Mycetococcus ligae Granara de Willink, 2023

Granara de, María C., Willink, González, Patricia & Stumpf, Christof F., 2023, Revision of the family Asterolecaniidae (Hemiptera: Coccomorpha) in Argentina, Insecta Mundi 2023 (996), pp. 1-23 : 9-12

Mycetococcus ligae Granara de Willink , new species

( Fig. 4 )

Type material. Holotype. Adult female holotype marked with a black circle. Argentina. Tucumán, Colalao del Valle, Tafí. 7/vii/2010, on Phoradendron liga (Gillies ex Hook. and Arn.) Eichler (Santalaceae) , J. Carrizo col. 1(4, 3 N 3). IFML. Paratypes. 6 (10, 3 N 1, 2 N 2 female, 2 N 2 male, 3 N3); same data as holotype. IFML.

Material examined. Argentina, Salta, Alemanía, 31/vii/1996, on Loranthaceae (Viscaceae) , Claps col. 2(8). IFML.

Diagnosis. Antennae and labium bisegmented; caudal process with numerous long and stout setae enveloping anal lobes; eight-shaped pores at the bases of narrow tubular ducts, present on dorsum and venter; with areas formed by concentrations of microspicules, small setae, and transverse and medial disk pores on ventral abdominal segments; anal ring with pores and setae.

Biological data. Viviparous. Three first-instar nymphs were found inside a female.

Habitus. Body of the adult female completely covered by a felt-like structure with a cottony appearance. These asterolecaniids do not produce a pit; they were found on the leaves of their hosts.

Microscopic description. Body oval, elongated, length 1.2 (1.4–1.6) mm and width 0.9 (0.7–1.0) mm. Dermis membranous, except in the caudal process area formed by the last two strongly sclerotized abdominal segments on dorsum and venter. Legs absent.

Dorsum. Tubular ducts abundant, with internal eight-shaped ends formed by two rounded protrusions, each with one medium filament and one simple external opening, 14–21 µm long and 2–3.5 µm wide, forming transverse bands on the abdomen. Dorsal setae very small, like spicules, 4–5 µm long, basal diameter 3–3.5 µm, similarly distributed like disk pores. Small disk pores, 1–2 µm long, in submarginal longitudinal bands on thorax and abdomen. Large disk pores, 4 µm long, in transverse rows on the last 2–3 segments anteriad to and at the base of the caudal process.

Venter. Antennae 27 (24–31) µm long, bisegmented, the basal segment without setae and the distal segment with four fleshy setae at the apex and two long spiniform setae. Clypeolabral shield 174 (160–184) µm long and 140 (128–142) µm wide. Labium bisegmented, 97 (97–98) mm long and 117 (97–98) µm wide, basal segment with two pairs of setae on the anterolateral corners, apical segment with three pairs of thin setae at the tip, and a mid-segment pair. With two pars of spiracles of equal size, 58 µm long and 22 µm wide at the peritreme, located in a dermal depression; multilocular pores with 9–10 locules, 10 µm in diameter, only around the spiracular opening, with 18–22 pores around the anterior pair and 26–30 around the posterior pair. They are usually found in radial dermal striations around the peritreme. Tubular ducts similar to the dorsal ones, the smallest in the middle and the largest in the lateral and submarginal areas from the head to segment VIII. Quinquelocular pores absent. Disk pores only in the middle of the abdomen. Submedial areas covered with large numbers of microspicules, small setae, and disk pores, wider in lateral areas of abdominal segments III-VII.

Caudal process. Formed by abdominal segments X-XI, strongly sclerotized dorsally and ventrally, 200 (202–206) µm long and 366 (312–316) µm wide. Tip rounded with approximately 20 thick setae, 46–54 µm long, with pointed tips and thick, tall, protruding bases; remaining setae with rounded tips, thinner, but of same length as the other setae; 14–15 dorsal and 13–15 ventral setae. On the anterior part of the caudal process there is a band of 7–8 dorsal setae, approximately 10 µm long, and disk pores; ventrally they are distributed on the surface of the lobe. Anal ring 105 (97–100) µm wide, dorsal, located at the bottom of a strongly sclerotized depression and surrounded by the anal lobes; with 2–3 pore circles and three pairs of long setae, 136 (125–140) µm long. The anal plates and the arched plate which surround the anal opening and are in turn surrounded by the strong anal ring are difficult to see.

Systematic considerations. Mycetococcus ligae shares with M. ehrhorni eight-shaped ducts and a caudal process. They are differentiated by ( M. ehrhorni characters in parentheses, taken from Ferris 1955): 1) anal lobes with numerous long and stout dorsal and ventral setae (with short setae, two dorsally and three ventrally); 2) anal lobes strongly sclerotized forming part of the caudal process (forming two cones, one for each lobe, separated by an indentation); 3) with multilocular pores (9–10 locules) close to spiracles (with quinquelocular pores); and 4) areas formed by concentration of microspicules, small setae, and disk pores (areas absent).

