Argulus elongatus (Branchiura, Argulidae) in fish in the upper São Francisco river, Brazil / Argulus elongatus (Branchiura, Argulidae) de peixes do alto rio São Francisco, Brasil

Abstract Among 164 fish from the upper São Francisco river, caught in the Três Marias reservoir (18º 12' 59" S; 45º 17' 34" W) or downstream from this reservoir (18º 12' 32" S; 45º 15' 41" W) in 2007, 2008, 2016 and 2017, four specimens of Argulus elongatus Heller, 1857 were found, one specimen per fish, in the following host species: Brycon orthotaenia Günther (two fish parasitized out of 38 examined) and Salminus hilarii Valenciennes (one fish parasitized out of 45 examined) (both in Bryconidae); and Metynnis lippincottianus (Cope) (one fish parasitized out of 81 examined) (Serrasalmidae). This opportunistic ectoparasite deserves attention even in the case of low infestation in fish in a natural water system. This is the first record of a branchiuran species in B.orthotaenia; the host list of A.elongatus is extended through addition of the three fish species examined in this study, and the known Brazilian geographical distribution of this argulid is enlarged to the São Francisco river basin.

Resumo De 164 peixes do alto rio São Francisco, capturados no Reservatório de Três Marias (18º 12' 59" S; 45º 17' 34" O) ou à jusante dele (18º 12' 32" S; 45º 15' 41" O), em 2007, 2008, 2016 e 2017, quatro espécimes de Argulus elongatus Heller, 1857 foram encontrados, sendo um branquiúro por peixe nas seguintes espécies de hospedeiros: Brycon orthotaenia Günther (dois peixes parasitados de 38 peixes examinados), Salminus hilarii Valenciennes (um peixe parasitado de 45 examinados) - ambos Bryconidae, e Metynnis lippincottianus (Cope) (um peixe parasitado de 81 examinados) - Serrasalmidae. Esse ectoparasito oportunista merece atenção, mesmo no caso de infestações baixas em peixes de ambientes hídricos naturais. Esse é o primeiro registro de Branchiura em B.orthotaenia. A lista de hospedeiros de A. elongatus é ampliada com a adição das três espécies de peixes examinadas neste estudo. A distribuição geográfica conhecida desse argulídeo no Brasil, é ampliada para a bacia do rio São Francisco.

Ultrastructure of the anterior adhesive apparatus of the gill parasite Macrogyrodactylus clarii and skin parasite M. congolensis (Monogenea; Gyrodactylidae) from the catfish Clarias gariepinus.

Transmission electron microscopy (TEM) was used for the first time to study the anterior adhesive apparatus of the monogeneans Macrogyrodactylus clarii Gussev, 1961 and M. congolensis (Prudhoe, 1957) Yamaguti, 1963 inhabiting gills and skin respectively of the same catfish Clarias gariepinus. Despite the different microhabitats occupied by these parasites, the present study revealed that they have a similar anterior adhesive system. In both parasites, the anterior adhesive apparatus consists of three types of gland cells: G1 cells that produce rod-shaped bodies (S1), G2 cells manufacture irregularly shaped bodies (S2) and G3 cells form mucoid-like secretions (S3). In the cytoplasm of G1 cells, a single layer of microtubules encloses each developing rod-shaped body. A unique feature of S1 secretory bodies is that some fully developed S1 bodies are attached to each other, forming large condensed globules in the cytoplasm of G1 gland cells and terminal portion of the G1 ducts, but none were detected in the adhesive sacs outside the ducts. In the adhesive sacs, G1 ducts open with multiple apertures whereas each of the G2 and G3 ducts have a single opening. The adhesive sacs are lined with two types of tegument (st1 and st2). A third tegument type (st3) connects the st2 tegument with the general body tegument. Only st1 has microvilli. Each adhesive sac is provided with a spike-like sensillum and single uniciliated sense organ. The possible functions of microvilli in increasing the surface area and assistance in spreading and mixing of the adhesive secretion, and the role of sense organs associated with the adhesive sacs are discussed.

Description of female adult and praniza larva of Tenerognathia visus Tanaka, 2005 (Crustacea; Isopoda; Gnathiidae) with notes on mating behavior.

Male adults of gnathiid isopods (Crustacea; Isopoda; Gnathiidae) have remarkably developed rectangular-shaped cephalosomes and mandibles in most species. Tenerognathia visus Tanaka, 2005 belongs to a monospecific genus having remarkable characters in male morphology; reduced mandibles and large eyes occupying the whole of an elliptical cephalosome. The original description of T. visus is based on male adult specimens from coral rubble. This study found adult males and their larvae of T. visus attracted by light. Furthermore, specimens of female adults were observed by laboratory rearing of praniza larvae. In this study, morphologies of larvae and female adults of T. visus are described and notes on mating behavior in a laboratory aquarium are provided.

