Parasites of economically important bivalves from the southern coast of Bahia State, Brazil / Parasitos de bivalves de interesse econômico no Litoral Sul do Estado da Bahia, Brasil

This study investigated the parasites of three commercially important bivalve species (Crassostrea rhizophorae, Mytella guyanensis and Lucina pectinata) from the southern coast of Bahia, Brazil. A total of 540 specimens were collected in August 2009 and February 2010, at three localities. The bivalve specimens were measured on their longest axis, opened, and macroscopically examined for the presence of parasites or signs of disease. They were then fixed in Davidson' solution and subjected to routine histological processing, with paraffin embedding and H&E staining; next, the specimens were examined under a light microscope. No parasites were observed associated with L. pectinata. Rickettsia-like organisms (RLOs), Sphenophrya sp. (Ciliophora), Nematopsis sp. (Apicomplexa), Urastoma sp. (Turbellaria) and Bucephalus sp. (Digenea) were observed in both C. rhizophorae and M. guyanensis, as well as Ancistrocoma sp. (Ciliophora) and Tylocephalum sp. (Cestoda) in the former. A high prevalence of Nematopsis sp. was seen, but caused no apparent damage to the host. Bucephalus sp. caused the destruction of tissues, with castration, but showed low prevalence. The other parasites occurred in low prevalence and intensity, without causing significant damage.(AU)

Neste estudo foram investigados os parasitos de três espécies de bivalves de interesse econômico (Crassostrea rhizophorae, Mytella guyanensis e Lucina pectinata) da Bahia. Foram analisados 540 exemplares, obtidos em duas coletas (agosto-2009 e fevereiro-2010), em três localidades. Os bivalves foram medidos quanto ao seu maior eixo, abertos e examinados macroscopicamente quanto à presença de parasitos ou sinais de enfermidades. Depois disso, foram fixados em solução de Davidson e processados por rotina de histologia, com inclusão em parafina e coloração com H&E. O material foi examinado ao microscópio de luz. Nenhum parasito esteve associado a L. pectinata. Bactérias do tipo RLOs (organismos assemelhados a Rickettsia), Sphenophrya sp. (Ciliophora), Nematopsis sp. (Apicomplexa), Urastoma sp. (Turbellaria) e Bucephalus sp. (Digenea) foram observados tanto em C. rhizophorae quanto em M. guyanensis, sendo que a primeira apresentou ainda Ancistrocoma sp. (Ciliophora) e Tylocephalum sp. (Cestoda). Nematopsis sp. ocorreu em alta prevalência, porém, aparentemente, não causou danos aos bivalves. Bucephalus sp. causou destruição de tecidos, com castração, mas foi pouco prevalente. Os demais parasitos ocorreram em baixa prevalência e intensidade de infecção e sem causar danos.(AU)

Ultrastructural studies of spermiogenesis of the clamLucina pectinata (Bivalvia, Lucinidae) from Northern Brazil

Spermatogenesis and sperm ultrastructure of the clam Lucina pectinata (Lucinidae) from northern Brazil were studied using light and transmission electron microscopy. The uniflagellate spermatozoa are grouped into characteristic rings within somatic cells (Sertoli-like cells), with the acrosome oriented toward the peripheryof these cells. The spermatozoa are long cells of the primitive type (ect-aquasperm) with a total length of 50.2 ± 2.5 mm, consisting of head (acrosome + nucleus), midpiece and tail. Acrosome is formed by an, acrosomal vesicle with a conical cylinder-like shaped (0.9 ± 0.1 mm length and 0.4 ± 0.1 mm in basal diameter) having a deeply infolded basis occupied by the subacrosomal space, containing flocculent material without axial rod. The acrosomal vesicle is formed by a membrane-bounded containing a broad basal ring of electron-dense material. The nucleus (7.5 ± 0.8 mm long) is an elongated, subcylindrical rod-shaped, slightly and gently curved, with a basal invagination (0.2-0.4 mm). It contains dense chromatin without any electron-lucent lacunae.The midpiece (1.0 ± 0.3 mm long; 1.1 ± 0.2 mm width) consist of four equal mitochondria located at the same level, surrounding two centrioles arranged at right angles. The proximal centriole lies at 90° relative the distal centriole and sperm longitudinal axis. The tail (40.5 ± 2.1 mm long) contains the common 9 + 2 pattern which in tapering end piece is successively reduced and sheated by the plasmalemma.