North-Western Journal of Zoology Vol. 4, No. 1, 2008, pp.42-49 [Online: Vol.4, 2008: 08]

An unusual worker morph of rugulosa Nyl. (: Formicidae)

Wojciech CZECHOWSKI1,*, Alexander RADCHENKO1 and Piotr ŚLIPIŃSKI1

1. Laboratory of Social and Myrmecophilous , Museum and Institute of Zoology, Polish Academy of Sciences, Wilcza 64, 00-679 Warsaw, Poland * Corresponding author: Wojciech Czechowski, E-mail: [email protected]

Abstract. A morphologically highly atypical worker found in the nest of Myrmica rugulosa Nyl. in the Gorce Mountains (southern Poland) is described. The finding is discussed in the context of so far known manifestations of teratological mutability in . This unique specimen, noticeably bigger than its normal nestmates, was characterised by a lack of the propodeal spines and a reduced number (from 11 to 8) of funicular segments. The spurs on the middle and hind tibiae were reduced and not pectinate. At the same time, the main specific diagnostic features of M. rugulosa (sculpture, proportions) were well retained.

Key words: Ants, Myrmica rugulosa, morphology, teratology, mutation.

Introduction category (i.e. traumatic variability), one should also count morphological modi- Myrmecological literature abounds fications (often symmetrical) brought with reports and descriptions of on by internal parasites, as well as gyne teratological, i.e. developmental mor- intercastes (sensu Heinze 1998) of phological abnormalities, afflicting parasitogenic origin (e.g. Espadaler & ants. The majority of cases of such mal- Riasol 1983, Czechowski et al. 2007a,b, formations are manifestations of Csősz, pers. comm. 2007; for review see traumatic (non-genetic) variability Passera 1975). Another category of caused by mechanical injuries, toxic relatively frequent developmental ab- factors and other harmful physical and normalities (of a genetic nature, sex- chemical environmental conditions linked) comprises gynandromorphs which have an impact on an organism (including ergatandromorphs) (e.g. in early stages of its development. Donisthorpe 1929, Wheeler 1937, Consequently, monstrous, usually Buschinger & Stoewesand 1971, asymmetric, individuals with their Parapura 1972, Wiśniewski 1981, body parts deformed in different ways Kutter 1986, Kinomura & Yamauchi have been observed (e.g. Buschinger & 1991). Stoewesand 1971, Berndt & Wiśniewski Ants of the subfamily 1984, Glancey & Lofgren 1986, seem to be especially prone to Wiśniewski & Sokołowski 1987, López teratological distortions both in terms & Ortuño 1992). In the same general of monstrousness and gynandro-

