Pseudocollinia brintoni gen. nov., sp. nov. (Apostomatida: Colliniidae), a parasitoid ciliate infecting the euphausiid Nyctiphanes simplex

A novel parasitoid ciliate, Pseudocollinia brintoni gen. nov., sp. nov. was discovered infecting the subtropical sac-spawning euphausiid Nyctiphanes simplex off both coasts of the Baja California peninsula, Mexico. We used microscopic, and genetic information to describe this species throughout most of its life cycle. Pseudocollinia is distinguished from other Colliniidae genera because it exclusively infects euphausiids, has a polymorphic life cycle, and has a small cone-shaped oral cavity whose left wall has a field of ciliated kinetosomes and whose opening is surrounded on the left and right by 2 'oral' kineties (or ciliary rows) that terminate at its anterior border. Two related species that infect different euphausiid species from higher latitudes in the northeastern Pacific Ocean, Collinia beringensis Capriulo and Small, 1986, briefly redescribed herein, and Collinia oregonensis Gómez-Gutiérrez, Peterson, and Morado, 2006, are transferred to the genus Pseudocollinia. P. brintoni has between 12 and 18 somatic kineties, and its oral cavity has only 2 oral kineties, while P. beringensis comb. nov. has more somatic kineties, including 3 oral kineties. P. oregonensis comb. nov. has an intermediate number of somatic kineties. P. beringensis comb. nov. also infects Thysanoessa raschi (a new host species). SSU rRNA and cox1 gene sequences demonstrated that Pseudocollinia ciliates are apostome ciliates and that P. brintoni is different from P. beringensis comb. nov. High densities of rod-shaped bacteria (1.7 μm length, 0.2 to 0.5 μm diameter) were associated with P. brintoni. After euphausiid rupture, high concentrations of P. brintoni and bacteria cluster to form 3 to 6 cm long filaments where tomites encyst and transform to the phoront stage; this is a novel place for encystation. P. brintoni may complete its life cycle when the euphausiids feed on these filaments.     

Gymnodinioides pacifica, n. sp., an exuviotrophic ciliated protozoan (Ciliophora, Apostomatida) from euphausiids of the Northeastern Pacific

A new species of apostome ciliate, Gymnodinioides pacifica n. sp. from the euphausiid Euphausia pacifica is described. The ciliated protozoan encysts on the setae of the appendages, telson and antennae. It excysts and enters the exoskeleton of the host after moulting, where it feeds on exuvial fluid. The phoront and trophont stages of this ciliate are described. The ciliature of the trophont has the following characteristics that distinguish it from the other species of Gymnodinioides: (1) a short kinety 9a (ciliary row 9a or K9a), approximately half of the length of falciform field 8, that extends from the anterior end of the cell posteriorly to the level of K1, (2) a straight K5a, perpendicular to K5b, K6, and K7, and (3) two distinct bands of kineties, K9b-K5b and K4-K1. In addition to those on the host E. pacifica, phoront cysts of similar shape were observed on Thysanoessa spinifera, T. gregaria, T. inspinata, T. longipes, and Nematoscelis difficilis. High prevalence rates were recorded (83%) for these apostome cysts on E. pacifica and T. spinifera during summer collections from the Oregon and Washington coasts. Additionally, we report other apostome ciliate symbionts of euphausiids, including Phtorophrya sp., which preys on apostomes in the genus Gymnodinioides.     

Relative contribution of euphausiid prey species and timing of breeding to Cassin's auklet Ptychoramphus aleuticus growth: within-season effects

