Distributional ecology of milkfish,Chanos chanos,larvae in the Great Barrier Reef and Coral Sea near Lizard Island,Australia

Synopsis Plankton hauls captured 682 milkfish larvae (2.1–12.3 mm) in the Great Barrier Reef Lagoon and Coral Sea during 1979–1986. Larvae were present from November to March, and absent in April, July and October. We analyzed concentration, abundance and size-frequency data and concluded that spawning took place in the Coral Sea or at the outer edge of the continental shelf, apparently following an adult spawning migration of at least 50 km. Larvae then moved inshore to at least our most inshore routine sampling site near midshelf. Some larvae may have remained for a period in the lee of reefs along the shelf edge. Larvae apparently occupied the upper few metres of the water column, thereby becoming susceptible to shoreward movement in the wind-driven surface layer. Movement from spawning sites to midshelf probably required active maintenance of vertical position by larvae which enabled passive movement with favourable currents, and perhaps horizontal swimming. By the time larvae reach midshelf, continued inshore movement by horizontal swimming alone is possible.     

Incorrect size correction

In critiquing some size-removal algorithms for morphometric data, Hartman professes to find error in Corruccini's approaches. Actually the error is Hartman's: he assumed identity of different algebra symbol systems, in fact ultimately using the inverse of the proper coefficient of adjustment.     

The role of kleptoplasts in the survival rates of Elysia timida (Risso, 1818): (Sacoglossa: Opisthobranchia) during periods of food shortage

The importance of photosynthetic products derived from kleptoplasts in several sacoglossan species is being investigated in different fields, such as chemistry, biomolecular genetics and ecology. This study analyzes the effect of kleptoplasts on the survival rates of Elysia timida by evaluating the development of chlorophyll concentration, total length and survival rates of starved E. timida specimens kept in the light and in the dark. Although chlorophyll concentration values were similar in both cases, after 28 days specimens kept in the dark showed a greater size decrease and a lower survival rate (up to 30% lower) than those kept in the light. It is evident that kleptoplasts provide the mollusc with extra energy at the primary metabolism level to compensate for a shortage in food.     

Probable evolution of the coelacanth's reproductive style: lecithotrophy and orally feeding embryos in cichlid fishes and in Latimeria chalumnae

Synopsis The living coelacanth is a livebearer. Yolk seems to be the main source of nutrients and of oxygen to the embryo (fetus). Long before birth, young may also possibly feed orally on histotrophe secretion and egg debris. This type of reproduction evolved, as in most other fishes, from oviparity. The Carboniferous coelacanth Rhabdoderma exiguum had eggs of much lesser yolk volume and may represent an earlier form of oviparity with hiding, guarding or brooding type of parental care. The Jurassic coelacanth Holophagus (Undina) and the Cretaceous Axelrodichthys appear to have already evolved the internal-bearing style. Much of this evolutionary sequence is similar to that in cichlids. Ancestral cichlids are substrate tenders and nesters, with small eggs, little yolk and a feeding larva with indirect development. Mouthbrooding cichlids evolved a few, large eggs with denser yolk, direct development and, ultimately, orally feeding embryos while yolk is still in ample supply. Mixed feeding from yolk and orally ingested food in cichlids and in coelacanths is shown to be an enhanced mode of food delivery to the embryos over that from each source separately, in order to produce directly a better developed or larger young at the time of release, i.e. independence. Increase in egg size is regarded as an environmentally induced, altered pattern of yolk synthesis and an initial component of the epigenetic mechanism leading towards greater specialization. Carotenoids are incorporated within the yolk to assist the oxidative metabolism of the developing embryo.     

Variation due to maternal age in the onion root maggot,Hylemya antiqua (Meigen)

A variety of characteristics were studied in populations of the onion root maggot, Hylemya antiqua, to determine the extent to which the age of the female producing a batch of eggs might affect heterogeneity in her offspring. Early-born offspring were found to be reproductively most successful. They had the longest mean expectation of life, a relatively low mortality rate into mid-life, the highest average fecundity, the highest mean rate of egg production, and they produced the highest percentage of female offspring. On the other hand, mid-born offspring were hardiest. They also had a long mean expectation of life, comparable to that for early-born offspring but, in addition, they had the lowest sustained mortality rate and the greatest ability to survive food stress. Their robustness may have been acquired at the expense of certain reproductive capabilities however, in that their average fecundity was lower than their early-born siblings', and their rate of egg production was more variable. Late-born offspring were the most mortality-prone and the least fecund, but they had the shortest mean generation time. These differences must be evaluated in terms of their effects on the rate of natural increase and on population growth. Maternal age was found to influence pupal size, although the provenance groups differed significantly from each other and, in fact, showed opposite trends within their respective cohort groups. Size itself, and the ability of a species to alter the size at which it pupates, may be characteristics which have evolved to fit a specific set of environmental conditions.     

Notes in Case-Control Studies with Matched Pairs under Inverse Sampling

In case-control studies with matched pairs, the traditional point estimator of odds ratio (OR) is well-known to be biased with no exact finite variance under binomial sampling. In this paper, we consider use of inverse sampling in which we continue to sample subjects to form matched pairs until we obtain a pre-determined number (>0) of index pairs with the case unexposed but the control exposed. In contrast to use of binomial sampling, we show that the uniformly minimum variance unbiased estimator (UMVUE) of OR does exist under inverse sampling. We further derive an exact confidence interval of OR in closed form. Finally, we develop an exact test and an asymptotic test for testing the null hypothesis H₀: OR = 1, as well as discuss sample size determination on the minimum required number of index pairs for a desired power at α-level.     

Honeybees are poor pollinators — why?

Contrary to most other bee species honeybees are highly eusocial and hold extremely long-lived societies. Their all-season activities force them to use whatever plants available and prevent any specific adaptations — in the flowers, in honeybees, and in all competing bees. This flexible behaviour in flowers has been a precondition for perennial colony life. But as bees evade becoming contaminated by pollen their visits often do not result in pollination. Honeybee monocultures thus must be avoided by all means.     

Evidence for Handedness in Bumblebees

We describe a simple study of how bumblebees (Bombus spp.) behave when visiting florets which are arranged in a circle around a vertical inflorescence. In four species of bees, individuals showed a tendency for rotation in the same direction around each inflorescence on successive visits, i.e., each individual tended to go either clockwise or anticlockwise. Similar behavior has also been observed in mammals including humans. The implications of this tendency to repeat tasks in the same way are discussed, particularly in relation to our understanding of the phenomenon known as flower constancy. In humans, the tendency for individuals to turn in a particular direction is strongly related to handedness. In three of the four bee species there was a significant overall tendency for the bees to rotate in a preferred direction, suggesting that they too may exhibit handedness.     

Gestation length, metabolic rate, and body and brain weights in primates: epigenetic effects

The relationship of brain and body weights can be expressed in log-log regression: log (brain weight) = log (A) + B log (body weight). To investigate further the weights' similarity, gestation length and brain and body weights were determined from the literature for 46 primate genera. The results of allometric and path regression analyses suggest that the relationship between brain and body weights may not be mainly pleiotropic in the order Primates. The correlation between brain and body weights appears to be due to epigenetic factors in hyperplastic growth related to time constraint by gestation length and to energy utilization limitations imposed by metabolic rate.