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morphs (see especially Buschinger & measurable morphological features of the Stoewesand 1971). Species of the genus atypical specimen with those of its normal Myrmica Latr. frequently suffer from nestmates. The measurements were as follows: morphological abnormalities, e.g. M. HL – maximum length of head in dorsal rubra (L.), M. ruginodis Nyl., M. view, measured in a straight line from sulcinodis Nyl., M. scabrinodis Nyl., and anterior-most point of clypeus (including any M. sabuleti Mein. (among others: carinae or rugae, if they protrude over the Donisthorpe 1938, Bibikoff 1949, anterior margin) to mid-point of occipital margin; Sweeney 1950, Kutter 1986, Krzyszto- HW – maximum width of head in dorsal fiak & Krzysztofiak 1989). In M. view behind (above) eyes; rugulosa Nyl., only mermithised FW – minimum width of frons between individuals, males (Czechowski et al. frontal lobes; 2007) and gynandromorphs (Łomnicki FLW – maximum width between external 1924), have been recorded. The present borders of frontal lobes; SL – maximum straight-line length of paper reports a case of a curious antennal scape in profile, from its articulation morphological anomaly in the latter with condylar bulb to proximal edge of scape; species, which does not seem to fall AL – diagonal length of alitrunk in profile, into any type of structural anomalies from the neck shield to posterior margin of previously observed in Myrmica ants. propodeal lobes; PW – maximum width of petiole from above; PPW – maximum width of postpetiole Study area, material and methods from above. Based on these measurements, made with Myrmecological studies that included a an accuracy of 0.01 mm, the following indices faunistic survey were conducted in the Gorce were calculated: Mountains (Western Beskidy, Western cephalic index – HL/HW; Carpathians, southern Poland) at the turn of frontal index – FW/HW; the 1980s and 1990s (see e.g. Czechowski frontal lobe index – FLW/FW; 1996). Among the rich faunistic material, scape indices – SL/HL and SL/HW; seven M. rugulosa nest samples were collected petiolar index – PW/HW; during a qualitative search on the shoulder of postpetiolar index – PPW/HW. a country lane along the stream Jaszcze in the village of Ochotnica Górna (49º 31’ N, 20º 15 E) in July 1989. One of these samples contained a highly atypical individual and Results four normal M. rugulosa workers. Photos of the abnormal specimen and a normal M. rugulosa worker from the same The atypical individual, though colony were taken with an IC3D camera and a larger than normal workers of M. Leica MZ16 stereoscopic microscope. Some rugulosa, was undoubtedly a worker; it standard morphometrics (measurements and had no ocelli, no trace of a scutum and indices), most representative of M. rugulosa, scutellum, and a gaster typical of out of those employed in the of the genus Myrmica (Radchenko & Elmes 1998, workers. All its measurements 1999) were obtained with an Olympus SZX-12 exceeded the means of those of the stereoscopic microscope to compare the main typical workers from the same nest

North-West J Zool, 4, 2008 44 Czechowski, W. et al.

from 5% (PW, PPW) to 15% (HL, HW, variability of the normal workers. The SL) (Tab. 1). However, the shape of the values of the remaining three indices scape and the proportions of the body, were slightly beyond this range (Tab. characteristic of the species, seemed to 1). One should not emphasise too much be well retained. The values of four out the latter observation, however, of seven indices obtained were because the comparative group contained within the range of contained only four specimens.

Table 1. Morphometric characteristics (measurements and indices) of the abnormal worker of M. rugulosa and its normal nestmates: the means and, in brackets, SD and ranges of values respectively. The index values of the atypical individual, which are out of the range of variability of the normal nest-mates are marked with an asterisk.

Feature Abnormal Normal (n = 1) (n = 4) HL 1.10 0.960 (0.050; 0.89-1.00) HW 0.96 0.838 (0.030; 0.80-0.87) FW 0.45 0.413 (0.015; 0.40-0.43) FLW 0.48 0.438 (0.015; 0.42-0.45) SL 0.86 0.745 (0.039; 0.69-0.77) AL 1.51 1.348 (0.085; 1.22-1.40)

Measurements (mm) (mm) Measurements PW 0.24 0.228 (0.050; 0.22-0.23) PPW 0.40 0.348 (0.010; 0.34-036) HL/HW 1.149 1.148 (0.026; 1.11-1.17) FW/HW 0.471* 0.493 (0.005; 0.49-0.50) FLW/FW 1.073* 1.058 (0.010; 1.05-1.07) SL/HL 0.780 0.778 (0.050; 0.77-0.78)

Indices SL/HW 0.897 0.893 (0.024; 0.86-0.91) PW/HW 0.253* 0.273 (0.013; 0.26-0.29) PPW/HW 0.414 0.418 (0.010; 0.41-0.43)

What was the most striking about The dorsal and posterior surfaces of the its appearance and what made it propodeum met at a blunt angle, but different from normal M. rugulosa the propodeum (seen in profile) was workers, and even from all other rounded, with no distinct angles, Myrmica ants, was the complete lack of tubercles or denticles (Fig. 4). The propodeal spines (Figs 1, 2) and the antennal funiculus consisted of eight, considerably reduced number of the rather than the usual 11, joints, i.e. the funicular segments of antennae (Fig. 3). antennae were nine-segmented (Fig. 5).

