Seasonal variations in size and morphology of Acanthocyclops robustus (Copepoda Cyclopoida)

The variations in the body length, swimming legs and some setaeof the freshwater cyclopid Acanthocyclops robustus were analysedduring an annual cycle in the field, and in laboratory experimentsat different culture temperatures. In Lake Créteil. ashallow temperate sand-pit lake, there is a seasonal morphologicalvariation of the setae: the plumose forms were restricted tothe warmer season and the spinose ones to colder periods. Contraryto other years, the specific ‘spine formula’ ofthe swimming legs (3-4-4-4) did not vary during the referenceyear. In laboratory experiments, both sex and post-embryonicdevelopmental temperatures had an effect on the length of adults.A significant parental effect on body length was detected. Pairswith anomalous spine formulae produced offspring either withanomalous spine formulae or typical 3-4-4-4 formulae. No significanteffects of parental culture temperatures, offspring culturetemperatures and sex on the total number of spines were found.Modification of plumose into spinose setae did not occur, whateverthe offspring developmental temperatures. The results presentedhere suggest that the alterations of the appendages of the cyclopidA.robustus could be compared to the cyclomorphosis in otherzooplanktonic groups, and contribute to our understanding ofthe role of phenotypic induction in aquatic biology.     

Prey features affecting ingestion rates by Acanthocyclops robustus (Copepoda: Cyclopoida) on zooplankton

Summary (1) Ingestion rates by adult female and juvenile Acanthocyclops robustus on a number of prey types were measured at a prey concentration of 100/l in experimental volumes of 300–400 ml. (2) For the adult predator, Synchaeta pectinata was most vulnerable (22.3, standard error 1.4, prey ingested per predator per day) as compared to Brachiomus calyciflorus, Brachionus diversicornis, Keratella cochlearis (two morphs), Asplanchna priodonta, Polyarthra major, Synchaeta kitina, Pompholyx sulcata, Daphnia spec., and Bosmina longirostris. For these latter prey, the lowest ingestion rate was on one morph of K. cochlearis and the highest on A. priodonta, being, respectively, 1.0, SE 0.5, and 11.3, SE 1.0, prey per predator per day. (3) With regard to the juvenile predator (mostly copepodite stages I, II and III), ingestion rates on K. cochlearis and P. sulcata were low (respectively 1.2, SE 0.7, and 0.3, SE 0.1, prey per predator per day) but quite high on S. kitina (5.7, SE 0.6). (4) In addition, the effect of increasing prey concentration on the ingestion rate (functional response) by the adult female predator was examined for B. calyciflorus, K. cochlearis, S. pectinata, S. kitina and Daphnia spec.. Increases in ingestion rate with prey density were minimal for B. calyciflorus and K. cochlearis, greater for Daphnia spec., still greater for S. pectinata and of greatest magnitude for S. kitina. (5) The reasons for these results are discussed with particular reference to prey features.     

Molecular and morphological patterns across Acanthocyclops vernalis‐robustus species complex (Copepoda,Cyclopoida)

Bláha, M., Hulák, M., Slouková, J. & Tě?itel, J. (2010). Molecular and morphological patterns across Acanthocyclops vernalis‐robustus species complex (Copepoda, Cyclopoida).—Zoologica Scripta, 39, 259–268. Morphological traits within Acanthocyclops (Kiefer, 1927) are highly variable, and morphology is too constrained to give complete information of phylogenetic relationships. This study combined morphological and molecular techniques to investigate the taxonomic and phylogenetic relationships of three species of Acanthocyclops (Acanthocyclops trajani, Acanthocyclops einslei and Acanthocyclops vernalis) inhabiting continental Europe. Morphological indices subjected to principal component analysis (PCA) separated sample populations into three distinct clusters corresponding with the taxonomic status of the species analysed. In addition, the taxonomy status of A. trajani and A. einslei was in agreement with molecular data; however, the intraspecific variation in sequences of 12S rRNA was lower in contrast to specimens morphologically determined as A. vernalis, which were divided into two deeply divergent clades, based on mtDNA sequence divergences. Moreover, high sequence divergence (26%) between these clades indicated the existence of another species that may not be a sister taxon of A. vernalis s.s. Results point to the need for further taxonomic work on Acanthocyclops.     

Variations in the embryonic development times and hatching success of three Boeckella species (Copepoda: Calanoida)

Embryonic development times of Boeckella triarticulata, B. dilatata and B. hamata are compared. Two species, B. triarticulata and B. hamata had widely varying embryonic development times. Variable development times often resulted in greater hatching success.     

