Carapace Length Research Articles

Diet of loggerhead turtles in the Gulf of Manfredonia, South Adriatic Sea: evidence of winter feeding and anthropogenic impacts

Investigating biological aspects of migratory marine animals like sea turtles is challenging. The Adriatic Sea is a key Mediterranean foraging ground for loggerhead turtles, yet certain feeding behaviors remain poorly known, including winter feeding and foraging within the neritic area of the Gulf of Manfredonia. With high fishing effort, this area experiences considerable turtle bycatch from trawlers during winter, representing an important conservation issue. Insights on how and to what extent the species interacts with anthropogenic threats such as trawlers and debris can be obtained from diet analysis. We examined feces and gut contents from 57 bycaught or stranded turtles to assess active feeding and digestion time during winter, identify and quantify prey items, evaluate feeding patterns among size classes, and ascertain the anthropogenic impact via debris and fishing discard ingestion. Our findings show that turtles feed actively during winter, primarily on benthic items, starting from a small size (32 cm Curved Carapace Length). No size effect was observed on dietary diversity or biomass percentage. We identified 37 Operational Taxonomic Units (OTUs) across 10 dietary groups, with crustaceans and mollusks being most prevalent. Osteichthyes and cephalopods, likely scavenged from trawl discard, were also common, implying intensive local trawling may attract turtles, increasing bycatch and mortality rates. The frequency of anthropogenic material ingestion was comparable to other Mediterranean regions and its presence in feces suggests non-lethal effects, if any. This study shows how information on seasonal feeding behavior can provide insights into how the relationship of the species with the environment and threats changes over time, ultimately steering conservation efforts.

Single nucleotide polymorphisms of the SIF gene and their association with growth traits in swimming crab (Portunus trituberculatus)

The swimming crab (Portunus trituberculatus) is an economically important aquaculture species in China. Mining candidate single nucleotide polymorphisms (SNPs) and genes associated with growth traits of P. trituberculatus is of great importance for the genetic breeding of this species. Among the genes associated with growth traits, “protein still life, isoforms C/SIF type 2 (SIF)” is thought to be an important gene affecting animal growth and development. In the current study, we investigated the SIF gene from P. trituberculatus to better understand its biological function. The full-length cDNA of SIF was 6185 bp, with a 5208 bp open reading frame encoding 1735 amino acids. Homology analysis showed that SIF shared 90.07% identity with Procambarus clarkii and 40.25–86.95% with other species. Expression pattern analysis of SIF in fast- and slow-growing groups revealed a significantly higher expression level in the former than in the latter (P < 0.05). qPCR studies revealed the ubiquitous expression of SIF in seven tissues tested, but most abundantly in the heart compared with muscle, testis, ovary, seminal vesicle, gill, and hepatopancreas (P < 0.05). A total of 38 SNPs in the UTRs and exons of SIF were screened and genotyped in 184 individuals of swimming crabs by targeted resequencing. Association analysis showed that four SNPs were significantly associated with growth traits (full carapace width, carapace length, body height, and body weight; P < 0.05). Two SNPs out of the four SNPs were shaped as a haploblock containing three haplotypes (GC, TA, and TC), and the TA haplotype showed significantly higher growth traits than the GC haplotype. Overall, the results provided potential candidate genes and SNP markers for the genetic improvement of growth traits in P. trituberculatus breeding.

Assessing T45 vs T0 and T90 meshes and covered codend effects in southeastern Australian penaeid trawls

