Length‐weight relationship of three cichlid species in a stream in southwestern Amazon,Brazil

The paper investigates the length‐weight relationship of three cichlids species for the southwestern Amazon, Acre state. The individuals were collected at five sites during one year among august/2016 and june/2017 in Quinoá stream (10°06′03.33″S/67°40′11.50″W). The individuals were collected using: seine net, 6 m length, 2.25 high, and mesh size 5 mm, two dip nets, 5 mm mesh, 30 cm width, and 50 cm in length and two sieve with 5 mm mesh, 50 cm width, and 80 cm in length. The results show that one species presented positive allometric growth (Aequidens tetramerus) and the others negative allometric growth (Apistogramma acrensis and Crenicichla semicincta).     

Shape differentiation and characterization in the two morphotypes of the Antarctic limpet Nacella concinna using Elliptic Fourier analysis of shells

The Antarctic limpet Nacella concinna (Strebel 1908) presents two ecotypes (littoral and sublittoral) differing in morphological and behavioral characteristics and more recently discovered, in physiological traits and genetic population structure. Previous works, based on traditional morphometry, used only three measurements (length, width and height of the shell) and their relationships. However, this methodology could not describe in detail the shape of the morphotypes. In the present work, Elliptic Fourier analysis (EFA) of shells was used to study the shape of the two morphotypes in six localities along the Antarctic Peninsula. The use of EFA confirmed the morphometric differences. The littoral morphotype has higher and globose shells with the apex displaced to the anterior part; the sublittoral individuals are more flat and pointed, and have the apex very well defined. Low allometric effect was detected in SL individuals, whereas L specimens did not show an allometric relationship within the examined size range. Differences in shell shape among localities were recorded. EFA analysis reflected the overall shell shape and allowed to characterize the main differences in shell shape between ecotypes that were difficult to quantify using the standard morphometric approach.     

Ontogenetic Diet Shifts of a Neotropical Catfish, Pimelodus maculatus (Siluriformes, Pimelodidae): An Ecomorphological Approach

This study analyses the ontogenetic diet shifts of a Neotropical catfish, Pimelodus maculatus (Siluriformes, Pimelodidae), from an ecomorphological standpoint. We collected 241 individuals in the Piracicaba River (Brazil) and, in the laboratory, seven morphometric variables were recorded from each specimen: standard length (SL), body depth, head length, snout length, eye diameter, mouth height and mouth width. After standardizing these measurements (as a proportion of SL), linear regressions were run to determine whether their growth was isometric or allometric in relation to SL. The diet analysis shows that the main food item for fish in the smaller size classes is aquatic insects, while the largest individuals feed mainly on other fish. As the great majority of the morphometric variables analyzed showed isometric growth as a function of SL – which means that these fish do not change their shape significantly during their lives – the ontogenetic diet shifts may be seen as a consequence of the absolute size increment of their mouth gape, which allows individuals to maximize their energetic gain by ingesting larger prey with a higher caloric content.     

Relative growth and onset of morphological sexual maturity of the freshwater crab Sylviocarcinus pictus in a river of the Caatinga of northeastern Brazil

The aim of this study was to investigate the relative growth and onset of morphological sexual maturity of the freshwater crab Sylviocarcinus pictus. Specimens were collected every month from October 2013 to September 2014, at night, on a stretch of the river Guaribas, Piauí, Brazil. Crabs were sexed and their carapace width (CW, independent variable), carapace length (CL), cheliped propodus length (PL) and height (PH), gonopod length (GL), and abdomen width (AW) (dependent variables) were measured. These measurements were related to characterise relative growth and possible sex differences. On average males were larger than females (p = 0.0001). Size at the onset of morphological sexual maturity was defined by relating CL vs. PL for males (30.82 mm) and CL vs. AW for females (28.63 mm). These are considered secondary sexual characters and reflect initial size at morphological sexual maturity with greater precision. The differential cheliped growth of males may be related to courting and disputes with other males, while the allometric growth of the abdomen of females indicates increased probability of reproductive success.     