A New Acanthocyclops Kiefer, 1927 (Copepoda: Cyclopoida) from Central Mexico with Comments on the Distributionof the Genus in Middle America

A new species of Acanthocyclops Kiefer is described from central Mexico. It differs from its congeners by a combination of characters including mainly: 11–13 antennular segments, a spine formula of 3444 and modified setae on legs 2–4. The presence of a compound distal antennular segment is aberrant within the Cyclopoida. The new species seems to be related to Nearctic forms of the vernalis –robustus clade. Ancestors of this lineage probably reached central Mexico as a result of glaciation events and the new species is a remain of stranded postglacial populations; some of these forms were succesful in colonizing tropical lands. A key for the identification of the species of Acanthocyclops recorded in Mexico is included. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The reproductive biology of Euchaeta antarctica Giesbrecht (Copepoda: Calanoida) at South Georgia

The reproductive biology of the predatory calanoid copepod Euchaeta antarctica Giesbrecht was investigated in two interconnected fjord systems at South Georgia. Counts of the number of spermatophores attached to adult females and the number of egg sacs encountered, indicated probable peaks of reproduction in summer and winter. Patterns of spermatophore placement were examined and compared with data for E. norvegica (Boeck) from boreal waters. Elemental analysis indicated a high proportion of carbon and a low proportion of nitrogen in adult females and egg sacs from both sites.High winter carbon levels in adults seem related to their predatory feeding habits allowing high food intake throughout the year whereas in egg sacs it probably reflects extended development times and/or non-feeding naupliar stages.Mean adult female and egg clutch dry weights were higher in Cumberland East Bay during winter than in Moraine Fjord during summer. These differences are discussed in the context of relationships between fjord morphology and production levels.     

Temperature-dependent development and growth of Calanus sinicus (Copepoda: Calanoida) in the laboratory

The calanoid copepod Calanus sinicus was reared in the laboratory under excess food conditions, and its development and growth rates were measured at various temperatures. Egg development time (D_H, days) was dependent on temperature (T °C), and was expressed as D_H = 55.3 (T + 0.7)^–1.44. Post-embryonic development followed the equiproportional rule. The stage duration was short in NI and NII, but compensatingly longer in NIII. Between NIV and CII, it was nearly isochronal, and beyond CII, it tended to increase gradually. The time from egg to adult was expressed as D_CVI = 1258 (T + 0.7)^–1.44. The specific growth rate was also temperature-dependent and highest from CI to CIII, intermediate from NII to CI and from CIII to CV, and lowest from CV to CVI. The growth rates of C. sinicus are higher than those of co-occurring small copepods such as Paracalanus, Acartia and Microsetella.     

Molecular phylogeny of the Calanoida (Crustacea: Copepoda)

The order Calanoida includes some of the most successful planktonic groups in both marine and freshwater environments. Due to the morphological complexity of the taxonomic characters in this group, subdivision and phylogenies have been complex and problematic. This study establishes a multi-gene molecular phylogeny of the calanoid copepods based upon small (18S) and large (28S) subunits of nuclear ribosomal RNA genes and mitochondrial encoded cytochrome b and cytochrome c oxidase subunit-I genes, including 29 families from 7 superfamilies of the order. This analysis is more comprehensive than earlier studies in terms of number of families, range of molecular markers, and breadth of taxonomic levels resolved. Patterns of divergence of ribosomal RNA genes are shown to be significantly heterogeneous among superfamilies, providing a likely explanation for disparate results of previous studies. The multi-gene phylogeny recovers a monophyletic Calanoida, as well as the superfamilies Augaptiloidea, Centropagoidea, Bathypontioidea, Eucalanoidea, Spinocalanoidea and Clausocalanoidea. The phylogeny largely agrees with previously-published morphological phylogenies, including e.g., enlargement of the Bathypontioidea to include the Fosshageniidae.     

Egg production rates and stage-specific development times of Clausocalanus furcatus (Copepoda, Calanoida) in the northern Gulf of Mexico

The calanoid copepod Clausocalanus furcatus is widely distributedin tropical and subtropical oceans, yet knowledge of its reproductionand development remains limited. We estimated egg productionrates and stage-specific development times from laboratory incubationsand field samples collected at a petroleum platform in the northernGulf of Mexico. Egg production experiments were performed in2002 and 2003 at a laboratory on the platform using freshlycollected female copepods. Median stage development durationswere also measured during the incubations. Logistic regressionmodels were used to estimate median stage durations. The mediandevelopment times of Clausocalanus furcatus from hatching toadulthood ranged from 13 to 20 days. Field samples were collectedfrom waters beneath the platform at 12-h intervals using a 30-LNiskin water bottle during March–April and May–June2003, and the Edmonson egg ratio method was used to estimatethe mean in situ egg production rate. This field-derived meanegg production rate was significantly lower than the 12.08 eggsfemale^–1 day^–1 measured from incubation experiments,and this difference may reflect high in situ egg mortality.In situ egg production rates also showed high variability andwere almost five times higher during March–April comparedto May–June.     