Square-mesh codends (i.e. turned 45 degrees or ‘T45′) made from a minimum stretched mesh opening (SMO) of 27-mm mesh hung on the bar are mandated for estuarine-trawl fisheries targeting penaeids (mostly school prawns, Metapenaeus macleayi) in New South Wales, Australia. However, owing to variable mesh shrinkage over time, often slightly larger SMOs are supplied, and sometime too large to be oriented as T45 for the targeted school prawns (>13–15 cm carapace length; CL). During three experiments involving paired trawls with and without codend covers, we sought to investigate if, compared to a conventional 27-mm T45 codend, lateral openings in 30-mm SMO could be appropriately maintained by orientating diamond-shaped (‘T0′) meshes at narrow (experiment 1) or normal (experiment 2) circumferences, or turned 90 degrees (‘T90′; experiment 3). Analyses of size selection was done after first testing for species-specific cover effects, which required fish sizes to be assessed via a paired-hauls approach while sizes for school prawns were modelled using a covered-codend approach. Compared to the 27-mm T45 codend, only the T0 mesh hung at a normal circumference provided the same size selection for school prawns, with the two other alternative configurations producing wider selection. But, while incidental fish catches were low (14% of total catch), all new codends caught between ∼2 and 7 × more individuals of some small fish cross all sizes, including juveniles of an economically important species (tailor, Pomatomus saltarix). The data reiterate that among the codends tested, T45 mesh is the optimal configuration for regional penaeid trawls in terms of consistently maximining school prawn size selection and the escape of small fish, and so high-quality material in the required sizes needs to be sourced.

Evaluation of crystalline amino acids as potent stimulatory chemoattractants for the slipper lobster Thenus orientalis.

Intensive research on the effectiveness of chemoattractants has been widely explored to improve the feed qualities in expanding crustacean farming. Taste preferences in slipper lobster remained unknown despite their significant contribution to the lobster fisheries. Chemoattractants allow better performance in aquaculture species by increasing food attractiveness and palatability. Amino acids (AA) have been leading in previous research on crustacean feeding behavior. Given that slipper lobster possesses chemoreceptors to detect and orient towards food, this study investigated an approach to identify the AA with the most potent chemoattractant in eliciting a response from slipper lobster. Behavioral assays were performed to evaluate the responses of slipper lobster Thenus orientalis (carapace length, 52.34 ±1.52 mm) on 15 crystalline AA and three derivatives of AA (DAA) at three concentrations between 10-1 and 10-3 M as test substances (TS). Meretrix sp. extract was used as a positive control and clean filtered seawater as a negative control. The behavioral responses of 14 T. orientalis were evaluated based on their antennular flicking rate, third maxillipeds activity, and substrate probing by the pereiopods. T. orientalis responded to the solutions of single AA down to a concentration of 10-3 M, excluding histidine and serine. The behavioral activity displayed by T. orientalis increased with the TS concentrations. L-glutamic acid monosodium salt monohydrate, betaine, and glycine solutions elicited the most behavioral responses, whereas histidine exhibited the lowest behavioral responses. Conclusively, L-glutamic acid monosodium salt monohydrate, betaine, and glycine can be potential chemoattractants for T. orientalis.

Blood recovery of wild Mekong snail-eating turtles (Malayemys subtrijuga Schlegel and Müller, 1845) in captivity from leech infestation

Blood cell counts are valuable diagnostic tools for assessing the health status of chelonians, however, reference standards for healthy blood parameters in various turtle species are lacking. In this study, forty wild female Malayemys subtrijuga were captured from ponds in Kasetsart University, and transported to laboratory for recuperating in captivity. All turtles were infected with a single leech species, Placobdelloides siamensis, with a mean of 513.7 ± 164.9 individuals per turtle, and exhibited penetrating and lesion wounds from leech infestations on both their skin and shell. Subsequently, they were cleaned and treated to eliminate ecto- and endoparasites before the recuperation period began. The turtles did not exhibit significantly differences in weight, carapace length (CL), red blood cell count (RCC), and white blood cell count (WCC) with a mean of 654.2 ± 199.9 g, 15.0 ± 2.5 cm, 327,080 ± 70,156 cells/mm3, and 73,340 ± 15,859 cells/mm3, respectively, during the initial records (week 0). However, after being maintained for 17 weeks, their health significantly improved in term of their blood parameters (RCC and WCC) and weight, except CL which remained unchanged, with a mean of 491,470 ± 16,169 cells/mm3, 18,790 ± 1496 cells/mm3, and 738.9 ± 191.5 g, respectively. Therefore, the health status obtained in this study can be used as a reference for blood parameters, weight, and recuperation period for the treatment of ill wild M. subtrijuga in captivity or as part of conservation management programs for turtles.

INFLUENCE OF SEASON, ENVIRONMENT, AND SEX ON SELECTED BLOOD PARAMETERS OF GEOFFROY'S SIDE-NECKED TURTLES, PHRYNOPS GEOFFROANUS (SCHWEIGGER, 1812).

