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.     

Relative growth and morphological sexual maturity of the freshwater crab Trichodactylus fluviatilis Latreille 1828 (Decapoda,Trichodactylidae) from west central São Paulo State,Brazil

An analysis of relative growth was performed to determine the size at morphological sexual maturity of Trichodactylus fluviatilis Latreille 1828. Samples were collected by trapping at night from January 2010 through June 2011 from the Barreiro River (22°34′42″S; 49°11′92″W), west central São Paulo State, Brazil. The following measurements were obtained (mm): carapace width (CW) (independent variable), cheliped propodus length (PL), cheliped propodus height (PH), cheliped propodus width (PW), first pleopod length, and abdomen width (AW). The males showed positive allometry in the juvenile and adult stages for the following relationships: PL vs. CW, PH vs. CW, and PW vs. CW. In the females, a positive allometry was observed for AW vs. CW in the juvenile stage, and a negative allometry was observed for this relationship in the adult stage. The differential growth of the chelipeds in males could be related to territorial conflict and courtship, whereas the changes in the growth of the female abdomen most likely favor higher reproductive success.     

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.     

Relative growth and morphological sexual maturity of the caridean shrimp Nematopalaemon schmitti (Decapoda: Caridea: Palaemonidae) in an upwelling region in the Western Atlantic*

In crustaceans, successful reproductive processes, such as the transition from juvenile to adult, exhibit important morphological changes that can be detected by analyzing relative growth. This study describes the relative growth of body structures in Nematopalaemon schmitti and its secondary sexual characteristics, and also estimates the morphological sexual maturity of this species in a region influenced by upwelling. The carapace length (CL), second pleuron length (PlL), cheliped carpus length (CaL), cheliped propodus length (PrL) and the length of appendix masculina (AML) of the shrimp were measured. The relationships that best demonstrated the changes in allometric coefficient between demographic categories were AML vs. CL for males, and PlL vs. CL for females. The estimated CL for morphological sexual maturity in males was 8.51 mm and 9.30 in females. Our results showed the appendix masculine and the second pleuron were secondary sexual characteristics that play roles in reaching the morphological sexual maturity necessary for reproductive success and to assure the life cycle of this species.     

Insights of the life history in the porcellanid crab Petrolisthes armatus (Gibbes, 1850) (Crustacea: Anomura: Porcellanidae) from the Southwestern Atlantic coast

Petrolisthes armatus (Gibbes, 1850) life history was evaluated based on growth and reproduction. Specimens were captured at Ubatuba (Brazil), identified, sexed and measured: carapace (CL, length; CW, width), larger cheliped propodus (PL, length; PW, width; and PH, height), and 2th and 5th abdominal somite (AW₂ and AW₅, width). Relative growth was studied using CL as independent variable and its relation with other variables (dependents), to estimate puberty size and morphological maturity. Fecundity was represented by number of eggs vs. body size CL, with a better fit using a power function. Considering the 257 specimens analyzed, males were larger than females, and the overall sex ratio was 1:1, with some differences among size classes. Maturity (puberty size) was revealed by: AW₂ × CL (males: 8.6 mm CL; females: 7.6 mm CL); and AW₅ × CL (7.1 and 7.6 mm CL, respectively). Reproduction was continuous, but more intense in rainy season and recruitment occurring in dry season. Fecundity of this species was 228 ± 163 eggs, with better fit by a power function (R² = 0.72). Maturity size and growth differed when a pristine area (Ubatuba) was compared with a polluted area (São Sebastião), in the same Brazilian area (São Paulo State).     