Within-season variation in life-history parameters is characteristic of long-lived seabirds breeding in dynamic marine environments. Zooplanktivorous Cassin's auklets Ptychoramphus aleuticus breeding in central California feed primarily on euphausiid crustaceans, and switch from provisioning their offspring with Euphausia pacifica early in the nestling period to Thysanoessa spinifera later in the nestling period. I examined the effects of seasonal variation in nestling diet composition and meal mass, and timing of breeding and breeding attempt number (only/first or second breeding attempt) on the growth rate of individual nestlings on Southeast Farallon Island, California. For individual years, there were variable seasonal trends in growth, but no trends were apparent when all years were combined. Along with the predicted seasonal shift in prey use, there was a concurrent decrease in meal mass. In multivariate models, there were significant and positive effects of the mass proportions of E. pacifica and T. spinifera in the diet, meal mass and breeding attempt number on nestling growth, while the effect of hatching date on growth was negative. The relative influence of T. spinifera on growth was stronger than that of E. pacifica , the effects of hatching date on growth were likely dependent on the effects of breeding attempt, and breeding attempt exerted the strongest effect on nestling growth of all parameters examined. These suggest that the seasonal switch in prey use is advantageous (whether intentional or otherwise). Results illustrate the importance of adequate availability of both E. pacifica and T. spinifera to auklets in the Gulf of the Farallones. This study represents a unique approach in the investigation of linkages between individual nestling growth rate and diet and breeding phenology parameters by focusing on a fine temporal scale.     

Hatching mechanism and delayed hatching of the eggs of three broadcast spawning euphausiid species under laboratory conditions

Three different egg hatching mechanisms were observed underlaboratory conditions in Euphausia pacifica Hansen, Thysanoessaspinifera Holmes and Thysanoessa inspinata Nemoto: backward,forward and flipping. Like all broadcast spawning euphausiids,these species usually hatch as nauplius 1 (N1). Some hours beforehatching the vitelline membrane breaks and the embryo is freelysuspended within the chorion; later the embryo takes on a slightlyoval shape. When ready to hatch, the N1 pushes against the chorionwith the posterior part of the abdomen producing a protuberance.No spine or egg tooth is present to break the chorion. The pressurebreaks the chorion, and the nauplius pushes itself backwardswith the first and second antennae and mandible to slide fromthe chorion. After about three quarters of the body is outside,the nauplius brings all the appendages together to move backwardswithout becoming stuck in the chorion. This is the backwardhatching mechanism. The vitelline membrane remains within theegg after the nauplius leaves the chorion. Hatching takes 5–20s, and most of the eggs in a clutch hatch during <2 h. Severaleggs of E. pacifica hatched as meta-nauplii (MN) (>200 hafter spawning) or as calyptopis 1 (C1) stage (>232 h), ratherthan as N1. Delayed hatching of embryos also was observed inT. spinifera as nauplius 2 (N2) (>120 h) or as MN stage (>180h), and in T. inspinata as N2 (106 h) after spawning. Eggs withlarvae in stages of development beyond N1 have not been observedfrom preserved zooplankton samples. However, eggs spawned inthe field and incubated in the laboratory also had extendeddevelopment and late hatching but with low frequency (<0.06%).It is proposed that, if the backward hatching mechanism fails,alternate hatching mechanisms can be used by the euphausiid.There is high flexibility in their hatching modes. The N2 andMN break the chorion with the first and second antennae, hatchingforwards, and the C1 breaks it with the telson spines and byflipping of the abdomen, resembling the decapod hatching mechanism.Delayed hatching using the forward and flipping mechanisms wereassociated with low hatching success in comparison with thebackward hatching mechanism.     

Quantitative analysis of the invasion with gregarinids (Sporozoa: Gregarina) of the euphausiid Thysanoessa raschii (Crustacea: Euphausiacea) from the Barentsev sea

An occurrence of the gregarinids in the gastrointestinal tract of euphausiid Thysanoessa raschii was studied in summer 1982 and winter 1983 in the southern part of the Barents Sea. The infection rates of T. raschii with gregarinids was 0% in winter and 89.4% in summer. The highest level of infection was 1035 gregarinida per crustacean. The level of infection was found to be related mainly to be food composition (no gregarinids was found in euphausiids with copepods in stomach, the high level--in crustaceans with phytoplankton in the gastrointestinal tract).     