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Figures 1.-2. Atypical worker of M. rugulosa (1) and its normal nestmate (2).

North-West J Zool, 4, 2008 46 Czechowski, W. et al.

Figures 3.-6. Details of structure of the atypical worker of M. rugulosa: 3 – head and antennae, 4 – alitrunk and waist, 5 – antenna, 6 – middle tibia.

The six basal funicular joints were maximal width of the first tarsal of the same size and proportions as in segment (Fig. 6). The spur on the right normal workers of M. rugulosa. The middle tibia was somewhat better terminal joints were reduced, and the developed, distinctly longer than the most apical of the retained ones formed maximal width of the first tarsal a small two-segmented club (instead of segment, subequal in length to ½ of the 4-segmented club in normal workers) maximal width of the tibia, but simple (Figs 3, 5). Besides the two above- (with no pectination). The different mentioned most spectacular features, degree of reduction of the spurs on the the spurs on the middle and hind tibiae left and right middle tibiae was the were reduced to a different extent. only visible asymmetry in the body Those on the hind tibiae were slightly structure of this odd individual. All the shortened, almost simple, pectinate other morphological features of the only at the apex. The spur on the left specimen under discussion were middle tibia was considerably reduced, typical of M. rugulosa, and particularly simple, barely visible, shorter than the a not angularly (but also not ideally

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curved like in M. gallienii Bondr.) bent Radchenko and some social parasites scape without any trace of a ridge or previously assigned to the genera carina on its base (the latter present in Sifolinia Em. and Symbiomyrma Arnoldi M. hellenica Finzi), a wide frons, an (for details see Radchenko & Elmes almost straight frontal carina and not 2003). In these cases, however, only one extended frontal lobes, and the funicular joint has been reduced (not to sculpture of the head and mesosoma say that the thing concerns males). (Figs 3-5). Several dozen years ago, a new genus could have been easily described based on this unique specimen, Discussion especially if it had been found alone outside its nest. Even the present The morphology of the M. rugulosa authors found it quite tempting to individual presented in this paper describe their find as a possible new undoubtedly goes much beyond the social parasite within the genus normal variability of ant species, Myrmica (see Discussions in: especially those with monomorphic Czechowski et al. 2007a, b). Eventually, workers, such as the species of the in view of the circumstances of the genus Myrmica. Its most spectacular finding (an undoubted member of the peculiarities, i.e. the absence of the M. rugulosa colony) and the fact that propodeal spines and a drastic the main diagnostic features strictly reduction of the funicular segments, corresponded to those seen in M. have never been reported as mani- rugulosa, we recognised the odd festations of individual, even patho- specimen as a worker, though a highly logical, variability in this genus. atypical one, of this species. However, ‘spinelessness’ occurs within The question remains about the the genus Myrmica as a species-specific nature of such a peculiar deviation feature, so is a trait of genetic origin. from the norm. It did not look like a Namely, the only known Myrmica ants simple teratological change of with an angularly rounded propodeum traumatic origin. The possibility of its are the gynes (not workers) of M. parasitogenic background ought to be luteola Kupyanskaya – a supposed rejected, too. It is true that infestation temporary social parasite distributed in with internal parasites in the larval the Russian Far East, Japan and Korea stage (Kutter 1958, Csősz, pers. comm. (Radchenko 1994, Masuko & Terayama 2007) may cause conspicuous 2002, Radchenko & Elmes 2003). A symmetrical modifications of ant body similar situation occurs in the case of structures (including even taxonomic the number of antennal joints. There features and caste traits), but they are are few Myrmica species whose males accompanied by evidently pathological have 12-segmented (instead of nor- malformations, directly or indirectly mally 13-segmented) antennae, like M. resulting from the presence of the arnoldii Dlussky, M. tschekanovskii parasite, such as a distended gaster,

