Macroscopic Maturity Research Articles

Reproductive Dynamics of Spot Tail Mantis Shrimp (Squilla mantis): Insights from the Central Mediterranean Sea.

Fisheries management requires improvement in scientific knowledge to ensure sustainable exploitation of important commercial species and population renewal. Within this context, this study focused on the reproductive biology of spot tail mantis shrimp, Squilla mantis, in the Central Mediterranean Sea, aiming to understand the reproductive pattern of this species and validate the macroscopic maturity scale through histological analysis. A multi-year sampling was performed from 2016 to 2020 by a commercial fishing fleet in the Northern Central Adriatic Sea (GSA 17), and a total of 2206 individuals were collected. The monthly average value of the total sex ratio of S. mantis was 0.524 ± 0.044 (mean ± SEM) in favor of females, which dominated the population from September to April. The proposed 5 stage macroscopic maturity scale was validated histologically through histological analysis, confirming synchronous ovarian development. The somatic indexes (GSI and K Fulton) and monthly incidence of macroscopic ovarian maturity stages highlighted a protracted reproductive season from winter to spring (January-May). Although the length-weight relationship showed a similar growth trend between genders, males reached a bigger size in terms of carapace length (C.L.) and dominated the population from 32 mm (C.L.). The macroscopic L50 estimated was 25.94 mm (C.L.).

Macro and microscopic maturation stage key of green crab (Carcinus maenas, Linnaeus 1758): Reproductive cycle and differences among estuarine systems

Gonadal histology is a helpful tool to validate species' macroscopic maturity stages in fisheries biology. Regardless of the many studies on Carcinus maenas, there are still few concerning gonads tissue histology and description of maturity stages. In Portugal, information regarding this species' biology to help support the regulation of crab fisheries, including the minimum landing size, has not yet been defined. In this work, the macro and microscopic characteristics of the reproductive cycle of C. maenas, oogenesis, and spermatogenesis development stages along the Portuguese coast are described, and a new macroscopic scale based on the histological analyses is suggested. During 2019 and 2020, adult C. maenas (both males and females) were collected from the Ria de Aveiro estuary, Rio Sado estuary, and Ria Formosa lagoon, respectively, North, Center, and South Portugal. No-significant differences (P > 0.05) were observed in carapace width and individual weight between all systems. Significant differences (P < 0.05) were observed in gonad weight, gonadosomatic index, and Fulton's condition index between the Rio Sado estuary and Ria Formosa lagoon. Furthermore, significant differences (P < 0.05) in the oocyte diameter between the northern and southernmost locations suggest a geographic variation related to the local environmental conditions of each system. Principal component analysis (PCA) revealed maturity stage and carapace width an association, and a similar morphometry between Ria de Aveiro and Ria Formosa. Temperature was correlated to both maturity stage and carapace width in Ria de Aveiro and Ria Formosa. From the histological analysis and based on microscopic criteria, it was observed that females previously classified within the late macroscopic development stage 2 should be considered mature, so a classification change in the current ovary's developmental stage is proposed. These findings can allow fisheries researchers to reclassify the estimations of maturity ogives and help support the regulation of this species' fishery. The proposed macroscopic scale was validated by histological analyses and can be used elsewhere.

Blondes do it better? A comparative study on the morphometry and life-history traits of commercially important skates blonde ray Raja brachyura, thornback ray Raja clavata, and spotted ray Raja montagui, with management implications

