Ectatomma parasiticum Feitosa & Fresneau , Feitosa, R. M., Hora, R. R. & Delabie, J. H. C., 2008

Feitosa, R. M., Hora, R. R. & Delabie, J. H. C., 2008, A new social parasite in the ant genus Ectatomma F. Smith (Hymenoptera, Formicidae, Ectatomminae)., Zootaxa 1713, pp. 47-52: 49-52

publication ID

21396

persistent identifier

http://treatment.plazi.org/id/08B2B916-C0CD-FCCE-0238-361C7FD509FB

treatment provided by

Christiana

scientific name

Ectatomma parasiticum Feitosa & Fresneau
status

sp. nov.

Ectatomma parasiticum Feitosa & Fresneau  HNS  , sp. nov.

Figures 1, 2

Holotype gyne. MEXICO: Apazapan, Veracruz, 19°19'38"N 96°43'21"W, ix.1999, D. Fresneau col. [INEC]. Paratypes. same data as holotype (1 gyne) [ CPDC]; (1 gyne) [ UNCB]; (1 gyne) [INEC]; vii.2000, D. Fresneau & R. Hora cols. (1 gyne) [ LACM]; (2 gynes) [ MZSP]; (1 gyne) [ USNM].

Diagnosis. Size relatively small (WL approximately 3.80 mm); clypeus and frontal area without sculpture; antennal scapes longer than the maximum head width (SI> 108); petiole relatively thick in lateral view.

Gyne description. Holotype (paratypes): HL 2.10 (2.06-2.16); HW 1.85 (1.73-1.88); SL 2.04 (1.92- 2.06); EL 0.51 (0.50-0.58); PW 1.69 (1.62-1.77); WL 3.88 (3.65-4.04); PTL 0.79 (0.78-0.88); PTW 0.92 (0.92-1.07); CI 88.07 (84.11-88.89); SI 110.42 (108.57-113.04); OI 27.50 (27.50-31.25); PTI 85 (82.14- 85.71). Color yellowish brown to dark reddish brown, including appendages. Mandibles finely and densely striate, with sparse piligerous punctures; clypeus, genae, and frontal area predominantly smooth, but opaque; dorsal surface of head densely and coarsely reticulated, except for the areas of antennal articulations, which are finely punctate; ventral surface of head with sparse longitudinal striae; antennal scapes finely and longitudinally striate. Mesosoma with variously oriented costulae, from sparse and transverse on dorsum of pronotum and propodeum to dense and subconcentric on the dorsum of scutum and scutellum; forecoxae with dense, fine, regular transverse striation; legs mostly smooth and shining. Lateral and posterior faces of petiolar node with sparse, short, longitudinal costulae; sculpture of gaster consisting of arched, transverse costulae, becoming gradually finer from first to terminal segment.

Pilosity cream-colored. Body covered by relatively sparse, long, suberect hairs; antennal scapes and legs with short, suberect hairs; antennal funiculi and tarsi covered by fine apressed pubescence.

Head subrectangular, with weakly convex lateral borders and vertexal margin straight; masticatory margins of mandibles multidenticulate and with a large apical tooth; clypeus strongly convex anteriorly; frontal lobes reduced; scapes in repose fairly surpassing the posterolateral margins of vertex; funicular segments gradually thickened distally; compound eyes placed near the posterolateral portions of head; ocelli present and reduced in size.

Pronotum with a distinct median eminence directed forward and a conspicuous pair of dorsolateral (humeral) projections; scutum large and rounded; notauli almost indistinct among sculpturation; parapsidial lines feebly visible and subparallel; scutoscutellar sulcus deeply impressed; scutellum relatively narrow and strongly convex, in lateral view; dorsal face of propodeum meeting the declivous face in a pair of reduced, blunt teeth; propodeal spiracle elliptical. Wing venation fully developed. Forewing with a weakly colored stigma; longitudinal veins Sc+R, SR, M, Cu, and A present; SR extending distally beyond stigma, forming 1R and 2R cells; cross vein 1r vestigial, not forming the 2R cell; M and Cu also extend distally as tubular veins for most of their length; A not extending beyond the junction with Cu; C, R, Cu, 1M, 1Cu, and SR cells closed. Hind wing with Sc+R extending beyond point where they connect to M, which continues as a tubular vein as much as Sc+R and then extends as spectral vein to wing distal border; basally M+Cu extending as a tubular vein beyond junction with Anal vein, which continues shortly beyond this point; seven submedian hamuli present.

