The Gyrinidae ( Coleoptera ) of the Maritime Provinces of Canada : new records , distribution , and faunal composition

Th e Gyrinidae (whirligig beetles) of the Maritime Provinces of Canada are surveyed. Twenty-two species are now known to occur in the region, 19 of which have been recorded from Nova Scotia, 17 from New Brunswick, and 9 from Prince Edward Island. Seven species are newly recorded in Nova Scotia, and four in New Brunswick. Two of these, Gyrinus dichrous LeConte and Gyrinus gehringi Chamberlain, are newly recorded in the Maritime Provinces. Th e zoogeographic composition of the fauna within the region is briefl y examined, the species falling into six categories. Islands portions of Atlantic Canada (Prince Edward Island, Cape Breton, and insular Newfoundland) have a diminished fauna, roughly 40% that of neighbouring mainland areas. Th e proportionate composition of the gyrinid fauna in various portions of Atlantic Canada is similar to that of the Carabidae (a much larger suite of beetles that have been more extensively investigated) with the exception of New Brunswick, where a diminished number of recorded gyrinids would appear to indicate an insuffi cient collecting eff ort for this family in the province. Finally, a preliminary examination of multispecies associations is presented which indicates that some species more frequently engage in such aggregations than others.


Introduction
Th e beetle family Gyrinidae are colloquially known as whirligig beetles from their habit of swimming rapidly in circles, particularly when threatened.Adults cluster together, sometimes in large multispecies aggregations, on the surface of both lotic and lentic environments.Th eir eyes are divided so that the upper pair remain above the waterline, and the lower set is below the waterline as the beetles swim on the water surface.Adults are generalist scavengers and predators, feeding on dead or living animal material fl oating on the water surface, but will also feed on vegetative material if suitable animal prey are not available.Larvae are predaceous and feed on aquatic insect larvae and nymphs (Oygur and Wolfe 1991;Roughley 2000).
Th ere are 56 species in four genera known in North America, 35 of which have been recorded in Canada (Roughley 1991(Roughley , 2000)).Nineteen species were recorded by Roughley (1991) in the Maritime Provinces of Canada: 14 from New Brunswick, 11 from Nova Scotia, and 4 from Prince Edward Island.Subsequently Majka (2008) added fi ve species (and removed one) from the faunal list of Prince Edward Island.Th ere has, however, been comparatively little attention to this family in the past two decades in the region, and in the present account we report eleven new provincial records, and two new regional records as result of recent investigations, and the examination of voucher material in reference collections.Pro-tibia yellowish or reddish brown.Elytra slightly acuminate at the apex in the male (Fig. 3); elytra sinuate and fairly acuminate at the apex in the female (Fig. 4).10.5-11.5 mm ...........Dineutus assimilis [syn.D. americanus Linnaeus] -Pro-tibia black or reddish-brown.Elytra fairly acuminate at the apex in the male (Fig. 5); elytra sinuate and fairly acuminate at the apex in the female (Fig. 6).11.0-12.0mm .Dineutus assimilis is newly recorded in Nova Scotia (Fig. 7).It was reported from Prince Edward Island by Roughley (1991) and Majka (2008).

Dineutus discolor Aubé, 1838
Dineutus discolor was reported from Nova Scotia by Roughley (1991).It has been recorded from the mainland of the province (Fig. 7).Morrissette (1979) reported that it preferred clear, running water.Majka (2008).It is widely distributed in the region (Fig. 7).Note: this species has sometimes been referred to as "Dineutus horni" a name which Majka (2008) designated as an incorrect subsequent spelling of "Dineutus hornii."Morrissette (1979) reported it from boggy and semi-boggy lakes.Dineutus nigrior is newly recorded in New Brunswick and Nova Scotia.It was reported from Prince Edward Island by Majka (2008).It is widely distributed in the region (Fig. 7).Morrissette (1979) reported it from semi-boggy lakes where the water is stagnant.