Relative Growth and Sexual Maturity of the Hermit Crab Paguristes erythrops (Anomura, Diogenidae) from South Atlantic

Some morphometric relationships were studied in the hermit crab Paguristes erythrops to describe its relative growth and the size at which sexual maturity is reached, as well as the shell influence on this process. Individuals were collected monthly from January to December/1999, by SCUBA diving and 12 different characters were measured on males and females. Sexual size dimorphism was observed in length and width of left cheliped. Size at sexual maturity was estimated between 2.8 and 3.5 mm shield length based on the left cheliped relations of the males and on the endopod and exopod of the second pleopod of the females. Differences in the allometry of individuals occupying different shell species were observed. The present work demonstrated the importance of characterizing the type of growth of some parts (pleopods) not yet used in other studies on relative growth of hermit crabs that may correspond to indicators of the size at sexual maturity.     

Swimming behavior and morphometry of the file shell Limaria fragilis

Swimming has evolved in only a few orders of Bivalves. In this study, the behavior, morphometry, and mechanics of swimming in the file shell Limaria fragilis were characterized and compared to the better understood scallops. Absolute swimming speed (cm?sec^?1) increased with increasing shell height, although relative swimming speed (body lengths?sec^?1) did not covary with shell height. The increase in absolute swimming speed was due to an increase in the distance covered during each valve clap as clap distance (cm?clap^?1) also increased with shell height while clapping frequency (claps?sec^?1) did not covary with animal size. Limaria fragilis displayed a variety of morphological changes related to size. Shell length was negatively allometric with shell height indicating the shell became proportionately slimmer in larger animals. Dry shell mass was negatively allometric with shell height, while both dry adductor muscle mass and dry mantle + tentacle mass were positively allometric. Autotomy of mantle tentacles significantly decreased clap distance by 13% without affecting clapping frequency or swimming speed.     

Age and growth of invasive round goby <Emphasis Type="Italic">Neogobius melanostomus</Emphasis> from middle Danube

Age and growth of the invasive population of round goby Neogobius melanostomus from the Slovak stretch of River Danube was examined. The samples (n=1130) were collected soon after the invasion was recorded (2004–2005), and later, when the population was already established (2008–2010). Invasive round goby in newly-occupied areas were found to reach smaller body size (15–153 mm standard length) compared to native populations. Age from 0+ to 4+, determined from scales, was recorded in both sexes. Annulus formed in April–May, which varied with age. Growth of freshly established gobies was negative allometric, suggesting increased allocation of their sources to reproduction, which corresponds to less specialized life-history. However, positive allometric growth found in longer established individuals suggests a shift in allocation towards somatic growth, which corresponds to more specialized life-history typical for native populations. None of the three parameters predicted by the theory of alternative ontogenies and invasive potential met the expectations, though two parameters, i.e. growth rate and age at maturation remain equivocal. This can be explained by too short of a time span that has elapsed from the beginning of invasion, or by ecological disturbances that have broken up otherwise stable environment in the habitat studied.     

Geometric mean shape of the shell in lacustrine and riverine limpets, Ancylus fluviatilis Müller

SUMMARY. Geometric mean (GM) shell shape in populations of limpets from three rivers was compared with that of populations from two lakes in England. The GM ratio of width on length was 0.78 in both river and lake limpets, but they respectively had GM ratios of 0.55 and 0.47 for height on width. The difference was compared statistically by prediction of mean values for height and width using linear logarithmic regressions. Shell height was significantly different ( P 0.05) in river limpets, which were about 20% taller than lake limpets at shell widths of 5.0–6.0 mm. The relationship between shell height and width or length was allometric in limpets from two rivers and isometric in a lake population. Similar results and conclusions were obtained using the GM regression (Teissier, 1948; Ricker, 1973) and the ordinary predictive regression.     

