Abiahy B.B. do1, Rocha C.E.F. da2, Ferrari F.D.3 2007. Redescription of Limnoithona tetraspina Zhang et Li, 1976 (Copepoda, Cyclopoida) with a discussion of character states shared with the Oithonidae and older cyclopoids // Invertebrate Zoology. Vol.3 (for 2006). No.2: 115–135 [in English].

1 Avenida Manuel Hipolito do Rego 1270/ap. 09, 11.600-000 Sao Sebastião, SP, Brasil.

2 Universidade de São Paulo, Instituto de Biociências, Departamento de Zoologia, Rua do Matгo, travessa 14, No. 321, 05508-900 São Paulo, Brazil.

3 Department of Invertebrate Zoology, MRC-534, National Museum of Natural History, Smithsonian Institution, 4210 Silver Hill Rd., Suitland, MD 20746 U.S.A.

KEY WORDS: Copepoda, Cyclopoida, Limnoithona, taxonomy, brackish water, zoo-plankton.

ABSTRACT: Limnoithona tetraspina Zhang et Li, 1976 is redescribed, and the morpho-logy of the cephalosome, rostral area, oral appendages, legs 1–6 and urosome of adult males and females is illustrated. Morphological features separating L. tetraspina from its only congener, L. sinensis, include: a more pronounced rostrum; 1 seta more on the proximal lobe of the basis of the maxillule; 1 seta more on the endopod of the maxillule; middle endopodal segment of swimming legs 2–4 with 1 seta more; proximal and distal seta of the middle endopodal segment of swimming leg 4 with a flange; exopod of leg 5 with a proximal lateral seta; male cephalosome ventrally with pores with cilia. A rounded projection between labrum and rostrum is a shared derived state for both species of Limnoithona. Derived morphological features of the remaining species of Oithonidae, which are not shared with L. tetraspina and L. sinensis, include: elongation of the mandibular basis; fusion of the proximal endopodal segment of the mandible of females to the basis; 2 setae of the fused proximal endopodal segment of the mandible extend ventral to labrum; 3 setae on the proximal complex of three endopodal segments of the maxilliped. The two species of Limnoithona do not belong to the Oithonidae. They appear to be closely related to species of Cyclopettidae, but at this time it would not be meaningful to assign them to a known family of the Cyclopoida or to propose a new family for them. The following morphological attributes which are shared with different related cyclopoids also are discussed: shape of female cephalosome; pores with cilia on male cephalosome; setation of basis and proximal segment of the endopod of the mandible; brush-like setae on the exopod of the mandible; setation of the maxillule including brush-like seta on the exopod; hyaline flange on setae of the endopod of swimming leg 4; lateral location of copulatory pores and leg 6 of females, and of leg 5 in both genders; configuration of leg 5.

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