Hatching and survival of the salmon ‘gill maggot’ Salmincola californiensis (Copepoda: Lernaeopodidae) reveals thermal dependence and undocumented naupliar stage

Salmincola californiensis is a Lernaeopodid copepod parasitizing Pacific salmon and trout of the genus Oncorhynchus. Salmincola californiensis is of increasing concern in both native and introduced ranges because of its potential fish health impacts and high infection prevalence and intensity in some systems. Discrepancies in the documented life history phenology of S. californiensis with the sister species Salmincola edwardsii, as well as our laboratory observations, led us to question the existing literature. We documented a naupliar stage, thought lost for S. californiensis. In addition, we found a high degree of thermal sensitivity in egg development, with eggs developing faster under warmer conditions. Survival of copepodids was also highly dependent on temperature, with warmer conditions reducing lifespan. The longest lived copepodid survived 18 days at 4°C in stark contrast to the generally accepted <48 h survival for that life stage. We also note a consistent relationship between egg sac size and the number of eggs contained. However, egg sac sizes were highly variable. Our findings demonstrate that revisiting old assumptions for S. californiensis and related taxa will be a necessary step to improving our knowledge of the parasite life history and development that will be critical to disease management.

Production characteristics of the copepods Arctodiaptomus salinus and Calanipeda aquaedulcis fed with a mixture of microalgae Dinophyceae and Prymnesiophyceae

The ubiquitous copepod species Arctodiaptomus salinus (Daday, 1885) and Calanipeda aquaedulcis (Krichagin, 1873) are important components of food chains of numerous fresh- and saltwater areas. These copepods are suitable for feeding larvae of both marine and freshwater fish species; however, influence of nutrition on the production characteristics of these species is not well understood. Previously we determined that monocultures of microalgae Dinophyceae and Prymnesiophyceae are optimal feeding objects for egg production by females of A. salinus and C. aquaedulcis, survival rate, and development time of these copepods throughout ontogenesis. The aim of this work was to determine the production characteristics of copepods A. salinus and C. aquaedulcis under optimal temperature conditions depending on the model of the feeding with a mixture of microalgae Dinophyceae and Prymnesiophyceae. The highest survival rates of A. salinus from the naupliar stage to the adult one (93–95 %) were observed when copepods were fed with a monoculture of microalga Isochrysis galbana (Parke, 1949) or a mixture I. galbana + Prorocentrum cordatum (Ostenfeld) J. D. Dodge, 1975; the shortest development time (19 days) – when copepods were fed with a mixture of three microalgae I. galbana + P. cordatum + Prorocentrum micans (Ehrenberg, 1834). The shortest development time of C. aquaedulcis from the naupliar stage to the adult one (13 days) was observed when copepods were fed with a mixture of microalgae I. galbana + P. cordatum. The shortest duration of the naupliar stage of development of both copepod species was observed when their diet included I. galbana as a monoculture or one of mixture components. During the copepodit stage, the pattern remains the same, only with P. cordatum. The maximum absolute fecundity of C. aquaedulcis reached 24 eggs per female (I. galbana), of A. salinus – 16 eggs per female (P. cordatum). Egg hatching of C. aquaedulcis when being fed with both monocultures of microalgae P. cordatum and I. galbana and with their mixture reached 100 %. The highest egg hatching rate for A. salinus was reached only when copepod females were fed with a mixture of microalgae I. galbana + P. micans.

Improvement of survival and development of Pacific white shrimp Litopenaeus vannamei larvae by feeding taurine enriched rotifers

<p>ABSTRACT</p><p><br />The objective of the present experiment was to study the most optimum taurine enrichment concentration of rotifers in improving Pacific white shrimp larva Litopenaeus vannamei survival and development. White shrimp larvae at sixth naupliar stage were reared in 12 units of 500 L fibre glass tanks with a stocking density of 125 ind/L. Starting from zoea two stage (Z-2), the larva was provided with rotifers with different taurine enrichment concentration according to the treatments, i.e. 0 mg/L enrichment medium (A), 25 mg/L (B), 50 mg/L(C), and 100 mg/L (D). The results show that different taurine concentration in the enrichment media increased taurine level in rotifers. Furthermore, the administration of taurine enriched rotifers up to 50 mg/L significantly improved larval survival and may accelerate larval development. The experimental results also concluded that a concentration of 50 mg/L is the most optimum taurine enrichment concentration of rotifers for the improvement of white shrimp larval survival and developmental stage.</p><p><br />Keywords: taurine, rotifer, white shrimp, enrichment</p><p><br />ABSTRAK<br />Penelitian ini bertujuan untuk mengkaji konsentrasi optimum taurin melalui pengayaan pada rotifera terhadap tingkat kelangsungan hidup dan perkembangan stadia larva udang vaname Litopenaeus vannamei. Larva udang vaname stadia naupli-6 dipelihara dalam 12 tangki fiberglass volume 500 L dengan kepadatan 125 ind/L. Dimulai sejak stadia zoea 2 (Z-2) larva diberi rotifera yang diperkaya dengan taurin dengan konsentrasi yang berbeda sesuai dengan perlakuan, yaitu 0 mg/L media pengkaya (A), 25 mg/L (B), 50mg/L (C), dan 100mg/L (D). Hasil penelitian menunjukkan pengayaan taurin pada konsentrasi yang berbeda menyebabkan peningkatan kandungan taurin rotifera. Sementara pemberian rotifera yang diperkaya taurin hingga 50 mg/L meningkatkan kelangsungan hidup dan mempercepat perkembangan stadia larva udang. Berdasarkan hasil penelitian ini dapat disimpulkan bahwa pemberian rotifera yang diperkaya taurin dengan konsentrasi 50 mg/L menghasilkan tingkat kelangsungan hidup tertinggi (53,5%) dan perkembangan larva yang tercepat (p&lt;0,05) dibandingkan perlakuan lainnya.<br /><br />Kata kunci: taurin, rotifera, udang vanname, pengayaan</p>

