First record of the genus Colosmittia Andersen & Sæther (Chironomidae: Orthocladiinae) from the Neotropical region

Primeiro registro do gênero Colosmittia Andersen & Sæther (Chironomidae: Orthocladiinae) para a região Neotropical

SYSTEMATICS, MORPHOLOGY AND PHYSIOLOGY

First record of the genus Colosmittia Andersen & Sæther (Chironomidae: Orthocladiinae) from the Neotropical region

Primeiro registro do gênero Colosmittia Andersen & Sæther (Chironomidae: Orthocladiinae) para a região Neotropical

Humberto F Mendes; Trond Andersen

Dept. of Natural History, Bergen Museum, Univ. of Bergen, Pb 7800, N-5020 Bergen, Norway; [e-mail]; [e-mail]

ABSTRACT

Colosmittia brasileira sp. n. from São Paulo state, Brazil, is described and illustrated based on a male imago. The genus Colosmittia Andersen & Sæther was described based on a single species, C. clavata Andersen & Sæther, from the West Usambara Mountains, Tanzania, East Africa. The discovery of the new species shows that Colosmittia has an Afro-Brazilian distribution pattern.

Key words: New species, Brazil, Diptera, biogeography, Inabrezian pattern

RESUMO

Colosmittia brasileira sp. n., proveniente do estado de São Paulo, é descrita e ilustrada com base no macho. O gênero Colosmittia Andersen & Sæther foi descrito com base em uma única espécie, C. clavata Andersen & Sæther, de "West Usambara Mountains" na Tanzânia, leste da África. A descoberta de C. brasileira sp. n. indica que o gênero Colosmittia possui padrão de distribuição geográfica do tipo afro-brasileira.

Palavras-chave: Espécie nova, Brasil, Diptera, biogeografia, padrão Inabreziano

The genus Colosmittia Andersen & Sæther was erected for C. clavata Andersen & Sæther, from the West Usambara Mountains in Tanzania, East Africa by Andersen & Sæther (1994). The genus differs from other known orthoclads by the combination of a strongly reduced 4-segmented palp, absence of anal point, and lack of squamal setae. The genus was tentatively placed in the Pseudosmittia group of genera, but does not appear to resemble any other described genus (Andersen & Sæther 1994).

Material and Methods

The species was taken in a Malaise trap in a primary Atlantic forest. The specimen was slide-mounted in Canada balsam following the procedures outlined by Sæther (1969). The general terminology follows Sæther (1980).

The holotype is deposited in the Museu de Zoologia da Universidade de São Paulo (MZUSP), São Paulo, Brazil.

Colosmittia brasileira sp. n. (Figs 1-6)

 

Type material. Holotype male: Brazil, São Paulo state, Parque Estadual Intervales, Ribeirão Grande, Barra Grande, 10-13.xii.2000, Malaise trap (Bosque 4), M T Tavares et al (MZUSP).

Diagnostic characters. The new species can be separated from C. clavata as it has antennae with 13 fl agellomeres, AR of about 0.30, and three strong postorbitals.

Etymology. From Portuguese, brasileira, meaning Brazilian in the feminine gender. The name should be regarded as noun in apposition.

Description. Male (n = 1). Total length 1.54 mm. Wing length 962 µm. Total length / wing length 1.61. Wing length / length of profemur 4.02. Coloration dark brown with lighter legs and antennae.

Head. Antenna with 13 flagellomeres, AR 0.30, ultimate flagellomere 119 µm long. Temporal setae reduced to three postorbitals. Clypeus with four setae. Tentorium, stipes and cibarial pump as in Fig 1. Tentorium 54 µm long, 10 µm wide at sieve pore. Stipes 57 µm long, 11 µm wide. Palp segment lengths / widths (in µm): 7 / 8; 16 / 10; 20 / 11; 23 / 9. Third palpomere with one sensilla subapically, 11 µm long (Fig 2).

Thorax (Fig 3). Antepronotum with single, very weakseta. Dorsocentrals 3; acrostichals 2 very weak in midscutum; prealar 1. Scutellum with two setae.

Wing (Fig 4). VR 1.39. Costal extension 95 µm long, false vein extending to 244 µm. Cu1 weakly sinuate. Brachiolum with one seta; R₄₊₅ with fi ve weak setae, other veins bare. Squama bare.

Legs. Spur of foretibia 32 µm long; midleg lost; longest spur of hind tibia 29 µm long, shortest spur broken. Width at apex of foretibia 18 µm, of hind tibia 19 µm. Comb with six setae, longest 20 µm, shortest 14 µm long. Lengths (in µm) and proportions of legs as in Table 1.

Hypopygium (Figs 5-6). Tergite IX with five setae; laterosternite IX with two setae. Phallapodeme 59 µm long; transverse sternapodeme 66 µm long. Virga very weak, 3 µm

Wing (Fig 4). VR 1.39. Costal extension 95 µm long, false six setae, longest 20 µm, shortest 14 µm long. Lengths (in vein extending to 244 µm. Cu₁ weakly sinuate. Brachiolum µm) and proportions of legs as in Table 1. with one seta; R₄₊₅ with five weak setae, other veins bare. Hypopygium (Figs 5-6). Tergite IX with five setae; Squama bare. laterosternite IX with two setae. Phallapodeme 59 µm long;

Legs. Spur of foretibia 32 µm long; midleg lost; longest transverse sternapodeme 66 µm long. Virga very weak, 3 µm long, apparently surrounded by tiny spines. Gonocoxite 116 µm long; superior volsella low, densely covered with setae basally; inferior volsella rounded, 21 µm long, reaching 0.65 of gonocoxite length. Gonostylus 50 µm long; megaseta 5 µm long. HR 2.32, HV 3.09.

