Effect of replacing maize with plantain peels on the performance traits and haematological characteristics of African giant land snail

The study was carried out at the Niger Delta University, Faculty of Agriculture Teaching and Research Farm, Bayelsa State. A total of Ninety six (96) growing snails (Archachatina marginata). Using Plantain peel as an additive, four diets were formulated at the levels of 0%, 3%, 6%, and 9% to form the treatment diets. The experiment lasted for eight (8) weeks during which the weight gain, feed intake, shell width, shell length, shell thickness and hematological parameters were obtained. The weight gain, shell width, shell length and shell thickness are not significantly different (p<0.05) whereas, the feed intake differed significantly (p<0.05) for all the treatment diets in the experiment. From the results, it was concluded that concentrate with 0% inclusion of Plantain peel meal was suitable for snail diets as it gave the best performance. The hematological parameters measured in the African giant land snails are White blood cell, Neutrophile and Lymphocyte differed significantly (p<0.05). Plantain peel can serve as source of potassium for other animals, as the highest percentage of potassium was found in the hemolymph of snails fed with 9% inclusion of plantain peel. It is recommended that; there should be no inclusion of plantain peels in the diet of the African giant land snails in order to achieve higher weight gain and feed intake.

Evaluation of remodeling and geometry on the biomechanical properties of nacreous bivalve shells

Mollusks have developed a broad diversity of shelled structures to protect against challenges imposed by biological interactions(e.g., predation) and constraints (e.g., $$pCO_2$$ p C O 2 -induced ocean acidification and wave-forces). Although the study of shell biomechanical properties with nacreous microstructure has provided understanding about the role of shell integrity and functionality on mollusk performance and survival, there are no studies, to our knowledge, that delve into the variability of these properties during the mollusk ontogeny, between both shells of bivalves or across the shell length. In this study, using as a model the intertidal mussel Perumytilus purpuratus to obtain, for the first time, the mechanical properties of its shells with nacreous microstructure; we perform uniaxial compression tests oriented in three orthogonal axes corresponding to the orthotropic directions of the shell material behavior (thickness, longitudinal, and transversal). Thus, we evaluated whether the shell material’s stress and strain strength and elastic modulus showed differences in mechanical behavior in mussels of different sizes, between valves, and across the shell length. Our results showed that the biomechanical properties of the material building the P. purpuratus shells are symmetrical in both valves and homogeneous across the shell length. However, uniaxial compression tests performed across the shell thickness showed that biomechanical performance depends on the shell size (aging); and that mechanical properties such as the elastic modulus, maximum stress, and strain become degraded during ontogeny. SEM observations evidenced that compression induced a tortuous fracture with a delamination effect on the aragonite mineralogical structure of the shell. Findings suggest that P. purpuratus may become vulnerable to durophagous predators and wave forces in older stages, with implications in mussel beds ecology and biodiversity of intertidal habitats.

Linear growth and yield of bivalve mollusks Mya Arenaria linnaeus, 1758 in the conditions of the littoral of the barents and white seas

Mya arenaria are large bivalve mollusks burrowing into the ground. Mollusks are widespread in the northern hemisphere. The growth patterns of M. arenaria were studied in the arctic part of the species’ geographic range. As a result of the research, it was revealed that the mollusks from the Severnaya Inlet of the Kandalaksha Bay of the White Sea have the highest growth rate. The limiting shell length is L∞=174.7 mm, and the rate of growth retardation is k=0.0518 year–1. The mollusks from the Yarnishnaya Inlet of the Barents Sea have the lowest growth rates L∞=84.27 mm, and the rate of growth retardation is k=0.0721 year-1. A positive correlation was found between the nature of the soil and the limiting shell length of mollusks (r = 0.94).

Assessment of Corbicula moltkiana Growth by Different Methods on Variation of Substrates in Lake Maninjau, West Sumatera, Indonesia

Corbicula moltkiana is a mussel species in Lake Maninjau and one of the targeted fisheries resources in the lake. This study aimed to determine the feasibility of a controlled growth experiment of mollusk biota in describing their natural growth. The assessment was carried out in areas with different habitats in shore lake, namely sand and gravel-stone substrates. A consecutive 12 month- sampling was carried out from June 2013 to May 2104 using a Surber sampler at a 1-3 m depth were used to assess the wild population growth. Moreover, the growth of the controlled population was observed by rearing various sizes of mussels in artificial substrate namely three small baskets which installed in the shore area with 1-3 m depth at each station for four months. Monthly sampling was carried out to measure the shell length. The growth of C. moltkiana on wild population by VBGF methods show that at the gravel-stone substrate was higher, but the growth a controlled population in artificial substrate seemed in the sand substrate was higher than that in the gravel-stone substrate. The growth of aquatic biota in a controlled system (especially C. moltkiana) does not always reflect similar conditions to their wild growth.