Laboratory tests help to determine a diagnosis, to plan treatment, and to indicate prognosis of diseases. However, the interpretation of test results in reptiles is challenging, because they are influenced by environmental and individual factors. Therefore, the objective of this study was to establish hematologic parameters of Geoffroy's side-necked turtle (Phrynops geoffroanus), including variables such as season, environment, sex, and straight carapace length (SCL). Blood samples were analyzed from 38 P. geoffroanus (23 males and 15 females) collected during the rainy and dry seasons. Some of the animals were from captivity and others from an urban stream. To verify the influence of the variables on blood parameters, the general linear model was performed. The Pearson correlation coefficient was also used to verify the association between SCL and hematologic parameters. Among these parameters, hemoglobin (P = 0.008) and mean corpuscular hemoglobin concentration (P = 0.001) were statistically higher during the rainy season. On the other hand, WBC (P = 0.011), heterophils (P = 0.045), eosinophils (P < 0.001), lymphocytes (P = 0.014), and monocytes (P = 0.039) were higher in the dry season. The RBC count (P = 0.035), PCV (P = 0.029), basophils (P = 0.013), and monocytes (P = 0,013) were significantly higher in individuals from captivity, but lymphocytes (P = 0.033) were higher in the urban turtles. Only eosinophils (P = 0.025) were higher in females than in males. There was no influence of the variables season, environment, and sex on the mean corpuscular volume (P = 0.071; P = 0.458; P = 0.052), total solids (P = 0.773; P = 0.121; P = 0.131), and heterophil:lymphocyte ratio (P = 0.992; P = 0.58; P = 0.119). No influence of the size on hematologic parameters was observed. Season, environment, and sex may influence the blood parameters of P. geoffroanus, and these factors should be routinely considered in the interpretation of laboratory results.

Measurement of live shrimp carapace length and its swimming speed in the cage culture using Multiple Object Tracking

The carapace length of live shrimp is one of the important parameters to monitor the growth of the shrimp from time to time in cage culture, while its swimming speed is one of the key indicators to understanding the behavior and health of the shrimp. To estimate live shrimp carapace length and its swimming speed, we recorded a live shrimp in the cage culture using an underwater video camera. The collected datasets then being preprocessed and labeled. Before measuring the carapace length of the shrimp, we used the You Only Look Once (YOLO) v5 algorithm with K-fold cross-validation to detect shrimp heads. The accuracy value obtained is 85.6%, recall 85.4%, precision 77.3%, and F1-score 81.1%. Then the multiple object tracking (MOT) DeepSORT method was used to measure the shrimp’s carapace length and its swimming speed. The measurement results showed that the average length of the shrimp was 13.5-14.8 pixels, and the average speed of the shrimp was 62-78 pixels/second. We obtained that there is a strong linear relationship between carapace length and swimming speed of shrimp, namely SS = 11.864 CL + 43.419, where CL and SS are carapace length and swimming speed, respectively, with R-square = 0.9095. In conclusion, the live shrimp carapace length and its swimming speed can be measured using YOLO v5 and MOT DeepSORT directly and accurately.

Shell shape-habitat correlations in extant turtles: A global-scale analysis

Animal morphological structure can influence behaviour and interaction with the environment. Owing to their wide range of habitats, from aquatic to terrestrial, and their variation in shell shapes, turtles are highly suitable for ecomorphological studies. However, previous studied have encountered several limitations, including small sample sizes, simplified habitat classification, and no consideration of sexual dimorphism, that may prevent the identification of the ecological mechanisms responsible for divergent morphologies of turtles on a global scale. In this study, we collected the carapace length (CL), carapace width (CW), and carapace height (CH), as an indicators of body size, from 6664 adult individuals of 115 species, 61 genera, and 11 families and calculated the ratio between the CH and CW to delineate shell shape. These turtle species were divided into four habitat types (marine, freshwater, mainland, and island) and eight subtypes (freshwater: large lentic, large lotic, small lentic, small lotic, all water bodies; mainland: desert, flatland, highland) to better understand the ecomorphological alteration of their shell shape. The results of the linear regression showed that shell shape became flat with increasing body size in aquatic turtles, whereas the opposite trend was observed for male mainland tortoises. According to the results of the general linear model, there was a gradual increase in the domed shape of turtle shells from sea to freshwater habitats, from freshwater to mainland terrestrial habitats, and from mainland to island terrestrial habitats. There were no significant differences between the shell shape and habitat subtype for freshwater turtles and mainland tortoises. To the best of our knowledge, this study represents the first investigation into the variation pattern of shell shape in turtles living in habitats ranging from marine to island and its relationship to body size. The study results suggest that conservation strategies for turtles should consider both their shell shape and habitat characteristics.