Notes on the habitat. The new species was collected in a Malaise trap in a primary Atlantic forest in the Parque Estadual Intervales, São Paulo State. The park is situated in the Serra de Paranapiacaba, inside the nature reserve of the Serra do Mar mountain range. The park covers an area of 417 km² and includes parts of the municipalities of Ribeirão Grande, Eldorado, Guapiara, Iporanga and Sete Barras (Campos 2001). The main vegetation type is tropical Atlantic rain forest. The climate is tropical and super humid, with a dry season. The annual precipitation ranges from 1000 mm to 2000 mm and the mean annual temperature is about 20ºC (Nimmer 1989). Recently, several other orthoclad species collected in the park have been described, among them the so far endemic Antillocladius biota Mendes, Andersen & Sæther, and Gynocladius scalpellosus Mendes, Sæther & Andrade-Morraye (Mendes et al 2004, 2005).

Discussion

The African and the South American continents became completely separated at the end of middle Cretaceous, 98 to 93 million years ago. The formation of the Serra do Mar mountain range along the southeast coast of Brazil is complex; it evolved in response to tectonic forces like uplifting and volcanism (see e.g. Ribeiro 2006). These mountains are today covered with humid Atlantic forest. However, during glacial periods when a cooler and dryer climate prevailed, the humid forest shrunk to small refugia in sheltered places.

The West Usambara Mountains, where C. clavata was collected, belongs to the Eastern Arc, a chain of mountains stretching along the east coast of Tanzania. The Eastern Arc was formed by uplifting in connection with the formation of the Rift Valley (Windley 1995). It has been believed that these mountains are Neogene in age (40 Myr), but according to Griffiths (1993), studies have indicated that at least the Uluguru Mountain fault-block started to form as a distinct unit as far back as the Karoo period (290 Myr). At the end of Cretaceous, Africa was 15-18º south of its present position and humid forest covered the present North Africa in the Palaeocene (60 Myr). When Africa moved northwards, the pan-African forest fragmented. In eastern Africa, tropical rain forest has grown continuously during the last 30 million years (Wasser & Lovett 1993). The mountain forests in the Eastern Arc have thus been isolated and comparatively stable for a long period of time, and the mountains are considered to be among Africa's most important centers of endemism.

Banarescu (1990, 1995) discussed main biogeographical categories of freshwater animals. The northern Gondwanian or Inabrezian lineages include warm-eurythermic animals distributed in tropical South America, Africa, Australia and Southeast Asia; animals shared only by South America and Africa have an Afro-Brazilian distribution pattern. Sæther (2000) gave an overview of general distribution patterns of different chironomid genera or subgenera based on geographic co-evolutionary analyses using Brooks' Parsimony Analysis (see e.g. Brooks et al 2001, 2004 for a review of the method).

Sæther & Ekrem (2003) studied the Afrotropical chironomids in more detail and lists three non-cosmopolitan chironomid genera which are taken both in Africa and South America; two of these apparently exhibit an Inabrezian vicariance pattern. The Tanypodinae genus Djalmabatista Fittkau has its main distribution in South America, but is also present in Africa, Arabian Peninsula, East Asia and Australia. The single Afrotropical species, D. reidi (Freeman) was redescribed in detail by Sæther & Andersen (2000). The Pseudochironomini genus Manoa Fittkau, first described from the Amazon, Brazil, also exhibit Inabrezian vicariance following the discovery of one species from the West Usambara Mountains in Tanzania (Andersen & Sæther 1997) and one from the Everglades in Florida (Jacobsen & Perry 2002). Recently, the discovery of several new species of the chironomini genus Nilothauma Kieffer in South America also indicates Inabrezian vicariance (Adam & Sæther 1999, Mendes & Andersen 2009).

With the discovery of Colosmittia brasileira sp. n. in southeast Brazil, Colosmittia might thus be the first Orthocladiinae genus to show an Afro-Brazilian vicariance pattern. However, true vicariance is difficult to establish and might be rare within chironomids as many species apparently disperse easily.

Acknowledgments

We are greatly indebted to Dr Carlos J E Lamas, Museu de Zoologia, Univ. de São Paulo, and Dr Dalton S Amorim, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, USP, campus Ribeirão Preto, for the loan of material from the BIOTA-FAPESP project ["Limites geográficos e fatores causais de endemismo na Floresta Atlântica em Diptera" proc. 03/12074-9 - within The Biodiversity Virtual Institute Program (www.biota.org)]. Gladys Ramirez made the slide preparation.

Received 13/X/08.

Accepted 06/IV/09.

Edited by Roberto A Zucchi - ESALQ/USP

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Publication Dates

• Publication in this collection
  18 Nov 2009
• Date of issue
  Oct 2009

History

• Accepted
  06 Apr 2009
• Received
  13 Oct 2008