Reproductive patterns of three intertidal salt-marsh gammaridean amphipods

Among three sympatric species of epibenthic amphipods found at different tide marks at Jamaica Bay, New York (USA), the length of time juveniles spend with the mother increases and the number of juveniles per brood decreases as tidal height increases. Each brood has two developmental periods: (1) the embryonic period, from ovulation to hatching; (2) the juvenile period, from hatching to emergence from the marsupium. Gammarus palustris, found at the high-tide mark, has a mean juvenile period of 1.7 days and a mean brood size of 12.4 offspring; G. mucronatus, found at mean-tide mark, has a mean juvenile period of 0.8 days and a mean brood size of 27.4 offspring; Melita nitida, found at low-tide mark, has a mean juvenile period of 0.5 days and a mean brood size of 30.0 offspring. Further, the range of days that a juvenile may emerge is widest for G. palustris (0 to 8 days after hatching) and narrowest for M. nitida (0 to 2 days).This work was submitted in partial fulfillment of the requirements for the Ph.D. at the City University of New York.     

Effects of receptive females' secretion on some male reproductive behaviors in the amphipod crustacean Microdeutopus gryllotalpa

The use of a choice test apparatus has shown that receptive females of the tube-building amphipod crustacean Microdeutopus gryllotalpa (Costa) secrete a waterborne substance which attracts males. This substance (1) increases the level of activity of males, and (2) orients the males' movements towards its source. Males do not secrete this substance. In this species, females tend to remain inside their residential tubes, and males generally travel from receptive female to receptive female. Thus, in the field, the attractant may stimulate the male to accelerate his movements toward, and guide him directly to a receptive female. On the other hand, at the concentration tested, the substance alone does not elicit intermittent pleopod beats, a male-specific behavior that only occurs in a reproductive context. The expression of intermittent pleopod beats is shown to require the presence of a female plus its tube.     

What can a hazard function teach us about drivers’ perception of hazards?

Objective: Hazard perception (HP) is typically defined as the ability to read the road and anticipate hazardous situations. Several studies have shown that HP is a driving skill that correlates with traffic crashes. Measuring HP differences between various groups of drivers typically involves a paradigm in which participants observe short videos of real-world traffic scenes taken from a driver’s or a pedestrian’s perspective and press a response button each time they identify a hazard. Young, inexperienced drivers are considered to have poor HP skills compared to experienced drivers, as evident by their slower response times (RTs) to road hazards. Nevertheless, though several studies report RT differences between young, inexperienced and experienced drivers, other studies did not find such differences. We have already suggested that these contradictory findings may be attributed to how cases of no response—that is, a situation where a participant did not respond to a hazard—are being treated. Specifically, we showed that though survival analysis handles cases of no response appropriately, common practices fail to do so. These methods often replace a case of no response with the mean RT of those who responded or any other central tendency parameters. The present work aims to show that treating cases of no response appropriately as well as selecting a distribution that fits the RT data is more than just a technical phase in the analysis.

Method: This work used simulation of predefined distributions and real-world data.

Results: It was demonstrated that selecting the appropriate distribution and treating nonresponse cases appropriately affect the shape and characteristics of the density, survival, and hazard functions.

Conclusions: The suggested process has the ability to provide researchers with additional information regarding the nature of the traffic scenes that enables differentiating between various hazardous situations and between various users with different characteristics such as age or experience.     

Reproductive behavior of three tube-building peracarid crustaceans: the amphipods Jassa falcata and Ampithoe valida and the tanaid Tanais cavolinii

Laboratory observations indicate that Jassa falcata, Ampithoe valida, and Tanais cavolinii have quite similar patterns of behavior: males attend females until ovulation and copulation occur, then the male and female separate. Females tend to remain inside their own tubes, and males tend to move between the tubes of receptive females. This pattern of behavior (called “cruising males”) may be common in crustaceans that exhibit some fidelity to a specific site, especially if the females produce several broods in succession, do not store sperm, and reproduce asynchronously relative to each other. Male J. falcata have a terminal molt which is marked by the presence of a specific sexually dimorphic characteristic, the “thumb” on the second gnathopod. Alternating ovulatory and anovulatory molts occur in T. cavolinii.     

Excess amylase in Gammarus palustris (Crustacea: Amphipoda); its release into and possible roles in the environment

Gammarus palustris Bousfield (1969) individuals, of both sexes, contain levels of amylase activity sufficient to hydrolyze their dry weight in starch in less than an hour. We suggest that this is in excess of their needs for internal digestion. Experiments show that amylase is released by the amphipod into the environment, especially when they are maintained in the presence of food. Gammarus palustris amylase can be recovered from their natural habitat. The enzymes retain activity over the wide salinity range (5 to 30) encountered by this species in nature. It is hypothesized that released amylase plays a role external to the amphipod, perhaps in predigestion of food, perhaps as an aid in finding food.     

The significance of a small, level-3 'semi evacuation' hospital in a terrorist attack in a nearby town

Terrorist attacks can occur in remote areas causing mass-casualty incidents MCIs far away from level-1 trauma centres. This study draws lessons from an MCI pertaining to the management of primary and secondary evacuation and the operational mode practiced. Data was collected from formal debriefings during and after the event, and the medical response, interactions and main outcomes analysed using Disastrous Incidents Systematic Analysis through Components, Interactions and Results (DISAST-CIR) methodology. A total of 112 people were evacuated from the scene-66 to the nearby level 3 Laniado hospital, including the eight critically and severely injured patients. Laniado hospital was instructed to act as an evacuation hospital but the flow of patients ended rapidly and it was decided to admit moderately injured victims. We introduce a novel concept of a 'semi-evacuation hospital'. This mode of operation should be selected for small-scale events in which the evacuation hospital has hospitalization capacity and is not geographically isolated. We suggest that level-3 hospitals in remote areas should be prepared and drilled to work in semi-evacuation mode during MCIs.