Bycatch reduction devices exclude diamondback terrapins and maintain blue crab catch in two Virginia tidal creeks

AbstractObjectiveThe diamondback terrapin Malaclemys terrapin is frequently caught as bycatch in both commercial and recreational blue crab Callinectes sapidus fisheries throughout its range along the Atlantic and Gulf coasts of North America. Bycatch reduction devices (BRDs) are plastic or wire rectangles mounted in the entrance funnels of crab traps, designed to exclude terrapins while still allowing crabs to enter. In this study conducted in two tidal creeks in Virginia, USA, we assessed the effectiveness of four BRD designs, including two novel oval designs, against control traps with no BRDs.MethodsWe tested four replicates of each of the five trap treatments (1.75‐inch oval BRD, 2‐inch oval BRD, 1.75‐inch rectangular BRD, 2‐inch rectangular BRD, and a control trap without a BRD) in each tidal creek, for a total of 20 traps per creek and 40 traps total. We fitted traps with wire chimneys that extended above the high tide water line to allow trapped terrapins to surface for air. For eight weeks during summer 2021, we baited traps with Atlantic Menhaden Brevoortia tyrannus each day, beginning on Monday. Tuesday–Friday, we emptied traps of any animals inside, and recorded terrapin sex, terrapin carapace length, terrapin carapace width, and terrapin shell height, as well as blue crab carapace length.ResultWe found that all four BRD designs were highly effective at excluding terrapins and maintaining crab catch when compared to control traps. We found a significant difference (p = 0.003) in catch per unit effort (CPUE) of diamondback terrapins among treatments, with the control group (those without BRDs) having the highest CPUE (0.97 ± 0.18). All traps fitted with BRDs decreased terrapin capture significantly compared to the control group. Oval BRDs excluded more terrapins than their rectangular counterparts with the same height dimension, although these differences were not significant. We found no significant difference in CPUE of blue crabs among treatments (p = 0.392), or in the size of legal crabs caught in each treatment (p = 0.216).ConclusionThis study provides evidence of the effectiveness of both rectangular and oval‐shaped BRDs to exclude terrapins and maintain crab catch in Virginia waters, where BRDs are not currently required.

Identification of anthropogenic debris in the stomach and intestines of giant freshwater prawns from the Trang River in southern Thailand.

Anthropogenic waste, especially microplastics, is becoming more prevalent in the environment and marine ecosystems, where it has the potential to spread through food chains and be consumed by humans. Southeast Asian countries are home to giant freshwater prawns, a common freshwater species that is eaten around the world. Microplastic pollution in river water, sediment, and commercially significant aquatic species such as fish and mollusks has been observed, yet few studies have been conducted on giant freshwater prawns in the rivers of southern Thailand, where microplastics may contaminate prawns via the food they ingest. The purpose of this research was to investigate the accumulation of anthropogenic material in the organs of river prawns (Macrobrachium rosenbergii). Microplastics in the stomachs and intestines of giant freshwater prawns were the focus of this study. Samples were digested with 30 ml of 10% potassium hydroxide (KOH), heated for 5 min at 60°C, and then digested at room temperature. The quantity, color, and appearance of microplastics were assessed using a stereomicroscope after 12 h. Furthermore, polymers were examined using a Fourier transform infrared spectrophotometer (FTIR). Microplastic counts were compared between sexes. A T-test was used to compare male and female microplastic counts in the stomach and intestine, and the Pearson correlation was used to compare the association between microplastic counts in the stomach and intestine and carapace length (CL), length of abdomen (LA), and body weight (BW) of male and female giant freshwater prawns. The threshold of significance was fixed at p<0.05. Based on the study results, a total of 370 pieces of anthropogenic debris were discovered in the stomachs and intestines of both female and male prawns. The average number of microplastics per individual was 4.87 ± 0.72 in female stomachs and 3.03 ±0.58 in male stomachs, and 1.73 ±0.36 in female intestines and 2.70 ±0.57 in male intestines. The majority of microplastics found in females were within the <100 µm range, while males contained microplastics in the range of 100-500 µm. Both male and female prawns contained fibers (72.70%) and fragments (27.30%). Various polymers were identified, including cotton, rayon, and polyvinyl chloride (PVC). The study also explored the relationship between carapace length, length of abdomen, body weight, stomach weight, and the number of microplastics. The findings reveal a significant association between the number of microplastics and stomach weight in male prawns (R=0.495;p=0.005). These findings provide alarming evidence of anthropogenic debris ingestion in prawns and raise concerns about the future effects of anthropogenic pollution on giant freshwater prawns.

