Morphometric Maturity Research Articles

Size at maturity, reproductive cycle, and fecundity of the southern California brown box crab Lopholithodes foraminatus and implications for developing a new targeted fishery

AbstractObjectiveThe brown box crab Lopholithodes foraminatus is a member of the king and stone crab family (Lithodidae) that occurs in deepwater along the eastern Pacific coast. Historically, landings in California have been low for this species, but an increase in fishing pressure prompted the state to designate it as an emerging fishery and implement an experimental fishery program. With no known biological studies of California brown box crab, essential fisheries information is needed to evaluate the feasibility of a new targeted fishery.MethodsUsing field sampling and observations, along with laboratory studies, we investigated elements of reproductive capacity of the brown box crab in southern California.ResultWe found that females reach physiological maturity at a carapace width (CW) between 50.8 and 71.7 mm, and males do so at a CW between 43.3 and 66.3 mm. Morphometric maturity analysis showed a clear inflection point of abdomen width between immature and mature females. Females were 50% functionally mature at 75 mm CW. Morphometric and functional maturity was not detected for males, albeit samples of small male crabs were extremely limited, thus warranting further study. Females followed a biennial reproduction pattern: mating occurred in the fall, followed by an approximately 18‐month brooding period, with hatching in the second spring after mating. Fecundity was positively related to size and ranged from 8352 eggs/brood for a 67.8‐mm‐CW female to 62,181 eggs/brood for a 130.5‐mm‐CW female.ConclusionThese findings can inform the evaluation of a fishery for the brown box crab, including potential management strategies and models for assessing stock condition.

Comparing the Size at Onset of Sexual Maturity of Edible Crab (Cancer pagurus, Cancridae) in Berwickshire and Northumberland

The literature suggests regional variations in the size at which sexual maturity is reached for commercially important edible crab (Cancer pagurus), worth GBP 74.3 million annually, which could have implications for regional fisheries management. Berwickshire and Northumberland are geographically divided by the Scotland and England border and remain within the Berwickshire and North Northumberland Coast SAC (Special Area of Conservation). Each are managed by differing fisheries authorities and Minimum Conservation Reference Sizes (MCRS). Morphometric measurements were recorded for each C. pagurus individual to categorise morphometric maturity using segmented regression, with gonadal maturity categorised using visual gonad characteristics and general linear model regressions to compare onset in sexual maturity. Results showed regional variations for gonadal maturity with males reaching sexual onset at a carapace width size of 108.5 mm in Berwickshire and 109.9 mm in Northumberland; females at a size of 126.8 mm in Berwickshire and 120.8 mm in Northumberland. This was also true for morphometric maturity based on chelae height, that males (141.1 mm) and females (134.7 mm) from Berwickshire were morphometrically mature at greater sizes than males (130.1 mm) and females (120.8 mm) from Northumberland. This study shows that the respective MCRS in both regions are appropriate for the C. pagurus populations, but implications for fisheries management could be present.

Grooved tanner crab <i>Chionoecetes tanneri</i> in the north-western Bering Sea: criteria for choosing the optimal fishing measure

Spatial and bathymetric distribution and aggregation density is considered for bathyal crabs, including the grooved tanner crab <i>Chionoecetes tanneri</i>, on the data of specialized deep-water trap survey and two bottom trawl surveys within the depth range of 300‒1080 m conducted by TINRO in the northwestern Bering Sea in 2019–2020. The size of grooved tanner crab is determined as 9.0–17.0 cm for the morphometrically mature males and 6.5–15.5 cm for the morphometrically immature males, by carapace width. The size of 50 % morphometric maturity is evaluated for males of <i>Ch. Tanneri</i> in the northwestern Bering Sea. A new fishing measure is substantiated for this population taking into account its size composition.

