Apetaeninae

Munari, Lorenzo, 2007, Studies on the Canacidae (Diptera), subfamily Apetaeninae. I. Apetaenus enderleini, nomen novum for Listriomastax litorea Enderlein, 1909, with remarks on the chaetotaxy, morphology, and habitats of the Apetaeninae from the Kerguelen Biogeographical Province, Zootaxa 1542 (1), pp. 21-34 : 22-23

The Apetaeninae of the Kerguelen biogeographical province

The Apetaeninae are a group of subantarctic, litoral flies inhabiting the seashores of small archipelagos around the Antarctic continent. In the past, and also recently, these kelp flies were considered as belonging to the families Coelopidae or Canacidae (see in particular Tonnoir & Malloch, 1926, as a subfamily of Ephydridae ; Hardy, 1962; Harrison, 1953, 1959). Later, Griffiths (1972) transferred the Apetaeninae to the family Tethinidae , which he considered to be “well characterized as a monophyletic group”. This was also “corroborated in every respect” by Papp (1983). Since Griffiths (1972), the Apetaeninae have been treated in the family Tethinidae . An antithetic point of view was very recently expressed by Buck (2006) and D. K. McAlpine (2007), for which the family ‘Tethinidae’ should be considered as a paraphyletic group with regard to the Canacidae , as suspected informally by other students of these families. Buck (2006) also stated that “without further analysing canacid subfamily relationships, the Apetaeninae seem the most likely sister group to the Canacidae (s. str.)”. This opinion is founded on the phylogenetic analysis of some putative synapomorphies, such as (1) antennae broadly separated, inserted on more or less protuberant facial tubercles, (2) clypeus distinctly enlarged and anteriorly produced, (3) prementum apically distinctly emarginate, (4) tentorial arms of head capsule enormously developed and strongly sclerotized ( Buck, 2006). In my opinion, the first synapomorphy needs verification, since this character state was not found in the material examined or it was quite inconsistent.

D. K. McAlpine’s (2007) view to consider all the currently recognized subfamilies of “ Tethinidae ” (sensu Mathis and Munari, 1996) as subgroups of the Canacidae s. l. is herein accepted. Accordingly, the Apetaeninae are also regarded here as a subfamily of the Canacidae .

Until now, the subfamily included two genera, namely Apetaenus Eaton, 1875 (type species A. litoralis Eaton, 1875 ) and Listriomastax Enderlein, 1909 (type species L. litorea Enderlein, 1909 ). Both species occur sympatrically on the subantarctic French islands ( Mathis & Munari, 1996). In the last thirty-five years, however, all dipterists and ecologists dealing with these subantarctic flies have inexplicably overlooked the synonymy proposed by Hennig (1971), who downgraded Listriomastax as a junior synonym of Apetaenus (see further).

Apetaenus litoralis was also recorded from Macquarie Island ( Womersley, 1937; Mathis & Munari, 1996). According to Hardy (1962), this last record was based on Womersley’s misidentification. Indeed, the two specimens that Womersley identified as litoralis Eaton could belong to a new species, A. watsoni , described later by Hardy (1962). Thanks to the courtesy of Dr. N. Wyatt (BMNH) I had the opportunity to study two paratypes of Hardy’s species. This taxon perhaps represents a valid, micropterous species of Apetaenus , characterized mainly by the following combination of characters: postocellar setae strongly cruciate; only one pair of dorsocentral setae (prescutellar ones); wing strongly reduced as in A. litoralis ; body regularly covered with an apparently soft, dense villosity formed by a multitude of long and fine hairs, distinctly different from the characteristically bristly body (in particular the abdomen) of A. litoralis . Awaiting to find out additional material available for examination, I have for the time being intentionally avoided to dissect the abdomen of the sole paratype male preserved in BMNH, because the specimen appears rather sclerotized and extremely dried. Furthermore, it is very precariously attached on the micropin by a microscopic drop of glue.

Thus, I currently assume that Hardy’s taxon is either a very closely related species or even a well characterized geographical race of A. litoralis Eaton inhabiting the coastal environments of Macquarie Island, a remote place over 3550 nautical miles from Kerguelen area. Further studies, currently in progress, will hopefully clarify the taxonomic status of Hardy’s species.