Gyrinus cavatus Atton, 1990
Gyrinus cavatus was reported from Nova Scotia by Atton (1990) and Roughley (1991).In Nova Scotia it has only been found on Cape Breton Island (Fig. 9).Prior to Atton's (1990) description of the species, separating it from the Gyrinus minutus Fabricius, 1798 (a Holarctic species recorded by him in North America from northern sites in British Columbia and the Yukon Territories east to Labrador and northern Newfoundland), previous records of G. cavatus were reported under the name of G. minutus.Roughley (1991) appears to have confused Atton's (1990) fi ndings, reporting both species from Nova Scotia and treating G. cavatus in the subgenus Gyrinus (s.str.) rather than in Gyrinulus Zaitsev.Oygur and Wolfe (1991) were apparently unaware of Atton's (1990) separation of G. minutus (sensu lato) into two species.Kenner (2000) subsequently reported G. cavatus from Ontario, Québec, and Maine.
Gyrinus minutus is consequently removed from the faunal list of New Brunswick and Nova Scotia.Th e ecology of this G. cavatus has not been documented, however, Oygur and Wolfe (1991) reported G. minutus from woodland pools, rocky pools, semi-peaty lakes, peat-ringed bogs, and dystrophic habitats.Presumably G. cavatus is found in similar habitats.We have not been able to fi nd voucher specimens of this species from New Brunswick in any Canadian collection.Consequently, further research should be conducted to ascertain if this species actually occurs in the province as reported by Roughley (1991).

Gyrinus affi nis Aubé, 1838
Gyrinus affi nis was recorded from New Brunswick by Oygur and Wolfe (1991), Nova Scotia by Oygur and Wolfe (1991) and Roughley (1991), and Prince Edward Island by Majka (2008).It is one of the most abundant and widely distributed species in the region (Fig. 8).Oygur and Wolfe (1991) recorded the species from streams and lakes while Morrissette (1979) reported it from stagnant water.It is found in both lotic (41%) and lentic (59%) habitats (Oygur and Wolfe 1991).

Gyrinus analis Say, 1823
Gyrinus analis was reported from Nova Scotia by Roughley (1991) (Fig. 8).It has not been recorded from New Brunswick (Table 1).Oygur and Wolfe (1991) recorded the species from backwaters along larger rivers and also from smaller streams while Morrissette (1979) reported it from slow-moving portions of rivers.It is found in primarily in lotic (71%) habitats (Oygur and Wolfe 1991).

Gyrinus aquiris LeConte, 1868
Gyrinus aquiris was reported from New Brunswick by Oygur and Wolfe (1991) and Roughley (1991) and from Nova Scotia by Campbell et al. (1987) (Fig. 8).In Nova Scotia it has only been found on Cape Breton Island (Fig. 2).Although Roughley (1991) reported it from Prince Edward Island, Majka (2008) removed it from the province's faunal list since there are no voucher specimens or published records.Morrissette (1979) reported the species from ponds and lakes invaded by aquatic plants.Oygur and Wolfe (1991) reported 80% of specimens from lentic habitats.

Gyrinus latilimbus Fall, 1922
Gyrinus latilimbus was reported from New Brunswick and Nova Scotia by Roughley (1991) (Fig. 10).Robert (1955) and Morrissette (1979) reported it from small deep lakes near dense emergent vegetation (i.e., Carex and Scirpus spp.).Oygur and Wolfe (1991) reported it primarily (71%) from lentic habitats.We have not been able to fi nd voucher specimens of this species from New Brunswick in any Canadian collection.
Consequently, further research should be conducted to ascertain if this species actually occurs in the province.Gyrinus lecontei is newly recorded in Nova Scotia.It was recorded from New Brunswick and Prince Edward Island by Oygur and Wolfe (1991) and Roughley (1991), and from Prince Edward Island by Majka (2009) (Fig. 10).Morrissette (1979) reported it from small deep ponds and lakes invaded by aquatic plants.Oygur and Wolfe (1991) reported it primarily (80%) from lentic habitats.

Gyrinus pleuralis Fall, 1922
Gyrinus pleuralis was reported from New Brunswick (as well as Ontario and Québec) by Roughley (1991).Oygur and Wolfe (1991), however, pointed out that this species is easily confused with G. affi nis because the variations in body shape and colour overlap.Gyrinus pleuralis is a western species recorded in Canada from British Columbia to Saskatchewan (Oygur and Wolfe 1991).Th us, previous reports of the species from New Brunswick would certainly have been in error and the species is removed from the faunal list of New Brunswick.