The ontogenetic development of refracting superposition eyes in crustaceans: Transformation of optical design

We have investigated, comparatively, the ontogenetic development of the compound eye in larvae of a mysid (Neomysis) and a euphausiid (Thysanoessa) species and found it to be close to identical in the two species. The larval eye is of apposition type with special adaptations for planktonic life. The elongated dioptric apparatus is devoid of screening pigment and instead has a proximal lens optically isolating the ommatidium. The pigmented retina is extremely compressed making the eye largely transparent and presumably suitable for a planktonic life. The presence of this specialized type of eye in the planktonic larvae of euphausiids was known before but it is intriguing to find exactly the same type in mysids, spending their entire larval life as embryos in the female marsupium. A possible explanation is offered if mysids earlier in evolution had planktonic larvae. Upon reduction of free-living larvae, the transparent type of eye may have been preserved because there is no selection pressure on the larva to change it. In late larval life, both species transform their eyes to a refracting superposition type typical for adult mysids and euphausiids. The process of transformation and the functional connection between transparent apposition and superposition is described.     

Terebrospira chattoni sp. n., a Parasite of the Endocuticle of the Shrimp Palaemonetes pugio Holthuis*

SYNOPSIS. Terebrospira chattoni sp. n. may be a species in transition between ectosymbiosis and endosymbiosis. It penetrates the epicuticle of Palaemonetes pugio and feeds on the endocuticle by dissolving galleries through it and absorbing the products of dissolution. Although similar in some respects to species of the endosymbiotic apostome genus Synophrya, T. chattoni is clearly related to ectosymbiotic apostomes that feed on exuvial fluid. However, instead of stimulating the metamorphosis of a phoront to a trophont, the host's ecdysis stimulates T. chattoni to metamorphose from a dedifferentiated trophont with 13 meridional kineties to a protomont, a predivision stage with 10 spiralled kineties. The protomont encysts and dedifferentiates to the division stage, an orthotomont with 13 kineties, either on the new exoskeleton before ecdysis, within a chamber in the endocuticle of the old exoskeleton, or on a substrate away from the host and the molt. The site of division determines the product of the division. On the new exoskeleton, the tomites in the reproductive cyst secrete walls around themselves thereby forming the lenticular, compartmented cysts characteristic of Terebrospira. Each daughter tunnels out of its compartment into the endocuticle. Although its infraciliature remains undifferentiated like that of the orthotomont, the ciliate in the gallery is the trophont, the only feeding stage in the life cycle. Daughters originating from the division of the orthotomont in a chamber in the endocuticle swim out of the exoskeleton at ecdysis. encyst on the substrate, and presumably form tomites. When the protomont itself leaves the molt, it encysts on the substrate and divides to form daughter cells with a rosette and the pattern of ciliature of the conventional tomite of other apostome genera. Tomites carry the infection to new hosts while compartmented cysts insure that the original host retains the infection. Terebrospira chattoni is always astomatous, although a dedifferentiated oral ciliature appears in the orthotomont and persists in the trophont. Terebrospira chattoni sp. n. is separated from T. lenticularis Debaisieux the other species in the genus because the latter species may divide outside a cyst and because T. chattoni has an extra reproductive stage in its life cycle.     

The Biology of Vampyrophrya pelagica (Chatton & Lwoff, 1930), a Histophagous Apostome Ciliate Associated with Marine Calanoid Copepods

ABSTRACT. The histophagous apostome. l'ampyrophrya pelagica , occurs on calanoid copepods in North Carolina. Its life cycle has two pathways: one when the copepod host is injured; the other when the host is ingested by an invertebrate predator. The ciliate, immediately after encysting on a copepod. metamorphoses to a feeding stage. When its host is injured or ingested by a predator, it excysts enters the wound and ingests the host's cytoplasm. In the single-host life cycle, after feeding, the ciliate encysts within the cadaver; in the two-host life cycle, after feeding it encysts upon a substrate. Encysted cells divide into 2–32 migratory tomites. Freed tomites are motionless in the water column until the water is disturbed, at which time they spring in the direction of any vibration, which many times results from a feeding copepod. Tomites select specific hosts, since not all species of copepods are infested. We hypothesize that the single-host life cycle yields many tomites that heavily infest hosts at random, and passage through the predator (two-host life cycle) results in fewer, but more widely dispersed tomites that are released continuously. The two-host life cycle is facultative for the individual, but may be obligate for the continuation of the species.     