Despite Hennig’s (1971: 54) synonymy of Listriomastax Enderlein with Apetaenus Eaton : “Gattung Apetaenus (Syn. Listriomastax)”, some authors continued to maintain these two genera separate. Papp (1983) even affirmed that “these two genera are not closely related” without giving further comments, whereas other renowned dipterists of the past, such as Séguy (1940) and Hennig (1971), regarded the two taxa to be closely related or even congeners ( Hennig, 1971).

After studying the type species of these two genera, I am now able to corroborate Hennig’s (1971) synonymy of Listriomastax Enderlein, 1909 with Apetaenus Eaton, 1875 . Both external and genitalic characters are consistent enough to justify the differences between the two type species, but, conversely, they are quite negligible and inconsistent on the generic level, in particular if we consider the evident morphological affinity of the male terminalia.

In the past, the main feature used to distinguish these two genera from the subantarctic French islands related to the different degrees of wing development that is micropterous in Apetaenus and macropterous in Listriomastax . Aptery is not known in the Apetaeninae . The contradictory citations by Crafford et al. (1986) about aptery and brachyptery in Apetaenus litoralis must be considered incorrect, as this species is exclusively micropterous.

Hennig (1971) stated that “Zweifellos bilden die 3 Arten ( litoralis Eaton , litorea – Hennig’s minor oversight: as the genus Apetaenus is of masculine gender, the specific epithet changes to litoreus , see further – Enderlein und watsoni Hardy ) der Gattung Apetaenus (Syn. Listriomastax ) auf den subantarktischen Inseln eine monophyletische Gruppe”. As far as I know, this is the only indication that Hennig gave about this synonymy. Furthermore, he clearly noted that the separation of these two genera was unjustified: “Als einziger Unterschied zwischen den Gattungen Apetaenus und Listriomastax , die schon Séguy (1940) mit Recht für nahe verwandt hielt, galt bisher die Ausbildung der Flügel (normal bei Listriomastax , rudimentär bei Apetaenus ). Nachdem nun Séguy (1965) nachgewiesen hat, dass auch bei Listriomastax litorea mikroptere Individuen neben brachypteren und makropteren vorkommen, ist der einzige Grund zur Trennung der Gattungen weggefallen“. As a matter of fact, as far as the wings of Listriomastax are concerned, Séguy (1965) stated unequivocally that “Leur plus ou moins grand développement permet de reconnaître trois types: macroptère, brachyptère et microptère” ( figs. 10 and 11 ). Tréhen & Vernon (1982), Tréhen et al. (1985) and Tréhen & Vernon (1986) also reported macropterous to micropterous phenotypes of L. litorea , a phenomenon formerly observed by Dreux on Cochons Island ( Séguy, 1965). I also found two distinctly brachypterous phenotypes among the specimens from “île aux Cochons” (MNHN) that had erroneously been determined by L. Papp as Apetaenus litoralis .

In the present work the above synonymy is definitely confirmed, and the following nomenclatural changes are also proposed:

Apetaenus Eaton, 1875 [masculine gender]

Macrocanace Tonnoir & Malloch, 1926 ; ( Mathis & Sasakawa, 1989, synonymy) Listriomastax Enderlein, 1909 ; ( Hennig, 1971, synonymy)

Accordingly, the type species Listriomastax litorea Enderlein, 1909 (by original designation) changes its name as follows:

Apetaenus enderleini , nomen novum

for Apetaenus litoreus ( Enderlein, 1909) , [from litorea to litoreus , relating to the masculine gender of Apetaenus ]

nomen preoccupatum by Apetaenus littoreus (Hutton, 1902) , [ICZN, 1999 (see art. 58 and 58.7)].

Figures

FIGURES 8–10. 8. Internal copulatory apparatus of Apetaenus enderleini [nomen novum], lateral view. Scale bar = 0.1 mm; 9. vestigial wing of Apetaenus litoralis; 10. Range of wing reduction, brachypterous to micropterous, in Apetaenus enderleini. (Figure 9 after Séguy, 1940; figure 10 after Séguy, 1965; © Publications Scientifiques du MNHN, Paris).

FIGURES 11–16. Specimens from the Crozet archipelago (figures 11–14). 11. Apetaenus enderleini, habitus of macropterous male; 12. Apetaenus litoralis, habitus of male; 13. Apetaenus enderleini, female abdomen showing the deep, median split on syntergite 1+2 (specimen photographed in alcohol); 14. Apetaenus litoralis, female abdomen dorsally; 15. Apetaenus litoralis, habitus of female; 16. ditto, head lateral view. (Figures 15–16, after Séguy, 1940, © Publications Scientifiques du MNHN, Paris).