Integumental Structures in the Oral Field of Eurytemora Affinis and Acartia Tonsa (Copepoda, Calanoida) in Relation To Their Trophic Habits

Abstract

Scanning electron microscopy (SEM) was used to study the morphology of the integumental structures in the oral field of the copepods Eurytemora affinis and Acartia tonsa. Structures observed in these two copepods were different in type, number, and location. E. affinis presented only structures of a filiform type, distributed all over the oral field, whereas in A. tonsa three different types of structures were observed: filiform, papilliform, and conical, distributed according to a complex pattern. The results obtained on the chaetotaxy of the oral field demonstrate a strong morphological adaptation of each copepod to its trophic habits. The ecological implications of these results on the coexistence of populations of both species in the Bahía Blanca estuary are discussed. RESUMEN Se estudió la morfología de las estructuras tegumentarias del campo oral de los copepodos Eurytemora affinis y Acartia tonsa utilizando Microscopía Electrónica de Barrido. Las estructuras observadas en ambos copepodos difirieron en tipo, número y localización. E. affinis presentó un patrón morfológico simple constituído por estructuras de tipo filiforme distribuídas en todo el campo oral, mientras en A. tonsa se observó un patrón morfológico complejo con tres tipos de estructuras: filiforme, papiliforme y cónico distribuídas en áreas determinadas del campo oral. Los resultados obtenidos sobre la quetotaxia del campo oral, demuestran una fuerte adaptación morfológica en cada uno de los copepodos relacionada con sus hábitos tróficos. Se discute la importancia ecológica de estos resultados, con respecto al fenómeno de coexistencia de las poblaciones de ambas especies, en el estuario de Bahía Blanca.

<i>Eurytemora americana</i> Williams, 1906, not <i>Eurytemora affinis</i> (Poppe, 1880), inhabits the Bahía Blanca estuary, Argentina

“…americana inhabits the upper reaches of the Bahía Blanca estuary (Villarino Viejo to approximately buoy 24) (De Aracama, 1987). It occurs in the plankton from July to October every year (Hoffmeyer, 1994;Hoffmeyer and Prado Figueroa, 1997), reaching maximum numbers in August-September. Like other congeners (Uye, 1985;Ban and Minoda, 1991;1994), it persists during the rest of the year as diapause eggs in the sediment (Marcus, 1984;Naess, 1991).…”

“…The scant knowledge of the biology and ecology of E. americana at present compared to other congeners such as E. affinis and E. herdmani Thompson and Scott, 1897, and its apparent important ecological role in a number of estuaries and coasts where it occurs (Deevey, 1960;Jeffries, 1967;Frolander et al, 1973;Tremblay, 1942in Bousfield et al, 1975Miller, 1983;Marcus, 1984;De Aracama, 1987;Naess, 1991;Hoffmeyer, 1993;1994;Hoffmeyer and Prado Figueroa, 1997;Ban et al, 1997;Avent, unpubl. result.…”

“…Subsequently it was reported and discussed by Hoffmeyer (1994) who described the seasonal succession of copepods and other zooplankters in the Bahía Blanca estuary during 1990-1991. E.affinis was covered in two additional papers: (a) its oral field chaetotaxy was compared with that of the copepod Acartia tonsa (Hoffmeyer and Prado Figueroa, 1997); and (b) in a study devoted to the egg production and egg viability in different species of copepods feeding on high concentrations of diatoms (Ban et al, 1997). E. affinis was also mentioned in various unpublished progress reports during 1993-1998(Hoffmeyer, 1997IADO, 1997).…”

The coastal-estuarine copepod, Eurytemora affinis (Poppe) (Calanoida, Temoridae), from arid inland areas of Mexico: an expected occurrence?

“…americana Williams, 1906; in some instances the latter species can be confused with E. affinis (cf. Hoffmeyer & Prado-Figueroa, 1997;Hoffmeyer et al, 2000). Our specimens were compared with these other species and distinctive characters with taxonomic relevance (i.e., the male and female fifth legs, the wings of the last pedigerous somite, the ornamentation of the caudal rami and anal somite) were examined (Hoffmeyer et al, 2000) to confirm that our specimens are in fact E. affinis.…”

Sewage pollution effects on mesozooplankton structure in a shallow temperate estuary

“…On the other hand, E. americana was negatively correlated with the concentration of phosphate and silicate, both of which are necessary nutrients for the development of diatoms (Margalef 1977). Its mostly herbivorous habits as well as its adaptation to cold temperatures and intermediate salinities would facilitate its presence at CV station (Avent 1998;Hoffmeyer and Prado-Figueroa 1997;Sage and Herman 1972). Unlike E. americana, A. tonsa has omnivorous habits and feeds on algae, flagellates and ciliates (Petipa 1959).…”