Metacystis borrori n. sp. (Ciliophora: Metacystidae) on the seagrass Thalassia testudinum

A new epibiontic ciliate of the genus Metacystis is described on the seagrass Thalassia testudinum of the coral reef lagoons of Veracruz, Mexico. The ciliate was studied in living and stained specimens and under the scanning electron microscope. The cell body (10-35 x 10-18 microm in vivo) is transversely annulated (4-6 rings). The somatic ciliature consists of 22-30 longitudinal kineties, and patterned as 5-7 transverse kineties. The circumoral kinety is composed of kinetosomes closely spaced. The macronucleus diameter measures about 3-7 microm. The lorica (18-61 x 11-26 microm) has the posterior end round to conical or irregular with mucoid filaments. This prostomatid colonizes both natural and artificial substrates placed in an aquarium. Metacystis borrori n. sp. is a species that forms part of the ciliate community on Thalassia testudinum with a temperature range of 21-26 degrees C and a salinity of 32-40 per thousand.     

Distribution and abundance of euphausiids and pelagic amphipods in Kongsfjorden,Isfjorden and Rijpfjorden (Svalbard) and changes in their relative importance as key prey in a warming marine ecosystem

Euphausiid (krill) and amphipod dynamics were studied during 2006–2011 by use of plankton nets in Kongsfjorden (79°N) and adjacent waters, also including limited sampling in Isfjorden (78°N) and Rijpfjorden (80°N). The objectives of the study were to assess how variations in physical characteristics across fjord systems affect the distribution and abundance of euphausiids and amphipods and the potential for these macrozooplankton species to reproduce in these waters. The abundances of euphausiids and amphipods were higher in Kongsfjorden than in Rijpfjorden and Isfjorden, and the highest abundances were observed at the innermost stations of Kongsfjorden, where Thysanoessa inermis and Themisto libellula dominated. The Atlantic species Thysanoessa longicaudata, Meganyctiphanes norvegica and Themisto abyssorum dominated at the outside Kongsfjorden. Inter-annual and seasonal variability in abundances of euphausiids and amphipods were evident. The presence of ripe euphausiids outside Kongsfjorden indicates that they may reproduce in these areas. Mature individuals of T. abyssorum were recorded mainly outside Kongsfjorden, whereas no mature or ripe T. libellula were present in both the inner and outer parts of this fjord. If the warming trend persists, as seen during the last decade, this would favour the Atlantic/boreal euphausiid species, while Arctic species, such as the amphipod T. libellula, may decline. Euphausiids and amphipods are major food of capelin (Mallotus villosus) and polar cod (Boreogadus saida), respectively, in this region, and changes in prey abundance will likely have an impact on the feeding dynamics of these important fish species.     

Distribution of euphausiids in the Kuroshio front and warm water tongue with special reference to the surface aggregation of Euphausia pacifica

The distribution of euphausiids and other macrozooplankton wasinvestigated in and around the Kuroshio front formed in theKa.shima-nada Sea. Japan. during the summer of 1993. Zooplanktonwere dominated by copepods, chaetognaths and euphausiids. andtheir biomass was significantly higher at the frontal stations.Eighteen species belonging to six genera of euphausiids werecollected. The species composition and community structure ofeuphausiids changed drastically with the ‘areas’corresponding to the hydrological conditions. In the area underthe influence of the Kuroshio. most euphausiids were warm-waterspecies. In contrast. euphausiids found in the frontal areawere those usually predominating in subarctic or cold Oyashiowaters. In the area of the warm water tongue. where warm Kuroshiowater lay above cold Oyashio water, the species compositionof euphausiids represented a mixture of both warm- and cold-waterspecies. Surface aggregations of Euphausia pacifica were observedin the frontal area during the night. The biomass and densityof the aggregations ranged between 90 and 136 mg C m^–3and 164 and 238 md. m^–3 respectively. These aggregationswere mostly made up of immature individuals of < 12 mm. Passivetransportation by convergent flow at the front seems to explainthe observed surface aggregations of E.pacifica.     