Population structure,relative growth and morphological sexual maturity of the snapping shrimp Alpheus brasileiro Anker, 2012 (Caridea: Alpheidae) from the south-eastern coast of Brazil

The present study investigated the population structure of the snapping shrimp Alpheus brasileiro. We tested the hypotheses that the sex ratio of the population differs from the expected 1:1 and that the growth pattern differs between adults and juveniles and between sexes. Reproductive period, juvenile recruitment and morphological sexual maturity were estimated. Samples were collected in two periods. The first sampling occurred bimonthly from March 2013 to January 2014. The second sampling occurred monthly from April 2015 to March 2016. The population structure was determined based on the size-frequency distribution of different demographic categories. To analyse the relative growth, we measured the second pleuron length, major cheliped propodus length, major cheliped propodus width, major cheliped propodus height, appendix interna length, appendix masculina length. The results showed that the sex ratio did not differ from 1:1 (male:female). Reproduction and juvenile recruitment were continuous throughout the study period. The analysis of relative growth confirmed the hypothesis that males and females, and juveniles and adults, have different growth patterns, indicating distinct strategies of energy allocation. The estimated carapace length at the onset of morphological sexual maturity was 4.9?mm in males and 4.7?mm in females. The results obtained in this study are probably related to the monogamous social behaviour of A. brasileiro. Monogamy can influence demographic parameters such as sex ratio and the size at which males and females reach morphological sexual maturity.     

Size at the onset of sexual maturity in the anomuran crab, Aegla uruguayana (Aeglidae)

The size at maturity was studied in the crab Aegla uruguayana from the Areco River (31°14′ S, 59°28′ W), Argentina. Size at sexual maturity was determined according to three criteria: morphometric (change in the relative growth of reproductive characters), histological (first maturation of gonads) and functional (capability to mate and carry eggs). Regarding females, morphometric maturity occurred at a carapace length (CL) of 11.50 mm, considering abdomen width as a reproductive character. Gonad maturity of females could be observed at a minimum size ranging from 15 to 17 mm CL. The smallest ovigerous female observed in the field was 15.60 mm CL, although a relevant population incidence of ovigerous females (86.6%) has just been observed at values higher than 17 mm CL. As for males, the relative growth of the left chela length changed at a value of 15.40 mm CL, while morphological changes in sexual tube occurred between CL of 14 and 16 mm. Testicular maturation occurred at a CL ranging from 17 to 19 mm. The smallest size of males having spermatozoids in their vasa deferentia was 18.70 mm CL. The results obtained indicated that, in both sexes, functional maturity occurred after morphometric maturity and at a size similar to that of gonad maturity. Comparing sexes, females acquired sexual maturity (morphometric, gonad and functional maturity) at sizes statistically smaller than those of males.     

Relative growth and morphological sexual maturity of the deep-water velvet shrimp Metapenaeopsis sibogae (Crustacea,Decapoda, Penaeidae)

Metapenaeopsis sibogae inhabits the South Pacific and Southeast Asia and is an emerging fisheries resource. However, studies on the population biology of M. sibogae are scant, and their morphometric relationships have not been examined. Thus, we studied the relative growth of M. sibogae, hypothesizing that its morphological sexual maturity can be estimated based on abrupt shifts in allometry. The relationships of body length (BL) and body weight (BW) with carapace length (CL) were determined by the least squares method. Data for each sex were repeatedly partitioned into two size-delimited subsets (early and late phases), considering a CL value as a hypothesized transition point. Analysis of the sum of squared residuals indicated that two separate linear BL/CL models fit the data better than a single linear model showing clear transition points in both males (13.2 mm CL) and females (15.0 mm CL). The changes in allometry in the BL/CL relationships between early- and late-phased males and females were indicated by a 20.5 and 21.5% decrease in the slope, respectively. These transition points could be associated with sexual maturity. The growth rate of BW vs. CL slowed significantly after morphological sexual maturity was reached in both sexes, demonstrating the existence of dimorphic growth.     