Relative growth and sexual maturity of the spider crab Libinia spinosa Guérin, 1832 (Brachyura: Majoidea: Epialtidae), from the Southeast Brazilian coast

ABSTRACT We investigated the relative growth and sexual maturity (gonadal and morphometric) of Libinia spinosa. Crabs were sampled at Ubatuba from January to December 2000, using trawls. Based on allometric growth, males were grouped into juveniles (MJ), adolescents (MAd) and adults (MA) based on the relationship CPL (major cheliped propod length) vs. CW (cephalothorax width), all with positive allometric growth. For females, the relationship AW (abdomen width) vs. CW allowed segregating juveniles (FJ) from adults (FA), with positive allometric growth for FJ but isometric growth for FA. The morphometric maturity evidenced for MAd varied from 33.7 mm to 34.5 mm and for MA and FA. The size at which 50% of individuals reach the morphometric sexual maturity was L50 = 50.1 mm for males and L50 = 37.3 mm for females. Gonad maturity was L50 = 33.7 mm for males and L50 = 36.9 mm for females. Through relative growth analyses, we identified an adolescent male group (prepuberal phase). These individuals presented mature gonads, enabling them to copulate with females. These adolescent males may reproduce while avoiding competition with adult males, as it happens in other species of Majoidea that present more than two morphotypes in the population.

Size Distribution, Length-Weight Relationship, and Size at Morphometric Maturity of the Mud Spiny Lobster Panulirus polyphagus (Herbst, 1793) in the Johor Strait

Spiny lobsters of the genusPanulirusare economically important and support local fishing communities. However, mud spiny lobsterPanulirus polyphagusis among the least known species within this genus in terms of their biological information. This study relates to the size distribution, length-weight relationship, and size at morphometric maturity ofP. polyphagusin the Johor Strait. Within the year 2010, 300 specimens were collected off the coast of Johor Strait, Malaysia. There was no significant difference in body size (cephalothorax length, CL) and body weight (BW) between sexes. CL and BW were highly correlated and males ofP. polyphagusdisplayed positive growth allometry, whereas the opposite was observed in females. Based on the merus (ML) and carpus length (CPL) of the third right walking leg, the piecewise linear regression analysis estimated that the size at maturity for male was 6.58 cm CL (based on ML) and 7.58 cm CL (based on CPL), whereas it was 8.18 cm CL (based on ML) and 6.75 cm (based on CPL) for females. Two discriminant functions of high classification and revalidation rates (> 98.6% in males and > 98.7% in females) that can discern maturation status in males and females ofP. polyphaguswere derived using the discriminant function analysis. Biological information derived from this study serves as an essential baseline for future fishery management and conservation ofP. polyphagus.

Population and reproductive structure in the endangered and highly endemic freshwater crab Aegla concepcionensis (Decapoda:Pleocyemata:Aeglidae) from Chile

AbstractPopulation and reproductive information of highly endemic species allow us to understand their underlying conservation problems. Aegla concepcionensis is restricted to a small and intervened Chilean basin, and its conservation status has varied from extinct in nature to endangered. We characterized their life history measuring population, morphological and environmental variables during an annual cycle capturing individuals with a catch and release method based on electroshocking. Although the maximum water temperature was related to the recruitment, it can be physiologically risky for the remaining macroinvertebrate community. The relationship between abundance and narrow pH variations indicates a condition of unstable equilibrium given the environmental deterioration by deforestation. Sex ratio was predominantly male biased during copulatory activity, and sexually dimorphic body size distributions supported the hypothesis of greater natural selection in females and sexual selection in males. The period of ovigerous females was comparatively restricted, late and consistent with an efficient ecophysiological strategy of reproductive investment. Patterns of pubertal moult, onset of morphometric maturity, absence of morphological differentiation in both sexes suggested that A. concepcionensis tends to maximize reproductive performance favouring the recovery of their relict populations.

