Length weight relationship of bivalves definition

The length weight relationship of three benthic bivalves namely, Senilia are defined in the implicit form b1-b5=Regression coefficients of variables X1-X5 a. The length-weight, girth-length and weight-girth relationships were positively correlated. West Africa and on the bivalve mollusk than the gastropods in other parts of the world. Nair and . This definition was used by. PDF | The length-weight relationship of the threatened freshwater clam, and as reported for bivalves by Wilbur and Owen () in Obirikorang et al.

The advantage of this is that bivalves sampled from a range of environmental settings can provide reliable and accurate information on their individual ontogenetic life history, including their chronological age Despite an increasing focus on bivalves from a biogerontological perspective, the relationship of their other life history traits to maximum age is not as comprehensively understood as those in vertebrate groups, such as mammals and birds. It would therefore be interesting to understand how life history traits and development schedules in bivalves are related to longevity and compare these with the relationships observed in humans and with traditional vertebrate model aging organisms.

Factors correlating with the maximum longevity in animal groups other than molluscs have received considerable attention, particularly with regard to life history theory 11 In mammals and birds, adult body size most commonly represented as body mass correlates positively with longevity, larger animals living, on average, longer than smaller ones 13 — The most plausible explanation for the widely established relationship between body size and longevity appears to be the role of ecological factors.

For example, larger animals are less prone to predation and thus have lower mortality rates, which in turn leads to a greater longevity and, according to evolutionary theory, the evolution of a slower aging process 17 Developmental schedules, such as time to maturity and postnatal growth rate, have also been associated with longevity in birds and mammals 16 Specifically, age at maturity is positively correlated with maximum species longevity 20 and negatively correlated with demographic aging rate 19whereas postnatal growth rate are negatively correlated with maximum longevity in mammals 16 and with demographic aging rates in terrestrial vertebrates 19 The present study explores whether the same relationships hold within the Bivalvia.

In the only study to investigate these life history traits in bivalves 22concentrating on the freshwater mussels, concluded that overall, longevity was negatively related to the growth rate, which explained a high percentage of variation in longevity.

By contrast, size and relative shell mass explained little variation in longevity. The length of time a mammal will live after maturity, that is, its adult life span, is proportional to the amount of time it took to reach maturity.

Ricklefs 19 noted the same relationship between time to maturity and actuarial aging more generally across all terrestrial vertebrates. We investigate the allometric scaling of longevity and whether there is a relationship between development schedules and longevity in bivalves. Using a traditional nonphylogenetic approach ie, simple regression of species values at the tip of the phylogenythe relationship between maximum asymptotic size and maximum longevity was initially analyzed see Table 1.

Maximum Shell Size, Growth Rate, and Maturation Age Correlate With Longevity in Bivalve Molluscs

Although traditional nonphylogenetic approaches have been historically used in comparative biology; it has been clearly demonstrated during the last 20 years that interspecific comparisons can be potentially compromised by statistical nonindependence of species values 23 — 26leading to unacceptably high Type I error rates incorrectly accepting alternate hypotheses and inaccurate estimations of correlations or slopes 27 — 29although under what circumstances such concerns are warranted is not clear In addition, species that do not fit the allometry of life span may hold clues about the evolutionary forces shaping longevity and aging In this article, we specifically investigate using previously published data three hypotheses related to bivalve longevity a that bivalve size correlates positively with maximum longevity, b that postmaturational longevity is proportional to time to maturation, and c that the earlier a bivalve attains its maximum asymptotic size, the shorter will be its life span.

Unfortunately, body mass and maximum age data are unavailable for molluscs in sufficient quantities to allow meaningful analyses to be undertaken. We have therefore used this dimension rather than mass in our analyses.

The values for Tmax that we have used refer to the published reported maximum life span of the oldest animal recorded in a population or the longevity estimate obtained from an age frequency analysis.

Many species of bivalves contain a growth record in the form of annually deposited internal shell increments, and therefore, estimates of the age of individual bivalves are accurate and reliable 9. To what extent Tmax is an accurate estimation of the rate of aging depends critically on the number of individuals sampled in a population, and the rate of mortality increase with age, so its utility has been a source of debate 15 The consensus is that to the extent that it measures real differences in achieved longevity, differences in Tmax are proportional to genetic limitations on longevity among species.

There are additional estimates of aging rate, which could be used in place or alongside Tmax, such as the mean adult longevity or adult mortality rate doubling time, which is a demographic measurement of aging.

However, the greater availability of estimates of Tmax in the literature governed our decision to use this parameter as the estimator of aging rate. Developmental Schedules and Longevity In the second part of our study, we investigated the relationship between developmental rate and longevity. Despite its economic and nutritional importance, there is a dearth of biological information on the G.

It is on this basis that this research was conducted to assess the length-weight relationship of G. The results of this research will serve as a baseline data for other researchers and aid in the development of stock assessment models for the sustainable management of the threatened clam stock at the Volta Estuary.

Data reported in this study were collected at monthly intervals for the two-year period and covered the area between Ada and Aveglo at varying depths ranging from 0. At the shallow portions, samples were collected by wading through the water and hand-picking the clams.

At the deeper portions however, samples were obtained from fishermen who employed the Hookah technique in harvesting clams.

Maximum Shell Size, Growth Rate, and Maturation Age Correlate With Longevity in Bivalve Molluscs

All size classes harvested from the fishery were included in the sample collection. Samples were transported submerged in river water in insulated chests to the laboratory and processed within 12 h. In the laboratory, individuals were cleansed to remove mud and dried with blotting paper before length and weight measurements were taken. The clams were blotted dry in absorbent paper prior to weighing.

The length and weight data collected over the sampling period were used to evaluate the length-weight relationship of G. Mean length and weight values, length and weight ranges minimum and maximum of the clams, the parameters of length-weight relationships a and bthe Standard Error SE of b and the coefficient of determination r2 for each month are given in Table 1.

Length-weight relationships for the separate sexes of G. The clams exhibited different growth patterns at different periods of the study. W-L relationship parameters of G.

Length-weight relationship of benthic bivalves of the Andoni Flats, Niger Delta, Nigeria

Regression constant interceptb: Regression constant sloper2: Coefficient of determination The findings of this study corroborated that of Wilbur and Owenwho stated that, the values of equilibrium constant b lie between 2. A variety of environmental factors are known to influence shell morphology and the relative proportions of many bivalve species Gaspar et al. For examples, the type and quality of phytoplankton as a food source of the bivalve, Alunno-Bruscia et al.

The monthly growth patterns exhibited by G. Studies by Etim et al. This study observed that during these periods the clam growth patterns were generally isometric growth with unchanged body proportions and specific gravity and positive allometric weight increasing faster than length.

The allometric growth trends observed during the spawning period appear to be strongly linked to the build-up of proteins and carbohydrates in the tissues of the clams.

Prior to and during the spawning months, proteins and carbohydrates are accumulated in the clam tissues for gonad tissue production, energetic storage and consumption LaTouche and Mix, ; Paez-Osuna et al.