Alessandro Valbonesi

Description of two new species of Euplotes and Euplotes rariseta from Antarctica

SummarySpecimens of Euplotes were collected from Ross Sea (Antarctica), allowed to multiply in the laboratory, and taxonomically studied on the basis of classical diagnostic traits as seen under the optical and scanning electron microscope. They were assigned to three different morphospecies, all characterized by a dorsal silver-line system of the “double” type and a set of 10 fronto-ventral cirri. Two morphospecies were identified as new and named E. nobilii and E. euryhalinus; one was judged reconcilable with E. rariseta.

Biology of Euplotes focardii, an Antarctic ciliate

Euplotes focardii, a ciliate species recently collected from sand sediments of Terra Nova Bay (Ross Sea, Antarctica) reproduced in the laboratory with a duplication time of approximately 72 h, at 4°C. Strains representative of two different mating types were identified and mixed together to produce mating pairs. These showed traits rather unusual for Euplotes species. The two pair members remained united for at least 8–10 days. However, only one carried out fertilization and was able to give rise to a new clone of vegetative cells; the other underwent cell body shrinking after 4–5 days of union, lost the locomotory ciliary apparatus, and eventually died. By analyses of mating pairs formed in mixtures of cell samples cytologically distinct from each other, it was ascertained that the different cell behavior is strain-specific.

Inheritance of Suri and Huacaya type of fleece in Alpaca

Abstract The inheritance of the two types of fleece, Suri and Huacaya, observed in Alpaca (Lama pacos L.) is still not clearly defined. The objective of this work is to investigate the patter of inheritance of these two phenotypes, throughout 588 Suri x Suri and 2126 Huacaya x Huacaya offspring. The single gene and the three two-phenotype epistatic models were tested in the 19 Suri x Suri segregating families. The single dominant gene hypothesis best fitted our segregation data and could be, therefore, accepted (Gt=20.276, P=0.378). The gene frequency of the recessive Huacaya allele was 0.295, being the frequency of the dominant Suri allele 0.705. The frequency of heterozygotes, estimated in the whole population and among dominant individuals, was 0.416 and 0.455, respectively, with a “carrier” Suri to Huacaya ratio of 4.780. In three Huacaya families, 3 Suri were born, as a result of a new dominant mutation on some germinal lines of Huacaya animals. The direct mutation rate can be estimated at 0.0014.

Infestation of a lagoon zooplanktonic community with the epizoic peritrich Zoothamnium intermedium Precht (Peritrichia, Zoothamniidae)

Abstract An epizoic colonial peritrich, Zoothamnium intermedium Precht, collected from the lagoon Valle Fossa di Porto (Ferrara, Italy), is described on the basis of light and scanning electron microscope observations. It was found on the copepods Acartia clausi, A. latist‐tosa, Calanipeda aquaedulcis and zoeae of the shrimp Hippolyte longiros‐tris. In A. clausi, which was the most abundant species of the Zooplankton community, Z. intermedium was distributed over the whole body surface of 99.3% of specimens. Numerous rod‐shaped bacteria were found in association with the attachment sites of Z. intermedium.

Fleece variation in alpaca (Vicugna pacos): a two-locus model for the Suri/Huacaya phenotype

BackgroundGenetic improvement of fibre-producing animal species has often induced transition from double coated to single coated fleece, accompanied by dramatic changes in skin follicles and hair composition, likely implying variation at multiple loci. Huacaya, the more common fleece phenotype in alpaca (Vicugna pacos), is characterized by a thick dense coat growing perpendicularly from the body, whereas the alternative rare and more prized single-coated Suri phenotype is distinguished by long silky fibre that grows parallel to the body and hangs in separate, distinctive pencil locks. A single-locus genetic model has been proposed for the Suri-Huacaya phenotype, where Huacaya is recessive.ResultsTwo reciprocal experimental test-crosses (Suri × Huacaya) were carried out, involving a total of 17 unrelated males and 149 unrelated females. An additional dataset of 587 offspring of Suri × Suri crosses was analyzed. Segregation ratios, population genotype frequencies, and/or recombination fraction under different genetic models were estimated by maximum likelihood. The single locus model for the Suri/Huacaya phenotype was rejected. In addition, we present two unexpected observations: 1) a large proportion (about 3/4) of the Suri animals are segregating (with at least one Huacaya offspring), even in breeding conditions where the Huacaya trait would have been almost eliminated; 2) a model with two different values of the segregation ratio fit the data significantly better than a model with a single parameter.ConclusionsThe data support a genetic model in which two linked loci must simultaneously be homozygous for recessive alleles in order to produce the Huacaya phenotype. The estimated recombination rate between these loci was 0.099 (95% C.L. = 0.029-0.204). Our genetic analysis may be useful for other species whose breeding system produces mainly half-sib families.