Size distribution and sex ratio between populations of the artisanal harvested land crab Cardisoma guanhumi (Decapoda: Gecarcinidae), with the estimation of relative growth and size at sexual maturity in Puerto Rico

Introduction: Knowledge of growth patterns, sex ratio, and sexual maturity are of importance to exploited populations. The land crab Cardisoma guanhumi is an artisanal and subsistence exploited species in Puerto Rico. However, the growth patterns and sexual maturity of the local populations are not known. Objectives: This study has a double objective: (1) to compare the size and sex structure between populations and (2) to model the relative growth of structures related to reproduction to estimate the average size of morphometric sexual maturity (MSM) for both males and females. Methods: A total of 2 849 specimens were captured from nine dispersed populations on the island between 2001 and 2020. Carapace width (CW) was measured as an estimator of the absolute size of all individuals, together with the propodus length (PL) in males and the abdomen width in females (AW). Differences in length structure between sexes and populations were tested by applying goodness-of-fit tests based on Kernel Density Estimators (KDE). The relative growth pattern was modeled adjusting a spline from which the maximum of its second derivative was calculated as an estimator of the MSM, and bootstrapping was used to generate confidence intervals. Results: Differences were found in size structures, between sexes, and between sites. Our estimates of morphometric sexual maturity resulted in a sexual maturity size for males between 57.9 and 79.0 mm CW, while in females, morphological maturity occurs between 43.8 to 51.5 mm CW. Conclusions: We found inter-population differences in body size that can be attributed to differences in the history of changes of land use and the exploitation biased towards larger individuals, though differences in recruitment should also be considered. Current regulations in Puerto Rico protect female crabs but not to larger male crabs. The regulation establishes that crabs smaller than 64 mm carapace width cannot be captured, leaving immature male crabs over 64 mm CW unprotected. We suggest considering different size limits depending on the sex of the crab. This will allow the full range of sizes where sexual maturity is reached to be protected, increasing the likelihood of the population’s size to increase.

Application of the morphometric maturity coefficient to determine terminal molt in the crab Chionoecetes angulatus from the Okhotsk Sea

Results of studies on the relationship between the claw morphometric parameters and the carapace width (CW) of the triangle crab (Chionoecetes angulatus) crab from the Sea of Okhotsk presented. For the operational screening and separation of males into morphometrically mature (ММ – large-clawed) and immature (MI – small-clawed) species, it is proposed to use the coefficient of morphometric maturity (K%). This coefficient can be defined as the ratio of claw height to carapace width (KH%) or as the ratio of claw diagonal to carapace width (KD%), expressed as a percentage. When assessing the coefficient of morphometric maturity (K%), the boundary value for KH% is 16, and for KD% it is 35, which allows reliable identification of large-clawed (MM) males at K% values above the boundary values, and small-clawed (MI) males at K% values below the boundary values. Four functional groups were distinguished in males of C. angulatus: 1) MI physiologically immature — CW ≤90 mm, KH% <13.5, and KD% ≤29; 2) MI physiologically mature — CW 90.1–120 mm, KH% 12–16 and KD% 25–35; 3) MI large-sized physiologically sexually mature — CW >120 mm, KH% 13–16 and KD% 29–35; 4) MM morphometrically and functionally mature — CW 74–167 mm, KH% >16 and KD% >35. The correlation of the onset of morphometric maturity with biochemical parameters of hemolymph and with the development of muscle tissue is discussed. For various functional groups of males C. angulatus, an abundance estimate was implemented taking into account the K% coefficient.

