Mesodinium rubrum (Lohmann 1908) Jankowski 1976 (= Myrionecta rubra) is a common photosynthetic marine planktonic ciliate which can form coastal red-tides. It may represent a 'species complex' and since Darwin's voyage on the Beagle, it has been of great cytological, physiological and evolutionary interest. It is considered to be functionally a phytoplankter because it was thought to have lost the capacity to feed and possesses a highly modified algal endosymbiont. Whether M. rubrum is the result of a permanent endosymbiosis or a transient association between a ciliate and an alga is controversial. We conducted 'feeding' experiments to determine how exposure to a cryptophyte alga affects M. rubrum. Here we show that although M. rubrum lacks a cytostome (oral cavity), it ingests cryptophytes and steals their organelles, and may not maintain a permanent endosymbiont. M. rubrum does not fall into recognized cellular or functional categories, but may be a chimaera partially supported by organelle robbery.

No abstract

Larvae of crab species inhabiting the shallow water marine environment show a wide range in nutritional requirements that must be satisfied via the diet. The present study compares the dietary requirements of larvae of the deep sea red crab Geryon quinquedens Smith with those of the stone crab Menjppe mercenaria Say, a shallow water species. Stone crab larvae cannot survive to metamorphosis on a rotifer diet. Red crab larvae show no difference in survival to metamorphosis on rotifer and brine shrimp nauplius diets, although some delay in development is seen on the former diet. We speculate that increased nutritional flexibility exhibited by the red crab is related to its deep water habitat and that evolution of such flexibility may be required for penetration of that habitat.

The need for precise estimates of chemical components of fish is common among the fields of aquaculture, fish health, and bioenergetics in fisheries management. Proximate composition is a widely used tool for obtaining this level of information but is time consuming and requires homogenization of the entire fish, limiting the ability to obtain additional information from the same individual. Exploratory chemical component analysis of differing body regions of age‐1 (215‐290‐mm) striped bass Morone saxatilis suggests that the abdominal wall (belly flap) is an appropriate surrogate for estimating whole‐body proximate composition. Belly flaps showed strong linear relationships with total lipid composition (R2 = 0.91) and moisture (R2 = 0.82) but were more variable with respect to protein (R2 = 0.22) and ash (R2 = 0.26). Equations derived from these linear relationships allowed for accurate estimation of total‐body energy, water, lipid, dry mass, fat‐free dry mass, and protein (R2 > 0.89). Strong linear relationships were also found for belly flap lipid and moisture and the same components measured in fillets (lipid: R2 = 0.82; moisture: R2 = 0.73). We conclude that sampling an otherwise unused portion of the fish can provide precise chemical compositional information without sacrificing product and can allow for additional information to be obtained from the same organism.

Groups of 10 menhaden were placed in a round behavioral monitoring pool and exposed to repeated 200 kv/m electromagnetic pulses (EMP). Their swimming activity was recorded on video tape for a 30-min period before, during and after pulsing. The recordings were analyzed for fish swimming speed and rate of change of direction. No significant differences (P > 0.05) were detected in either parameter as a result of EMPexposure. Zusarnmenfassung Scbwimmreaktion des Menhaden (Brevoortia tyrannus) auf elektromagnetiscbe Impulse Grup en von jeweils 10 Menhaden wurden in runden Becken wiederholt elektromagnetischen ImpuEen (EMP) (200 kv/m) ausgesetzt. Ihre Schwimmaktivitat wurde jeweils 30 Minuten vor, whrend und nach der Behandlung auf Videobandern aufgezeichnet. Die Aufzeichnungen wurden in Bezug auf Schwimmgeschwindigkeit und den Richtungswechsel ausgewertet. Es konnten keinerlei si nifikante Veranderungen der untersuchten Parameter (P > 0.05) nach EMP-Exposition festgestellt werrfen. RCsumC Nage des menbadens (Brevoortia tyrannus) en riponse a une impulsion dectromagnitiqwe Des groupes de 10 menhadens ont i t i places dans des bassins &observation cylindriques et exposis 1 des impulsions electromagnitiques (EMP) ripities de 200 kv/m. Leurs activitis nautiques ont 6th enregistrees i I'aide d'une camera vidio pendant une piriode de 30 minutes avant, pendant et aprk I'impulsion: Les enregistrements ont it6 analysis en tenant compte de la vitesse de deplacement des poissons et le taux de changement de direction. Aucune diffirence significative (p > 0,05) n'a CtC detectie par ces parameues aprks exposition i I'EMP.