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Species: Mycocepurus castrator   Rabeling & Bacci, 2010 

Classification:
Download Data

Taxonomic History (provided by Barry Bolton, 2019)

Mycocepurus castrator Rabeling & Bacci, 2010 PDF: 382, figs. 1A,C,E; 2A,C,E,G (q.m.) BRAZIL. Neotropic. AntCat AntWiki

Distribution:

  Geographic regions (According to curated Geolocale/Taxon lists):
    Americas: Brazil
  Biogeographic regions (According to curated Bioregion/Taxon lists):
    Neotropical

Taxonomic Treatment (provided by Plazi)

Treatment Citation: Rabeling, Ch. & Bacci, M., 2010, A new workerless inquiline in the Lower Attini (Hymenoptera: Formicidae), with a discussion of social parasitism in fungus-growing ants., Systematic Entomology 35, pp. 379-392

Mycocepurus castrator Rabeling & BacciHNS, sp.n.

(Figs 1A, C, E, G; 2A, C, E, G)

Holotype, â??, BRAZIL: São Paulo, Rio Claro, Campus of São Paulo State University GoogleMaps (UNESP), 22.3955º S, 047.5424ºW, elevation 608 m, 29.ix.2006, C. Rabeling acc. no. CR 060929 - 14, ex Mycocepurus goeldiiHNS nest. Holotype deposited at MZSP. Measurements (in millimetres): HW 0.6, HL 0.64, SL 0.76, WL 1.07, PPW 0.62, PW 0.21, PL 0.24, PPL 0.19, CI 94, SI 127 GoogleMaps.

Paratypes, 104 â??, 78 â??, BRAZIL: same nest as holotype, 29.ix.2006 - 02.x.2006, col. C. Rabeling. Paratypes deposited at: AMNH, BMEL, CRC, MCZC, MZSP, UCDC, USNM.

Holotype, â?? (queen). Diagnosis. Small species (WL 1.07) with a unique morphology reflecting the parasitic life history. In full face view, head rectangular (CI 94); sides approximately parallel, slightly tapering above mandibular insertions; head widest directly above the eyes; posterior margin of the head heart shaped, with a slight but distinct median concavity; posterolateral corners rounded, in lateral view drawn out to form a short, rounded lobe forming the ventrolateral corner of the head. Antennae with 11 segments; antennal scapes extremely long (SL 0.76), surpassing the posterior margin of the head by nearly half their length (SI 127). In full face view, frontal carinae and antennal scrobes absent. Frontal lobes small and rounded, barely covering the antennal sockets in frontal view. Median triangular portion of clypeus raised

between the antennal insertions. Mandibles reduced, narrow, elongate, blade-like terminating in a pointed tooth; otherwise lacking teeth except for a small basal denticle. Maxillary palps reduced, with only three segments, labial palps with two segments. Ocelli slightly raised above the surface of vertex. Mesosoma with characteristic morphology related to wing bearing. Pronotal spines absent; propodeal spines well developed, stout, as wide as long at the base and sharply pointed; metapleural gland orifice very large and circular in oblique view, ventral margin forming small, vertical tooth. Petiole with a short peduncle; node triangular in side view, with sharp crest terminating in two thick pointed teeth. In dorsal view, postpetiole approximately 3× as wide as long (PPL 0.19, PPW 0.62); lateral borders tapering into pointed angles; translucent area near posterior margin forming broad u-shaped invagination. First gastric tergite strikingly concave in lateral view. Entire body surface more or less smooth and shiny, in most areas with hexagonal microsculpture resembling a honeycomb. Body sparsely covered with stiff setae; setae erect on vertex and frontal lobes, sub-decumbent on mesoscutum and scutellum, and appressed on postpetiole and metasoma. Wings infuscated with reduced venation, densely covered with setae; clear spot or fenestra in apical part of forewing absent; rsf1 faint, hardly visible. Colour: light to dark reddishbrown . - Paratype â??â??. Measurements (n = 15). HW 0.6-0.65, HL 0.63-0.64, SL 0.73-0.8, WL 1.07-1.23, PPW 0.62-0.65, PW 0.21-0.25, PL 0.24-0.28, PPL 0.18-0.2, CI 94-104, SI 115-128.