Heteroquely, laterality, maturity body size and shape variation of males and females of the endemic South American anomuran Aegla quilombola Moraes, Tavares & Bueno, 2017

ABSTRACT Aegla quilombola is an anomuran crab endemic to São Paulo State, Brazil. The present manuscript aims to provide information about sexual dimorphism using geometric morphometrics, as well as information about heterochely, laterality and sexual maturity. The specimens were sampled in Intervales State Park. The carapace and chelipeds of all animals were photographed and landmarks digitalized. In the analyses, the propodus of the first pair of pereopods (chelipeds) were used. The same structures were measured for morphometric sexual maturity, analysing the relationships between carapace length (CL) x propodus height for males, and CL x abdomen length (ABL) for females. For heterochely and laterality, the height of male and female chelipeds were evaluated. Morphological differences were found in the shape of the posterior margin of the carapace and in the chelipeds’ palmar region. Males reached morphometric maturity at smaller sizes and showed heterochely and laterality, usually having a larger left cheliped. These differences are probably related to differential energy use by males and females in fulfiling specific ecological roles. Females had larger abdominal margins to invest in reproduction and males invested energy in chelipeds that were more robust and larger than females, as chelipeds are often used in agonistic interactions and to obtain better resources.

Size-at-maturity of Brown Crab (Cancer pagurus) in Scottish waters based on gonadal and morphometric traits

Minimum landing sizes (MLS) are commonly used to manage crustaceans and are generally set above the size at first maturity to ensure that some protection is afforded to exploited stocks. Despite the economic importance of the brown crab fishery in Scotland, the species is considered data-poor and only limited information is available on size-at-maturity. This study provides, for the first time, estimates of the size-at-maturity of brown crab on the east and west coasts of Scotland using gonadal and morphometric criteria. Gonadal maturity was determined from female ovary and male testes, which were classified macroscopically into development stages and their relationship with body size modelled using a logistic regression. Body morphometric maturity was studied by analysing morphometric changes in growth in the male chelae and female abdomens using generalized additive models and regression models to estimate the size at which changes in allometric relationships occur. Estimates of size-at-maturity using gonad development were 101-106 mm carapace width (CW) for males and 127-128 mm for females. Size-at-maturity based on the morphometric characters were 120-148 mm CW for males and 131-142 mm for females. Results show that brown crab maturity is likely to occur at lower sizes than the current MLS in Scotland, implying that crabs may be able to reproduce at least once before being harvested. Regional variations in local populations should be considered when setting a MLS and this study suggests that the current MLS of 150 mm is appropriate for both areas considered.

Growth and longevity of the spider crab Libinia ferreirae (Majoidea, Epialtidae)

Abstract We estimated the growth parameters of the spider crab, Libinia ferreirae (age, asymptotic size and growth rate) using the von Bertalanffy growth equation model. We obtained nine cohorts for female carapace asymptotic width (CW∞) = 64.32 mm, growth coefficient (day-1) (k) = 0.0027 e t0= 0.77 days) and seven for males (CW∞ = 81.93 mm, k= 0.0021 e t0= 0.49 days). The longevity for males was higher than that for females, estimated 2,156 days (5.91 years) and 1,706 days (4.68 years), respectively. The growth curves for males and females differed (F = 34.67 e p < 0.001). Males reached gonadal maturity before morphometric maturity and occurred at 8.8 and 16.6 months of life, respectively. Females reach gonad and morphometric maturity synchronously and this was estimated to occur at about 11.42 months of life. These crabs invest a great amount of energy in growth during a brief period of their development until reaching the terminal moult. This growth strategy would bring less wear to the organism and consequently a greater longevity.

A simple method for classifying data in relative growth analysis of crustaceans

Abstract Relative growth in crustaceans is a topic of quite high importance that allows, among other things, to estimate their size at the onset of morphometric sexual maturity. In this process, it is usual to start from a transition point and then generate regressions that reflect phases of the sexual development of the individuals (i.e., mature and immature). There are several statistical methods that allow data to be classified into subsets, but according to the specific growth pattern at issue, those methods may or may not be usable. This paper proposes a simple method to classify data into two subsets, viz., when they are overlapping over a wide range of sizes. The actual procedure consists of a linear regression that divides the data. Subsequently, a linear regression is applied to the groups generated by adjusting the parameters through maximum log-likelihood. The observed values will be classified according to the smallest residual difference generated with each regression line. The proposed method was tested by separating the sexes of Goyazana castelnaui, using real data. The efficiency of the method was analysed based on the percentage value between the number of total data and the number of correctly classified data. Additionally, the k-mean cluster was used as a conventional method, the results of which were reclassified by a linear discriminant analysis. The efficiency of the proposed method was &gt;80% while that of the conventional method was &gt;60%. The values misclassified by the proposed method were mixed with those of the opposite sex, so it was expected to fail in those cases. The proposed method is a simple alternative that can serve as a basis for subsequent morphometric analysis, especially for acquiring an initial insight in the structure of a dataset collected for a study of relative growth.

