Redescription of the last instar larva and pupa of Bezzia roldani (Diptera: Ceratopogonidae)
Redescripción del último estadio larval y de la pupa de Bezzia roldani (Diptera: Ceratopogonidae)
Ronderos, Maria M., Gustavo R. Spinelli And Florentina Diaz
División Entomología Museo de La Plata, Paseo del Bosque, 1900, La Plata, Argentina; e-mail: ronderos@fcnym.unlp.edu.ar; spinelli@fcnym.unlp.edu.ar; mfdiaz@fcnym.unlp.edu.ar
RESUMEN. Se redescribe e ilustra el último estadio larval y la pupa de Bezzia roldani Spinelli & Wirth, utilizando microscopio de contraste de fase y microscopio electrónico de barrido. Los estados inmaduros se capturaron con la ayuda de embudos Berlesse a partir de hidrófitas flotantes, de los géneros Lemna, Wolfia, Wolfiella y Spirodella (Lemnaceae) de las lagunas Chascomús y Los Talas, ambas en la provincia de Buenos Aires, Argentina. La larva presenta las características típicas de larvas carnívoras, se compara con la de Bezzia nobilis (Winnertz) y con una especie similar del género Palpomyia Meigen, P. guarani Lane. La pupa se compara con la de Bezzia blantoni Spinelli & Wirth.
PALABRAS CLAVE. Larva; Pupa; Bezzia roldani; MEB; Argentina.
ABSTRACT. The fourth instar larva and pupa of Bezzia roldani Spinelli & Wirth is redescribed and illustrated by using phase-contrast microscope and scanning electron microscope. Immatures were collected by placing floating hydrophytes of the genera Lemna, Wolfia, Wolfiella and Spirodella (Lemnaceae) in Berlesse funnels. The hydrophytes were collected in the Chascomús and Los Talas ponds, both in the province of Buenos Aires, Argentina. The larva show features typical of carnivorous larvae, and it is compared with that of B. nobilis (Winnertz) and with a similar species of the genus Palpomyia Meigen, P. guarani Lane. The pupa is compared with its similar congener B. blantoni Spinelli & Wirth.
KEY WORDS. Larva; Pupa; Bezzia roldani; SEM; Argentina.
INTRODUCTION
The worldwide genus Bezzia Kieffer, 1899
includes midges which are important
predators of small invertebrates, mainly
chironomid midges. The immature stages are
relatively common inhabitants of different
kind of wetlands, mainly streams, lakes and
ponds, as well as other breeding habitats,
such as sphagnum bogs, rice fields, hoofprints
in a sandy creek bed, water in tree holes, and
water in bromeliads (Spinelli & Ronderos,
2001).
Borkent & Spinelli (2000), in their catalog
of the ceratopogonids south of the United
States of America, recorded 46 species for
this area. After that, only one species, Bezzia
chilensis Spinelli & Ronderos was described
from Central Chile (Spinelli & Ronderos,
2001).
Bezzia roldani was described by Spinelli
& Wirth (1981) based on adult, larva and
pupa from Argentina, and subsequently
redescribed by Spinelli & Wirth (1989)
placing it in the glabra group. Although both
are relatively modern descriptions, the
description of the immatures was incomplete.
The purpose of this paper is to redescribe the
fourth instar larva and pupa of Bezzia roldani from specimens collected in Los Talas and
Chascomús ponds in the province of Buenos
Aires, Argentina, with phase-contrast
microscope and with scanning electron
microscope (SEM).
MATERIAL AND METHODS
Larvae and pupae were collected by
placing floating hydrophytes of the genera
Lemna, Wolfia, Wolfiella and Spirodella
(Lemnaceae) in Berlesse funnels. The
hydrophytes were collected in the
Chascomús and Los Talas ponds, both in the
province of Buenos Aires, Argentina, and
carried to the laboratory in plastic bags. The
immature midges were observed daily to
record development. For detailed
examination of larvae with phase-contrast
microscope at oil immersion, were slide
mounted in Canada balsam and placed with
ventral side upward to observe internal
structures in the head capsule. Pupae were
slide-mounted in Canada balsam, following
the technique of Borkent (2000) and
examined, measured, and drawn made of the
4th segment and their tubercles using a
binocular microscope with a camera lucida.
