Description and notes on the bionomics of a new species of ...molevol.cmima.csic.es/ribera/pdfs/asf_potamophilops_2012.pdf · Description and notes on the bionomics of a new species

Journal of Natural HistoryVol. 46, Nos. 11–12, March 2012, 717–727

Description and notes on the bionomics of a new species ofPotamophilops Grouvelle, 1896 (Coleoptera: Elmidae: Larainae), fromthe Cerrado biome in Brazil

André Silva Fernandesa,b* and Neusa Hamadac

aInstitut de Biologia Evolutiva (IBE, CSIC-UPF), Passeig Maritim de la Barceloneta 37-49,Barcelona, 08003 Spain; bCapes Foundation, Ministry of Education of Brazil, CEP: 70040-020,Brasília-DF, Brazil; cInstituto Nacional de Pesquisas da Amazônia, Coordenaçao deBiodiversidade, Manaus, Brazil

(Received 8 March 2011; final version received 17 December 2011; printed 8 February 2012)

Potamophilops bragaorum sp. nov. is described and illustrated based on adult speci-mens collected in a mountainous area in the Cerrado biome in Taquaruçú district,Tocantins state, Brazil. This is the second species described in the genus and itrepresents the northernmost record of Potamophilops, which is known only fromArgentina and Brazil. In this article we provide a diagnosis, details on the mor-phology and images of the habitus and structures used to determine the speciesand to distinguish the gender. Field observations permitted the description of someaspects on the biology of the new species that seem to be very similar to those ofother Larainae genera. Examination of gut contents revealed a diet based mostlyon periphyton.

Keywords: aquatic insects; riffle beetles; taxonomy; Cerrado biome; Neotropics

Introduction

Grouvelle (1896) created the genus Potamophilops to include the species Potamophiluscinereus Blanchard, 1841, because he considered that this species had character-istics that were not found in any previously known Larainae genus. The typespecies was then, Potamophilops cinereus (Blanchard, 1841), which was the onlyknown species in the genus (Spangler and Santiago 1987). In their revision of someNeotropical Larainae genera, Spangler and Santiago (1987) presented a diagnosis forPotamophilops and a detailed description and illustrations of P. cinereus. The genuswas known only from Argentina (Corrientes province) and Brazil (Mato Grosso doSul state and São Paulo state) (Blanchard 1841; Spangler and Santiago 1987; Vaninand Costa 2011) (Figure 1).

Based on Spangler and Santiago (1987) and on examination of specimens of thenew species, Potamophilops can be distinguished from all other Larainae genera by thefollowing combination of features: body elongated, densely pubescent; body lengthmore than 5.0 mm; labrum very broad, wider than clypeus; antennae widely sepa-rated at base, each antenna with 11 segments; pronotum wider than long, narrowedanteriorly, with deep and complete anterior transversal impression, posterolateral

*Corresponding author. Email: [email protected]

ISSN 0022-2933 print/ISSN 1464-5262 online© 2012 Taylor & Francishttp://dx.doi.org/10.1080/00222933.2011.651643http://www.tandfonline.com

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Figure 1. Potamophilops species distribution in Brazil and Argentina, South America.(1) Corrientes province, Argentina; (2) Mato Grosso do Sul state, Brazil; (3) Ribeirão Grande,São Paulo state, Brazil; (4) Taquaruçú, Tocantins state, Brazil.

angles depressed and flat; elytra without accessory striae, slightly broader thanpronotum at base, apex rounded to slightly angulated and weakly divergent; proster-num not triangular, prosternal process parallel between coxae, apex produced andligulated; pro-, meso- and metacoxae broadly separated; male genitalia elongated andslender, basal lobe longer than median lobe, median lobe with lateral callosity on eachside and more than twice as long as parameres.

Bertrand (1972) illustrated a larva and erroneously described it as belonging toPotamophilops. As Spangler and Santiago (1987) argued, in reality Bertrand describeda larva of Stegoelmis. True Potamophilops larvae have been described recently by Vaninand Costa (2011).

In this paper we describe and illustrate a new species of Potamophilops found in amedium-sized stream in a highland valley in the Brazilian savanna (Cerrado biome),in Taquaruçú district, Palmas municipality, Tocantins state, Brazil. Additionally, weprovide information on the bionomics of the species based on field observations andon preliminary studies of gut contents.

Materials and methods

The type series (six specimens) was collected directly from the substrate. The specimenswere preserved in vials with 80% or 99% ethanol. Some of the specimens were dried

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and pinned. Internal structures were dissected with the aid of pins and forceps in plateswith 70% ethanol and then cleared using potassium hydroxide, heated on a hot platefor about 14 minutes. After they had been examined and photographed, the dissectedstructures were stored in microvials with glycerin and kept together with the bodyremains from which they had been removed.

