World Congress of Malacology Antwerp ... - Unitas Malacologica

Allometric growth of Mytella charruana (Bivalvia: Mytilidae) based on information-theory
approach
Abrahão, Jolnnye R. 1 ; MacCord, Fábio S. 1 ; Yokoyama, Leonardo Q. 1,3 ; Amaral, A. Cecília Z. 1
1. Departamento de Zoologia, Instituto de Biologia, Universidade Estadual de Campinas, CP. 6109,
Campinas, CEP 13083-970, SP, Brazil,
Email:jrabra@unicamp.br; maccord@ib.usp.br
3. Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP,
Brazil,
Email: lqyokoyama@gmail.com; ceamaral@unicamp.br
The allometric growth of the mussel Mytella charruana (Orbigny) was investigated and compared in
two different intertidal mussel beds on soft bottom at Camaroeiro and Cidade beaches, southeastern
Brazil (23 0 37’ S; 45 0 27’ W). The relation among shell length (SL), height (SH), and width (SW),
and the allometric growth of the one body part in relation to other (reference dimension) was studied.
Three candidate models were fitted to the log-transformed data (natural logarithms) of each dataset,
with least squares: the linear (L), quadratic (Q) and cubic (C). The L model was fitted with simple
linear regression, while polynomial regression was used for the Q and C models. In the case, the
‘best’ model was selected by minimizing the small-sample, bias corrected form of the Akaike
Information Criterion (AIC). To quantify the plausibility of each model, given the data and set of
three models, ‘the Akaike weight’ wi of each model was estimated for each case. A total of 1264
individuals with shell lengths ranging from 3.9 to 69.0 mm were measured at Camaroeiro beach,
while at Cidade beach, a total of 1614 individuals were measured, with the shell lengths ranging from
1.3 to 66.6 mm. In the Camaroeiro beach, L was the best model to the relationship between SW and
SL. For the relationship SH and SL, L was the best model with Q also having some support. For SH
and SW, L was the best model, but the rest of models were supported by the data. In the Cidade
beach, C model was the best model for all relationships with essentially no support for any model.
Multi-model inference based on Akaike weights is recommended for making robust parameter
estimations, and may reveal more information than the classical approach.
Financial support: CNPq, FAEPEX/Unicamp
Are there still rivers suitable for threatened unionid bivalves in Poland (Central Europe)?
Abraszewska, Anna
University of Lodz, Department of Invertebrate Zoology and Hydrobiology, Banacha 12/16, 90-237,
Lodz, Poland,
Email: anabra@biol.uni.lodz.pl
Among six native unionids reported from Poland there are three rare species, Unio crassus
Philipsson, Anodonta cygnea (Linnaeus) and Pseudanodonta complanata (Rossmässler), included in
the Red List of Threatened Animals in Poland and IUCN Red List as being endangered. As for the
knowledge of their distribution in Poland is still fragmentary, detailed studies of diverse aquatic
habitats in various parts of the country are required. My investigations were carried out in two river
catchments. The 342 km long lowland Pilica River in Central Poland is under anthropogenic
pressure.
The 1995-1998 studies included 103 localities on the river, tributaries, oxbows, and the dam reservoir
on the river. I collected altogether 5700 unionid individuals and recorded presence of all native
species, including those form the Red List. In terms of unionid distribution the mid-section of Pilica
was the most favourable (varied microhabitats, low degree of pollution) in terms of density, biomass
and condition of the bivalves. It was the only section where all the six species were present. Below
the dam species composition was reduced to two unabundantly occurring U.pictorum and A.anatina.
Additionally, at the backwater zone of the Sulejowski reservoir a colony of A.cygnea was studied (the
density reached 30 indiv./m 2 ).
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