Sex ratio, gonadal and condition indexes of the Asiatic hard clam, Meretrix meretrix in Marudu Bay, Malaysia

Duisan L, Salim G, Ransangan J. 2021. Sex ratio, Gonadal and Condition indexes of the Asiatic Hard Clam, Meretrix meretrix in Marudu Bay, Malaysia. Biodiversitas 22: 4895-4904. Asiatic hard clam, Meretrix meretrix is one of the important shellfishery resources in Marudu Bay, Sabah, Malaysia. It is among the most popular clam species being widely traded in the local wet markets around Sabah, Malaysia. Unfortunately, the shellfishery management for this species has not been well established. In addition to overexploitation, habitat destruction is also one of the significant threats to this species due to the extensive land use of the coastal areas in Sabah. Hence, conservation and breeding efforts for this species are greatly required. Therefore, the current study was conducted to examine the sexual maturity of the clam with respect to shell length classes for artificial seed production purposes. For this study, a total of 86 clam specimens were randomly collected from mudflats in Marudu Bay. The specimens were utilized for gonad histological and condition analyses. The clams were grouped into three shell length classes; (3.00-4.99) cm, (5.00-6.99) cm, and (7.00-8.99) cm prior to the analyses. Results showed the natural stock of the Asiatic hard clams in Marudu Bay was dominated by females (1.39:1) over males with no hermaphroditism observed. The gonadal index was recorded higher among clams with shell lengths between 5.00 and 6.99 cm. The condition index analysis also recorded high (>4.0) for clams in all the shell length classes. The findings of this study suggest that the clams with shell lengths between 5.00 cm and 7.00 cm are already fully matured and can be utilized as a broodstock candidate for an artificial breeding program in the hatchery.

Ascorbic Acid Regulates the Immunity, Anti-Oxidation and Apoptosis in Abalone Haliotis discus hannai Ino

The present study was conducted to investigate the roles of ascorbic acid (AA) in immune response, anti-oxidation and apoptosis in abalone (Haliotis discus hannai Ino). Seven semi-purified diets with graded levels of AA (0, 50, 100, 200, 500, 1000 and 5000 mg/kg) were fed to abalone (initial weight: 12.01 ± 0.001 g, initial shell length: 48.44 ± 0.069 mm) for 100 days. The survival, weight gain rate and daily increment in shell length were not affected by dietary AA. The AA content in the gill, muscle and digestive glands of abalone was significantly increased by dietary AA. In terms of immunity, dietary AA significantly improved the total hemocyte count, respiratory burst and phagocytic activity in hemolymph, and lysozyme activity in cell-free hemolymph (CFH). In the digestive gland, the TLR-MyD88-dependent and TLR-MyD88-independent signaling pathways were suppressed by dietary AA supplementation. The mRNA levels of β-defensin and arginase-I in the digestive gland were significantly increased by dietary AA. In the gill, only the TLR-MyD88-dependent signaling pathway was depressed by dietary AA to reduce inflammation in abalone. The level of mytimacin 6 in the gill was significantly upregulated by dietary AA. After Vibrio parahaemolyticus infection, the TLR signaling pathway in the digestive gland was suppressed by dietary AA, which reduced inflammation in the abalone. In terms of anti-oxidation, superoxide dismutase, glutathione peroxidase and catalase activities, as well as total anti-oxidative capacity and reduced glutathione content in CFH, were all significantly upregulated. The malondialdehyde content was significantly downregulated by dietary AA. The anti-oxidative capacity was improved by triggering the Keap1-Nrf2 pathway in abalone. In terms of apoptosis, dietary AA could enhance the anti-apoptosis ability via the JNK-Bcl-2/Bax signaling cascade in abalone. To conclude, dietary AA was involved in regulating immunity, anti-oxidation and apoptosis in abalone.

When size matters: the first comprehensive anatomical study of a species of “Condylocardiidae”, an extremely miniaturized bivalve

‘Miniaturization’ is a widespread phenomenon among the Metazoa. In the molluscan class Bivalvia, records of miniaturization are numerous. Among the Archiheterodonta, Warrana besnardi (Klappenbach, 1963) has attracted attention for its tiny size, which does not exceed 1.5 mm in shell length, and because it belongs to a group with limited anatomical information and often-debated status, the “Condylocardiidae” (which recent molecular studies place deeply nested within the family Carditidae). All species of Warrana Laseron, 1953 are small-bodied, and so miniaturization presumably occurred from a large-bodied ancestor within the Carditidae sensu lato. South American W. besnardi is here studied in detail. Its small size and the enlargement of the anterodorsal region during growth, reflects (and likely led) to infaunal habit, living as a burrowing bivalve that passively feeds on deposit particles entering the pallial cavity anteriorly. Mantle glands, previously reported as a common feature of other archiheterodonts, are missing in W. besnardi, but spongiform tissue in the antero-ventral portion of the mantle lobes presumably represents a blood sinus that might compensate for the great reduction of the ctenidia. Lecithotrophy is reported, with yolky oocytes bearing a thick non-cellular capsule layer; brooding was not observed, and it is here hypothesized that the extreme miniaturization, with the great reduction of ctenidia, is responsible for a shift in the reproductive mode of condylocardiids, contrasting with the commonly reported ovoviviparity of the carditids.

