Juan Carvajal

Life cycle of Caligus rogercresseyi, (Copepoda: Caligidae) parasite of Chilean reared salmonids

Caligus rogercresseyi, [Contrib. Zool. 69 (2000) 137] is the only caligid known to affect the salmon industry in Southern Chile. Economic losses due to reduced fish quality, cost of chemical treatment and outbreaks of other diseases such as the Piscirickettsiosis occur. The life cycle of C. rogercresseyi is described in rainbow trout reared in seawater tanks from observations made under natural conditions of light and temperature between January 1997 and April 1998. Fish were infected with laboratory-cultured larvae obtained from ovigerous females. Rainbow trout were periodically slaughtered for parasite collection and identification. C. rogercresseyi life cycle includes the following stages: two nauplius, one copepodid, four chalimus and the adult. No preadult stage was observed. Timing of the different stages of development was directly dependent on water temperature. The maturation of the eggs or the time for a complete life cycle took place at 45 days in July at 10.3 °C, 31-32 days in April at 12.4 and 12.8 °C, respectively, and at 26 days in November at 15.2 °C. In January, at 16.7 °C, only the appearance of first eggs were observed at 18 days. A simple degree-day (dd) model is proposed for each developmental stage between 4 and 17 °C, where the development rate is a linear function of the average temperature of water. Using this degree-day model, the proportion of fourth stage chalimus was maximum at 172 dd of effective temperature, adult males at 193 degree-days, adult females at 208 dd. The minimum temperature threshold is at 4.2 °C where there is no development of the parasite. The appearance of first eggs occurred at 231 dd and the first pigmented eggs at 277 dd. The temperature-independent degree-days value allowed to predict the timing of C. rogercresseyi life cycle at any temperature within the evaluated range.

Native sea lice (Copepoda: Caligidae) infestation of salmonids reared in netpen systems in southern Chile

A survey of parasitic copepods carried out in three introduced salmonid species in Southern Chile and 5 native fish species commonly found in the vicinity of the fish farm cages yielded 5 caligid species. Caligus flexispina, formerly found in the oceanic islands of the Pacific ocean, is currently the dominant species found in continental waters on native fish species (Eleginops maclovinus and Odonthestes regia) as well as on cultured trout Oncorhynchus mykiss from the south of Chile. Coho salmon O. kisutch and Atlantic salmon Salmo salar are more resistant to this parasite. Among the native fish species associated with netpen aquaculture, E. maclovinus harbours 4 caligid copepods, namely Lepeophtheirus mugiloidis, C. flexispina, C. teres and C. cheilodactylus (in the same order of ranked abundance). Odonthestes regia only harbours C. flexispina, whereas Paralichthys microps is a host of Lepeophtheirus edwardsi and C. flexispina. It is highly likely that the transfer of C. flexispina to salmonids is mediated by the presence of these native fish species.

Differential infectivity of Caligus flexispina (Copepoda, Caligidae) in three farmed salmonids in Chile

Abstract The ectoparasitic copepod, Caligus flexispina, is causing increasing problems in farmed salmonids in southern Chile. Field and experimental approaches were used to assess whether any of the three host species, rainbow trout Oncorhynchus mykiss, atlantic salmon Salmo salar and coho salmon Oncorhynchus kisutch, is preferentially colonized. Prevalence, abundance, density and developmental stages attained by the parasite in three host species were compared. Results clearly revealed that rainbow trout is the most susceptible species: under field conditions, C. flexispina is more prevalent and abundant and there is a higher proportion of adult stages. No ovigerous females were found in coho salmon. In experimental infestations, rainbow trout were more heavily colonized by infective copepodids, and these were more likely to reach the adult stage. A mixture of factors inherent to each host-parasite relationship is considered to play a role in these observations because coho salmon is also colonized by copepodids but a low proportion of the parasites reach the adult stage. However, atlantic salmon is less suitable for colonizing larva.

Critical studies on the genus Callitetrarhynchus (Cestoda: Trypanorhyncha) with recognition of Rhynchobothrium speciosum Linton, 1897 as a valid species of the genus Callitetrarhynchus

SummaryCallitetrarhynchus speciosus (Linton, 1897) n. comb. for Rhynchobothrium speciosum is redescribed from Pomatomus saltatrix and is compared with the only other species of the genus. C. gracilis (Rudolphi, 1819), also found in the same fish. The arrangement of hooks on the tentacle of both species is illustrated. The two species, which have been included under the name C. gracilis in the past, differ mainly in the oncotaxy, different shape of the hooks of the chainette, distinct distribution of frontal glands and in the different depth of the marginal bothidial groove. ac]19840904

Progrillotia dollfusi sp. n. (Cestoda: Trypanorhyncha) parasito de pescada do litoral brasileiro

Progrillotia dollfusi sp. n. (Cestoda: Trypanorhyncha) from the visceral cavity of Cynoscion (Pisces, Sciaenidae), taken in Rio de Janeiro is described. The fishes were extensively para sited. Distinguishing characteristic of the species include: 2 bothridia, poecilacanthous hooks and tipical basal armature.