Due to data limitation and challenges with species-specific reporting, the management of European skate fisheries currently lacks measures tailored to individual species. Given these caveats, detailed information about skate stocks at the species level is warranted. The morphometry and life-history parameters were determined for samples of 170 individuals (58 Raja brachyura, 92 R. clavata, 20 R. montagui) collected by observers in commercial fisheries, and two bottom trawl surveys (December 2020 – August 2021) in the Southern North Sea and Eastern English Channel. A combination of three morphometric measurements were considered and proven successful (3.846% misclassification, N = 78) in species discrimination for easily confusable species R. brachyura and R. montagui. Through the application of these morphometric descriptors in electronic catch monitoring via Artificial Intelligence (AI), the misidentification of easily confusable species may be reduced in future catch reporting from surveys, fisheries-dependent data, and market sampling. Additionally, the morphometric differences between species may have implications for species’ catchability, and gear modification to avoid bycatch of skates under the European Landing Obligation (LO). The length-weight relationships indicated a faster rate of increase in body mass per unit of size for R. montagui. Life-history trait parameter estimates were obtained for R. clavata and R. brachyura. Age was determined through digital processing of images from visually enhanced whole vertebral centra (0.01% crystal violet staining). Age reading precision was low (CV > 45%, PA < 60%). The von Bertalanffy and logistic growth models provided more accurate fits for the length-at-age data than the Gompertz model. Macroscopic maturity assessment revealed that male R. montagui matured at the smallest size (Lm = 57.5 cm), while female R. brachyura matured at the largest size (Lm = 87.6 cm). Maturity ogives were fitted for males (L50 = 65.4 cm) and females (L50 = 84.1) of R. clavata and females of R. brachyura (L50 = 82.7 cm), with statistically significant intersexual differences for R. clavata. The Legal Minimum Landing Size (LMLS) measures of smaller sizes may not offer adequate protection (to immature specimens) of the skate species in the present study, that mature at larger sizes. The life-history trait parameters for growth and maturity are discussed in relation to published results of earlier studies, and no major changes in the life-history parameter traits were observed in recent years. The interspecific differences in the morphometries and life-history traits of R. brachyura, R. clavata, and R. montagui highlight the need for species-specific data collection and management considerations of skate stocks in the Northeast Atlantic Region at the local and EU level.

New insights upon the reproductive biology of the sea cucumber Holothuria tubulosa (Echinodermata, Holothuroidea) in the Mediterranean: Implications for management and domestication

Holothuria tubulosa is one of the most common sea cucumber species inhabiting the Mediterranean Sea. Due to its commercial interest for the international market, it has been harvested without proper management causing the overexploitation of its stocks. Inadequate management is also caused by lack of information on basic biology and ecology not allowing the estimating of the species vulnerability and resilience to growing anthropogenic pressures. In this paper, we have investigated basic life-history traits of H. tubulosa (population structure and reproductive cycle) in a population of Central-Western Mediterranean (Sardinia, Italy). A macroscopic maturity scale for both sexes was defined through an instrumental colorimetric analysis of the gonads and the ramification level of the gonad’s tubules, subsequently confirmed by histological analysis. The seasonal trend of the Gonado-Somatic Index, the changes in color of the gonads and tubules ramification indicated that the spawning period of H. tubulosa was concentrated in summer with a peak in late August, closely related to the increase in water temperature. A synchronous development of the gonads, with a unique and short reproductive event during the year, was also detected. In conclusion, this study provides new evidence on the biological and ecological features of H. tubulosa, essential data for developing a scientifically-based stock assessment as well as conservative management at a local scale. Finally, we provided basic information for the domestication of broodstock in a conservative hatchery.

Observations of sperm storage in some deep-sea elasmobranchs

The presence of sperm storage was evaluated in several deep-sea elasmobranchs (Centrophorus squamosus, Centroselachus crepidater, Deania calcea, Brochiraja spinifera, Brochiraja asperula, Apristurus ampliceps, A. exsanguis, A. garricki and A. sinensis), all considered at risk to the impacts of fishing in New Zealand. Biological measurements of reproductive organs (e.g. follicle size and number, oviducal gland size, uterus width and gonad weight) were recorded in addition to conventional macroscopic maturity assessment measures. Histology was conducted on a sample of oviducal glands to investigate the occurrence of sperm storage. Sperm storage was confirmed in three of the nine species: Centroselachus crepidater, Centrophorus squamosus and Brochiraja asperula. To the best of our knowledge, these are the first observations of sperm storage for these genera, and the first in the family Centrophoridae. Sperm storage was observed in macroscopically mature females and also in some females considered macroscopically as maturing. The female reproductive tract may regress substantially between reproductive events to the extent that a mature fish is mis-classified as maturing, and would be consistent with long periods of resting between reproductive events. Alternatively, it is equally possible that aggrieve male mating behaviour results in premature copulation of maturing females. We summarise published occurrences of sperm storage in chondrichthyans, and conclude that sperm storage is most likely ubiquitous in chondrichthyans, and an adaptive benefit to traumatic mating behaviour, that may also be adaptive to low fish densities in the relatively unproductive environment of the deep-sea.