Relative growth and morphological sexual maturity of the mangrove crab Aratus pisonii (H. Milne Edwards, 1837) (Decapoda,Brachyura, Sesarmidae) on the southern coast of the state of São Paulo,Brazil

Growth in crustaceans is characterized by ontogenetic differentiation during the development of their body structures, so studies on relative growth are widely applied in this group. In this study, the growth pattern of the body structures was verified through the analysis of relative growth, and then, morphological sexual maturity of the mangrove crab Aratus pisonii (H. Milne Edwards, 1837) was estimated. The carapace width (CW), cheliped propodus length (PL), cheliped propodus height (PH), propodus width (PW), abdomen width (AW), and first pleopod length (FPL) of the crabs were measured. The relationships that best showed changes in the allometric coefficient among demographic categories were FPL vs. CW for males and AW vs. CW for females. This study verified the increased size of the cheliped in terms of length, width, and height, which occurred mainly in adult males. This increase reflects the importance of this structure in the reproductive processes of A. pisonii. For females, the increase in abdomen growth reflects their reproductive potential, since it is a structure that provides protection for eggs.     

Growing and shrinking in the smallest tortoise, <Emphasis Type="Italic">Homopus signatus signatus</Emphasis>: the importance of rain

Climate change models predict that the range of the world’s smallest tortoise, Homopus signatus signatus, will aridify and contract in the next decades. To evaluate the effects of annual variation in rainfall on the growth of H. s. signatus, we recorded annual growth rates of wild individuals from spring 2000 to spring 2004. Juveniles grew faster than did adults, and females grew faster than did males. Growth correlated strongly with the amount of rain that fell during the time just before and within the growth periods. Growth rates were lowest in 2002–2003, when almost no rain fell between September 2002 and August 2003. In this period, more than 54% of the tortoises had negative growth rates for their straight carapace length (SCL), shell height (SH), and shell volume (SV); maximum shrinking for SCL, SH, and SV was 4, 11, and 12%, respectively. The shell of H. s. signatus has some flexibility dorso-ventrally, so a reduction in internal matter due to starvation or dehydration may have caused SH to shrink. Because the length and width of the shell seem more rigid, reversible bone resorption may have contributed to shrinkage, particularly of the shell width and plastron length. Based on growth rates for all years, female H. s. signatus need 11–12 years to mature, approximately twice as long as would be expected allometrically for such a small species. However, if aridification lowers average growth rates to the level of 2002–2003, females would require 30 years to mature. Additionally, aridification would lower average and maximum female size, resulting in smaller eggs and hatchlings. These projected life history responses to aridification heighten the threat posed by the predicted range contraction of this red-listed species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Length–weight relationships for 10 elasmobranch species from the Oman Sea

Length–weight relationships (LWRs) were estimated for ten elasmobranch species from Iranian waters of the Oman Sea. All specimens were collected by bottom trawl (mesh size 80 mm in the cod end) between May and December 2014. A total of 509 individuals (107 Torpedo sinuspersici, 68 Rhinobatos punctifer, 63 Chaenogaleus macrostoma, 72 Himantura walga, 80 Himantura gerrardi, 58 Gymnura poecilura, 4 Himantura uarnak, 4 Rhinoptera javanica, 14 Aetobatus flagellum, and 39 Pastinachus sephen) were sampled and studied. Results showed that most species had positive allometric or isometric growth but that more studies were needed for final decisions on growth patterns. Both the disk length‐body weight (DL/BW) and disk width‐body weight (DW/BW) relationships also showed a good fit, reinforcing the credibility of the data in relation to the LWRs. This study is the first report of LWRs for these elasmobranchs in the northern Oman Sea.     

Notes on the biology of Cancer bellianus (Brachyura, Cancridae) around the Canary Islands

Information on biometric and biological parameters of Cancer bellianus Johnson, 1861 (Crustacea, Decapoda, Brachyura, Cancridae) off the Canary Islands is given. Crabs examined were collected during experimental fishing surveys during 1974–1998. Carapace length, carapace width, total wet weight, sex and ovigerous condition were determined. This species was caught at depths from 153 to 750 m, the deepest ever recorded. Size frequency distributions were assembled and size-weight relationships were estimated by sex. Sex-ratio as a function of size and depth was determined. The size at first maturity was calculated by analysing the relative growth between the carapace length and the left chela width: 103.5 mm CL in males, 101.2 mm CL in females. Ovigerous females, egg size and fecundity estimates are reported apparently for the first time.     