Diet affects the growth and behavior of Argiope bruennichi spiders and correlates with the species richness of their vertically and horizontally transmitted tissue-resident bacteria

The ability to spread and build quality webs is crucial to spider survival. These abilities may differ in response to dietary adjustments and changes in assemblages of tissue-resident bacteria, including vertically transmitted endosymbiotic taxa, particularly when expanding outside the native ranges. We measured the physical and behavioral parameters of the invasive wasp spider Argiope bruennichi subjected to four types of diets, including protein-rich and lipid-rich diets. We used 16S rDNA sequencing to evaluate vertically and horizontally transmitted tissue-resident bacteria, including endosymbionts, in the cephalothorax and legs of the tested spiders. The diet composition affected the body weight and carapace length as well as the locomotor parameters but not the orb-weaving abilities. Dietary treatments led to changes in the diversity and operational taxonomic unit (OTU) richness of facultative and obligate tissue endosymbionts, with Wolbachia and Rickettsia having higher relative abundance in spiders fed a lipid-rich diet. The higher OTU richness of facultative and obligate endosymbionts was associated with better locomotor performance. The other tissue-resident microbes were dominated by Firmicutes; the dominance and diversity of tissue-resident microbiomes also differed among spiders treated with different diets. The highest alpha diversity of tissue-resident microbes was present in spiders fed the standard diet, whereas all other diets led to a decrease in alpha diversity and various changes at the level of individual genera and OTUs. In conclusion, the tissues of A. bruennichi host tremendously diverse assemblages of bacteria, including obligate or facultative endosymbionts, which are sensitive to differences in diet composition and affect the locomotion of their hosts.

Wooden traps can replace coral stone traps harvesting the wild lobster seed in mitigating the negative impact on the marine environment

Lobster seacage aquaculture has a significant social-economic contribution to many coastal communities throughout the central provinces of Vietnam. One of the issues of lobster aquaculture is that the industry entirely relies on the wild juvenile lobster (lobster seed) captured using traps made of coral stones, which affects the coastal ecology and environment. The present study was carried out to compare the catch efficiency of traps made of round timber poles (wooden trap) with conventional dead corals (coral stones) during the juvenile lobster fishing season in 2019 in the coastal area of Nha Trang city, Vietnam. Results showed that experimental wooden traps maintained the conventional catch rate level, with a significant proportion of Panulirus ornatus caught at larger carapace length than those caught by the coral stone traps. Our findings show the biological and environmental benefits of using alternative fishing methods would eliminate collecting coral stones to make lobster seed traps and contribute to coastal protection while maintaining the fishing operation and seed supplies for the lobster seacage farmers.

