Pauciconfibula patagonensis sp. nov. (Monogenea: Microcotylidae) parasitizing the horsefish, Congiopodus peruvianus (Pisces: Congiopodidae), from the Patagonian Shelf, Argentina

Pauciconfibula patagonensis sp. nov. (Monogenea: Microcotylidae), parasite of gill filaments of the horsefish, Congiopodus peruvianus (Congiopodidae) collected in the Patagonian Shelf, Argentina, is described and illustrated. The new species is characterized by having intestinal caeca not confluent and entering into the haptor, vitelline follicles extending from the genital pore to near the posterior portion of haptor, two parallel rows each comprised of 16-20 microcotylid clamps in the haptor, 25-43 testes and a fusiform egg with one very long tangled polar filament. P. patagonensis is the only member of the genus known to parasitize a scorpaeniform host and represents the first record of a representative of this genus in the southern Atlantic Ocean.     

The mammalian CHORD-containing protein melusin is a stress response protein interacting with Hsp90 and Sgt1

Melusin is a mammalian muscle specific CHORD containing protein capable of activating signal transduction pathways leading to cardiomyocytes hypertrophy in response to mechanical stress. To define melusin function we searched for molecular partners possibly involved in melusin dependent signal transduction. Here we show that melusin and heat shock proteins are co-regulated. Moreover, melusin directly binds to Hsp90, a ubiquitous chaperone involved in regulating several signaling pathways. In addition, melusin interacts with Sgt1, an Hsp90 binding molecule. Melusin does not behave as an Hsp90 substrate but rather as a chaperone capable to protect citrate synthase from heat induced aggregation. These results describe melusin as a new component of the Hsp90 chaperone machinery.     

A new species of Capillaria (Nematoda: Capillariidae) parasitizing Conger orbignianus (Pisces: Congridae) from Argentina

Capillaria (Procapillaria) navoneae n. sp. is described from the congrid fish Conger orbignianus from waters off Mar del Plata, Argentina (38 degrees 08'S, 57 degrees 32'W) (prevalence 29.17%, mean intensity +/- SD 6.07 +/- 6.59). The new species is assigned to the subgenus Procapillaria Moravec, 1987, despite the absence of vulvar appendages in gravid females. Of the 3 species so far known in the subgenus, the new one most closely resembles C. (P.) margolisi, from which it is distinguished by lacking a medial expansion in the spicule and a slightly elevated anterior lip of vulva, and by having a shorter esophagus, a larger number of stichocytes, and a shorter tail.     

Ultrastructural observations on the male gametes in Austrognathia sp. (Gnathostomulida,Bursovaginoidea)

The male gametes of the gnathostomulid bursovaginoid Austrognathia sp. were investigated by electron microscopy. All stages of sperm development can be observed in the single saccular male gonad, which is enclosed by a relatively thick basement membrane internally reinforced by thin smooth muscle cells. The spermatogonia are situated close to the testicular theca and produce generally separate primary spermatocytes. From secondary spermatocytes onwards, the nuclear envelope is no longer visible. The spermatids develop synchronously in groups of four, in contrast to arthropod and vertebrate spermatogenesis. A single, large nurse cell, or trophocyte, never observed previously, surrounds each spermatid; perhaps it represents an altered germ cell functioning in nutrition. The spermatid nucleus, initially ovoid, lengthens and takes on the shape of a mushroom head extending into a stalk. Three degrees of chromatin condensation are visible. Anteriorly, a palisade-shaped structure is present just over the highly heterochromatic nuclear zone and is considered to have an acrosome-like function. The outer sperm cytoplasm is characterized by a peripheral tubular labyrinth. Axonemal structures have never been found, but centriole-like structures are present among the medium-density chromatinic strands of the mushroom-like nucleus. No cortical microtubules are evident beneath the cell membrane. The external sperm morphology recalls that of nematode gametes, and some internal features are also similar. Phylogenetic considerations and hypotheses on sperm locomotion are proposed. J. Morphol. 237:165–176, 1998. © 1998 Wiley-Liss, Inc.     

Co-dominant markers for the selection of somatic dihybrids and polyhybrids

Resistance to ouabain and puromycin are shown to represent very useful co-dominant characters for the selection of somatic hybrids between mammalian cells, after fusion with polyethylene glycol. We therefore used, with success, a number of Chinese hamster and mouse cell lines carrying these markers in association with thymidine kinase and hypoxanthine-guanine-phosphoribosyl transferase deficiency for selection of hybrids of triparental origin.