Response to host age of the egg parasitoid Anaphes n.sp. (Hymenoptera: Mymaridae)

The mymarid Anaphes n.sp. was observed to parasitize the eggs of the carrot weevil Listronotus oregonensis (LeConte) up to 138 h old at 23±1°C and 18L:6D. Adult emergence of the parasitoid was observed in 85%‐97.5% of the weevil eggs 42–138 h old and host embryogenesis was interrupted in nearly 100% of these eggs. In host eggs of 18 h old, parasitism was very high but not all parasitoids completed their development and their subsequent emergence was generally retarded. An.sp. could parasitize host eggs 162 h old, but such an attack rarely retarded the normal development of the host. The parasitoid was unable to complete its development in sterile carrot weevil eggs.     

Levisunguis subaequalis n. g., n. sp., a tongue worm (Pentastomida: Porocephalida: Sebekidae) infecting softshell turtles, Apalone spp. (Testudines: Trionychidae) in the southeastern United States

A new tongue worm (Pentastomida) belonging to the Sebekidae Sambon, 1922 (Porocephaloidea Sambon, 1922) is described based on exemplars collected from softshell terrapins Apalone spinifera aspera (Agassiz) and Apalone ferox (Schneider) in the southeastern United States; a new genus is erected to accommodate the new species. The new species belongs in the Sebekidae because adults possess four simple hooks arranged in a trapezoid pattern on the ventral surface of the cephalothorax, a mouth opening between the anterior and posterior pairs of hooks, a terminal anus, an elongated uterus with preanal uterine pore, and a Y-shaped seminal vesicle. Nymphs possess geminate hooks, and the new species has an aquatic life-cycle in which nymphs become encapsulated in the body cavity of a freshwater fish and mature in the lungs of a terrapin. The new genus is distinct from other genera in the Sebekidae primarily by differences in hook morphology and the fact that representatives use a terrapin as a definitive host. Nymphs infecting fish and presumed to be the new species matured as postlarval juveniles conspecific with the new species when they were fed to the eastern mud turtle, Kinosternon subrubrum (Lacépède). Nymphs of the new species are anatomically similar to but larger than nymphs of Sebekia mississippiensis Overstreet, Self & Vliet, 1985 found in the mesentery of fishes captured in Florida, U.S.A. Adults of the new species differ from those of S. mississippiensis based on hook features, chloride cell pore pattern on annuli, body size, and use of a turtle rather than crocodilian definitive host. The new species is the third North American member of the Sebekidae.     

Relationship between the distribution of euphausiids and baleen whales in the Antarctic (35°E – 145°W)

Simultaneous whale sighting and hydroacoustic surveys were conducted from a research vessel in the Antarctic to examine the relationship between the distribution of euphausiids and baleen whales. High densities of minke whales and large aggregations of euphausiids were observed along the ice edge over the continental slope in the southeast region of area IV and in the southwest region of area V. The results suggest that the continental slope zone that coincides with the ice edge would be an important minke whale feeding area. Minke whales were rarely sighted in the offshore region even if euphausiids were abundant. Distributions of humpback whales were correlated with high euphausiid density zones, regardless of the bottom topographic features. Several groups of blue whales were sighted in the small area along the ice edge where euphausiids were abundant, but sightings were too few to draw any general conclusion about the relationship between blue whales and euphausiids. Both baleen whales and euphausiids were scarce in the area east of 170°W where sea ice covered the continental shelf and slope zone.     

The Structure of Colpoda elliotti n. sp.

SYNOPSIS. Colpoda elliotti n. sp., found in an enrichment culture from deer droppings, is a small (15–28 by 7.5–17 μ) member of the genus with prominent, rigid, tooth-like processes set between the kineties in the posterior 2/3 of the body. These "teeth" give it a distinctive outline even when viewed at low magnifications. The usual number of kineties is 12; the number of keel notches is 4. Multiplication occurs in reproductive cysts yielding typically 4 tomites. Thick-walled, resting cysts are also formed.
The nuclear apparatus includes a single, crescentic ***micronucleus and a broadly elliptical macronucleus. The latter contains Feulgen-positive material in a few large masses, but no central nucleolus.
The possibility that this species along with other members of the genas is perhaps more closely related to the Hymenostomatida than to the Trichostomatida as now defined is discussed.     