Size distribution,length–weight relationship and size at the onset of sexual maturity of the orange mud crab,Scylla olivacea,in Malaysian waters

The size distribution, length–weight relationship and size at the onset of sexual maturity of the orange mud crab (Scylla olivacea) from four geographically distinct locations (Taiping, Setiu, Kota Marudu and Lundu) representing Malaysian waters were analysed and estimated. Scylla olivacea was found in the size range of 47–134?mm carapace width. Males were significantly smaller in size but heavier than females. Geographical variation in carapace width and body weight were significant, but no interaction was found between sexes and locations. As shown by the length–weight relationships of S. olivacea, the males exhibited positive growth allometry whereas the females exhibited negative growth allometry. Males mature physiologically prior to attaining morphometric sexual maturity. Females, however, achieve physiological and morphometric sexual maturity in synchrony. No significant variation was found in the estimates of size at the onset of sexual maturity of males and females among different locations. We recommend the use of the third right walking leg merus length and carapace width to estimate the size at the onset of sexual maturity (morphometric maturity) for S. olivacea. Data obtained in this study serve as important baseline data for future mud crab resource management in Malaysia and were used to recommend minimum landing sizes for S. olivacea in each respective location based on the largest size at the onset of sexual maturity estimates were suggested.     

Relative growth,morphological sexual maturity,and size of Macrobrachium amazonicum (Heller 1862) (Crustacea,Decapoda, Palaemonidae) in a population with an entirely freshwater life cycle

The objective of this study was to estimate the size of morphological sexual maturity based on the study of relative growth, to determine the maximum size of individuals, and to determine if there are different morphotypes of males in a population of Macrobrachium amazonicum with an entirely freshwater life cycle. Collections were made monthly, with the use of a net, from September 2006 through August 2007. In each individual, the following structures were measured: carapace length (CL, in mm), width of the second pleuron (PlL, mm), length of the carpus (CaL, mm), and length of the propodus (PrL, mm). Relative growth was analyzed by observing the change in growth patterns of certain parts of the body in relation to the independent variable CL. The maximum sizes found were 8.5 and 11.4?mm CL for males and females, respectively. The morphometric variables: length of the carpus (CL?×?CaL) for males, and width of the second pleuron (CL?×?PlL) for females gave the best estimates for the size at maturation, which was 4.26?mm CL for males and 5.39?mm CL for females. The growth pattern in the different stages and the beginning of differential growth seemed to be closely related to reproductive aspects. No indices were found that separated the males into four different morphotypes, as proposed in the literature for coastal or artificially farmed populations. Only the male morphotype termed translucent claw was found in this population. The different morphological patterns in different regions are probably explained by ecological differences in the environments inhabited by these groups, principally in the availability of nutrients and the salinity in which the larvae develop.     

Juvenile morphology of the xanthid crab Leptodius exaratus (H. Milne-Edwards, 1834) (Decapoda: Brachyura), with notes on the appearance of sexual dimorphism

Summary

The morphometrical and meristic features of the carapace, cephalic appendages (antenna, antennule), mouthparts (maxillule, maxilla, first-third maxillipeds), sternum, pereiopods, abdomen, and pleopods of juveniles and the onset of morphological sexual dimorphism were described for the xanthid crab Leptodius exaratus (H. Milne Edwards, 1834), based on laboratory-reared and wild adult specimens collected from Tateyama Bay, Japan. First instar juveniles shared some of the features of adults (e.g. gross appearance of the carapace and cheliped propodus proportions), but differed from adults on almost all other morphological parameter examined. Morphological development was still not complete at the ninth instar; extrapolation from the rate of morphological changes between instars 1–9 suggests that L. exaratus requires about 13 ecdyses to transform into adults, including development of reproductive structures. Differences in the number and morphology of pleopods and abdomen width allowed early distinction of the sexes. Thus, males formed gonopods in the first abdominal somite and lost the paired vestigial pleopods in somites 3–5 from the fourth instar; females retained the pleopods in somites 2–5, but these became biramous and had increased setation. The abdomen grew wider in females than in males from the fifth instar. Several morphological features of juveniles have phylogenetic and taxonomic implications: carapace motifs clearly place L. exaratus in the superfamily Xanthoidea, whereas the patterns of setation in the scaphognathite and first maxilliped epipod allow separation of this (xanthid) species from crabs of other Xanthoidean families.     

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.     

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.     