Spatial growth rate variability in <Emphasis Type="Italic">Callista brevisiphonata</Emphasis> (Carpenter, 1865) (Bivalvia: Veneridae)

The features of the group linear growth of the bivalve Callista brevisiphonata were studied over a large part of its range in the Sea of Japan along the mainland coast of Russia. It was found that in the south of the species range in the Peter the Great Bay, the shell length in individuals of the same age can differ by almost 1.5 times, depending on the position of the population relative to the open sea. With propagation from south to north, trends to a decreasing growth rate and a narrowing of the range of age variation in shell length were recorded in C. brevisiphonata populations. It was shown that the clams need 5–18 years to reach their commercial size (a shell length of more than 70 mm). The observed differences in growth rate are considered in connection to the habitat environment of C. brevisiphonata.     

Relative growth,morphological sexual maturity,heterochely, and handedness in Panopeus occidentalis (Brachyura,Panopeidae)

Studies on relative growth and sexual maturity are important to understand the reproductive biology of a species. The aims of this study were to determine the relative growth and to estimate the size of Panopeus occidentalis at morphological sexual maturity, as well as to confirm whether this species demonstrates heterochely or handedness. Individuals were collected every two months from March 2013 to July 2014 in the intertidal estuarine zone of Cananeia, São Paulo, Brazil. The following measurements were taken: carapace width (CW), carapace length (CL), right and left cheliped propodus length (CPL), right and left cheliped propodus height (CPH), right and left cheliped propodus width (CPW), abdomen width (AW), and first pleopod length (FPL). The morphometric relationship used to estimate the size at morphological sexual maturity were CW vs. AW for females and CW vs. FPL for males; these comparisons yielded estimated CW values of 15.60 mm and 16.67 mm, respectively. Heterochely was observed but handedness was not present. The species has a major cheliped on one side, but the side is not constant. This study provides the first insights on the relative growth, sexual maturity, heterochely, and handedness on a population of P. occidentalis in a conserved area.     

Notes on the biology of the Oriental amblyoponine ant Myopopone castanea: Queen‐worker dimorphism,worker polymorphism and larval hemolymph feeding by workers (Hymenoptera: Formicidae)

Queen‐worker dimorphism, worker polymorphism and worker behavior in the Oriental amblyoponine ant Myopopone castanea were studied. Queen body size was large (head width, 3.0 mm) with 24 to 32 ovarioles while workers showed a remarkable size variation in both body size (head width 1.48 to 2.18 mm) and ovariole number (6 to 22). Both head width and abdomen width showed allometric growth against thorax width. Workers performed larval hemolymph feeding as was described for Amblyopone silvestrii queens.     

Relative growth and morphological sexual maturity size of the freshwater crab Trichodactylus borellianus (Crustacea,Decapoda, Trichodactylidae) in the Middle Paraná River,Argentina

The relative growth of a number of morphological dimensions of the South American freshwater crab Trichodactylus borellianus (Trichodactylidae) were compared and related to sexual dimorphism. Crabs were collected from ponds in the Middle Paraná River in Argentina. A regression model with segmented relationship was used to test for relative growth between these measurements where breakpoints infer the body size at which crabs reach sexual maturity. In both sexes the carapace width and the length, height, and thickness of the right and left chelae were measured, as well as the male pleopod length and the female abdomen width. All of these measurements were found to show positive allometry with the exception of the male pleopod length and the left chelae, which did not show a breakpoint. In females the breakpoint for the abdomen width inferred a morphological sexual maturity at carapace width 6.9 mm. In males the break point for the pleopod length was at carapace width 6.6 mm, with that for the chelae measurements was between carapace widths 6.4 and 6.9 mm. The relative growth pattern in Trichodactylus borellianus was found to be similar to that recorded for other species of the family Trichodactylidae.     