Differential use of zooplankton prey by Ancient murrelets and Cassin's auklets in the Queen Charlotte Islands

The distribution at sea and the food of two similar sized plankton-feedingalcids were examined during the 1981 breeding seasons in thenorthwestern Queen Charlotte Islands, British Columbia. Thetwo alcids, the Ancient murrelet (Synthliboramphus antiquus)and the Cassin's auklet (Prychoramphus aleuticus) have differentchick-rearing strategies. Both species fed predominantly atthe shelf break, although the Cassin's auklet also foraged overseamounts. The feeding distributions of the species appear tobe related to those of their prey. Zooplankton sampling indicatedthat each alcid selects a small and different portion of thezooplankton available in surface waters. The Ancient murrelet'smain foods were euphausiids (Thysanoessa spinifera and Euphausiapacifica) and larval and juvenile fishes. The Cassin's aukletchicks fed chiefly on calanoid copepods (Neocalanus cristatus).euphausiids (mostly Thysanoessa longipes in 1981, but in otheryears also Thysanoessa spinifera), and larval and juvenile fishes.The Cassin's auklets took smaller prey than the Ancient murrelet.Differences in the diets of the two alcid species were associatedwith differences in morphology and chick-rearing strategies.     

Adaptive value of the volume of perivitelline fluid in the eggs of euphausiids (Crustacea: Euphausiacea)

The perivitelline space of the euphausiid egg serves to maintain eggs buoyancy. It is believed that in oceanic species the volume of the perivitelline space is smaller than in neritic [32, 37, 40]. Published and original data suggest a more complicated tendency for perivitelline space volume and, correspondingly, egg buoyancy in euphausiids, which decrease in the direction: continental slope → shelf → ocean. This tendency is well explicable by adaptations of euphausiid species to the specific conditions of these biotopes. The possible mechanisms of these adaptations are discussed.     

Ten years after: krill as indicator of changes in the macro-zooplankton communities of two Arctic fjords

A macro-zooplankton study from 1996 was repeated in 2006 and focused on euphausiid species as indicators of advection and warming effects in Kongsfjorden, West Spitsbergen, Svalbard. The influence of warmer Atlantic water in Kongsfjorden was indicated by the findings of three additional euphausiid species of typically Atlantic origin, relative to the previous study 10 years ago. The predominant presence of Thysanoessa inermis in Hornsund suggested persisting cold conditions in this more southerly, but more Arctic influenced fjord. In this species, moult stage analysis showed that trophic effects can override temperature forcing. Histology and lipid analysis suggest that reproductive activity should be monitored as an indication of warming and possibly a shift in food web composition.     

Plant patch structure modifies parasitoid assemblage richness of a specialist herbivore

1. The spatial structure of plant patches has been shown to affect host–parasitoid interactions, but its influence on parasitoid diversity remains largely ignored. Here we tested the prediction that parasitoid species richness of the specialist leafminer Liriomyza commelinae increases in larger and less isolated patches of its host plant Commelina erecta. We also explored whether parasitoid abundance and body size affected the occurrence of parasitoid species in local assemblages. 2. A total of 893 naturally established C. erecta patches were sampled on 18 sites around Córdoba city (Argentina). Also, two experiments were performed by creating patches differing in the number of plants and the distance from a parasitoid source. For these tests, plants were infected with the miner in the laboratory prior to placement in the field. 3. Plant patch size, independently of host abundance, positively affected the number of parasitoid species in both survey observations and experimental data. However, plant patch isolation did not influence parasitoid species richness. 4. The probability of finding rare parasitoid species increased with patch size, whereas occupation of isolated patches was independent of dispersal abilities (body size) of parasitoid species. 5. Overall, the results highlight the importance of considering spatial aspects such as the size of plant patches in the study of parasitoid communities.