Nesting activity of Lepidochelys olivacea, and the effect of artificial shade at Cascajilloso beach, a newly inhabited nesting site in Pacific Panama

AbstractSea turtle nesting activity on newly monitored beaches yield important data to support future regional and global conservation assessments. Here, we report on nesting activity of Olive Ridley (Lepidochelys olivacea) at Cascajilloso beach in Pacific Panama based on data from a new hatchery during seasons 2019, 2020 and 2021. Further to this, we conducted a field experiment analyzing the effects of artificial shade versus unshaded treatments on hatchlings' biometric characteristics, hatching success, incubation success and the incubation period. The analyses of three seasons showed that nesting activity, based on number of egg clutches transferred to the hatchery, reached a peak between September (33%) and October (25%). Curved carapace length (CCL) of nesting females (64.3–66.2 cm) was similar to other populations of the Eastern Tropical Pacific (ETP). The number of eggs clutches were 80 in 2019, 73 in 2020 and 108 in 2021; however, the clutch size was slightly smaller (93.92 ± 18.78 eggs) compared with other populations of the ETP. This could be a phenotypic variation of nesting females at this beach. The ability to move egg clutches to the hatchery was affected during 2020 season due to COVID19 restrictions. Heavy rainfall during the incubation period caused a reduction in ambient temperature resulting in cooler (maximum average 29.9°C) nest temperatures registered under artificial shade and unshaded treatments. This could result in males hatchlings during the 2020 season. The warmer temperatures in our experimental nests produced heavier hatchlings contrary to general assumptions, but this was also related to straight carapace length only after a threshold value of 40 mm. Hatchlings under the artificial shade were able to grow to a certain size but potentially at the costs of storing less mass (trade‐off). Ongoing beach patrolling and hatchery management techniques with long‐term baseline data collection are needed to secure the nesting population of L. olivacea in this recently surveyed beach.

Relationship fecundity – morphometrics in the green tiger shrimp, Penaeus semisulcatus De Haan, 1844 (Decapoda, Penaeidae), along the Palk Bay, southern Peninsular India

Abstract The green tiger shrimp, Penaeus semisulcatus, is a commercial species supporting important fishery along the Palk Bay coasts. It is a much sought-after seafood commodity influencing the livelihood of the local fishers. This study aims to investigate the fecundity of the species in relation to its morphometry. Fecundity is an index of reproductive capacity used to calculate a stock’s reproductive potential and the egg’s survival. The absolute fecundity of the shrimp ranged from 26 100 to 750 000 ova alive per female, and the mean absolute fecundity from 59 100 to 583 000 ova alive per female. The relationship between fecundity and the morphometric measurements showed a positive exponential correlation. One-way ANOVA indicated a significant difference in the different size classes’ carapace length, total weight, ovary weight, absolute fecundity, stomach weight, and gastrosomatic index. There was no significant difference between the relative fecundity and the gonadosomatic index. This study provides insight into the reproductive potential of P. semisulcatus for efficient management of the resource in Palk Bay, Tamil Nadu, India.

Determination of physicochemical parameters and assessment of trace metals bioaccumulation in the Lagos lagoon and edible tissues of the southern pink shrimp (Farfantepenaeus notialis - Pérez-Farfante, 1967)

Abstract. Bio-inorganic chemistry is found as an endearing aspect to research in today’s epoch. It deals with chemical reactions between the metals with natural resources, such as air, soil, water and byproducts (foods). To assess the decline in the quality of southern pink shrimps and water quality on samples from the Lagos lagoon, the morphometric assessment of the crustacean (Farfantepenaeus notialis – F. notialis), physicochemical parameters (pH, temperature, salinity, conductivity, total hardness, total dissolved solids, total suspended solids, biological oxygen demand, chemical oxygen demand, dissolved oxygen, sulphates, nitrate and phosphate) and levels of six (6) trace metals (Cadmium, Chromium, Zinc, Iron, Manganese and Copper) were collected from three sampling points with renowned anthropogenic activities along the stretch of the Lagos Lagoon using standard analytical procedures and the results were compared with standard acceptable limits. The crustaceans used had total length (4.0 – 14.4 cm), carapace length (1.6 – 6.4 cm), total weight (1.1 – 20.8 g) and carapace weight (0.9 – 11.5 g). The results obtained in the physicochemical analysis revealed that a few parameters such as biochemical oxygen demand and total suspended solids were beyond acceptable limits, while the trace metals were present in the samples at different levels but still within the maximum residual levels in the edible tissues of the pink shrimps. The obtained results showed that the crustacean and water from the lagoon contained metals but did not exceed both local and international standards of limit and thus, they are still safe for consumption and domestic uses.