Static Bending of Isotropic Circular Cylindrical Shells Based on the Higher Order Shear Deformation Theory of Reddy and Liu

In this paper, a displacement based shear deformation theory formulated on the cubic in-plane displacement field equation of Reddy and Liu is presented for the static bending analysis of isotropic circular cylindrical shells. The adopted displacement field accounts for a quadratic (parabolic) distribution of the transverse shear through the shell thickness as well as satisfies the need for a stress free upper and lower boundary surfaces of the shell. The equations of static equilibrium are obtained on application of the principle of virtual work. Numerical results of the bending analysis for the displacements and stresses are presented for the simply supported shell. A comparison made to those of the Kirchhoff-Love theory for varying shell length to mean – radius of curvature ratios, shows good agreement for thin shells irrespective of the shell length to radius of curvature ratio (l / a). The transverse sharing effect is found to be noticeable in the deformation of thick shells, however, this effect diminishes with a continuous increase in l / a ratios.

Resources and structure of horsemussel Modiolus kurilensis settlements in Peter the Great Bay (the Sea of Japan)

Modiolus kurilensis F. R. Bernard, 1983 (Mollusca, Bivalvia) can be found in Peter the Great Bay (the Sea of Japan) both on soft and hard substrates, often together with the mussel Crenomytilus grayanus (Dunker, 1853); it is a promising commercial species. This mollusc is a by-catch when catching C. grayanus. The aim of the work was to assess M. kurilensis resources and settlement structure in Peter the Great Bay. The research was carried out in 2007–2018 by scuba-diving methods of hydrobiological research at the depths of down to 20 m. In total, the data were analyzed for 2,409 stations; M. kurilensis was found at 308 stations. Sampled molluscs were measured and weighed. The material was processed statistically and cartographically; the mean biomass and distribution density of M. kurilensis settlements were calculated. In total, 870 horsemussels were analyzed for studying the settlement structure. The following indicators were estimated: index of settling (ratio of the abundance of juvenile molluscs with a shell length of 1–30 mm (spat, yearlings) to the abundance of adults with a shell length of > 50 mm); index of maturation (ratio of the abundance of pre-reproductive molluscs with a shell length of 35–50 mm to the abundance of adults with a shell length of > 50 mm); index of replenishment of the commercial stock (ratio of the abundance of molluscs with a shell length of 95–100 mm (recruits) to the abundance of molluscs of commercial length of > 100 mm). The state of M. kurilensis population in Peter the Great Bay is stable: the ratio of molluscs of non-commercial length varies 52 to 86 % in most settlements, which indicates active natural reproduction and regular replenishment of the benthic part over many years. Replenishment of settlements with settling of both spat and yearlings depends on the presence of pelagic larvae in the plankton, while replenishment of the mature molluscs depends on favorable conditions for juvenile survival. In 2007–2018, the mean values of the indices of settling and maturation in M. kurilensis settlements in Peter the Great Bay were of (0.18 ± 0.07) and (0.05 ± 0.01), respectively. M. kurilensis resources are estimated at 27.1 thousand tons, and the commercial stock – at 16.4 thousand tons. The annual replenishment of the commercial stock of M. kurilensis in Peter the Great Bay is possible in a volume of more than 3 thousand tons. The mean value of the index of replenishment of the commercial stock is of (0.21 ± 0.03).

Shell morphology, growth and longevity of Unio tumidus (Bivalvia: Unionidae) from an archaeological site and contemporary population inhabiting the Oder estuary

Mussel shells are often found in archaeological excavations and can provide information useful for ecological reconstruction and assessment of anthropogenic impact on waters. In this study, two sample groups of swollen river mussel (Unio tumidus) which occurred during the Early Middle Ages (EMS) and currently (MS) in the Oder river estuary (Baltic basin) were compared. Allometric shell growth, morphological characteristics of the shell (length, width, height and thickness), age structure and growth of mussels were analysed using the von Bertalanffy equation. All three types of allometric growth (isometry and both positive and negative allometry) were observed in the studied mussels. In both groups, typical values of shell length, width, height and thickness were recorded. However, higher values of these morphological characteristics were recorded in the EMS group. Moreover, the EMS group, compared with the MS group of U. tumidus, was characterised by a higher longevity (12 and 10 years, respectively) and asymmetric length (L∞) (93.09 and 83.23 mm, respectively). Both groups of mussels had a similar growth rate (k). Larger shell sizes in the EMS group were probably caused by differential preservation and/or differential archaeological recovery, and resulted from differences in the age structure, especially higher mortality rate amongst individuals older than 6 years in the MS group.