Population features of Microphrys bicornutus Latreille, 1825 (Brachyura, Majidae) from Isla Margarita, Venezuela

The aim of this study is to characterize the population biology (sex ratio, size structure, relative growth of reproductive characters and realised fecundity) of the crab Microphrys bicornutusfrom Isla Margarita, Venezuela. Nearly 100 crabs were collected and fixed monthly during 1998. In the laboratory, crabs were sexed and measured: maximum carapace length, chelae length, chelae and abdomen width for females and first pleopod length for males. Additionally, 96 ovigerous females were collected to determine fecundity. The following measurements were taken for each female: body wet weight (BWW), body dry weight (BDW), egg wet weight (EWW), egg dry weight (EDW) and number of eggs (NE). The following determinations were made: relative fecundity (RF) = NE/BDW and reproductive output (RO) = (EDW/ BDW) × 100. Relative size at the onset of maturity (RSOM) was calculated as minimum ovigerous female/female's maximum size. The results indicate that the sex ratio is nearly 1:1 during the entire year. Ovigerous females and moulted males and females were observed throughout the year. Size frequency distribution and size at the onset of sexual maturity, estimated by relative growth of the sexual secondary characters and RSOM value, differed from those estimated in studies done in Jamaica and Buchuaco, Venezuela.     

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.     

Aspects of the biology of the big-handed crab,Heterozius rotundifrons (Decapoda: Brachyura), from Kaikoura,New Zealand

Abstract

From January 1975 to June 1976, samples of Heterozius rotundifrons A. Milne Edwards, 1867 were taken monthly from the intertidal zone at First Bay, Kaikoura Peninsula (42°25′S, 173°42′E). Small crabs (< 8 mm carapace width) were never common; they were either too cryptic to be collected in quantity, or have a different habitat from larger crabs. Ovigerous females were present in all months except February (in both 1975 and 1976), but generally formed less than 50% of the total sample of females each month. The number of newly deposited eggs (0.75×0.81 mm) carried by females increased with increase in carapace width according to the equation y = -1123.56+102.97x (r ² = 0.8213). Egg development lasted 3–5 months, and egg mortality during this period was almost 10%. The overall sex ratio for the 18-month sampling period was 1846 ♀ : 993 ♂, which suggests that females were approximately twice as numerous as males. However, when crabs were sorted into size classes it was evident that the sex ratio was not significantly different from 1:1 in crabs of 6–12 mm carapace width, whereas females significantly (P<0.001) outnumbered males in the 13–21 mm size range. The right and left chela were approximately equal in length in females of all sizes, but the right chela of large males was greatly enlarged compared with the left, and with the chelae of females of comparable carapace width. Increase in the growth rate of the males’ right chela commenced at a carapace width of approximately 11.0 mm. Since the smallest ovigerous female collected also had a carapace width of 11.0 mm, it is concluded that both males and females attain sexual maturity at this size.     

Growth and reproduction in the freshwater crab, Potamon fluviatile (Decapoda, Brachyura)

SUMMARY. 1. The patterns of relative and absolute growth and the reproductive biology of the freshwater crab Potamon fluviatile were studied in a natural population inhabiting a hill stream close to Florence, Italy, over an annual cycle. Periodical inspections of a stretch of the stream were made and morphological and anatomical analysis carried out.
2. As in other decapods, the females are smaller than the males (they can however occasionally reach larger dimensions). This may be determined by a lengthening of the moulting interval in the females, by their higher energetic cost of reproduction (since reproduction occurs simultaneously with moulting, at least in this habitat) and/or by a higher mortality rate resulting from the risks associated with carrying eggs and vagility.
3. The analysis of relative growth in secondary sexual characters (abdomen width and major chela length) with respect to carapace length, shows that the pre-puberty and puberty ecdysis occur at 15 and 35 mm carapace length respectively, which was also confirmed by the gonad weight, vas deferens in males, and the onset of vitellogencsis in females.
4. A delay between anatomical and functional (i.e. the ability to copulate successfully) maturity was observed in the males. Being larger may be an advantage in intra-sexual competition for mating, but larger males, being more vagile, are also more likely to meet receptive females. The females may mate before their puberty moult and store sperms in their seminal receptacles for when they attain full maturity; this could be adaptive since opportunities of encountering males are few and far between in their adult phase, characterized by their vagile and amphibious habits.     