Larvae and pupae were also examined using
scanning electron microscopy (SEM) (JOEL
2000) by using the technique of Ronderos et
al. (2000); measurements and ratios of the
larval head capsule were taken using phasecontrast
microscope.
For terminology of larvae see Ronderos
et al. (2004) and for pupae Nevill & Dyce
(1994). Studied specimens are deposited in
the collection of the Museo de La Plata,
Argentina.
RESULTS
Bezzia roldani Spinelli & Wirth, 1981 (Figs. 1-28)
Figs. 1-4. 1-3. Larva of Bezzia roldani. 1, mandible; 2, epipharynx, VC: ventral comb, DC: dorsal comb, AS:
auxillary sclerite, MF: fossa mandibularis; 3, hypopharynx; 4. Pupa of Bezzia roldani, 4th abdominal segment,
abdominal tubercles: lateral anterosubmarginal tubercle (lasm); dorsal posteromarginal tubercle (dpm); dorsal
anterosubmarginal tubercle (dasm); ventral posteromarginal tubercle (vpm); lateral posteromarginal tubercle (lpm).
Bezzia roldani Spinelli & Wirth, 1981: 187 (female, male, pupa, larva; Argentina); Spinelli & Wirth, 1989: 769 (redescr.; Argentina); Borkent & Spinelli, 2000: 61 (Neotropical catalog).
Redescription of fourth instar larva (Figs. 1-3, 5-13)
Figs. 5-13. Larva of Bezzia roldani. 5, head capsule, dorsal view; 6, head capsule, ventrolateral view; 7, head
capsula, frontoventral view; 8, palatum anterior; 9, palatum posterior; 10, mouthpart, posterior view; 11, maxilla,
lateral view; 12, caudal segment, frontal view; 13, insertion of setae of caudal segment. Head capsule chaetotaxy:
j, collar pits; n, anterolateral pit; o, parahypostomal setae; p, posterior perifrontal setae; r, postnatal pits; s, anterior
perifrontal setae; t, prefrontal setae; u, mesolateral setae; v, posterolateral setae; w, anterolateral setae; x, paranntenal
setae; z, frontal pits; collar (CO); antennae (AN); labrum (LB); hypostoma (HY); mandible (Mn); palatum (PL);
sensilla trichoidea (ST); sensilla styloconica (SS); sensilla campaniformia (Sca); messors (MS); maxilla (MX);
galeolacinia (GL); maxillary palpus (MP); lacinial sclerites (LC); sensilla basiconica (SB); palatal bar (PB). Larva
caudal segment chaetotaxy: «o» outer setae; «i» inner setae; l1 first lateral setae.
