First occurrence of hermaphrodite pike, Esox lucius L., in the Esla basin (Spain)

Abstract

Pike have been in Spain since 1949(Gutierrez-Calderon, 1954) and the first specimen in the Esla basin, in north-western Spain, was caught in 1964(Pena, 1988. Since then pike have altered the existing autochthonous fish communities in several ways.Agundez et al. (1987) reported the finding of three hermaphrodite specimens in 1986; their study was only macroscopic. The present study shows that the 18 hermaphrodite specimens caught by electrofishing between March 1986 and October 1987 in different rivers and localities in the Esla basin, comprising 094% of all pike collected, were functional hermaphrodites. Histological investigation revealed the existence of spermatogonic isles within functional ovaries.Biometric and gonad state data were taken for each specimen (Table I). Gonads were preserved in 8% formaldehyde. The gonads were cut into serial sections and stained with haematoxylin for light microscopic observation. Photographs were taken with a Nikon OPTIPHOT photomicroscope.Most of the hermaphrodites were collected in the spawning period for the species, when macroscopic detection is least troublesome. Sizes ranged between 134 and 494 mm, and all specimens were found mature for both sexes.Histological study revealed different kinds of gonad disposition: ovary and testis, ovotestis and ovary, or two ovotestes, although separation between the sexes in the gonad was not clear. TABLE I. Details of hermaphrodite pike from the R. Esla basin Date Locality Weight Length (9) (m)

Ovarian alterations in wild northern pike Esox lucius females

“…Kipfer et al 2009 (and intersex) gonad tissues (Jobling et al 1998, van Aerle et al 2001, Noaksson et al 2001, Kavanagh et al 2004, Hanson 2009). Hermaphroditic histological changes in the ovaries have also been reported in northern pike (Dominguez et al 1989, Vine et al 2005. However, the results pre sented in the present pa per are the first data about extreme alterations of ovaries in northern pike, the top pre dator in freshwater food webs.…”

Endocrine (sexual) disruption is not a prominent feature in the pike (Esox lucius), a top predator, living in english waters

“…Examples of intersex pike have been reported in the literature, and to date, intersex pike have been found in the Elsa basin (Spain) [20]. However, despite continued efforts to sample pike from a variety of rivers having different water quality, we were unable to obtain any fish from sites with poor water quality.…”

“…Pike ( Esox lucius ) was chosen as the investigative species for the present study, because it is the top predator fish in English rivers and concentrates chemicals from food [19]. Actual evidence of endocrine disruption in pike also has been reported in the Elsa basin (Spain), where intersex pike have been found [20].…”

Functional hermaphroditism in teleosts

“…Occasionally gonads have both mature testicular tissue with sperm and ovarian tissue containing vitellogenic stage oocytes, but this is unusual, as far as we can determine. Such gonads arise with low incidence and mature testicular and ovarian tissue configurations may be inconsistent between individuals of a species (Turner 1931; Dence 1938; Lagler and Chin 1951; Gutherz 1969; Dorfman and Heyl 1976; Dominguez et al. 1989).…”