Allometric growth, sexual maturity, and life cycle of Aegla lata (Decapoda, Anomura), a critically endangered species

AbstractAegla lata Bond-Buckup &amp; Buckup, 1994 is a critically endangered species, extinct in its type-locality. Its currently known geographical distribution is restricted to small streams of the lower Tibagi River Basin (Paraná state, southern Brazil), where it is vulnerable to the environmental degradation that takes place in these watersheds. Scientific knowledge on the species is limited to the original description and a few occurrence records. No information about its biology is available. Aiming to fill this gap, we investigated the relative growth, sexual maturity, sexual dimorphism, and the reproductive and recruitment periods of A. lata. Monthly sampling occurred from May 2014 through June 2015 in the Bule stream in the southern limit of Mata dos Godoy State Park, Londrina, Paraná state, Brazil (23°27ʹ20.86″S, 51°16ʹ32.44″W). The analysis of allometric growth was used to differentiate juveniles and adults. According to the development stage of the chelae, two sequential groups of adult males were recognized (morphotypes I and II). The estimated average cephalothorax length (CL) at the onset of morphometric maturity of males and females are similar, suggesting puberty molt takes place at nearly the same size in both sexes. Males and females are heterochelous, with a clear predominance of the left chela as the most developed of the pair. Both chelae are larger in adult males than in adult females of similar CL. The reproductive period is markedly seasonal, extending from the austral autumn to winter (May to August), as well as those recorded in other species of Aegla from similar latitudes. A single annual recruitment pulse was detected from October 2014 to February 2015.

Reproductive biology of the freshwater crab Goyazana castelnaui (Brachyura: Trichodactylidae) in a semiarid region of Brazil

ABSTRACTThe reproductive pattern of Goyazana castelnaui is described based on the variation of gonadal maturation stages and secondary sexual characteristics. We analyzed 89 specimens from the Pajeú River in the semiarid region of Brazil from September 2014 to August 2015. The average sex ratio was 1F: 0.5M. The carapace width (CW) and weight of females ranged from 1.18 to 4.97 cm and 1.76 to 37.46 g. Male carapace width and weight were between 1.05 and 4.34 cm and 1.11 to 39.71 g. Goyazana castelnaui had a seasonal reproductive cycle that was more active between September and December. Gonad maturation was before the pubertal moult. The spawning season began in August when temperature increased, and ended in February. The onset of the rainy season (November) is thought to be the trigger for a decline in spawning. The gonads of females and males became mature at the same CW50 (2.84 cm). This size is smaller than the morphometric maturation size: 3.85 cm CW in females and 3.65 cm CW in males. This first contribution to the reproductive biology of G. castelnaui should be a basis for further research on its reproduction, especially in other areas of its distribution.Abbreviations: AM: adult male; AF: adult female; °C: Celsius degree; cm: centimeters; Cw: carapace width; CNPq: Brazilian National Council for Scientific and Technological Development; F: female; FC: folicular cells; g: grams; h: hour; INPE: National Institute of Space Research; JF: juvenile female; JM: juvenile male; M: male; MO: mature oocytes; mm: millimeters; µm: micrometer; OO: oogonia; PCA: Principal Component Analysis; PE: Pernambuco; PRPPG: Pro-Rectory of Research and Post-Graduate; PSW: pleon segment width; PVO: pre-vitellogenic oocytes; PVD: posterior vas deferens; RCL: right chela length; RC: ruptured cells; SM: spermatophoric matrix; SP: Spermatophores S: south; Tw: Total weight; UFRPE: Federal Rural University of Pernambuco; VO: vitelogenic oocytes; W: west;