The feasibility of using Udonella sp. (Platyhelminthes: Udonellidae) as a biological control for the sea louse Caligus rogercresseyi, Boxshall and Bravo 2000, (Copepoda: Caligidae) in southern Chile

Caligus rogercresseyi is a sea louse of native and farmed fish in southern Chile. Due to the impact that this copepod has on the Chilean salmonid production, it is necessary to search for control mechanisms that can effectively reduce its population. This study focuses on determining the feasibility of using Udonella sp., a common flatworm found on copepod ectoparasites of the Chilean rock cod, Eleginops maclovinus, as a biological control for sea lice. The following aspects were studied: distribution and preference of Udonella sp. regarding both host sex and body location on copepods collected from both the Chilean rock cod and cultured salmonids; the effect of Udonella on both fecundity and survival of the free-living stages; and seasonal variations of population of both Udonella and the copepod. Results indicated that Udonella sp. is frequently found on copepods collected from the Chilean rock cod, but is absent on those from cultured salmonids. The flatworm showed a marked preference for female copepods and the main body locations used by Udonella are the genital complex and egg sacs. The three life stages of Udonella are distributed across the copepod body in different ways since different body locations represent feeding and nursery areas. Udonella has no significant effect either on fecundity or survival of free-living stages. Udonella may maintain its population relatively independent of the Caligus infra-population all year round. Seasonal patterns of variation were not evident for the population parameters of either Caligus or Udonella, probably due to the exceptional environmental conditions that occurred during 1997 that allowed Caligus populations to remain high during fall and winter, instead of decreasing as it has been reported previously. Results suggest that Udonella cannot be used as a biological control for sea lice since it is not found naturally on salmonid species and because the presence of Udonella did not reduce either fecundity or survival of free-living stages of copepods.

Udonella australis n. sp. (Monogenea), an epibiont on sea-lice from native fish off southern Chile.

Udonella australis n. sp., an epibiont monogenean living on caligid copepods that infest a native fish, Eleginops maclovinus (Valenciennes), off Chile, South America is described. The species can be separated from other species by its difference in size, especially body size, and the distribution of cephalic glands, vitelline follicles and genital organs. Egg-size is intermediate in comparison with that of other species. The posterior attachment mechanism consists of few muscle fibres and clumped cement-producing glands. All previous descriptions of Udonella caligorum Johnston, 1835 from off Chile correspond to this new species.

Larval trypanorhynch cestodes from peruvian teleost fishes, with descriptions of two new species

Examination of 60 teleost fishes (9 spp.) for cestodes from the Southeastern Pacific Ocean off Paita (5° 7´S, 81° 11´W) and Salaverry (8° 15´S, 78° 59´W) Peru, resulted in the recovery of eight species of trypanorhynchs, two of which are new. The new species are Pterobothrium acanthotruncatum and Pseudogrillotia peruviana. New host and distribution records are: Dasyrhynchus pacifiais Robinson in Sciaena deliciosa (Tschudi); Poecilancistrium caryophyllum (Diesing) from Sciaena gilberti Abbott; Floriceps saccatus Cuvier from Centropomus nigrescens Gunther; Tentacularia coryphaena Bosc from Coryphaena hippurus Linnaeus, Katsuwonus pelamis (Linnaeus) and Centropomus nigrescens: Callitetrarhynchus gracilis (Rudolphi) in Sciaena deliciosa, Polyclemus peruanus (Steindachner) and Hemilutjanus macrophtalmos (Tschudi); Lacistorhynchus tenuis (Van Beneden) from Odontesthes regia (Humboldt).

Ogmogaster heptalineatus n.sp. (Trematoda: Notocotylidae) from the Chilean sea lion Otaria flavescens

SummaryOgmogaster heptalineatus n.sp. is described from the Chilean sea lion Otaria flavescens. Distinct characteristics of the species are: presence of 7 longitudinal ridges on the ventral surface, cirrus armed with scales, testes and ovary deeply lobed and eggs circular with short polar filaments. This is the first report of the genus Ogmogaster from South America and the first report of Otaria flavescens as a host for this genus. ac]19820320

Variabilidad de las comunidades de parásitos metazoos del róbalo Eleginops maclovinus (Cuvier & Valenciennes, 1830) (Pisces: Eleginopidae) en Chile

La comparacion de las variaciones en el tiempo cronologico y en el espacio es uno de los aspectos menos estudiados en la ecologia de las comunidades de parasitos. Por eso, en este estudio se compara la abundancia total, riqueza y composicion de las infracomunidades de parasitos del robalo Eleginops maclovinus (Cuvier & Valenciennes, 1830) (Pisces: Eleginopidae), entre muestras tomadas en Chile centro-sur en tres localidades geograficas (Talcahuano, Puerto Montt y Punta Arenas), y en dos momentos del tiempo en cada una de ellas. En el conjunto de las 126 infracomunidades examinadas se encontraron 18 taxa de parasitos. La abundancia total y la composicion de las infracomunidades se modificaban con la ontogenia del hospedador. Sin embargo, se encontro que la variacion entre anos en una localidad es de similar magnitud a la que hay entre lugares geograficos, luego de corregir por el efecto de la ontogenia del hospedador. Estos resultados resaltan la necesidad de implementar disenos de muestreo mas rigurosos al momento de usar a los parasitos como marcadores biologicos de las poblaciones de hospedadores. Se propone que futuros estudios en las fuentes de variacion de las comunidades de parasitos mejoren la descripcion de estas variaciones con disenos de muestreo con medidas replicadas en el tiempo y el espacio.