Comparative karyological analysis of three members of Allocreadiidae (Digenea): taxonomic and phylogenetic implications

Abstract

Chromosome number and morphology were studied in three allocreadiid species from mitotic metaphases of intramolluscan stages using karyometric analysis. Bunodera luciopercae has a diploid number 2n=14, with two large pairs of metacentrics, one pair of submeta-subtelocentrics, and four pairs of acrocentrics. Karyotype of Allocreadium isoporum, 2n=14, with two large pairs of metacentrics and five pairs of acrocentrics was recognized to be closely related to that of B. lucioperca. The most conspicuous interspecific difference occurs in the centromere position of the chromosomes of the pair 3. The possible reasons of the discrepancies between data reported therein and the karyological information previously published on these two species are discussed. Crepidostomum sp. has 2n=12, with one pair of large metacentrics and five pairs of acrocentrics and is more distantly related karyologically to the other two members of the family. Evolutionary considerations based on comparison of the chromosomes of Allocreadiidae and other studied families of the suborder Xiphidiata suggest that allocreadiids are karyotypically distinct. The placement of Allocreadiidae and Opecoelidae in the superfamily Allocreadioidea is questioned.

Prosthenhystera gattiin. sp. (Digenea: Callodistomidae), a gallbladder parasite ofBryconamericus ikaafrom the lower Iguazú River, described based on combined molecular and morphological evidence

“…In that family, the species studied until now have acrocentric, submetacentric and metacentric chromosomes. The present results provide new data and complement the description made by Petkevičiute & Stanevičiute (2008) about the karyotype homogeneity respect the number, morphology and number of chromosomes in these two close families.…”

Clarification of the systematic position ofCercariaeum crassumWesenberg-Lund, 1934 (Digenea), based on karyological analysis and DNA sequences

“…There are numerous cases of the detection of cryptic species with narrow host specificity within well-known generalist parasites (see Combes, 2001). Recent surveys based on morphology, random amplification of polymorphic DNA (RAPD) profiles, host specificity, karyology and DNA sequences (Sokolov et al , 2006; Petkevičiūtė & Stanevičiūtė, 2008; Petkevičiūtė et al , 2010) revealed the existence of a morphologically similar species complex within the allocreadiid B. luciopercae (Müller, 1776).…”

“…But 56 chromosomes were found in diploid sets of Clonorchis sinensis (Park et al , 2000). Allocreadiid species possess comparatively large chromosomes, up to 13–14 μm, but low haploid numbers of six, seven or eight were recorded in most species (for a review see Petkevičiūtė & Stanevičiūtė, 2008). The chromosome complement of C. crassum is unusual among digeneans due to the low number, 2 n = 10.…”

“…Comparative analysis of chromosomes of related trematode species indicated that the reduction of chromosome numbers resulted from centromeric fusion rather than elimination of chromosomes (Grossman et al , 1981). Acrocentric mono-armed chromosomes prevail in the karyotypes of larval B. luciopercae , 2 n = 14, and larval A. isoporum sensu Wiśniewski, 1959, 2 n = 14 (Petkevičiūtė & Stanevičiūtė, 2008). It is notable that the mean total length of haploid complements (TCL) of these two species does not exceed the TCL of C. crassum , despite different chromosome numbers.…”

Diversity of European lissorchiid trematodes from fish and snail hosts with comments on the validity of the genus Parasymphylodora Szidat, 1943

“…It should be noted that the chromosome sets composed of 22 or 20 elements are characteristic for the great majority of trematode species. Diploid number 2n = 14 is less common between digeneans but it was revealed in species of some unrelated families such as Paramphistomidae Fischoeder, 1901, Bucephalidae Poche, 1907, Echinochasmidae Odhner, 1910, Allocreadiidae Looss, 1900 or Opisthorchiidae Looss, 1899 (Baršienė, 1993; Petkevičiūtė & Stanevičiūtė, 2008; Petkevičiūtė et al, 2014). From the new data on the karyotypes of lissorchiids, it is obvious that representatives of some families of trematodes can demonstrate varying degrees of chromosomal diversification, sharing conservative and highly derived karyotypes.…”