Gyrinus sayi Aubé, 1838
Gyrinus sayi was recorded from New Brunswick and Nova Scotia by Oygur and Wolfe (1991) and from all three Maritime Provinces by Roughley (1991) (Fig. 11).It is one of the most common and widely distributed species in the region (Fig. 5).It has been reported from many aquatic habits; Oygur and Wolfe (1991) reported it from both lentic (65%) and lotic (35%) habitats.

Gyrinus ventralis Kirby, 1837
Gyrinus ventralis was recorded from New Brunswick by Roughley (1991).Morrissette (1979) reported that it prefers fl uvial lakes.Oygur and Wolfe (1991) reported it primarily (80%) from lentic habitats.We have not been able to fi nd voucher specimens of this species from New Brunswick in any Canadian collection.Consequently, further research should be conducted to ascertain if this species actually occurs in the province.

Discussion
As a result of the present investigations, 22 species of Gyrinidae are now known to occur in the Maritime Provinces of Canada; 19 of these have been recorded from Nova  Scotia, 17 from New Brunswick, and 9 from Prince Edward Island (Table 1).Two species, Gyrinus dichrous and Gyrinus gehringi, are newly recorded in the region.
It is clear that further fi eldwork needs to be conducted to obtain a fuller understanding of the gyrinid fauna of the region, particularly in many portions of New Brunswick where the collecting eff ort for this group has been meager.Nonetheless, this study off ers the opportunity to briefl y examine what is known of the fauna with regard to its composition and distribution.Th e scale of the fauna in the Maritime Provinces is exactly the same as that of the neighbouring state of Maine, 22 species (C.G.Majka, unpublished data).Th ere are fi ve species which have been recorded in Maine including Dineutus emarginatus Say, Gyrinus rockinghamensis LeConte, Gyrinus borealis Aubé, Gyrinus maculiventris Le-Conte, and Gyrinus pernitidus LeConte (Oygur and Wolfe 1991;Chandler 2001), which have not been recorded from the Maritime Provinces.In Newfoundland and Labrador (having a gyrinid fauna of 10 species), Gyrinus dubius Wallis and the Holarctic Gyrinus opacus Sahlberg, have been recorded in addition to species found in the Maritimes (Roughley 1991).All these species are potential candidates which could be found in the Maritime Provinces, and should be looked for in the region in appropriate areas and habitats.
Examining the distribution of the gyrinid fauna of the Maritime Provinces (Figs. 1-5), the species which are present appear to fall into several categories: 1) Widely distributed throughout the region: Dineutus hornii, D. nigrior, Gyrinus affi nis, G. gehringi, and G. sayi.Th ese are species found throughout the Maritime Provinces and on both Cape Breton Island and the Nova Scotia mainland.2) Scattered and apparently local throughout the Maritime Provinces: Gyrinus bifarius, G. confi nis, G. fraternus, G. lecontei, and G. pectoralis.More extensive collecting may show that these species are also widely distributed in the region, although perhaps not as abundant as those in the previous category.3) Very local distribution: Dineutus assimilis (NS and PEI), Gyrinus aquiris (NB and NS), G. analis (NS), G. aeneolus, G. gibber, and G. ventralis (NB).Th ese are species known from only a very small number of localities in the region.Further research is indicated to ascertain if they have a wider distribution than the present small number of records would indicate.4) Found only on Cape Breton Island: Gyrinus cavatus and G. impressicollis.Th e former may also occur in New Brunswick, but voucher specimens for the province are lacking.Th ese species appear to favour the climatic and physiographic conditions found in the Cape Breton Highlands Plateau-Fir Forest region of Nova Scotia (David and Browne 1996).5) Species apparently confi ned to the Atlantic coast of Nova Scotia: Dineutus discolor and Gyrinus dichrous.All records of both species are from the Atlantic coastal and Atlantic interior regions of Nova Scotia (David and Browne 1996).It is possible that these species favour, (or even are confi ned to) areas that exhibit the climatic and physiographic conditions found in these regions.6) Species recorded only in Nova Scotia: In addition to the above two categories, Gyrinus latilimbus and G. pugionis have only been recorded in Nova Scotia (on both the mainland and on Cape Breton Island) in the Maritime Provinces.Given that both species are known from both the province of Québec and the state of Maine, it would appear likely that an insuffi cient collecting eff ort in New Brunswick is the reason why these species have not been recorded there.