Reproductive traits and natural mortality of the cardinalfish Epigonus crassicaudus: crucial information for stock assessment and sustainable management measures

Reproductive traits and natural mortality rate of cardinalfish females (Epigonus crassicaudus) were studied from samples collected onboard commercial fishing vessels, from 2012 to 2015, on the Chilean coast. The reproductive cycles of females analyzed thought gonadosomatic index (GSI) showed a maximum reproductive activity in austral fall, between March and May. Length (L50%) and age (A50%) at maturity, estimated using a macroscopic scale of the developed ovary, was 22.3 cm fork length (FL) and 9.3 years, respectively. Natural mortality (M) was estimated by two age-related methods. Using maximum age (tmax) M was estimated in 0.063 yr-1 and through age-at-maturity (A50%) in 0.15 yr-1. A potential bias in the reproductive study is discussed when a macroscopic maturity scale is used. Nevertheless, its usefulness is validated when funding is scarce, and time is limited. Although M uncertainty was not evaluated, the estimated range appears to be into the expected values to long-lived species. The life history parameters estimated in the present study can be used to evaluate possible time variability in maturity and M rates. Also, these results could be used in stock assessment analysis and to apply effective management measures in the fishery.

The MEDITS maturity scales as a useful tool for investigating the reproductive traits of key species in the Mediterranean Sea

Maturity is one of the most important biological parameters used in stock assessment programmes. Indeed, the macroscopic stage of gonadal development is an essential feature in estimating the maturity ogive and spawning stock biomass. It is also useful for determining the spawning season of a species and for monitoring long-term changes in the spawning cycle as well as for many other research needs related to the biology of fish. Despite the efforts made during the last few decades to standardize maturity stage data among all the researchers, marine biologists continue without a manageable and unique maturity scale to describe the reproductive development of fish gonads. For these reasons, the objectives of this article are 1) to investigate the biological parameters of five selected key species (Mullus barbatus, Galeus melastomus, Etmopterus spinax, Aristeus antennatus, Loligo vulgaris) with different reproductive strategies following the macroscopic maturity scales based on the same univocal criteria adopted in the MEDITS programme and described in this work; and 2) to compare them among some Mediterranean geographical sub-areas (GSAs) involved in the programme. Neither spawning periods nor size at first maturity (SFM50) for the studied species showed particular differences in the investigated GSAs.

The Reproductive Biology of Female Atlantic Herring in U.S. Waters: Validating Classification Schemes for Assessing the Importance of Spring and Skipped Spawning

AbstractAtlantic Herring Clupea harengus are iteroparous (repeat spawners) with group‐synchronous oocyte development and determinate fecundity, and they are total spawners. However, they also exhibit plasticity in other aspects of their reproductive biology including spawning seasonality and skipped spawning. Previous studies in other regions have reported skipped spawning and errors in macroscopic classifications of maturity, both of which could bias estimates of reproductive potential, but a critical assessment of these in U.S. waters is lacking. In the Gulf of Maine and Georges Bank, herring are assessed as a single stock complex, where females typically mature as 3 to 4 year olds and may live up to 11 years. To evaluate the magnitude of skipped spawning, we collected the ovaries of Atlantic Herring from fishery‐dependent and fishery‐independent sources over multiple seasons and evaluated them histologically to assess imminent (indicated by vitellogenic or maturing oocytes) or recent spawning (evidenced by the presence of postovulatory follicles). Gonad histology allowed us to determine spawning seasonality and skipped spawning. Macroscopic maturity classification was more accurate in fall (1–4% incorrect maturity) than in spring (7% incorrect maturity). The spatial distributions of immature and mature fish from both fishery‐dependent and fishery‐independent sources differed, which affected the estimation of maturity at length and age. We estimated 9–14% spring spawners in the region, but we did not find evidence of skipped spawning. The time series of the macroscopic data that were available (1987–2018) showed increases in spring spawning with latitude, but the proportions have not changed much over recent decades. The effects of up to 30% spring or skipped spawning on a stock assessment of Atlantic Herring were evaluated. Spring spawning had little effect relative to assuming 100% fall spawning (the current assumption), and skipped spawning decreased the scale of spawning stock biomass (SSB) and related reference points, with the degree of change increasing with skipped spawning rates, but it had few consequences otherwise.