Identification of the Tubulin Gene Family and Sequence Determination of One β-Tubulin Gene in a Cold-Poikilotherm Protozoan, the Antarctic Ciliate Euplotes focardii

ABSTRACT. Four different tubulin genes were identified in the somatic nucleus (macronucleus) of Euplotes focardii, a strictly coldadapted, Antarctic ciliate: one of 1,800 bp for α‐tubulin and three of 2,150, 1,900, and 1,600 bp, respectively, for β‐tubulin. Preliminarily analysed for restriction fragment length polymorphisms, these genes showed remarkable differences in organisation from tubulin genes of other ciliates which live in temperate areas and were analysed in parallel with E. focardii. The complete coding sequence of the 1,600 bp β‐tubulin gene was then determined and shown to contain unique structural features of potential importance for E. focardii microtubule organization and activity. Of eight unique substitutions detected, seven were concentrated in the large amino terminal domain of the molecule that directly interacts with the carboxy terminal region of α‐tubulin for heterodimer formation. Sequence analysis of the cloned gene revealed, in addition, a potential new exception in the use of the genetic code by ciliates. A TAG codon was aligned in correspondence with Trp‐21 which is strictly conserved in every tubulin sequence so far determined.

Quantitative variation of melanins in alpaca (Lama pacos L.)

The amount of melanin pigments was investigated in 95 Peruvian alpaca, representative of six different fleece colours, by means of spectrophotometry assays: SpEM (Spectrophoto-metric Eumelanin), SpPM (Spectrophotometric Pheomelanin), SpASM (Spectrophotometric Alkali Soluble Melanin), and SpTM (Spectrophotometric Total Melanin). It was found that these melanin pigments were suitable for identifying three homogeneous groups, each consisting of two closely related colours. A low, an intermediate, and a high amount of SpASM, SpTM, and SpPM characterize pinkish grey and light reddish brown, brown and reddish brown, dark reddish brown and black fleeces, respectively. SpEM and SpTM provide a further split within this latter group; higher concentrations of these pigments distinguish black fleece from dark reddish brown.

A new species of Uronychia (Ciliophora, Hypotrichida) from Antarctica: Uronychia antarctica

Abstract A new species of Uronychia, U. antarctica, was collected from marine sand sediments of Terra Nova Bay (Ross Sea, Antarctica) and studied by means of scanning electron microscopical observations. It is a medium‐sized ciliate (54 × 45 μm) characterized by an anterior set of nine adoral ciliary membranelles, and a mid‐dorsal kinety (or kinety No. 4) which terminates at the level of the cell equator and contains no more than 23 bristle cilia.

Scanning electron microscope observations on Zoothamnium intermedium (Ciliophora, Peritrichia)

Abstract Zoothamnium intermedium was found attached to the exoskeleton of planktonic crustaceans, most of which were copepods Acartia clausi. It formed branching colonies that consisted of zooids characterized by: 1) a bell‐like shape; 2) peristomial cilia that formed a single haplokinety raised above a double polykinety; and 3) unbranched annular striae, regularly distanced from each other by about 0.5 μm, around the zooid circumference. Fully developed colonies contained also several roundish zooids that were identified as potential motile stages. In addition to colony members, free‐swimming dimorphic individuals were also occasionally observed: one type showed long trochal cilia and a scopula with a central area containing numerous protuberances; the other was characterized by short, stumpy cilia and a scopula endowed with a central finger‐like process surrounded by a pleated wrap. These free‐swimming individuals were tentatively identified as the microgamont and telotroch stage of Zoothamnium intermed...

Observations on the biology of Euplotes charon (Hypotrichida, Ciliophora)

A population of Euplotes collected from the mouths of the Rhone was assigned to the morphospecies E. charon. The 27 strains established in the laboratory were found capable of producing protective cysts in response to environmental salinities exceeding 502. and, with the exception of two, all of them formed mating pairs. Mating interactions appeared to be controlled by a system of multiple mating types, probably inherited via alleles condominant at the genetic locus mat. Cells in the G1 cell‐cycle stage, which occupies 62% of the generation time, as well as cells in the S stage could mate. Mating was followed by an unusually long period of immaturity of 120–180 fissions. In the conjugants, the micronucleus performed four divisions, one preliminary and three pregamic; the macronucleus persisted unchanged. Cytological observations suggested that the two gamete nuclei derive from different products of the preliminary micronuclear mitosis. The synkaryon regularly performed three metagamic divisions and, in th...