Survivorship of Cyclops abyssorum tatricus (Cyclopoida, Copepoda) and Boeckella gracilipes (Calanoida, Copepoda) under ambient levels of solar UVB radiation in two high-mountain lakes

We performed in situ experiments during the summer of 1995 and 1996 to assess the potential effect of solar ultraviolet B (UVB) radiation (290-320 nm) on the survival of Cyclops abyssorum tatricus Kozminski and Boeckella gracilipes Daday. These species are numerically dominant within the crustacean zooplankton living in two high-mountain lakes, one located in the Austrian Alps [Gossenkollesee (GKS), 2417 m above sea level, maximum depth 9.9 m] and another in the Chilean Andes (Laguna Negra, 2700 m above sea level, maximum depth 320 m). The copepods were incubated in quartz tubes (1 1) or in quartz tubes wrapped with Mylar D® to exclude most of the UVB radiation. The organisms were exposed at 0.5 m depth for 10-72 h on cloudless days. Both lakes were very transparent to UVB and 10% of the surface radiation at the nominal wavelength of 305 nm was still present at 9.6 m in GKS and at 12.8 in Laguna Negra. These species migrate vertically and have a maximum daytime distribution close to the bottom (C.abyssorum tatricus) or below 15 m depth (B.gracilipes). Both species were red, but the carotenoid concentration was higher in C.abyssorum tatricus than in B.gracilipes (6.5 and 2.3 g mg^-1 dry weight, respectively). UV-absorbing compounds with a maximum absorption at 334 nm were also detected. Cyclops abyssorum tatricus was highly resistant to UVB radiation and no significant lethal effect was observed. Boeckella gracilipes had a mortality 5 times higher in the treatment receiving full sunlight than in the Mylar treatment (3.2%) only when exposed for 70 h. The resistance of B.gracilipes was higher than that reported in the literature for the same species, suggesting the existence of intraspecific differences in UV sensitivity.      

Natural development time of Eodiaptomus japonicus (Copepoda: Calanoida) in Lake Biwa

Seasonal and ontogenetic changes in natural development timewere studied for Eodiaptomus japonicus in Lake Biwa in 1986and 1987. Wild individuals in a certain developmental stagewere collected, fed on natural food and examined until theyhad moulted twice. Natural development times fluctuated irrespectiveof temperature from May to October. Food deficiency delayeddevelopment in all feeding stages, and food availability probablydetermined natural development time. Serious food limitationraised mortality in copepodid stage I. In November developmentwas delayed even with enough food. The development of E.japonicuswas almost isochronal except for a short prefeeding naupliarstage I and a long copepodid stage V.     

Temperature effects on Calanus helgolandicus (Copepoda: Calanoida) development time and egg production

Effects of temperature on aspects of the life cycle and physiologyof the copepod Calanus helgolandicus (C. helgolandicus) wereinvestigated in the laboratory. Development times (DTs) weredetermined for organisms reared individually at 9, 12 and 15°Cunder saturated food conditions. While animals were successfullyreared from egg to adulthood at 12 and 15°C, at 9°C,all the individuals had died prior to entering NV. The cohortswere fed with a monoculture of Prorocentrum micans as food saturatingconditions. The cohorts were fed with monocultures of Prorocentrummicans which should represent saturated food concentrationswith a dinoflagellate diet used in many other experimental studies.However, the monoculture nature of the diet and/or the laboratorycontainment conditions may have caused the mortality rates encountered.Impacts of short-term temperature change on egg production (EP)and hatching success were also investigated over the courseof 1 year on individuals collected from station L4 (WesternEnglish Channel) and incubated in the laboratory. DTs increasedas temperature decreased, with longer DTs at comparable temperaturewith those in Thompson’s study [(1982) Growth and developmentof Pseudocalanus elongatus and Calanus sp. in the laboratory.J. Mar. Biol. Ass. UK, 62, 359–372.] Evidence is presentedto suggest that in this other study a mix of Calanus finmarchicusand C. helgolandicus may have been used. Equiproportional developmentwas observed for the nauplii, but no pattern was defined forthe copepodites. At low temperatures, mortality rates in theincubations were higher, but adult condition factor was higher,the longer DTs allowed greater body mass to be accumulated.EP rate was correlated with temperature at station L4, but theshort-term incubation temperature did not have a significantinfluence on EP when measured over a short timescale (24 h).Egg hatching success also did not differ between incubationswith small temperature differences.     