Molecular assessment of three species of Anilocra (Isopoda, Cymothoidae) ectoparasites from Caribbean coral reef fishes, with the description of Anilocra brillae sp. n.

A morphological review and molecular characterization of Anilocra haemuli Bunkley Williams & Williams, 1981, were completed using specimens collected from Haemulon flavolineatum Desmarest, 1823 (French grunt) and Epinephelus guttatus Linnaeus, 1758 (red hind). Molecular and morphological data suggest that the isopods parasitizing H. flavolineatum and E. guttatus are different species. The specimens collected from E. guttatus are recognized as a new species, Anilocra brillaesp. n. Differences between Anilocra brillaesp. n. and A. haemuli include but are not limited to the pleonites 1-3 of A. brillaesp. n. being wider than 4-5 and 4-5 subequal, whereas the pleonites 1-2 of A. haemuli are wider than 3-5, and 3-5 are subequal. The seventh pereopod of A. brillaesp. n. is proportionally larger, has more robust setae, and the setae are distributed more extensively over the articles when compared to A. haemuli. Additionally, this study provides the first genetic characterization of three Anilocra spp. from the Caribbean, and is based on mitochondrial cytochrome c oxidase subunit gene (COI) for A. haemuli from H. flavolineatum, A. brillaesp. n. from E. guttatus, and A. chromis Bunkley Williams & Williams, 1981 from Chromis multilineata Guichenot, 1853.

Tissue specific structural variations of mitochondria of fish ectoparasite Argulus bengalensis Ramakrishna, 1951 (Crustacea: Branchiura): Functional implications.

We studied the fine structure of some classical and six variant mitochondria from different tissues viz. proboscis gland, spinal gland, ovary, testis, and muscle of a fish ectoparasite, Argulus bengalensis. In the proboscis gland and spinal gland, mitochondria are protected within vesicle to preserve their structure and activity from exposure to glandular synthesis for its parasitic mode of feeding. In the oocytes, mitochondria are larger and cylindrical in appearance. Oocyte mitochondria are highly dynamic and exhibit frequent fission and fusion. Those are clustered in the cytoplasm of previtellogenic oocytes which prepare for different synthetic activities for successful reproductive investment. In contrast, mitochondrial abundance is less in the male gametic lineage. The spermatocytes and the nurse cells in the testis have an unusual type of mitochondria, nebenkern which is formed by the fusions of number of mitochondria. A completely different type of mitochondrion is discovered in the flagellum of the spermatozoa. It is provided with fifteen numbers of singlet microtubules at its outer periphery which is a salient feature of the flagellum of this Branchiuran genus. This unique mitochondrion uses the microtubule tract for its movement to distribute energy efficiently along the axoneme. Such mitochondrion and microtubular association provide evidence in favor of phylogenetic relationship between Argulus and pentastomid Raillietiella. In striated muscle of thoracic appendages, mitochondria maintain tight junctions with the endoplasmic reticulum and remain in close apposition of the myofibrils which helps in Ca(2+) uptake for stimulating continuous muscular activity required for ventilation of respiratory structures of the parasites.

Morphological characterization of testicular cells, spermatogenesis and formation of spermatophores in a fish ectoparasite Argulus bengalensis Ramakrishna, 1951 (Crustacea: Branchiura).

The present study has been carried out to describe the cell morphology of the developing male gametes in a fish ectoparasite, Argulus bengalensis Ramakrishna, 1951. With respect to cell volume and nucleoplasmic index, spermatogonia are the smallest and primary spermatocytes are the largest in this lineage. The spermatogonia and the differentiating spermatogenic cells are in separate niches and confined to different enclaves within each testicular lobe. Spermiogenesis occurs within the inner enclave of each testicular lobe. During this process the nucleus becomes streamlined; an acrosome is formed, axoneme is originated, and residual cytoplasm is discarded through the flagellum. The sperm cell morphology displays a general pattern comprising head, mid-piece, and a full length flagellum. In the axoneme 9+2 arrangement of the microtubule is conserved. In addition to the axoneme, some more singlet microtubules are found surrounding a fiber sheath and around one of the mitochondria adjacent to the axoneme. This arrangement indicates a close phylogenetic relationship with pentastomida. In the present study, structure and formation of spermatophore are described in this branchiuran parasite.