Exuviae pale yellowish. Head capsule (Figs. 5-7) 3.4 times longer than wide; apex slightly bent ventrally, setae minute, poorly visible, chaetotaxy as in figures 5-6; HL 0.255 (0.25-0.26, n=4) mm; HW 0.08 (0.07-0.09, n=4) mm; HR 3.20 (2.88-3.57, n=4); SGR 0.055 (0.05-0.06, n=3). Labrum (Fig. 7) longer than wide, not extending beyond hypostoma, with pair anterolateral sensilla styloconica (Figs. 7-8); palatum (Figs. 7-9) with 3 pairs of closely spaced sensillae (Figs. 7-9): 2 pairs of sensillae trichoidea, one pair of sensillae campaniformia (Figs. 7, 9-10); palatal bar represented by a small, W-shaped sclerite situated immediately posterior to messors; messors (Figs.7, 9) small, thin, gently sclerotized curved structures, situated away from mandibles. Maxilla (Figs. 7, 9-11) with pyriform sensillum, maxillary palpus long, cylindrical (Figs. 7, 9, 11), with three subapical papillae (Fig. 11); galeolacinia with stout, blunt setae (Fig. 11). Mandible (Figs. 1, 7-9) hooked, curved, tooth long, fosa mandibularis on the ectal surface (Fig. 1); ML 0.04 (0.03-0.05, n=3) mm. Hypostoma (Figs. 7, 10) finely toothed. Labium small, triangular. Epipharynx (Fig. 2 ) less massive, with 2 combs, ventral comb with 4-5 stout, short teeth, dorsal comb with rather long teeth on posterior edge, auxiliary sclerites located near lateral arms. LAW 0.04 mm (n= 2), DCW 0.02 mm (n=2). Hypopharynx (Fig. 3) long, thin, gently sclerotized, arms slender. Thoracic pigmentation uniformly pale yellowish. Caudal segment (Figs. 12-13) about 5 times longer than wide, posterior end with 6 pairs of setae, 4 of them long, stout, pale brown, the other 2 thin, short, brown (Fig. 13); CSL 0.47 (0.44-0.53, n=3) mm, CSW 0.086 (0.08-0.09, n=3) mm, CSR 5.42 (4.88- 5.88, n=3), OL 0.55 (0.50-0.77, n=5) mm; OW 0.38 (0.35-0.50, n=5) mm.
Redescription of pupa (Figs. 4, 14-28)
Figs. 14-20. Pupa of Bezzia roldani. 14, respiratory horn; 15, respiratory horn, apical view; 16, respiratory horn,
apical ventral view; 17, anteromarginal tubercle (am); 18, anterodorsal tubercle (ad); 19, dorsal tubercles (d); 20,
dorsolateral tubercles (dl). Prothoracic respiratory horm (PRH); pedicel (P); basal sensillum (bs); spiracle (sp).
Figs. 21-28. Pupa of Bezzia roldani. 21, 4th abdominal segment, lateral view; 22, lateral anterosubmarginal tubercle
(lasm) and lateral posteromarginal tubercle (lpm); 23, base and insertion setae lateral posteromarginal tubercle
(lpm); 24, ventral posteromarginal tubercle (vpm); 25, ventral setae: ventrolateral setae (vl), ventromedian setae
(vm); 26, insertion ventrolateral setae (vl); 27, insertion ventromedian setae (vm); 28, female, caudal segment,
ventral view, posterolateral proceses (PP).
Length 4.69 (3.66-5.90, n=5) mm. Exuvia brownish. Length of cephalotorax 1.40 mm, wide 0.70 mm. Cephalothoracic tubercles (Figs. 17-20) as follows: anterodorsal tubercle (ad) with 2 long, subequal, thin setae (Fig. 18); dorsolateral tubercle (dl) with 2 long, thin, subequal setae (Fig. 20); 5 dorsal tubercles (d) (Fig. 19), as follows: i, ii, with stout, subequal setae, both shorter than iii; iii with thin seta, longer than iv; iv with long stouter seta; v pore; 2 thin ventrolateral setae (vl) (Figs. 25-26); 3 stout, long ventromedian setae (vm) (Figs. 25, 27). Respiratory horn (Figs. 14-16) 4.4-4.7 times longer than broad, surface smooth, length 0.28 (0.20-0.36; n=5) mm, apex curved, with convoluted row of 50- 60 spiracles (Figs. 14-16); pedicel (Fig. 14) stout, short; length 0.04 (0.03-0.05, n=5) mm; P/H 0.14 (0.10-0.17, n=5). Operculum 1.4 times broader than long, anterior end rounded; grooved midway on lateral margins, spiculate on midportion, with 3 pairs of tubercles: anteromarginal tubercle (am) (Fig. 17) with one single, stout, long seta, basal sensillum (bs) present, remaining two without setae; OL 0.13 (0.12-0.14, n=3) mm, OW 0.23 (0.22-0.24, n=3) mm, OL/OW 1.76 (1.71-1.83, n=3). Abdominal segments with scattered small spinules. Fourth abdominal segment (Figs. 4, 21-22) with two anterosubmarginal tubercles (dasm): i-ii base rounded, with thin setae; 3 posteromarginal tubercles (dpm): i triangular, base flattened with thin seta, ii base small, seta minute, iii base small, flattened, seta thin, short; 2 ventral posteromarginal tubercles (vpm) (Figs. 4, 24): i base small, seta minute, ii triangular, base rounded, seta thin longer than i; 2 lateral posteromarginal tubercles (lpm), both triangular, base flattened (Figs. 4, 21-23), i with short, thin seta, ii with seta stouter; one lateral anterosubmarginal tubercle (lasm) with rounded, small base, medium-sized, thin seta (Figs. 4, 21-22). Caudal segment (Fig. 28) 2.53 times longer than broad, spinulose mesally, length 0.38 (0.30-0.41; n=3) mm; wide 0.15 (0.14-0.16; n=3) mm; dorsal surface with abundant posteriorly directed spinules; posterolateral processes divergent, with strong tubercles; length posterolateral processes 0.27 mm (n=3).