As is typical with respect to islands (McArthur and Wilson 1967), the gyrinid faunas of Prince Edward Island (37.5%),Cape Breton (41.7%), and insular Newfoundland (41.7%) are proportionately diminished in comparison with the total Atlantic Provinces fauna (Table 2).Th e scale of these faunas is almost identical, despite the considerable diff erences in size of these three island masses (PEI, 5,660 km 2 ; Cape Breton, 10,311 km 2 ; Newfoundland, 111,390 km 2 ), and diff erences in distance from the neighbouring mainland (PEI,13 km;Cape Breton,1.5 km;Newfoundland,35 km).
It is also instructive to consider the proportionate composition of the gyrinid fauna of various portions of Atlantic Canada (Table 2) in comparison with the region's native carabid fauna (adventive species excluded), a much larger suite of beetles that have been more extensively investigated (Majka et al. 2007;Webster and Bousquet 2008).A comparison of these indicates a relatively close proportionate correspondence for all areas except for New Brunswick, where 82.8% of the Atlantic Canadian Carabidae have been recorded.In contrast, only 70.8% of the Atlantic Canadian Gyrinidae have been found there, a further indication that the collecting eff ort in New Brunswick appears to have been insuffi cient to completely discern the province's gyrinid fauna.
As early as LeConte (1868), investigators have drawn attention to multi-species aggregations of gyrinids.Oygur and Wolfe (1991) summarized some of these accounts, pointing out that frequently as many as six species can be found together in swarms which may sometimes consist of hundreds of individuals.Robert (1955) found specifi c associations of Gyrinus pectoralis, G. sayi, G. aeratus, and G. affi nis in 25 of 28 collections, with G. pectoralis dominant in all but one of these sites.Th e functional signifi cance of these aggregate swarms has received some attention from investigators.Heinrich and Vogt (1980) showed that individual gyrinids were more readily caught by predaceous fi sh than individuals in swarms, and proposed that aggregations may serve a defensive role.Adult gyrinids secrete a complex of four norsesquiterpenes (the most important being gyrinidal, a precursor of the other three) from pygidial glands at the joints of legs and the edges of the thorax (Oygur and Wolfe 1991).Th ese chemical secretions are repugnant to many fi sh, and Benfi eld (1972) postulated that aggregate swarms might serve a function in advertising this defensive mechanism (i.e., aposematic displacement).Heinrich and Vogt (1980), however, argued against this, since individuals in such swarms do not continually secret these chemicals, only doing so when attacked.Gyrinid aggregations have not been the subject of specifi c research in the Maritime Provinces, although indirect evidence for interspecifi c associations can be gleaned from the data by examining records of specimens collected by the same collector, at the same site, on the same date.From such data one can infer potential interspecifi c associations.Table 3 presents this information from collections of gyrinids made in the Maritime Provinces.
Each numeral indicates that species pairs have been collected (at least once) in association (in some instances this may have been within a larger multi-species association).Th is information is (as noted above) from indirect data and is certainly incomplete, since there are a number of species (as also outlined above) for which there is very little collection data.Consequently the number of recorded species associations is inclined towards those species that have been frequently collected.Nonetheless, this data does off er a useful departure point for further investigation of this phenomenon.For example, Gyrinus sayi ranks fi rst in both the number of recorded interspecies associations (15) and number of specimens collected (267); whereas, the second most abundantly collected species in the region, Gyrinus dichrous (242 specimens), ranks sixth in recorded interspecies associations (7), an apparent indication that G. sayi much more frequently engages in multi-species aggregations.
Although all these observations must be treated as preliminary, and subject to further fi eldwork and research, they do off a useful departure point for an analysis of the region's gyrinid fauna.

Figure 11 .
Figure 11.Th e distribution of Gyrinus sayi and Gyrinus pugionis in the Maritime Provinces of Canada.

Table 1 .
Th e Gyrinidae fauna of the Maritime Provinces of Canada.
Notes: NB, New Brunswick; NS, Nova Scotia; PEI, Prince Edward Island.Numbers represent the number of county records in each province.Th ere are 15

Table 2 .
Zoogeographic composition of the native Atlantic Canadian Gyrinidae and Carabidae: number and proportion of species.
Webster and Bousquet (2008)are derived fromMajka et al. (2007)andWebster and Bousquet (2008).Note: Th e totals are the sum of species pairs indicated in both the horizontal row and vertical column for each species.

Table 3 .
Gyrinid Multi-species Associations in the Maritime Provinces.