Morphological terminology follows Hinton (1940), Brown (1972) and Spanglerand Santiago (1987).

During the collection, field observations were conducted to obtain informationabout the bionomics of the species; no information of this nature is available for thegenus. The body size and the conspicuous behaviour of the species made observationspossible from a distance (1.5–2.0 m) of relatively low interference.

A preliminary study of the diet of Potamophilops bragaorum sp. nov. was carriedout by examination of the foregut, mid-gut and hindgut in temporary microscopicmounts of the digestive tract of four specimens. The complete gut was removed, frac-tionated on a slide with distilled water and observed under a compound microscope.

The depository institutions are: Coleção de Invertebrados, Instituto Nacionalde Pesquisas da Amazônia (INPA), Amazonas, Brazil; Coleção Entomológica JoséAlfredo Pinheiro Dutra, Departamento de Zoologia (DZRJ), Instituto de Biologia,Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, and the NationalMuseum of Natural History, Smithsonian Institution, Washington D.C., USA(NMNH).

Results and Discussion

Potamophilops bragaorum sp. nov.(Figures 2–4)

Diagnosis

Body average length (pronotum and elytra) 6.08 mm (standard deviation 0.25); ventriteI without carinae between metacoxae; parameres of male genitalia without hairs orsetae; median lobe of male genitalia with flat-topped and irregularly shaped lateralcallosities; styli of female genitalia with apical segment measuring one-third the lengthof the basal segment.

Description

Holotype. Male (Figures 2, 3, 4A–F, I). Greatest length 6.32 mm and width (posteriorthird of elytra) 2.35 mm. Body (Figures 2, 3) elongated, subparallel, robust, denselypubescent, moderately convex dorsally.

Head (Figures 2, 3): Finely, densely punctuated; punctures separated by a distanceapproximately half their diameter; frontal margin slightly concave. Eyes moderatelyprotuberant, laterally rounded, separated by a distance 1.5 times wider than eye diam-eter. Antenna with 11 segments; first two segments combined are four-fifths the lengthof the remaining segments combined; segments 3–11 form a club. Frontoclypeal suturepresent between bases of antennae. Clypeus rectangular, as long as and wider thanlabrum; anterior margin concave; lateral angles rounded. Labrum rectangular; anterior

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Figure 2. Potamophilops bragaorum sp. nov., holotype habitus. Scale bar 2.00 mm.

margin truncated; anterolateral angles rounded, with row of moderately long goldensetae. Maxillary palpus with four segments; first segment very short, half the lengthof second segment; segments 2–4 subequal in length; last segment diagonally trun-cated at the apex, forming depressed surface on internal margin. Labial palpus withthree segments; last segment swollen, twice as wide as second segment, as long as theremaining segments combined. Gula, at base, with the same width as the submentumand 2.5 times narrower at the apex.

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Figure 3. Potamophilops bragaorum sp. nov., holotype in detail. (A) Dorsal view; (B) ventralview. Scale bar 2.00 mm.

Colour: Cuticle black, except base of head, first two segments of labial palpi,labium, maxillae, coxae, trochanters, bases of femora and centre of metaventrite, whichare light to dark yellowish brown.

Thorax (Figures 2, 3): Pronotum (Figures 2, 3A) wider at base (1.88 mm) than long(1.34 mm); wider at base than at apex (1.2 mm); with deep, transverse and completeimpression across apical third; disc convex behind transverse impression; anterolateral

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Figure 4. Potamophilops bragaorum sp. nov. (A) Male genitalia, dorsal view; (B) male genitalia,ventral view; (C) male genitalia, left face of median lobe; (D) male genitalia, right face of medianlobe; (E) spicule of male; (F) female genitalia, ventral view; (G) male sternite VIII; (H) femalesternite VIII; (I) posterior end of male ventrite V; (J) posterior end of female ventrite V. Scalebar 0.50 mm.

angles obtuse; base strongly sinuated with small fovea (length, 0.13 mm) on each sideof midline in front of scutellum; posterolateral angles slightly produced, subacute,depressed and flat, with a posterior shallow constriction adjacent to each angle; lat-eral margin trisinuated and smooth, with anterior deep constriction joining transverse

