Associations between gelatinous zooplankton and hyperiid amphipods (Crustacea: Peracarida) in the Gulf of California

Hyperiid amphipods are pelagic crustaceans that live associated with gelatinous zooplankton including medusae, ctenophores, siphonophores, and salps. Standard plankton sampling disrupts natural associations, so the most reliable way to determine an association is through direct observation of the organisms in their environment. The planktonic fauna of the Gulf of California dwelling between 10 and 3000 m was surveyed using SCUBA diving and a remotely operated submersible (ROV) during March 2003. Here we report our observations on a total of 14 symbiotic associations found between the hyperiid amphipods and various taxa of gelatinous zooplankton. We found parental care behavior in a group of amphipods (Oxycephalidae) in which this phenomenon has not been previously reported. For two hyperiid species, Euthamneus rostratus and Vibilia australis, we present the first information on their symbiotic relations. Additional hosts were discovered for other well-known and widely distributed hyperiid species (i.e. Brachyscelus crusculum, Hyperoche medusarum). Photographic evidence of some of these interactions is included in this contribution. This is the first survey of these relationships in the Gulf of California, and many aspects of the ecology and biology of these symbioses remain to be studied.     

Associations between gelatinous zooplankton and hyperiid amphipods (Crustacea: Peracarida) in the Gulf of California

Hydrobiologia - Hyperiid amphipods are pelagic crustaceans that live associated with gelatinous zooplankton including medusae, ctenophores, siphonophores, and salps. Standard plankton sampling...     

Impact of ZnSO and ZnO Nanoparticles on Seed Germination and Seedling Growth of Lettuce

Micronutrient nanoparticles (NPs) are currently an option for chemical fertilization and biostimulation in crops. However, there is little information on the phytotoxic or biostimulatory effects of NPs at low concentrations of some elements, such as Zn. In this study, the effect of low concentrations of Zn oxide (ZnO) NPs on germination, growth variables, and nutritional attributes of lettuce (Lactuca sativa L.) was evaluated in comparison to Zn sulfate. Romaine lettuce seeds were treated with ZnSO₄^-- × 7H₂O and ZnO NPs at Zn molar concentrations of 1 × 10⁻³, 5 × 10⁻³, 1 × 10⁻⁴, 5 × 10⁻⁴, 1 × 10⁻⁵, 5 × 10⁻⁵, 1 × 10⁻⁶, and 5 × 10⁻⁶. The seeds treated with ZnSO₄⁻ at 5 × 10⁻⁶ registered the highest radicle length, 73% more than the control treatment. The seeds treated with ZnSO₄⁻ at 5 × 10⁻³ registered the lowest values, with 50% less than the control treatment. ZnO NPs at 5 × 10⁻⁶ significantly increased content of chlorophyll A and B and total phenolics. These results indicate the possible existence of a mechanism related to the intrinsic nanoparticle properties, especially at low concentrations.

     

Dormancy in Garlic (Allium sativum L.) cv. Rosado Paraguayo II. The Onset of the Process during Plant Ontogeny

Dormancy in garlic cv. Rosado Paraguayo was studied during plantontogeny in relation to endogenous growth regulators and bulb-forming.The differentiation of seed cloves began coincidently with abulb-forming rate of 0.47 and a lack of gibberellin and moderateinhibitor activities. This hormone levels remained at harvest,when the seed cloves, which had completed their final size,were unable to sprout. Considering these and previous results,the lack of gibberellin like promoters could be the main factorwhich controls dormancy in garlic. (Received May 7, 1985; Accepted November 26, 1985)     

Protected from fire,but not from harm: seedling emergence of savanna grasses is constrained by burial depth

ABSTRACT

Background

The Cerrado is a fire-prone Neotropical savanna and grass seeds are the main component of the soil seed bank. Although grass seeds are presumed to tolerate heat pulses during fires, the assumption that these seeds will be recruited may be an overestimation, since it does not account for factors that limit seedling emergence from the soil.