Formicoccus yoshinoi Tanaka, 2021

Tanaka, Hirotaka, Suetsugu, Kenji & Kamitani, Satoshi, 2021, A parasitic insect on a parasitic plant: a new species of the genus Formicoccus Takahashi (Hemiptera, Coccomorpha, Pseudococcidae) from Ishigaki Island, Japan, ZooKeys 1060, pp. 171-182 : 171

Formicoccus yoshinoi Tanaka sp. nov.

Figures 1 , 2 , 3 Japanese common name: Tsuchitorimochi-Konakaigaramushi

Type material.

Holotype: Adult ♀, Japan / Okinawa prefecture / Ishigaki Is., Sakieda / 24.445794°N / 124.079765°E / on Balanophora / Balanophora fungosa / 14.xii.2019 / coll. K. Yoshino; mounted singly (ELKU). Paratypes: 2 adult ♀♀, same data as for holotype, mounted singly (1 EUMJ, 1 ELKU). 4 adult ♀♀, Japan / Okinawa prefecture / Ishigaki Is., Kabira / 24.451620°N / 124.159781°E /on Balanophora / Balanophora fungosa / 14. xii.2019 / coll. K. Yoshino; mounted singly (2 EUMJ, 2 ELKU)

Diagnosis.

Slide-mounted adult female mostly oval. Anal lobes with well-developed and narrow anal lobe bar. Antenna mostly with seven segments and many flagellate setae. Legs relatively short and stout, but well developed. Hind legs with numerous translucent pores present on both dorsal and ventral surfaces of coxae. Circulus present between ventral abdominal segments III and IV. Ostioles present. Anal ring situated ca. half length from apex of abdomen or end of posterior abdominal segments, bearing 6 setae. Cerarii numbering fewer than 6 pairs; all cerarii situated on posterior abdominal segments. Dorsal setae slender, relatively long and flagellate, densely present and covering almost entire body surface. Dosal trilocular pores evenly distributed. Oral rim ducts and oral collar tubular ducts absent on dorsum. Discoidal pores sparsely distributed on both body surface. Multilocular disc pores mostly present in medial area of ventral abdominal segments VI-IX. One size of oral collar tubular ducts present on venter, forming an irregular submarginal band on posterior abdominal segments and forming transverse rows on medial area of abdominal segments VI-IX.

Description

(n = 7). Live adult female feeding on the underground part of host plant (Figs 1 , 2 ) and secreting white powdery wax on all body surfaces (Figs 1 , 2 ). Body shape of mature adult female mostly hemispherical in shape (Fig. 2 ).

Slide-mounted adult female mostly oval, 2.4 (2.4-3.2) mm long and 1.6 (1.6-2.9) mm wide; derm membranous; segmentation relatively well-developed. Anal lobes distinct but not prominent, dorsal and ventral surfaces of each lobe with weakly sclerotised area, ventral surface with long apical seta, 192-194 (178-194) µm long and with well-developed and narrow anal lobe bar; anal lobe bar fairly conspicuous, but occasionally fainted and rarely difficult to see. Antenna 368-372 (322-407) µm long, with 7 (7-8) segments and many flagellate setae; subapical segment with one fleshy seta and apical segment with 4 (3-4) fleshy setae. Legs relatively short and stout, but well-developed, with many flagellate setae; hind trochanter + femur 319-332 (300-356) µm long, hind tibia + tarsus 243-250 (239-278) µm long; claw 38-43 (38-46) µm long. Ratio of lengths of hind tibia + tarsus: trochanter + femur 0.73-0.78 (0.73-0.82); ratio of lengths of hind tibia to tarsus 1.87-2.07 (1.60-2.13). Paired tarsal digitules present, subequal in length to the minutely knobbed claw digitules. Hind legs with numerous translucent pores present on both dorsal and ventral surface of coxae. Labium ca. 280 (220-285) µm long, slightly longer than clypeus. Circulus present between abdominal segments III and IV, 85 (50-100) µm long and 215 (140-235) µm wide. Ostioles present, each with inner edges of lips not sclerotised; anterior ostioles each with a total for both lips of 106-118 (46-118) trilocular pores and 19-21 (16-25) setae; each posterior ostiole with a total for both lips of 105-118 (64-122) trilocular pores and 18-23 (16-24) setae. Anal ring 108 (90-108) µm wide, situated ca. half the length from apex of abdomen to end of posterior abdominal segments, with two rows of cells, bearing six setae (Fig. 3 . AR); each seta 83-110 (83-118) µm long. Cerarii numbering 5 (3-6) pairs, all cerarii situated on posterior abdominal segments. Anal lobe cerarii (C18) each situated on sclerotised cuticle, containing 2 (1-4) conical setae, each seta 15-20 (15-28) µm long and ca. 4-6 µm wide at base; 12-16 (11-20) auxiliary setae and a concentration of trilocular pores. Penultimate cerarii (C17) each situated on weakly sclerotised cuticle, containing 2-4 (1-6) conical setae and many auxiliary setae. Cerarii situated further forward generally each with 0-4 conical setae and at least one cerarii contain more than three conical setae and many auxiliary setae.