Petiole ventrally carinate; in lateral view, petiolar node thick and subtriangular; anterior slope nearly concave and posterior slope slightly convex. Sternite of first gastral segment with a distinct anterior projection. Worker. Unknown (but see comments bellow). Male. Unknown.

Etymology. The specific epithet is a reference to the parasitic nature of this species.

Comments. Gynes of the socially parasitic Ectatomma parasiticum  HNS  can be distinguished from the gynes of its host species, E. tuberculatum  HNS  , by the following features: sparser sculpture on the body; smaller size (Fig. 2), with WL approximately 3.80 mm (around 5.40 mm in E. tuberculatum  HNS  ); clypeus and frontal area devoid of any sculpture (usually longitudinally striate in E. tuberculatum  HNS  ); antennal scapes longer than the maximum head width, with SI> 108 (<99 in E. tuberculatum  HNS  ); propodeal spines reduced to minute teeth; and petiole thicker in lateral view (flattened anteroposteriorly in E. tuberculatum  HNS  ). The reduced size and widener petiole of E. parasiticum  HNS  are also characteristic of the inquiline syndrome in other ant species (Wilson 1984; Radchenko& Elmes 2003).

Males produced by parasitized colonies were of a uniform morphology and indistinguishable from males of E. tuberculatum  HNS  . Thus it remains unknown if males of E. parasiticum  HNS  are lacking, present but not yet observed, or observed but indistinguishable from E. tuberculatum  HNS  . According to Hora et al. (2005), one of the 10 colonies of E. parasiticum  HNS  reared in laboratory produced four small "workers." However, these workers presented a developed spermatheca and six to 10 ovarioles, in contrast to typical workers of E. tuberculatum  HNS  which lack the spermatheca and possess only one to four ovarioles (Feneron & Billen 1996; Hora et al. 2001). The presence of developed reproductive structures in these specimens suggests that they are possibly intermediate(intercaste?) reproductive forms of E. parasiticum  HNS  and not true workers.

Up to now, the occurrence of this species is restricted to Apazapan, state of Veracruz, Mexico. However, its host, E. tuberculatum  HNS  , is widely distributed in the Neotropics, from Mexico to northern Argentina. We expect that the excavation and detailed examination of E. tuberculatum  HNS  colonies in different localities could reveal new populations of E. parasiticum  HNS  .

A detailed behavioral and genetic study on the interaction between E. tuberculatum  HNS  and E. parasiticum  HNS  (so far undescribed and treated as "microgynes") was conducted by Hora et al. (2005). Gynes and workers of E. tuberculatum  HNS  and gynes of E. parasiticum  HNS  were sequenced for the cyt b region and the results showed two haplotypes. The haplotypes differed in seven variable sites, with a nucleotide sequence difference of 0.93%. They clearly discriminate E. parasiticum  HNS  from the group composed of workers and gynes of E. tuberculatum  HNS  . According to the findings of Hora et al. (op. cit.), E. parasiticum  HNS  is a genetically distinct social parasite producing of almost exclusively sexual offspring. The co-occurrence of E. parasiticum  HNS  and E. tuberculatum  HNS  in the field (nine mixed colonies found) suggests that the parasite usurps established colonies of the host, but does not kill the resident gynes. Agonistic interactions were also observed, exclusively from workers and gynes of E. tuberculatum  HNS  against the parasites.

Microgynes are also found in Ectatomma ruidum  HNS  ; however, this is a truly gyne-polymorphic species, and the offspring of both microgynes and normal gynes consist of workers, males, and both microgynes and normal gynes. It was therefore suggested that the two gyne morphs in E. ruidum  HNS  represent alternative phenotypes adapted to different ways of dispersal and colony founding. Ectatomma ruidum  HNS  microgynes are thought to disperse and to found new colonies solitarily, while the macrogynes are a stationary morph (Lachaud et al. 1999).

The study of Hora et al. (2005) and the present paper raise the possibility of the occurrence of similar undescribed social parasites within other basal ant lineages.

CPDC

Brazil, Bahia, Itabuna, Centro de Pesquisas do Cacau

UNCB

Colombia, Bogota, Universidad Nacional de Colombia, Insituto de Ciencias Naturales de la Universidad Nacional

LACM

USA, California, Los Angeles, Los Angeles County Museum of Natural History

MZSP

Brazil, Sao Paulo, Sao Paulo, Museu de Zoologia da Universidade de Sao Paulo

USNM

USA, Washington D.C., National Museum of Natural History, [formerly, United States National Museum]