Reproductive effort in Chaenocephalus aceratus validated by gonadal histology: inshore sites serve as spawning grounds for some notothenioids

The knowledge of the reproductive biology of blackfin icefish Chaenocephalus aceratus in the southern Scotia Arc has been based, primarily on macroscopic observations of its maturation cycle, and lately, on histological analysis of ovaries in developing phase exclusively. Our study on reproduction of C. aceratus collected at Potter Cove (PC), South Shetland Islands (SSI), highlights the importance of histologic techniques to validate gonadal macroscopic maturity stages to estimate reliable reproductive parameters, in this work obtained from gravid females. Gonado-somatic index (GSI) of 7–21% (13.50 ± 4.20, n = 21), mature oocytes of 2.5–4.0 mm and total fecundity (TF) of 7372–17,212 oocytes/female (12,466 ± 2911, n = 13) were estimated. Although it is known that variations in the reproductive parameters of C. aceratus between areas of the Scotia Arc are linked to local environmental factors (i.e. hydrographic or biotic), we found close agreement between our results from PC and recent literature data for the South Georgia population, which also arose from the analysis of gravid females. Differently, lower GSIs and oocyte sizes, and higher TF reported lately for the offshore SSI population might be at least partially explained by the fact that these parameters were estimated from the analysis of developing ovaries. Based on our sampling and reproductive effort data, we suggest: (1) the spawning period of C. aceratus at the SSI might be more extended than previous belief, starting from late December until June; (2) the sheltered waters of PC might be a spawning site for C. aceratus, which highlights the role of nearshore areas as spawning grounds of notothenioids.

Reproductive biology and population structure of white warehou Seriolella caerulea and silver warehou Seriolella punctata in the austral zone off Chile

Using an extensive database compiled by scientific observers aboard commercial fishing operations between 1984 and 2014, we describe the maturity and size structures of white warehou Seriolella caerulea and silver warehou Seriolella punctata from by-catch of the trawling industrial fisheries operating in the austral zone off Chile. Macroscopic maturity stages and gonadosomatic (IGS ) index show mature females throughout the year and a pronounced spawning period in both austral autumn and winter seasons, with an IGS peak in July for S. punctata and August for S. caerulea. Reproductive patterns in both species show an extended spawning season (July to September) across the area between 43 and 47° S. Length-mass relationships showed significant differences between sexes in both species, where females reach a larger size. Fork length at 50% maturity was 43.5 cm for S. caerulea and 37.2 cm for S. punctata. Female catch composition is dominated by adult fish (96% for S. caerulea and 86% for S. punctata). Currently, both species are exploited with no assessment and management-decision framework. Therefore, information regarding reproductive biology and demographic traits becomes an important baseline to ensure adequate fisheries management for both species.