New estimates of weight-at-size, maturity-at-size, fecundity, and biomass of snow crab, Chionoecetes opilio, in the Arctic Ocean off Alaska

Snow crab (Chionoecetes opilio) were identified as a potential future target fishery species in federal waters of the Arctic Ocean off Alaska by the Arctic Fishery Management Plan (Arctic FMP) in 2009, but this plan currently prohibits commercial harvest until sufficient information is available to assess a sustainable commercial fishery. One drawback of the current Arctic FMP is that critical population and biomass estimates were based on limited data. Collaborative research efforts in the Chukchi and Beaufort seas over the past decade have yielded a much richer database on snow crab in the Arctic. Using these data, we generated new estimates of weight-at-size, maturity-at-size, fecundity, and biomass to recalculate sustainable yield of snow crab in the U.S. Arctic. Weight-at-size was generally similar for male and female snow crab between the Chukchi and Beaufort seas, with males reaching overall larger sizes than females in both seas and largest male crabs occurring in the Beaufort Sea. Compared with snow crab in other geographic regions, 50% morphometric maturity was reached at a slightly smaller size in the Chukchi Sea; low sample sizes in the Beaufort Sea prevented maturity-at-size analysis. Fecundity-at-size in the Chukchi Sea was similar to known values estimated for snow crab in other regions. Estimated total reproductive output, using fecundity estimates obtained here, suggest that local reproduction may be sufficient to account for a large portion of observed small juvenile benthic snow crab abundances; further investigation is warranted to determine whether Chukchi and Beaufort populations are self-sustaining at this time. Although snow crab had high abundances in the Chukchi Sea, harvestable biomass of male snow crab only occurred in the Beaufort Sea because crab larger than the minimum marketable size (≥ 100 mm carapace width, based on Bering Sea metric) were absent in the Chukchi Sea over the study period. Our biomass estimates in the Chukchi Sea were substantially higher than previous estimates, owing at least in part to high abundances of small crab that were greatly under-sampled with the large-mesh gear such as was used in surveys referenced in the Arctic FMP. Estimates of biomass and sustainable yield for the Beaufort Sea were over twice as high as previous estimates in the Arctic FMP, but harvestable biomass was largely limited to the slope (> 200 m depth) and is unlikely to support commercial harvest. Our results expand overall understanding of arctic snow crab dynamics in light of potential future fisheries or other, non-fishing activities and inform the management of the Alaskan Arctic stock.

Reproductive biology of the ghost crab, Ocypode rotundata Miers, 1882 (Decapoda, Ocypodidae) at Qeshm Island, Persian Gulf

AbstractThis study aimed to investigate some key aspects of the reproductive strategy ofOcypode rotundataMiers, 1882 from southwest beaches of Qeshm Island, Persian Gulf, Iran, by providing information regarding its sex ratio, sexual maturity, spawning period and fecundity. Samples were taken monthly, from February 2015 to January 2016. Size at the onset of morphometric maturity was estimated at 38.57 mm carapace width. The overall sex ratio (males/females) was observed as 1.13 : 1.00. On monthly based analyses, the sex ratio showed no significant differences, although a significant deviation was observed toward males in the larger size classes. According to the gonadosomatic index (GSI), gonad maturity and occurrence of ovigerous females, the main breeding season occurs from March to October, with a remarkable peak in June. Fecundity ranged from 24 152 to 10 5287 eggs per individual, with a mean value of 52 389 ± 25 660. The ratio between fecundity and carapace width varied from 632 to 2044 eggs/mm (mean: 1198 ± 472 eggs/mm) and fecundity relative to total mass varied from 771 to 1965 eggs/g (mean: 1336.66 ± 425.43 eggs/g). The reproductive output ranged from 1.04 to 3.78 (mean: 2.35 ± 0.90). The shape of the egg was spherical and it included 6 stages of growth, ranging from fully filled with yolk to fully occupied by the embryo. We concluded that reproduction inO. rotundatais seasonal, and that spawning occurs in an appropriate period to ensure maximum survival of the offspring. The fecundity ofO. rotundatais higher than that of other species of Brachyura, with GSI variations being related to temperature. Overall, the results of this study provide relevant information for the reproduction in general and the breeding seasons ofO. rotundata, whicht can be useful for conservation and management policies aimed at preserving the biodiversity of ghost crabs along the Persian Gulf’s sandy shores.