Distribution: Argentina (Buenos Aires and Entre Ríos provinces).
Material examined. ARGENTINA.
Buenos Aires: Chascomús pond, 20-VIII-
1979, Spinelli col., 4 pupae (MLP); same data
except 12-IX-1979, 3 pupae (type series)
(MLP); Buenos Aires, Berisso, Los Talas pond,
30-III-1979, Fernández col., 3 larvae, 3 pupae
(MLP).
For SEM: Los Talas pond, 30-III-1979,
Fernández col., 4 larvae, 4 pupae (MLP).
DISCUSSION
The behavior of all animals is inseparable
from their morphology (Joseph, 1979). As in
other groups, mouthpart and other structures
of ceratopogonid larvae often reflect their
feeding habitats. Particularly important are
the number, type and distribution of the
sensillae in the pallatum, which are intimately
related to feeding habits and searching for
food (Greenwood & Chapman, 1984;
Zacharuk, 1985). A similar relationship
between mouthpart morphology and feeding
habits also occurs in other insects (Bland,
1982, 1989).
The epipharynx and distribution of the
sensillae in the pallatum of B. roldani is very
similar to the widespread species B. nobilis
(Winnertz, 1852), except for the presence of
the palatal bar in the larva of B. roldani,
which is absent in B. nobilis (Hribar &
Mullen, 1991).
Bezzia is closely related to the large,
widespread genus Palpomyia Meigen (1818),
and both genera are placed in the tribe
Palpomyiini Enderlein (1936). The larvae of
Bezzia roldani show several similarities with
larvae of Palpomyia guarani Lane (1946),
which was also described based on the SEM
observations by Ronderos et al. (2004). The
most important similarities are the shape of
the ephipharynx and maxillary palpus, the
distribution pattern of the sensilla of pallatum
and messors, and the latter situated
immediately behind the last pair of sensilla
campaniformia, being this particular location
more similar than to other species of Bezzia.
Larvae of B. roldani are therefore interpreted
to be predatory-carnivorous midges, are
prognathous, exhibit an elongate, narrow
head, mandible hooked with a single strong
tooth and a fossa mandibularis, epipharynx
gently massive, hypostoma finely toothed and
cylindrical maxillary palpi (Thomsen, 1937;
Mullen & Hribar, 1988; Hribar, 1993;
Ronderos et al., 2004).
The pupae of B. roldani, are similar to B.
blantoni Spinelli & Wirth (1989), known from
the USA to Argentina, both species co inhabit
Los Talas pond in the province of Buenos
Aires. However, the respiratory horn of B.
blantoni is more slender, bears a straight row
of 36-38 spiracles and its apex is not curved.
Finally, the cephalothorax of B. blantoni has
2 ventromedian setae and one seta in the
dorsolateral tubercle.
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Recibido: 25-08-2006,
aceptado: 12-12-2006