The unique buckspoor webs of Seothyra optimize silk use and capture efficiency

Buckspoor-web spiders of the genus Seothyra are southern African endemics predominantly occurring in arid and semi-arid habitats. They have evolved a uniquely shaped web, comprising a burrow in which the spider rests, linked to a slightly asymmetrical two- to four-lobed web on the soil surface. We investigated the association between three web parameters (periphery, surface area and compactness) and three body size parameters (carapace length, total length and mass) of S. schreineri in central South Africa. Using a novel pixel-seeding image analysis, we were able to accurately determine the surface area of individual webs and compare their area:periphery ratio with that of hypothetical circular webs with the same perimeter length to determine the isoperimetric quotient of each. Isoperimetric quotients across all life stages indicated an average reduction of approximately 25% in silk investment, being highest in juveniles (∼35%). Web periphery was related to web area by a power function, but web area increased at a progressively faster rate than periphery with increasing web size, indicating that larger spiders build less compact webs, i.e. web shape is affected by spider size. Web area and periphery scaled positively and allometrically with the three measures of spider body size, but no significant effect of body size on web compactness was found. We conclude that the unique shape of Seothyra webs evolved as a mechanism to optimize the periphery and concurrently reduce the surface area, thereby enhancing their potential to capture prey and reduce silk investment in the web structure.

Morphometric Characteristics of Freshwater Crayfish (Pontastacus leptodactylus Eschscholtz, 1823) Caught in Sapanca Lake, Türkiye

This is the first study providing information on some morphometric parameters for Pontastacus leptodactylus from Sapanca Lake (Sakarya), Türkiye. This study was conducted from June - 2016 to October - 2017 and a total of 264 crayfish were caught, being 146 females and 118 males. The results revealed that the average total length for the population was 91.89±15.68 mm (TL±SD) (94.75±15.91 mm for females, 88.36±14.72 mm for males), and the average total weight for the total population was 27.27±16.84 g (TW±SD) (29.02±17.54 g for females, 25.09±15.74g for males). The sex ratio was computed as 1.24:1 (female to male). A strong positive statistical relationship was determined between the total length and total weight of females, males, and both sexes (r2: 0.90 – 0.95). This statistically strong relationship was also valid between other body parts, such as carapace length, width, and weight. The regression analyses for total length-total weight relationships also revealed that the whole population exhibited positive allometric growth (b=3.186) regardless of sex, and the condition factor for all sex groups was computed to be over 3 (K=3.23±0.60 SE).

Assessment of Three Major Shrimp Stocks in Bangladesh Marine Waters Using Both Length-Based and Catch-Based Approaches

Penaeus monodon (tiger shrimp), Metapenaeus monoceros (brown shrimp), and Fenneropenaeus indicus (white shrimp) are the most economically important shrimp species in the waters of the Bay of Bengal, Bangladesh. This is the first analytical study to assess three major shrimp stocks using both length-based and catch-based methods, such as length-based Bayesian biomass estimation (LBB), length-based indicator (LBI), and a catch-based method entitled JABBA (Just Another Bayesian Biomass Assessment), to explore and process the data; estimate the growth parameters, with length at first capture; present relative biomasses; and approximate the reference points. The parameters of the von Bertalanffy Growth Function (VBGF) analysis for the tiger, brown, and white shrimps were L∞ = 113.0 mm, 85.4 mm, and 76.4 mm, respectively, for carapace length. Our results showed that the relative biomass level (B/BMSY) of the tiger shrimp was 0.43, suggesting an overfished status, and brown and white shrimps were 0.84 and 0.96, indicating that they were fully exploited but not overfished. This study, therefore, advised an optimum carapace length limit to catch from 57.0–70.0 mm for tiger shrimp, 44.0–53.0 mm for brown shrimp, and 40.0–48.0 mm for white shrimp. The estimated maximum sustainable yield (MSY) reference points were as follows: optimal biomass BMSY = 3116 mt, 15,885 mt, and 2649 mt for tiger, brown, and white shrimp, respectively, and optimal harvest rate uMSY = 12%, 33%, and 8% for tiger, brown, and white shrimp, respectively. The average annual catch values for the last ten years were 265 mt, 2396 mt, and 115 mt below the estimated MSY values of 389 mt, 4899 mt, and 209 mt for tiger, brown, and white shrimp, respectively. But, brown shrimp had the estimated highest carrying capacity (31,770 mt) and intrinsic growth rate (0.66) than the tiger and white shrimp, which was replicated distinctly in the graphical representation of the Kobe plot and the surplus production plot. Hence, the brown shrimp stock is estimated to be in a better state than the tiger and white shrimp stocks.