Intertidal interstitial Halicyclops from the Brazilian coast (Copepoda: Cyclopoida)

H. tageae sp. n. and Halicyclops ytororoma sp. n. are described from the intertidal interstitial water of Brazilian beaches. H. tageae is distinguished from all congeneric species by the number of setae on legs 1–4 endopodite 2 (1, 1, 2, 2) and by possessing a reduced inner spine on the leg 5 exopodite. It shares with H. brevispinosus, H. pusillus and H. canui the spine formula 2, 3, 3, 3 on exopodite 3 of swimming legs 1–4. H. ytororoma closely resembles H. gauldi and differs from this species by having 4 setae on leg 1 endopodite 3; H. gauldi has 3 setae on this segment.This is the first record of Halicyclops from marine interstitial water in Brazil.     

Distribution and biogeography of the Paradiaptominae (Copepoda: Calanoida: Diaptomidae)

The Paradiaptominae, a subfamily of the large Diaptomidae family, is a small group of freshwater calanoids of which 24 species in four genera have been described. They are endemic to Africa with the exception of four species, Metadiaptomus asiaticus (Asia and Mongolia), M. gauthieri (Africa and Madagascar), Paradiaptomus greeni (India and Sri Lanka) and Neolovenula alluaudi (Canary Islands, North Africa, Baltic and Mediterranean countries). The North African species Metadiaptomus chevreuxi extends its range into Iraq and Iran. The Paradiaptominae are widely distributed in semi-permanent water bodies in the drier areas of Africa although most individual species have a restricted distribution. Only a few species have the ability to colonise permanent waters and these species are usually located at higher altitudes. The Paradiaptominae have not been recorded from the wet equatorial lowland areas of Africa. It seems likely that they are Gondwanian in origin as evidenced by their distribution (Africa, Madagascar, India and Sri Lanka). Neolovenula alluaudi (Mediterranean) shares morphological characters tenuously linked to the other species in the group and may either have a different origin or have branched off at an early stage in evolution of the group.     

Growth and development of Metridia pacifica (Copepoda: Calanoida) in the northern Gulf of Alaska

Juvenile growth and development rates for Metridia pacifica,one of the dominant larger copepods in the subarctic Pacific,were investigated from March through October of 2001–2004in the northern Gulf of Alaska. The relationship between prosomelength (PL, µm) and dry weight (DW, µg) was determined:log₁₀ DW = 3.29 x log₁₀ PL – 8.75. The stage durationsof copepodites ranged from 3 to 52.5 days but were 8–15days under optimal condition. Seasonally, growth rates increasedfrom March to October and typically ranged between 0.004 and0.285 day^–1, averaging 0.114 ± 0.007 day^–1(mean ± SE). After standardization to 5°C (Q₁₀ of2.7), growth rates averaged 0.083 ± 0.005 day^–1and were significantly correlated to chlorophyll a, with saturatedgrowth rates of 0.149 day^–1 for C1–C3, 0.102 day^–1for C4–C5 and 0.136 day^–1 for all stages combined.Measured juvenile growth rates were comparable with specificegg production rates in this species. The comparisons of ourrates in this study with those predicted by the global modelsof copepod growth rates suggested that further refinement ofthese models is required.     

The Malaysian Tropodiaptomus (Copepoda : Calanoida) and its distribution

In Peninsular Malaysia there are three species of Tropodiaptomus namely: T. hebereri Kiefer, T. ruttneri Brehm, and T. vicinus Kiefer. The last species is most common in swampy habitats along the west coast whereas T. ruttneri occurs only in the north and T. hebereri is present in the south. The affinity of the Malaysian tropodiaptomids and their Sunda counterparts is discussed.     

The freshwater Calanoida (Crustacea: Copepoda) of Thailand

14 Species of freshwater Calanoida in Thailand are reported in this study. The most common species is Neodiaptomus botulifer. Most of these belong to the Southeast Asian species, the remainder are either Indian or East Asian copepods. The zoogeographical demarcation of copepods in Thailand is not very distinct due to its interconnecting riverine and reservoir systems as well as frequent flood. The peculiarity of the Thai Calanoida and their distribution is discussed in a Southeast Asia context. A taxonomic key to the Thai Calanoida is formulated.     

The independence of the family Channaculinidae (Crustacea: Copepoda: Cyclopoida)

New family name Pillainidae Kazatchenko fam. nov. is suggested instead of family name Channaculinidae. The keys of the families and genera of fish parasitic copepods of suborder Cyclopoida are given.     

Siphonostomes (Copepoda -- Cyclopoida) from the Indian Ocean

Siphonostomes (Copepoda — Cyclopoida) from the InternationalIndian Ocean Expedition collections were studied. The groupwas represented by Pontoeciella abyssicola of family Pon-toeciellidaeand Ratania flava of family Rataniidae. This study has extendedthe distribution of both the species considerably, and includesthe first record of the male of P. abyssicola from the IndianOcean and of both species from the Bay of Bengal.