North-West J Zool, 4, 2008 48 Czechowski, W. et al. disproportionately small head and References strikingly enlarged (widened) petiole Berndt, K. P., Wiśniewski, J. (1984): Zur and postpetiole in Myrmica individuals Teratologie der Körperanhänge bei der infested with mermithid nematodes Pharaoameise Monomorium pharaonis (L.) (Czechowski et al. 2007a,b). No (Hymenoptera, Formicidae). Zoologischer abnormalities of this kind were seen in Anzeiger 213: 313-321. Bibikoff, M. (1949): Anomalies chez les fourmis the worker of M. rugulosa under du genre Myrmica. Mitteilungen der discussion (see Tab. 1). Quite the Schweizerishen Entomologischen Gessell- opposite: as an ant, apart from the schaft (Bulletin de la Société Entomologique question of its taxonomic status, it was Suisse) 22: 253-256. Buschinger, A., Stoewesand, H. (1971): Tera- well-proportioned, and as an organism tologische Untersuchungen an Ameisen. it appeared able-bodied. The very fact Beiträge zur Entomologie 21: 211-241. that it was sampled shows that it Czechowski W. (2006): Colonies of hybrids and belonged to the workers which were mixed colonies; interspecific nest takeover in wood ants (Hymenoptera, Formicidae). the first to react to a disturbance of the Memorabilia Zoologica 50: 1-116. nest. Czechowski, W., Radchenko, A., Czechowska, W. Considering the above arguments, it (2007a): Mermithid infestation strikingly cannot be ruled out that the reported alters the morphology of Myrmica rubra (L.) (Hymenoptera: Formicidae): possible taxo- morphological peculiarity had a nomical involvements. Annales Zoologici 57: possible genetic background. Un- 325-330. fortunately, with the small size of the Czechowski, W., Czechowska, W., Radchenko, A. sample, it cannot be established (2007b): Strikingly malformed host morphology: Myrmica rugulosa Nyl. and whether it was a completely isolated Myrmica sabuleti Mein. (Hymenoptera: case or whether there were more Formicidae) parasitised by mermithid similar individuals in that colony. As nematodes. Fragmenta Faunistica 50: 139- M. rugulosa is a polygynous species, it 148. Donisthorpe, H. (1929): Gynandromorphism in is not unthinkable that one of the ants. Zoologischer Anzeiger 82: 92-96. queens could produce such atypical Donisthorpe, H. (1938): An ergatandromorph of offspring. Myrmica laevinodis Nyl., and the list of gynandromorphs, etc., brought up to date (Hym., Formicidae). The Entomologist 71: 251-252. Acknowledgements. We thank Bálint Markó, Espadaler, G. X., Riasol, J. M. (1983): Cisticer- who, being amazed himself at the appearance of coides de Cyclophyllidea en hormigas our monstrous ant, encouraged us to publish this Leptothorax Mayr. Modificaciones morfologi- finding. We are also grateful to reviewers, the cas y etologicas del huesped intermediario. said Bálint, as well as Joanna Pętal and Günther Revista Ibérica de Parasitología 43: 219-227. Jansen, for their corrections and sound advice Glancey, B. M., Lofgren, C. S. (1986): A naturally how to improve the original version of the occurring teratology in the red imported fire manuscript. This paper has been prepared as part ant (Hymenoptera: Formicidae). The Florida of a research project sponsored by the Ministry of Entomologist 69: 764-767. Science and Higher Education, Warsaw – Grant Heinze, J. (1998): Intercastes, intermorphs, and No. 2P04C 064 29 assigned to A. Radchenko. ergatoid queens: who is who in ant reproduction? Insectes Sociaux 45: 113-124. Kinomura, K., Yamauchi, K. (1994): Frequent occurrence of gynandromorphs in the natural

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rubra, rugosa, arnoldii, luteola i schencki roda

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