Comparing applesnails with oranges: the need to standardize measuring techniques when studying <Emphasis Type="Italic">Pomacea</Emphasis>

Although invaders come in all shapes and sizes, several mollusks have recently achieved notoriety as both economically and ecologically costly invaders. Applesnails of the genus Pomacea get their name from reaching the size of an apple. Native to South America, the species P. insularum has recently established reproducing, and potentially invasive, populations in Texas, Alabama, Georgia, and Florida. In contrast to the widely invasive golden applesnail (P. canaliculata), few studies of the channeled species P. insularum exist. In studying similar invasive applesnail species, scientists use several methods of measurement. We have explored the relationships among shell height, operculum width, and weight among juvenile and adult P. insularum and tested their inter-measurer reliability. We also investigated the use of shell height, shell length, and operculum width measurements in P. canaliculata studies and observed whether or not those studies defined their measurements. We found that operculum width served as a significantly more reliable measure among researchers. Furthermore, operculum width better predicted weight than shell height. The majority of articles that measured P. canaliculata did not define their measurements, which may cause problems when comparing studies between native and exotic populations or when comparing the two species. We recommend that future studies of P. insularum use operculum width to measure snails and explore a possible sex dimorphism in the operculum width of adult P. insularum.     

Population structure and growth of the Japanese littleneck clam <Emphasis Type="Italic">Ruditapes philippinarum</Emphasis> in Amursky Bay,Sea of Japan

This paper deals with the size, age, and sex structure of population and growth of the Japanese littleneck clam Ruditapes philippinarum in Amursky Bay (Peter the Great Bay, Sea of Japan). One-year-olds and individuals with a shell length less than 19.8 mm were not found in the population under study. The population consisted mostly of 3-4-year-old clams (72.4%) with a shell length of 35–45 mm (67.8%). The maximum recorded age of R. philippinarum was 7 years, and maximum shell length was 52.7 mm. The male to female ratio was approximately 2: 1. Hermaphroditism (2.1%) and parasitic castration (1.4%) were observed. Linear growth rates of clams were found to increase until the age of three years old (11.6 ± 0.6 mm/year). Mollusks reach a commercial size of over 35 mm in shell length in the fourth year of life. The parameters of the von Bertalanffy equation describing group linear growth were L _∞ = 56.6 mm, k = 0.302 year^?1, and t ₀ = 0.468 year. The relationship between the shell length and the wet body weight is described by the equation W = 0.000253L^2.954.     

Osteology and morphology of the characiform fish Alestes stuhlmanniiPfeffer, 1896(Alestidae) from the Rufiji River basin,East Africa

The osteology of a population of the characiform fish Alestes stuhlmannii, from the Rufiji River basin of Tanzania, is described, and meristic and morphometric data from over 100 specimens, ranging from 15·5 to 218 mm standard length are given. Two allometric changes occur during growth of this fish: both the number of gill rakers and the interorbital width relative to the head length increase with size. There are also changes in tooth form associated with growth in A. stuhlmannii, with the unicuspid teeth of juveniles becoming almost molariform in adults. This change in dentition with age, and therefore size, may have implications for recognizing taxa, some of which (the fossil genera Sindacharax and Bunocharax, and the living dwarf petersiines) have been distinguished by jaw or dental characters.     

Relative growth and sexual dimorphism in the hermit crab Clibanarius signatus Heller, 1861 (Anomura,Diogenidae) from the northern coast of the Persian Gulf,Iran

The purpose of this study was to investigate the relative growth and sexual dimorphism in the hermit crab Clibanarius signatus. The evaluation was done with 955 specimens (494 males, 251 females, and 210 intersexes) captured in Persian Gulf (Iran) during January to December 2015. Animals were submitted to measurements related to weight (BW, total wet weight) and body size related to cephalic shield (SW, width; and SL, length) and propodus of both chelipeds (CPL, length; and CPW, width). Males were larger and heavier than females and intersexes. Both males and females showed a negative allometric growth for the SL–BW and SL–SW relationships, but a positive allometric growth to intersex specimens. To SL–CPL relationship, a negative allometric growth was confirmed in males and females independent of the laterality of the CPL, whereas a contrast was verified in intersexes, with a positive allometric growth occurred for both hands. To SL–CPW relationship, a negative allometric growth (b < 1) occurred in females, independent of the laterality of the CPW, while in males, a positive allometric pattern was confirmed. In intersexes, this relationship was positive except for the right CPW which was isometric. Sexual dimorphism was evident in Clibanarius signatus, with males being the largest and females the smallest specimens in the population.