Population structure and sexual maturity of Aegla castro (Decapoda,Anomura), an endemic freshwater crab from Brazil

Specimens of Aegla castro Schmitt, 1942 were monthly sampled from June 2012 to May 2013 from Couro stream (23°57′15″S 51°06′00″W), located in the Upper Paraná river region, southern Brazil. Population structure, morphometric and functional maturity were analyzed. Allometric growth analysis on chela dimension versus carapace length (CL) was employed to recognize juveniles and adult individuals. Two sequential groups of adult males (morphotypes I and II) were recognized according to the state of development of the pair of claws. The CL where 50% of the population of individuals are adults (CL₅₀) was used to estimate the size at the onset of morphometric maturity. Males attain morphometric maturity at same size class of females (8.0–9.0 mm CL). Males and females are heterochelous and they often show the left chela more developed. The reproductive period was extended from June to September 2012 and April to May 2013 (six months) with record of 22 ovigerous females. The recruitment occurred in the months following the reproductive period, with higher records in October and December 2012. All the information gathered here should be useful to better understand the biology of the species studied.     

Population structure and reproduction of the longtail grass shrimp Urocaris longicaudata (Decapoda,Caridea, Pontoniinae) in Laguna de Términos,SW Gulf of Mexico

The purpose of this study was to describe the population structure and some reproductive traits of Urocaris longicaudata collected in Laguna de Términos, Campeche, Mexico in October and December 2009, and February and April 2010. A total of 2977 specimens were collected of which 1596 were females (including 276 ovigerous) and 1381 were males. Females were larger than males (2.03 ± 0.63 vs. 1.97 ± 0.44 mm carapace length (CL), respectively). The overall sex-ratio differed significantly from 1:1. The reproductive period was apparently continuous, with most ovigerous females recorded from December 2009 to April 2010. The estimated size at sexual maturity in females was 2.90 ± 0.64 mm CL. A significant and positive linear relationship between CL and realised fecundity was estimated. The number of embryos ranged from 33 to 320. The average volume of newly spawned embryos was 0.038 ± 0.009 mm³ and that of those near hatching was 0.062 ± 0.012 mm³, representing a 63.15% increase throughout embryogenesis. The females lost on average 27.6% of the initially produced embryos during the incubation period, which favoured the survival of the remaining embryos. This is the first report on any biological trait of U. longicaudata along the southwestern Gulf of Mexico.     

Evolution of the relative width of the head and alveolar surfaces in map turtles (Testudines: Emydidae: Graptemys)

Replicate adaptive radiations are dichotomous morphological patterns related to resource use and repeated in a series of isolated habitats. Biologists have long noted a dichotomy in relative head width and alveolar width among species of map turtles ( Graptemys ), particularly with regard to adult females, which are much larger dian adult males in all 12 species. I measured plastron length (PL), head width (HW), and alveolar width (AW) of nearly 2300 specimens representing the 12 recognized species, and used allometric regressions to investigate this genus as an example of both sexual dimorphism in trophic morphology and replicate adaptive radiation. Sexual dimorphism was noted in HW after correction for PL, with females having wider heads than males of similar body sizes, but AW as corrected for HW was not dimorphic, thus absolute differences in AW are the simple result of differences in HW. Sexual differences in HW probably relate to the dimorphic niches of Graptemys , as females of three species have been reported to occupy deeper water further from shore than conspecific males. Based on predicted HW at maximum PL in adult females, species were categorized as mega-, meso-, or microcephalic. Differences in relative head width are related to differences in degree of molluscivory, with little molluscivory in microcephalic females, moderate to high molluscivory in mesocephalic females, and high molluscivory in megacephalic females. Distributions of Graptemys species in sympatry and allopatry reveal patterns consistent with structuring of distributions via competitive interactions. Superimposing data on relative HW on a phylogeny of the genus suggests there may have been one or two episodes of character displacement, widi subsequent character assortment, in Graptemys evolution. This conclusion is similar to the current model for the evolution of body size during the radation of Anolis lizards in the northern Lesser Antilles.