<i>Blastodinium</i> spp. infect copepods in the ultra-oligotrophic marine waters of the Mediterranean Sea

Blastodinium are chloroplast-containing dinoflagellates which infect a wide range of copepods. They develop inside the gut of their host, where they produce successive generations of sporocytes that are eventually expelled through the anus of the copepod. Here, we report on copepod infections in the oligotrophic to ultra-oligotrophic waters of the Mediterranean Sea sampled during the BOUM cruise. Based on a DNA-stain screening of gut contents, 16% of copepods were possibly infected in samples from the Eastern Mediterranean, with up to 51% of Corycaeidae, 33% of Calanoida, but less than 2% of Oithonidae and Oncaeidae. Parasites were classified into distinct morphotypes, with some tentatively assigned to species B. mangini, B. contortum, and B. cf. spinulosum. Based upon the SSU rDNA gene sequence analyses of 15 individuals, the genus Blastodinium was found to be polyphyletic, containing at least three independent clusters. The first cluster grouped all sequences retrieved from parasites of Corycaeidae and Oncaeidae during this study, and included sequences of Blastodinium mangini (the "mangini" cluster). Sequences from cells infecting Calanoida belonged to two different clusters, one including B. contortum (the "contortum" cluster), and the other uniting all B. spinulosum-like morphotypes (the "spinulosum" cluster). Cluster-specific oligonucleotidic probes were designed and tested by FISH in order to assess the distribution of dinospores, the Blastodinium dispersal and infecting stage. Probe-positive cells were all small thecate dinoflagellates, with lengths ranging from 7 to 18 μm. Maximal abundances of Blastodinium dinospores were detected at the Deep Chlorophyll Maximum (DCM) or slightly below. This was in contrast to distributions of autotrophic pico- and nanoplankton, microplanktonic dinoflagellates, and nauplii which showed maximal concentrations above the DCM. The distinct distributions of dinospores and nauplii argues against infection during the naupliar stage. Blastodinium, described as autotrophic in the literature, may escape the severe nutrient limitation of ultra-oligotrophic ecosystems by living inside copepods.

Oxygen uptake in a barnacle: scaling to body size from nauplius to adult

We measured the oxygen uptake of the barnacle Balanus eburneus Gould during the following stages of its life cycle: (1) naupliar stages 1, 4 and 6; (2) cyprid; (3) postmetamorphosis adult (pinhead); and (4) large adult. Mass specific oxygen uptake [Formula: see text] increased by 60% during development from naupliar stage 1 to stage 6. An eightfold drop in [Formula: see text] occurred with the molt from stage 6 to cyprid. [Formula: see text] increased by fourfold after metamorphosis of the cyprid into the pinhead, the smallest adult. The slopes of the regression lines describing the relationship between nonmass specific O2 uptake and dry body weight (Wb) were (1) 1.27 for nauplii, (2) 0.87 for large adults, and (3) 0.75 for all life cycle stages studied except cyprids.

On the Larval Development of Elminius Modestus Darwin

Nauplii of the first two stages were obtained from adult Elminius modestus and larvae of all stages, except the smallest, were obtained from the plankton over Essex oyster beds.Over 200 nauplii of all sizes were measured. Their size distribution, plotted graphically, showed six peaks corresponding to six naupliar stages. The later stages were much more variable in size than the earlier stages.The size limits and characteristics of each naupliar stage are given. Briefly, Stage I has the fronto-lateral horns pointing backwards. Stage II has the caudal spine much longer than the abdominal process. Stage III has the abdominal process about as long as the caudal spine, but has no carapace fold posteriorly. Stage IV has a carapace fold but no sign of the abdominal appendages. Stage V has the rudiments of these appendages showing indistinctly within the abdomen. In Stage VI the abdominal appendages are prominent.