Metacyclops laticornis (Lowndes, 1934)

Perbiche-Neves, Gilmar, Corgosinho, Paulo H. C., Previattelli, Daniel, Suárez-Morales, Eduardo, Nogueira, Marcos G. & da Rocha, and Carlos E. F., 2025, Catalogue for identification of the most common lacustrine and riverine cyclopoid copepod (Crustacea) species in plankton of La Plata Basin, South America, Zoologia (e 24023) 42, pp. 1-47 : 26-29

Metacyclops laticornis (Lowndes, 1934)

Fig. 26

Diagnosis. Adult female, 770 µm in length excluding caudal setae. Short P5 apical setae; seminal receptacle with thin lateral projections and a long and wide posterior projection ( Fig. 26A ). A row of spinules on the distal margin of the last urosomal segment, near the basis of the caudal ramus; caudal rami 2.3 times longer than wide; inner terminal setae of the caudal ramus shorter than the outer terminal setae (0.7:1) ( Fig. 26B ). P4 endopod outer terminal spine is 1.1 times longer than inner terminal spine ( Fig. 26C ). Intercoxal sclerite of P4 is ornamented with small spinules ( Fig. 26C ). P1 intercoxal sclerite with 3 spinules on each rounded projection ( Fig. 26D ).

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Remarks. The specimen illustrated was collected in the middle stretch of the Paraguay River. Reid (1985) reported this species in Paraguay, in swamps, and Dussart and Frutos (1985) found this species in the middle Paraná River, but did not provide a description. In our study this species occurred only in low numbers. The genus Metacyclops is diverse and in studies of planktonic organisms, few species are found. Most species occur in swamps, puddles, and ephemeral environments.

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Figures

Figure 26. Metacyclops laticornis, female: (A) ventral view of prosomite 5 and genital double-somite, arrow indicates P5; (B) ventral view of caudal rami; (C) P4 intercoxal sclerite, coxa, basis and endopod, arrow indicates spinules in intercoxal sclerite; (D) P1 intercoxal sclerite and spinules (arrowed). Scale bars: 50 µm.