Paratype â??â?? (males). Diagnosis. Remarkably similar to female, not resembling any other MycocepurusHNS male; characters as in female diagnosis with the following exceptions: head size of males smaller (HL 0.58-0.6, HW 0.58-0.6), whereas body length similar (WL 1.1-1.2). Mandibles reduced, narrow , elongate, blade-like, which do not terminate in a pointed tooth; otherwise lacking any teeth or denticles. Number of antennal segments reduced to 11; funicular segments approximately as long as broad, slowly increasing in length towards apex to 1.5× their width, only apical segment 5× as long as wide. Mesosoma lower and narrower; tiny opening present at the metapleuron, corresponding to the position of a metapleural gland opening in the female. First gastric tergite flat to slightly concave; male genitalia projecting forward from tip of metasoma. Basal apodeme lobed, separated from aedeagus by a deep constriction; ventral border lacking serration. Wing colour: medium to dark brown. Measurements (n = 15). HW 0.58-0.6, HL 0.58-0.6, SL 0.73-0.75, WL 1.1-1.2, PPW 0.63-0.65, PW 0.23-0.3, PL 0.25-0.28, PPL 0.18-0.2, CI 96-104, SI 121-126.

© 2010 The Authors Journal compilation © 2010 The Royal Entomological Society, Systematic Entomology, 35, 379-392

Fig. 1. Queens of Mycocepurus castratorHNS (A, C, E, G) and Mycocepurus goeldiiHNS (B, D, F, H). (A, B) Habitus in lateral view; scale bar represents 0.5 cm. (C, D) Posterior part of the mesosoma, petiole and postpetiole in lateral view; scale bar represents 0.5 cm. (E, F) Metapleural gland orifice in oblique view, metacoxa is visible in the lower left corner of the image; scale bar represents 50 μm. (G, H) Maxillary palp, scale bar represents 50 μm.

© 2010 The Authors

Journal compilation © 2010 The Royal Entomological Society, Systematic Entomology, 35, 379-392

Fig. 2. Males of Mycocepurus castratorHNS (A, C, E, G) and Mycocepurus goeldiiHNS (B, D, F, H). (A, B) Habitus in lateral view; scale bar represents 0.5 cm. (C, D) Posterior part of the mesosoma, petiole and postpetiole in lateral view; scale bar represents 0.5 cm. (E, F) Metapleural orifice in oblique view, metacoxa is visible in the lower left corner of the image; scale bar represents 50 μm. (G, H) Maxillary palp, scale bar represents 50 μm.

© 2010 The Authors Journal compilation © 2010 The Royal Entomological Society, Systematic Entomology, 35, 379-392

Worker. The worker caste is unknown and probably nonexistent.

Additional material examined. BRAZIL: SaË?o Paulo, Rio Claro, Campus of São Paulo State University (UNESP), 22.3955â?¦S, 047.5424â?¦W, elevation 608 m, 03.x.2008, C. Rabeling acc. no. CR 081003 -01, CR 081003 -02, CR 081003 -03, CR 081003 -04, CR 081003 -05; ex Mycocepurus goeldiiHNS nest.

Comments. Mycocepurus castratorHNS is an obligate, workerless social parasite of M. goeldiiHNS and is so far known only from Rio Claro, SaË?o Paulo State, Brazil. Mycocepurus castratorHNS occurs sympatrically with M. smithiiHNS and M. obsoletusHNS, but cannot be confounded with any other MycocepurusHNS species because of its multiple morphological adaptations for a parasitic lifestyle (Table 3). Mycocepurus castratorHNS can be recognized by the following characteristics: (i) the long antennal scapes surpassing the posterior margin of the head by half their length; (ii) reduced, blade-like mandibles lacking dentition of masticatory margin; (iii) concave shape of first gastric tergite; (iv) smooth and shiny body sculpture with hexagonal microsculpture; (v) reduced palpal formula (3,2); (vi) females and males with 11 antennal segments; (vii) males lacking serrated ventral border of aedeagus; (viii) absence of clear fenestra from forewings of queens and males; (ix) worker caste presumably absent; (x) metapleural gland orifice enlarged in females, and potentially present in males. Mycocepurus castrator malesHNS and females look extremely similar to each other, and males are distinguished most easily from the females by the genitalia protruding from the tip of the metasoma and their darker brown colour (vs reddish brown in the queens).