Mycetococcus ligae resembles M. corticis because both have a caudal process, multilocular pores close to the spiracles, and radial dermal striations around the peritreme. They are differentiated by ( M. corticis characters in parentheses, taken from Ferris 1955): 1) antennae bisegmented (one-segmented); 2) areas formed by concentration of microspicules, small setae, and disk pores (areas absent); 3) tubular ducts with internal ends eight-shaped (internal ends truncated); and 4) eight-shaped pores absent (present).

Mycetococcus ligae differs from M. sinensis by ( M. sinensis characters in parentheses, taken from Gavrilov-Zimin 2018): 1) antennae bisegmented, with four fleshy and two spiny setae (antennae vestigial, non-segmented, with one seta; 2) quinquelocular pores absent (present in groups between spiracles and body margin); 3) multilocular pores around spiracular peritremes (multilocular pores absent); 4) areas formed by concentration of microspicules, small setae, and disk pores (areas absent), and 5) legs absent (legs vestigial).

Unlike the known species in this genus, whose hosts belong to the Fagaceae , the new species described here was found on a species of Santalaceae .

First instar nymph ( Fig. 5 ). Oval body shape, 0.5 mm long and 0.3 mm wide. Dorsum: With trilocular pores, 4 µm diameter, forming longitudinal marginal, submarginal, lateral, and medial rows, present on abdomen and metathorax; toward the front of the body they become rare; with three pores near the base of the antennae. Spiniform setae very slender, arranged in longitudinal submarginal and median rows; abdominal segment VII with 8 setae, each 7 µm long. Anal ring 24.5 µm in diameter, exposed, with six setae, each 63 µm long, and 1–2 rows of pores. Undifferentiated anal lobes, represented by two dorsal setae and two trilocular pores. With a sclerotization of the last segment, 75–90 µm in diameter, which surrounds the anal ring and the anal lobes; with four setae and two trilocular pores. Venter: Antennae 70 µm long, with six segments; basal segment with two short setae, segment V with one fleshy seta, and apical segment with five slender setae and one fleshy seta. Eyes present. Clypeolabral shield 65 µm long. Labium 45 µm long, without visible segmentation. With trilocular pores, 3 µm long, smaller than the dorsal ones, on the pro-, meso-, and metathorax. Setae in marginal, lateral, and medial rows, on abdomen and anterior region, about 7µm long. Last segment sclerotized, with four setae and one trilocular pore. Legs developed, coxae of hind legs 14 µm long and 22 µm wide, trochanter plus femur 47 µm long, tibia plus tarsus 56 µm long, claw 10.5 µm long.

Second instar female nymph. With oval and rounded body. Antennae bisegmented. Legs missing. With bisegmented labium. Short eight-shaped pore ducts rare on both surfaces. With three multilocular pores close to anterior spiracles and four close to posterior spiracles, respectively. Anal ring with six setae, pores arranged in two bands. Caudal process with three short spiniform dorsal setae. With an anal plate inside the anal tube.

Third instar female nymph. Oval body. Bisegmented antennae. Without legs. Multilocular pores restricted to the spiracular peritreme, with 6–7 in the anterior ones and 10–11 in the posterior ones. Eight-shaped pores at the bases of tubular ducts, formed by two rounded protuberances, numerous on both surfaces. Anal ring sclerotized, with six setae. Anal tube sclerotized, with two lateral internal setae. Caudal process with three setae on external surface and seven lateral and marginal setae. With sporadic and very small setae, on three segments anterior to caudal process. With spicule-like setae on abdominal segments.

Second instar male nymph. With oval and rounded body. Antennae with six segments. Eyes present. Legs developed, tibiae longer than tarsi. Slightly sclerotized circular pores scattered on both surfaces. Very small invaginated eight-shaped pores scattered over both surfaces. One to three multilocular pores close to anterior spiracles, four to five close to posterior ones, respectively. Exposed anal ring with six setae, and pores arranged in two bands. Anal process not protruding, with three dorsal setae near the anal ring and four ventral setae, one larger than the others.

Etymology. The specific epithet of this species alludes to the specific epithet and common name (liga) of the host plant.

Figures

Figure 4. Mycetococcus ligae sp. nov., adult female. a) Dorsal (left), ventral (right) view. b, c, o) Tubular ducts. d, l, p, q) Setae. e) Small disk pore. f) Large disk pore. g) Caudal process. h, i, j, s) Different types of setae on caudal process. k) Antenna. m) Multilocular pore. n) Microspicules. r) Disk pores on caudal process.

Figure 5. Mycetococcus ligae sp. nov., first instar nymph. a) Dorsal (left), ventral (right) view. b, e) Disk pores. c, d) Trilocular pores.