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impression, adjacent to each anterolateral angle; posterolateral angles; anterior marginbroadly convex, extending over base of head; posterior margin with five arches, onenarrow and one broad on each side in front of the elytron, and one narrow in frontof scutellum. Elytra (Figures 2, 3A) subparallel; longer (4.7 mm) than wide, (max-imum width at basal third, 2.35 mm); humeral angle broadly rounded and tumid;without sublateral carinae; lateral margins smooth; disc with 10 rows of puncturesseparated by a distance equal to their diameters, half as wide as intervals betweenstriae; apex rounded to slightly angulated and dehiscent. Scutellum (Figures 2, 3A)slightly convex; subtriangular; wider than long; anterior margin convex; posteriorangle rounded. Prosternum (Figure 3B) longer (0.8 mm) than wide (0.54) betweenprocoxae (0.54 mm), with anterior margin truncated. Prosternal process with lateralmargins almost parallel between procoxae; apex abruptly narrowed and ligulated,starting after procoxae. Mesoventrite (Figure 3B) almost twice as wide (0.98 mm) aslong (0.53 mm) between mesocoxae; shorter than prosternum; posterior margin sin-uated and convex at median region. Metaventrite (Figure 3B) with median, glabrous,longitudinal impression extending to basal half; anterior margin between mesocoxaeconcave; posterior margin between metacoxae concave; posterior portion in frontof metacoxae with transverse arched impression on each side. Legs (Figure 2) longand slender; pro- meso- and metacoxae well separated, with mesocoxae more sepa-rated; mesotibiae with lateral surface poorly pubescent; metatibiae entirely and denselypubescent, except for alutaceous ventral surface. Tarsal claws well developed, long,without basal teeth.

Abdomen (Figure 3B): Longer (3.22 mm) than wide (maximum width, ventrite I,2.28 mm). Ventrite I (Figure 3B) with anterior margin moderately impressed, subtrian-gular between metacoxae; without carinae or impressions. Ventrite V (Figures 3B, 4I)densely pubescent with moderately long hair-like setae (longer in the posteromedialregion) extending beyond posterior margin; posterior margin sinuated, with moder-ately broad and deep concavity in the median region. Sternite VIII (Figure 4G) withlong and slender anterior region; anterior angle subacute; lateral angles slightly acuteand pointed backward diagonally; posterior region covered with medium to long hair-like setae; posterior margin sinuous, with angles rounded and a deep concavity in themedian region. Spicule (Figure 4E) long and slender, bifurcated at the middle; apicalmargin with few hair-like setae; paraprocts extending beyond apical margin of spicule.

Male genitalia (Figure 4A–D): Paramere (Figure 4A,B) short, less than 0.5 timesthe length of median lobe; moderately broad and rounded at base; narrowed towardsthe apex; apex subacute. Median lobe (Figure 4A–D) long and slender; in dorsalview (Figure 4A) wider than paramere; with dark stripe beginning at the same lineof paramere’s apex and extending until the apex of median lobe; lateral margins sin-uous and irregular, with asymmetrical callosities on each side; widened in the medianregion; apex ligulated. Median lobe in lateral view (Figure 4C,D) long and slender,curved to the venter, slightly widened in the median region and then narrowed towardsthe apex. Left face of median lobe (Figure 4C) with callosity beginning across medianregion of median lobe; callosity with upper shallow excavation and outer ventral mar-gin with granules. Right face of median lobe (Figure 4D) with callosity beginningabove median region of median lobe; callosity with moderately deep excavation andinner ventral margin with granules. Basal lobe (Figure 4A,B) longer than median lobeand slender; almost parallel from the base to the median region, slightly widened inthe median region and almost parallel from the median region to the apex.

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Female. Externally similar to male except for the elytral apex (more angulated andweakly curved to the external side) and the ventrite V (Figure 4J) (narrower at theapex, less sinuous at middle of apical margin and slightly denser pubescence). SterniteVIII (Figure 4H) with anterior portion as long as wide; anterior margin truncated;lateral angles acute, curved outward and pointed backward diagonally; posterior enddensely covered with medium to long hair-like setae; posterior margin with triangularangles and shallower, broad concavity in the median region.

Female genitalia (Figure 4F): Coxites longer than styli; wider at base than long,with irregular shape that resembles a boot positioned diagonally. Styli short; basalsegments curved and divergent, apical portion rounded and covered with setae thatvary from slender to stout and that curve to the external side; apical segment weaklynarrowed from the base to the apex, straight, cylindrical, with one-third the length ofbasal segment and pointed to the external side.

Intraspecific variation

Size range (n = 6): length 5.80–6.42 mm, greatest width 1.95–2.22 mm. Aside fromthe secondary sexual characters, the specimens examined did not have significantmorphological variation.

Comparative notes

Potamophilops bragaorum sp. nov. can be distinguished from P. cinereus by the smallersize (maximum 6.42 mm from the known specimens, compared with 7.0 mm for theP. cinereus holotype); by the coloration of first two maxillary palpi, mesotibiae andventrite I behind metacoxae (black, instead of reddish-brown in P. cinereus); by theabsence of carinae on ventrite I (instead of poorly defined carinae between the meta-coxae in P. cinereus); by the absence of hairs on parameres of male genitalia (insteadof short hairs present on lateral sides of parameres in P. cinereus); by the flattened andirregular lateral callosities on the median lobe of male genitalia (instead of roundedand well-defined callosities in P. cinereus); by the styli of female genitalia, with apicalsegment measuring one-third the length of the basal segment (instead of one-quarterthe length of the basal segment in P. cinereus).