Etymology. During collections of M. castratorHNS, the host colonies were not observed to produce any alate queens and males, although sympatrically nesting M. goeldiiHNS colonies released alates. Therefore, we assume that the inquiline inhibits the host queens ' production of sexual offspring, allowing only for the production of the sterile worker caste. This is essentially ‘social castration ', hence the specific name ‘castrator '.

Host species. Mycocepurus castratorHNS has been found only in nests of M. goeldiiHNS and is so far only known from the type locality (Rio Claro, SP). Mycocepurus goeldiiHNS is a conspicuous , widely distributed species ranging approximately from the 40th to the 67th meridian west and from the 2nd to the 31st latitude south, an area covering most of Brazil, parts of Bolivia, Paraguay and northern Argentina. The range of habitats occupied by M. goeldiiHNS is remarkably diverse and ranges from Amazon rainforest, savannahs (Cerrado) to the fertile South American lowlands (Pampas), and secondary habitats disturbed by human activities. It does not occur in elevated sites of the South American Cordilleras. Mycocepurus goeldiiHNS workers can be distinguished clearly from its congeners based on the size and spine pattern of the mesosoma: it is the largest species in the genus and has the most complete set of spine pairs on the mesosoma (Kempf, 1963: figs 2, 3). The natural history of this species has been studied near SaË?o Paulo City (Luederwaldt, 1918, 1926) and in the Manaus region of the Amazon Basin (Rabeling et al., 2007b), but these studies do not report the presence of a social parasite attacking M. goeldiiHNS. Like most inquilines for which we have data, M. castratorHNS probably has a patchy and locally restricted distribution. In addition, it is probable that M. castratorHNS is host specific, occurring only in nests of M. goeldiiHNS. Despite extensive excavation of nests of sympatrically occurring MycocepurusHNS species, the parasite was never encountered in the nests of M. smithiiHNS (Rabeling et al., 2009) or any other MycocepurusHNS species in Latin America (Rabeling, unpublished).

Natural history and nest biology. Mycocepurus castratorHNS has been found twice in adjacent nests of M. goeldiiHNS. The two host nests had five and eight chambers, respectively, which were distributed between 5 and 190 cm depth (Table 1). The colony studied in 2006 contained 105 alate queens and 78 alate males of M. castrator, and 771 workers of M. goeldiiHNS (Table 1). Dealate queens of either species could not be encountered, suggesting that the queenright chamber was either missed during the excavation or that the queens escaped into adjacent tunnels.

The 2008 colony contained 15 dealate and 66 alate M. castrator queens, only six alate males, 1034 M. goeldiiHNS workers, a single dealate M. goeldiiHNS queen and worker pupae (Table 1). The parasite 's numerical male/female sex ratio was strongly female biased (6/66 = 0.09). Twelve of the 15 dealate M. castratorHNS queens were encountered in the same fungus garden chamber as the reproductively active female of M. goeldiiHNS. Thus, M. castratorHNS is host-queen tolerant (Table 1). The other three dealate M. castratorHNS queens were found together in a separate fungus chamber (chamber 1; Table 1). The 12 queens encountered with the M. goeldiiHNS queen showed different reproductive activities: three were active egg layers, showing developed ovaries, yellow bodies and sperm-filled spermathecae. Thus, the parasite can be polygynous. In contrast, the remaining nine queens were prereproductive with filled spermathecae, but the ovaries were still developing, and yellow bodies were absent. The three dealate queens from chamber 1 were also prereproductive . The single M. goeldiiHNS queen was reproductively active.

The unparasitized M. goeldiiHNS colony studied in 2008 contained a single reproductively active queen, 33 alate queens,

Entomology, 35, 379-392

© 2010 The Authors

Journal compilation © 2010 The Royal Entomological Society, Systematic Entomology, 35, 379-392

Table 3. Life history and morphological characters of inquiline parasites in fungus-gardening ants.

Incipient inquiline parasites


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