Exploring the relationship between environmental drivers and the manifestation of fibropapillomatosis in green turtles (Chelonia mydas) in eastern Brazil.

Fibropapillomatosis (FP) is a disease characterized by epithelial tumors that can impede life-sustaining activities of sea turtles, especially green turtles (Chelonia mydas). FP is caused by a herpesvirus, but environmental factors are also thought to play a role in triggering FP tumor growth. In this study, we evaluate the epidemiology of FP tumors in green turtles along the coast of Espírito Santo, Brazil, a region where juvenile green turtles are known to aggregate with high FP prevalence. A dataset comprising 2024 beach-cast green turtles recorded through daily beach surveys on 400 km of coastline from 2018 to 2021 (inclusive) was evaluated. FP tumors were recorded in 40.9% of the individuals in this dataset, and presence of FP tumors was predicted by individual variables (presence of marine leeches, stranding code, curved carapace length, body mass-size residual) and characteristics of the stranding site (distance to nearest metallurgical plant, mean sea surface salinity (SSS), annual range of sea surface temperature (SST)). Additionally, a second dataset comprising detailed information about the size and anatomical distribution of tumors in 271 green turtles with FP from the same region was evaluated. Hierarchical clustering analysis revealed these turtles could be classified in three groups according to the anatomical distribution of their tumors, and in turn the group to which each turtle was assigned could be predicted by the study period (2010-2014 vs. 2018-2022) and by characteristics of the stranding/capture site (green turtle stranding density, mean sea surface chlorophyll-a concentration, mean SSS, mean SST, annual range of SST). These results corroborate that individual and environmental factors play a significant role driving FP epidemiology. Furthermore, the results suggest that rather than behaving as a single entity, FP may be seen as a mosaic of distinct anatomical patterns that are not necessarily driven by the same environmental factors.

Reproductive traits, dynamics of oogenesis and embryonic developments in the deep-sea shrimp Plesionika semilaevis from the southeastern Arabian sea

Reproductive traits are a crucial biological indicator of a population's resistance to anthropogenic and environmental pressures. The reproductive biology of Plesionika species from temperate and sub-tropical regions is relatively well known. However, a knowledge gap exists regarding the species' reproduction and life strategies in tropical waters like the Indian Ocean. This paper covers the reproductive period, ovarian and embryonic development, embryo size, brood size and size at sexual maturity of Plesionika semilaevis, a commercially important species from the tropical waters of the southeastern Arabian Sea. Histological analysis revealed asynchronous oocyte development with multiple oocyte stages present in each ovary sample, although with varying proportions. Maturation of the ovary was seen during the embryo incubation phase, which indicates that females are able to spawn several times during a reproductive cycle. A total of 1802 females of P. semilaevis were examined and sorted into ovigerous and non-ovigerous stages, and the embryos were divided into four stages of development. Although ovigerous females were present in every month's samples, the main reproductive season is from November to February, as evidenced by the larger percentage of ovigerous females during this time. Based on the percentage of embryos in various stages, the spawning and hatching periods were estimated to be December to February and March to May, respectively. Embryo size increased with the developmental stage (p = 0) but was independent of body size (p > 0.05). A positive correlation was observed between brood size and female body size in all four stages of embryo development but, as the embryos developed a significant decrease in brood size was noticed. Based on the size at which 50% of the females had matured ovaries and 50% were ovigerous, the size at sexual maturity, CL50ov and CL50em, was calculated to be 15.51 mm and 15.07 mm in carapace length, respectively. The brood size ranged from 2093 to 12887 embryos with a mean size of 0.51 × 0.40 mm following spawning and 0.66 × 0.50 mm prior to hatching.