Dorsum. Setae slender, relatively long and flagellate, each 21-68 (14-68) µm long, longest setae present on medial area of posterior abdominal segments, densely present and covering almost entire body surface. Trilocular pores ca. 3-4 µm wide, evenly distributed. Oral rim ducts and oral collar tubular ducts absent. Discoidal pores slightly smaller than trilocular pores, sparsely distributed on body surface.

Venter. Ventral derm with slender flagellate setae, each 31-123 (15-123) µm long, longest on medial area of posterior abdominal segments. Multilocular disc pores, each 7-9 (6-9) µm wide, mostly present in medial area of abdominal segments VI-IX. Trilocular pores ca. 3-4 µm wide, evenly distributed. Oral rim ducts absent. Oral collar tubular ducts present, of one size, each with outer ductule 2-4 µm in diameter (slightly smaller than that of a trilocular pore) forming an irregular submarginal band on posterior abdominal segments and forming transverse rows on medial area of abdominal segments VI-IX. Discoidal pores slightly smaller than trilocular pores, sparsely present on body surface.

Host plants.

Balanophora fungosa ( Balanophoraceae ).

Biology.

Balanophora fungosa is characterized by unusual mushroom-shaped inflorescences that emerge above the ground and warty tubers that are attached to their host plants ( Hansen 1972). Specimens of Formicoccus yoshinoi were found in aggregations on the tuber of this species. Given that (i) no other plants associated with F. yoshinoi Tanaka, sp. nov. were found during the survey and (ii) B. fungosa individuals infected by F. yoshinoi Tanaka, sp. nov. were found at two independent sites, this species might be a specialist on Balanophora species. It is worth investigating whether the species feeds on other plant species.

Remarks.

In his taxonomic revision of the genus Formicoccus Takahashi, 1928, in Southern Asia, Williams (2004) emphasised the following morphological character states as defining morphological features of the genus: the presence of 18 pairs of cerarii, the presence of anal lobe bars on the ventral side of the anal lobe, and the presence of more than two cerarian setae on at least some abdominal cerarii. However, there are exceptions in the first two-character states, with a species with fewer than 17 pairs of cerarii ( F. tripurensis ) and a species with an uncertain presence of anal lobe bars ( F. lingnani ) were included in the genus. The species described in this study also does not have 18 pairs of cerarii, and the species’ anal lobe bars are quite fainted and often difficult to see in a few specimens.

Danzig and Gavrilov-Zimin (2015) rejected the use of anal lobe bar as a generic character state of the genus Formicoccus . They regarded that the presence or absence of the anal lobe bar fell into individual variations and instead used the presence of more than six setae in the anal ring as a critical generic character state of the genus. According to their opinion, the species described in this study are not Formicoccus . However, the debate on the definition of the genus Formicoccus is still ongoing, and no consensus has been reached yet.

Zhang and Wu (2017) regarded the number of anal ring setae as having no generic significance. Based on their studies, the anal ring typically bears six basic setae, and when more setae are present, the extra setae are usually slender and short, and vary in their positions. They placed some species with anal lobe bars ( F. citricola and F. sinensis (Borchsenius, 1962)) in the genus Formicoccus . It is clear that a more detailed study is required to better understand the importance of such morphological character states, particularly using a combination of molecular and morphological characters. Under these circumstances, we tentatively included the species described in this study into the genus Formicoccus .

Formicoccus yoshinoi Tanaka, sp. nov. is similar to F. formicarius (Newstead, 1900) in having: (i) long flagellate dorsal setae; (ii) relatively short and stout legs; (iii) only one type of ventral oral collar tubular duct; and (iv) a round body shape, but differs from this species as follows (characters of F. formicarius are given in parentheses): (i) having fewer than six cerarii with 0-6 conical cerarian setae (with 18 pairs of cerarii with long and stout flagellate setae); and (ii) having a transverse row of ventral oral collar tubular ducts on the medial area of posterior abdominal segments (lacking ventral oral collar tubular ducts on medial area of abdominal segments). The species is also similar to F. erythrinae Williams, 2004, in having: (i) long flagellate dorsal setae; (ii) relatively short legs; and (iii) round body shape, but differs from the latter species as follows (characters of F. erythrinae are given in parentheses): (i) having fewer than six cerarii (having 18 cerarii); and (ii) having only one type of ventral oral collar tubular duct (with two types of ventral oral collar tubular ducts).

Etymology.

Named after the collector of type series, an independent researcher of plants in Ishigaki Is., Mr. Keiya Yoshino.

Figures

Figure 1. Live individuals of Formicoccus yoshinoi Tanaka, sp. nov. feeding on the underground part of the host plant, Balanophora fungosa.

Figure 2. Live mature adult females of Formicoccus yoshinoi Tanaka, sp. nov.

Figure 3. Formicoccus yoshinoi Tanaka, sp. nov., adult female. Abbreviations: ALC, anal lobe cerarius (C 18); ANT, antenna; AR, anal ring; DP, discoidal pore; LG, hind tibia. tarsus and claw; MP, multilocular pore; OCD, oral collar duct; PLC, penultimate cerarius (C 17); TP, trilocular pore. Scale bars: 200 µm for ANT and LG; 100 µm for ALC, AR, and PLC; 10 µm for other details.