14
setae
. Tentorium 150 µm long, 41 µm wide. Palpomere lengths (in µm): 38, 45, 70, 86, 90.
Thorax. Dorsocentrals 12, acrostichals 11, prealars 6. Scutellum with 13
setae
.
Wing. Squama with 25
setae
.
Legs not measurable.
FIGURES 13–22.
Orthocladius
(
Mesorthocladius
)
spp., female imagines, genitalia, 13–17:
O.
(
M.
)
lamellatus
sp. n.
, 13: ventral view, 14: ventrolateral lobe, 15: dorsomesal lobe, 16: apodeme lobe, 17: dorsal view, 18–22:
O.
(
M.
)
nimidens
sp. n.
, 18: ventral view, 19: ventrolateral lobe, 20: dorsomesal lobe, 21: apodeme lobe, 22 dorsal view.
Abdomen. Tergite VIII with 32
setae
, sternite VIII with 23
setae
.
Genitalia (
Figs. 13–17
). Tergite IX divided, with 24
setae
. Gonocoxite with 19
setae
. Cercus 131 µm long. Seminal capsule pearshaped with apical rugulosity, 84 µm long, 53 µm wide. Spermathecal ducts with one bend and separate openings. Notum 98 µm long.
Pupa
(
n
= 3–4 except when otherwise stated)
Total length
4.16–5.39 mm
. Exuviae pale greyish brown with brownish apophyses.
FIGURES 23–27.
Orthocladius
(
Mesorthocladius
)
spp., pupae, 23:
O.
(
M.
)
lamellatus
sp. n.
, tergites, 24: thoracic horn, 25–27:
O.
(
M.
)
nimidens
sp. n.
, 25: tergites, 26: thoracic horn, 27: frontal apotome.
Cephalothorax. Frontal
setae
143–150 µm long. Thoracic horn (
Fig. 24
) 270–428, 340 µm long; 41–53, 49 µm wide; 4.14–8.77, 7.00 times as long as wide; 1.16–1, 54, 1.35 times as long as anal macrosetae. Precorneal
setae
respectively 94–128, 105 µm; 150–171, 166 µm; and 68–101, 91 µm long. Anterior dorsocentral (Dc1) 79–90, 83 µm long; Dc2, 49–79, 66 µm; Dc3 56–75, 71 µm; and Dc4 64–83, 71 µm long. Distances (in µm): Dc1– Dc
2 26–49
, 40; Dc2–Dc3 98–131, 113; Dc3–Dc
4 19–34
, 24.
Abdomen (
Fig. 23
). Tergite I bare, tergite II with weak mediolateral shagreen, stronger posterior shagreen on tergites III–VII, shagreen relative extensive on tergites VIII–IX. Shagreen spinules about equal in size, anterior and posterior bands joined, anterior band not extending as far lateral as posterior bands. Sternites I and IX bare; II–III with anterolateral plus posterolateral shagreen, IV with lateral, V–VII with lateral plus anterolateral, VIII with anterolateral shagreen. Pedes spurii A on sternites IV–VII. Pedes spurii B absent. Caudal hooklets on tergite
II 46
–69, 57; in 3 rows. Segments II–V each with 3
L setae
, VI and VII each with 3–4, and VIII with 4
L setae
. Lengths of L1–L4
setae
on segment VIII (in µm) as: 64–113; 75–124, 98; 38–116, 65; 68–101, 85. Occasionally a forked V seta present on sternite III.
Anal lobe 364–443, 400 µm long. Anal macrosetae subequal in length; 225–278, 249 µm long; 0.59–0.64, 0.62 as long as anal lobe. Male genital sac overreaching anal lobe by 30 µm (2), female genital sac ending 105 µm short of apex of anal lobe.
Fourth instar larva
(
n
= 9–11 except when otherwise stated)
Total length 4.68–8.60,
6.06 mm
. Head capsule 0.44–0.50,
0.47 mm
long. Postmentum 195–212, 203 µm long. Head capsule dark brown.
Head. Antenna as in
Fig. 31
. Length of antennal segments (in µm): 49–64, 55; 12–15, 13; 4–7, 5; 3–4, 4; 3–4, 4. AR 1.75–2.32, 1.96. Ring organ 10–19, 15 µm from base; basal setal mark 14–22, 19 µm from base; apical setal mark 20–37, 26 µm from base. Basal antennal segment 19–23, 20 µm wide; blade 20–26, 23 µm (7) long; accessory blade12– 17, 15 µm (7) long. Lauterborn organs 5–9, 7 µm long; style 5–9, 7 µm long. Two labral lamellae (
Fig. 32
) each with 3–7, 5 spines. With 12 chaetae and 2–3 spinulae. One pair of chaetulae laterales slightly serrated, chaetulae basales tapering, bifid, with 1 long and 1 short apical tooth. Premandible (
Fig. 32
) bifid, 79–109, 89 µm long; brush consisting of 11–16, 14 (7) spines present. Mandible (
Fig. 35
) 146–165, 157 µm long, without seta interna. Mentum (
Fig. 36
) 120–144, 133 µm wide; median tooth 19–23, 20 µm wide; ventromental plate 4–12, 8 µm wide; with 5–7, 7
setae
underneath on cardo.
Abdomen. Claws of anterior parapods strongly serrated. Longest body
setae
131–278, 186 µm long. Posterior parapods 293–450, 352 µm (7) long. Procercus 38–53, 46 µm high; 34–45, 41 µm wide. Anal
setae
506–675, 595 µm long; supraanal seta 64–105, 84 µm (7) long, 0.11–0.20, 0.15 (8) as long as anal
setae
. Longer anal tubules 150–278, 183 µm (6) long, 56–83, 72 µm (4) wide at base; shorter anal tubules 113–184, 153 µm (6) long, 41– 60, 54 µm (7) wide at base.
FIGURES 28–34.
Orthocladius
spp., larvae, 28:
Orthocladius
(
Mesorthocladius
)
frigidus
(Zetterstedt)
labrum, epipharyngeal area and premandible, 29, 30:
Orthocladius
(
Orthocladius
)
nitidoscutellatus
Lundström
, 29: antenna, 30: labrum, epipharyngeal area and premandible, 31, 32:
Orthocladius
(
Mesorthocladius
)
lamellatus
sp. n.
, 31: antenna, 32: labrum, epipharyngeal area and premandible, 33–34:
Orthocladius
(
Mesorthocladius
)
nimidens
sp. n.
, 31: antenna, 32: labrum, epipharyngeal area and premandible.
Comments
The pupa of this species shows no synapomorphies with the other members of the subgenus and is practically inseparable from
O.
(
Orthocladius
)
chuzesextus
. However, the male imago has the characteristic anal point of the other species except
O.
(
M.
)
nimidens
and the larva shares several apparent synapomorphies such as presence of labral lamellae, absence of seta interna, and bifid premandible with one or more of the other species of the genus. The phylogenetic placement of this and the next species, however, cannot be regarded as completely ascertained.
Ecology and distribution
The species is known only from Ohio, inhabiting small streams and seeps.