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.

Life history traits and patterns of sexual dimorphism in the freshwater crab Potamon ibericum (Bieberstein, 1809) (Decapoda: Brachyura: Potamidae) from the western Alborz Mountains, Iran

The assessment of life history traits can help to better understand the population dynamics of the respective species. We present some life history traits of the freshwater crab Potamon ibericum (Bieberstein, 1809) from the western Alborz Mountains, Iran. Carapace size at the onset of morphometric maturity was estimated using the breakpoint of the relative growth of the chela and abdomen in males and females, respectively, by implementing piecewise linear regressions. In order to quantify variations in the estimated breakpoint, a bootstrap resampling method was applied. Allometric trajectories of chelar dimensions were also applied to juveniles and adults. Sexual size dimorphism was evaluated using the dimensions of the carapace and chelae, and patterns of the carapace shape dimorphism were investigated by implementing geometric morphometric analysis. The results showed that females reach morphometric maturity at smaller sizes than males, which could be of advantage in the fluctuating environment of their freshwater habitat in order to mate as soon as possible and increase fecundity. Positive allometric trends in the length of the major chela was observed in adults of both sexes, and the possible adaptive forces on the evolution of this pattern are discussed. Results of sexual dimorphism analyses confirmed male-biased sexual size dimorphism and functional adaptation of carapace shape in both sexes.

A Preliminary Assessment on the Herpetofaunal Diversity of the Taal Volcano Protected Landscape (TVPL), Batangas Philippines

The Taal Volcano Protected Landscape (TVPL) encompasses a prehistoric volcano caldera that caters to many documented endemic species. Although regarded as a unique area with the potential to house a diverse ecological community, biodiversity research in TVPL is still found wanting. The present paper aims to provide baseline information and increase research interests on the herpetofaunal diversity of TVPL, in light of its many undocumented terrestrial faunal species. Twelve study sites within the municipalities of Tanauan, Mataasnakahoy, and Balete were visited during survey trips from May to November 2015. A combination of transect and opportunistic sampling techniques were utilized, with morphometric data and sexual maturity recorded for each specimen collected. This preliminary survey provided 24 newly documented species of amphibians and reptiles occurring within TVPL. A total 10 frog species (from families Bufonidae, Ceratobatrachidae, Microhylidae, Dicroglossidae, Ranidae, and Rhacophoridae) and 14 reptile species (from families Agamidae, Gekkonidae, Scincidae, Varanidae, Acrochordidae, Colubridae, Elapidae, and Tryonychidae) were documented. Of the reptiles recorded, 3 are endemic species and widespread throughout the Philippines: Gekko mindorensis, Hydrosaurus pustulatus, and Draco spilopterus. Also recorded were the Philippine endemic frogs Kaloula picta and Limnonectes woodworthi along with the Luzon endemics Platymantis mimulus and Varanus marmoratus. The species-effort curve of amphibians showed a distinct plateau whereas the species-effort curve of reptiles has shown an increasing trend suggesting that additional sampling efforts should be done in the area to further increase knowledge of the TVPL herpetofaunal diversity.

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

ABSTRACTThe 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.