Relationship Between the Blue‐Green Alga Trichodesmium Thiebautii and the Copepod Macrosetella Gracilis in the Plankton off Northeastern South America

Macrosetella gracilis is closely associated with the epipelagic filamentous cyanobacteria OsciUatoria (Trichodesmiurn) spp., which serve as food for adults and as a substrate for the non-pelagic juveniles. Plankton sampling in the Red Sea in 1980-81, using a multiple opening-closing net with 0.1 mm mesh, revealed M. gracilis populations from the surface to the deepest stratum sampled (1650 m). Their population biology was investigated in the central and northern Red Sea, and included analysis of ontogenetic composition and size distribubon, sex ratio and percentage of egg-bearing females. By relating population structure differences to variations in the abundance of Tr~chodesmium spp. at the surface, a hypothetical life cycle for the copepod could be proposed. (1) Reproduction takes place only in surface waters during blooms of Trichodesmjum spp. (2) Short-term, diurnal vertical migrations are not apparent. (3) At the surface and in the lower meso-and bathypelagic zone, the female population consists mainly of small specimens; in the upper part of the oxygen minimum zone, a t 300 to 450 m, long-lived large, non-reproductive females are congregated. The significance of these midwater populations in the life cycle of M. gracilis is discussed under 2 alternative assumptions: (a) the copepods s u~v e periods of Trichodesmium spp. scarcity in a resting phase, or (b) the part of the population in deep waters is moribund. The unusually deep occurrence of M gracilis may have some significance for the nutrient cycle in these waters.

Section: Comparison With Other Pelagic Areassupporting

confidence: 43%

“…The abundance data for adult Macrosetella gracilis in the Red Sea can be compared with those from other fine mesh net sampling programs (c 0.1 mm mesh size) in the southern Atlantic Ocean (Calef & Grice 1966), the Caribbean Sea (Roman 1978) and the Sargasso Sea (own unpubl. data).…”

Section: Comparison With Other Pelagic Areasmentioning

confidence: 99%

Vertical distribution and population structure of Macrosetella gracilis (Copepoda: Harpacticoida) in the Red Sea in relation to the occurrence of Oscillatoria (Trichodesmium) spp. (Cyanobacteria)

Böttger-Schnack¹,

Schnack²

1989

“…A positive correlation between Trichodesmium spp. and M. gracilis abundances was also found in the Red Sea (Calef & Grice 1966, Böttger-Schnack & Schnack 1989, Böttger-Schnack 1991. However, no abundance data appears to be available for the North Pacific Gyre.…”

Section: Introductionmentioning

confidence: 85%

“…The relative abundance of M. gracilis among tropical copepods is poorly known, although Böttger-Schnack & Schnack (1989) estimated that M. gracilis comprises 1 to 3% of adult tropical copepods in the Red Sea. Calef & Grice (1966) showed that M. gracilis abundance in the western tropical Atlantic closely tracked Trichodesmium spp. abundance, and they found no M. gracilis in the absence of Trichodesmium spp.…”

Section: Introductionmentioning

confidence: 96%

Association of the copepod Macrosetella gracilis with the cyanobacterium Trichodesmium spp. in the North Pacific Gyre

Eberl¹,

Carpenter²

2007

The harpacticoid copepod Macrosetella gracilis is found in pelagic habitats in tropical and subtropical oceans associated with colonies of the N 2 fixing cyanobacterium Trichodesmium spp. ) and constituted an average of 10.8% of the total copepod population. However, we observed no statistically discernable correlation between M. gracilis and Trichodesmium spp. abundances, suggesting that availability of Trichodesmium spp. did not limit the abundance of M. gracilis during our study. In previous laboratory studies M. gracilis had been shown to have the ability to ingest Trichodesmium spp. trichomes and appeared immune to cyanobacterial toxins harmful to other species of copepods. Natural abundance of stable isotopes (δ 15 N, δ 13 C) in copepod tissue from field samples suggested that the diet of M. gracilis was not predominately composed of Trichodesmium spp. as proposed by previous research. Natural abundance of δ 15 N was similar for M. gracilis (3.06 ± 2.29), Miracia efferata (1.83 ± 0.88), and calanoid copepods (2.7 ± 1.95). No Trichodesmium spp. were observed in M. gracilis gut contents. Trichodesmium spp. was not a predominant food in the diet of this copepod, but colonies of the toxic cyanobacterium could provide shelter from predation and be used as a floating substrate for adult and juveniles of M. gracilis.

“…and Macrosetella gracilis (Bjornberg 1965, Calef & Grice 1966, Roman 1978. Blue-green algae and some green algae are generally believed to be poorly utilized by herbivorous copepods.…”

Section: Discussionmentioning

confidence: 99%

Feeding and reproductive performance of the harpacticoid Tisbe carolinensis (Copepoda, Crustacea) in four algal cultures

Lee¹,

Zhang²,

Baalen³

et al. 1985

The functional relation between the harpacticoid copepod Tisbe carolinensis and 4 algal strains was examined in the laboratory. T. carolinensis reared either in suspensions of the green alga Chlorella autotrophica (Strain 580) or the 2 blue-green algae Agmenellum quadruplicatum (Strain PR-6 ) and Anabaena sp. (Strain CA) showed marked differential mortalities between sexes, and had fecal production rates of < 0.2 ind-' h-'. T. carolinensisin these algal cultures produced smaller numbers of brood and fewer viable nauplii than those exposed to the pennate diatom Cylindrotheca sp. (Strain N-1) or a mixed diet of all 4 algae. T carolinensis fed actively on S t r a~n N -l and on the mixture, and fecal pellet production rates averaged > 1.2 ind-' h -' Under laboratory conditions (30 %, 24 "C) with Strain N -l , interclutch interval was estimated to be 4 to 4.5 d , of w h~c h 24 to 33 h was required for oviposition and 3 d for embryonic development. Successful f e e d~n g and reproduction on Strain N -l and on algal mixture may be associated with larger particle size and somewhat higher nutritional value (i.e. protein and l~p i d content) of the diatom. This study emphasizes the importance to the copepods of algal type, cell size, and algal protein, carbohydrate, and lipid content, and suggests how these factors may combine to affect T. carolinensispopulation in the field via their effects init~ally on feeding activity and survival rate, and subsequently on e g g production and development