Type locality

Ribeirão São João stream, Vai-Quem-Quer valley, Taquaruçú district, Palmas munic-ipality, Tocantins state (TO), Brazil (10◦23′43" S, 48◦07′55" W).

Type series

Holotype. Male (genitalia illustrated) BRAZIL: TO: Palmas, Taquaruçú, Vale do Vai-Quem-Quer, Ribeirão São João, 10◦23′43" S, 48◦07′55" W, manual collection, A.S.Fernandes leg., 28 December 2008 (INPA).

Paratypes. One male, same data as holotype (INPA); one female (genitalia illustrated),same data as holotype (INPA); one male, same data as holotype (DZRJ); one female,same data as holotype (DZRJ); one male, same data as holotype (NMNH).

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Etymology

The species epithet, bragaorum, is in honour of the Braga family, who hosted the seniorauthor and provided transport during his fieldwork in Tocantins, Brazil.

Bionomics

The type series was collected inside (depths around 0.05–0.5 m) or beside (rocks andlogs) a stream, around 5 m in width, with a bedrock streambed in a mountainous areaof the Cerrado biome, in the Central–West region of Brazil (Figure 5A,B). Specimensof P. bragaorum sp. nov. were found inhabiting different microhabitats; some weretaken from the riparian zone (with their bodies completely dry) and others fromcompletely submerged logs in the main channel of the stream, at depths up to approxi-mately 0.5 m. A few specimens were also collected while they were climbing (Figure 5C)against the strong water flow, on the rocky base of a small cascade (Figure 5B). Similarhabitats were described by Spangler and Santiago (1987) for Disersus Sharp, 1882 andPseudodisersus Brown, 1981.

Figure 5. Potamophilops bragaorum sp. nov. (A) Vai-Quem-Quer valley, Taquaruçú district,Palmas municipality, Tocantins state, Brazil; (B) cascade on the Ribeirão São João stream inthe Vai-Quem-Quer valley, type locality of the new species; (C) P. bragaorum sp. nov. out of thewater, as found in nature.

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Preliminary examination of the gut contents of four individuals revealed a poordiversity of items. Identifiable material was mainly diatoms, with no recognized fungalspores or hyphae. We conclude that the main food sources of P. bragaorum sp. nov. aregeneral detritus (unidentified) and unicellular algae (diatoms). Despite being unable toidentify the algae to the species level, we recognized at least three genera of diatoms:Gomphonema Ehremberg, Eunotia Ehremberg and a genus in the family Cymbellaceae,probably Encyonema Kützing. It seems clear that, as observed in Lara avara LeConte,1852, adults of P. bragaorum sp. nov. are scrapers, obtaining nutrients by ingestingthe microbial layer that adheres to wet or submerged wood and rocks (periphyton)(Steedman and Anderson 1985).

Potamophilops adults seem to have habits similar to those of other NeotropicalLarainae. They are riparian beetles, capable of entering the water and staying sub-merged for a long time, probably until the air reservoir in their elytra is exhausted(Brown 1987), and they can fly actively as described by Hinton (1940) and Spanglerand Santiago (1987).

Spangler and Santiago (1987), observing individuals of Disersus entering the waterat times, suggested that they could be either ovipositing females or adults foragingon periphyton. As we found a great abundance of periphyton in the gut contents ofP. bragaorum sp. nov., this foraging suggestion can be corroborated for Potamophilops.

Sometimes more than five individuals were seen together out of the water.However, no mating couples were observed during the short duration of our fieldobservations.

Acknowledgements

A.S.F. is grateful to Ariana S. Braga, Maria do Carmo Silva and Jerônimo P. Braga fortheir hospitality and support in Palmas and Taquaruçú, Brazil. Sincere thanks are due toWatson A. Gama Jr for identification of diatoms and Philip M. Fearnside, who reviewed themanuscript. We are also sincerely grateful to William D. Shepard, and two anonymous review-ers for their useful comments. Financial support was provided by the National Council forScientific and Technological Development (CNPq), Ministry of Science and Technology (MCT),Brazil, and by research projects supported by the Programa de Apoio aos Núcleos de Excelência(PRONEX)-CNPq-Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM)and INPA (MCT). Finally, A.S.F. is grateful to the Coordination for the Improvement ofHigher Education Personnel (Capes), Ministry of Education, Brazil, for the Ph. D. fellowship(CGBE/BEX – Proc. 5359-10-9).

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Brown HP. 1972. Aquatic Dryopoid beetles (Coleoptera) of the United States. Biota of fresh-water ecosystems, Identification manual no. 6. Columbus (OH): U.S. EnvironmentalProtection Agency. 82 pp.

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