The spawning strategy of European hake (Merluccius merluccius, L. 1758) across the Western and Central Mediterranean Sea

The oocyte maturation and spawning pattern of European hake Merluccius merluccius, one of the most important species in the Mediterranean fishery, were investigated using data collected in a scientific trawl survey (Mediterranean International Trawl Survey, MEDITS) as well as commercial landing data collected in several geographical sub-areas (GSAs): the Southern and Central Tyrrhenian Sea (GSA10), Sardinia (GSA11), the Southern Adriatic Sea (GSA18) and the Western Ionian Sea (GSA19). The lack of the validation of macroscopic maturity scales is one impediment to obtaining reliable estimates of the reproductive parameters used to assess a fish stock. The MEDITS maturity scale was validated for female European hake by histological analysis of the oocyte diameter frequency distributions and according to the gonadosomatic index. The oocyte diameter frequency distributions and histological analysis confirmed that the ovarian organisation of hake was asynchronous, including a batch spawning pattern and indeterminate fecundity.Females in spawning condition were recorded throughout the year in all GSAs although the main peaks of spawning activity were in winter and in late summer and early autumn. The L50 estimated for GSA10, GSA11, GSA18, GSA19 were 33.03 cm, 30.03 cm, 31.95 cm and 32.95 cm, respectively. Moreover, no significant trends in the annual estimate of L50 from 2007 to 2015 in any of the study areas were observed. Mean batch fecundity and relative fecundity (360,687 eggs/fish, 281.6 eggsg−1 in GSA10, 361,311 eggs/fish, and 262.2 eggs g−1 in GSA18) were higher than those reported in other Mediterranean areas.

Reproductive biology of Schizopygopsis younghusbandi Regan 1905 (Cyprinidae: Schizothoracinae) in the middle reaches of Yarlung Tsangpo River, China

The reproductive biology of Schizopygopsis younghusbandi (Cyprinidae: Schizothoracinae) was studied by 719 individuals that collected from August 2008 to August 2009 in the middle reaches of Yarlung Tsangpo River, China. We coupled monthly variations of the gonadosomatic index (GSI), monthly proportions of the macroscopic maturity stages with size distribution of oocytes to evaluate spawning seasons. Taken as a set, these results indicated that S. younghusband i spawned from March to April with high degree of the spawning synchronicity. The standard lengths and the ages at 50% maturity for male were 222 mm and 4.4 year, and 308 mm and 7.0 year for female. In addition, the estimated mean fecundity and mean relative fecundity were 18682 and 57.8 eggs per g body weight. The fecundity of S. younghusbandi increased linearly with increasing of standard length and body weight. This study provides details about the S. younghusbandi reproduction suggesting that may be this species is vulnerable to exploitation in the middle reaches of Yarlung Tsangpo River.

Assessing maturity, fecundity and hermaphroditism in blue cod Parapercis colias

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 26:137-148 (2017) - DOI: https://doi.org/10.3354/ab00679 Assessing maturity, fecundity and hermaphroditism in blue cod Parapercis colias K. K. Brandt1,3,*, M. R. Dunn1, S. L. Brouwer2 1School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand 2Oceanic Fisheries Programme, Pacific Community (SPC), BP D5, Noumea 98848, New Caledonia 3Present address: 100–104 Stoke Newington High Street, London N16 7NY, UK *Corresponding author: kasper.k.brandt@gmail.com ABSTRACT: Macroscopic assessments of maturity from whole fish gonads are well established and routinely used in fisheries research and are important in the estimation of size-at-maturity and the impacts of size-selective fishing. Histological assessment of maturity is more accurate, but much slower, more expensive, and so less frequently conducted. We made a comparison between macroscopic and histological maturity classifications for a diandric protogynous hermaphrodite, blue cod Parapercis colias. The agreement between macroscopic and histological maturity classifications was low. Female and male L50 (length at which 50% of the fish are mature) was estimated from histological data as 23 and 26 cm, respectively. Female spawning frequency was 4.6 d, and mean ± SD relative batch fecundity was 6.5 ± 3.3 hydrated oocytes per gram body weight. A single gonad with both testicular and ovarian tissue was found. Many blue cod were assigned incorrect maturity classifications. These results warrant a study of early gonadal development in blue cod to elucidate if and how sex change takes place. Difficulties in determination of sex and maturity may be most pronounced for species, like blue cod, that have complex maturation patterns. For blue cod, a review of the macroscopic maturity classification key and more thorough technician training are called for. KEY WORDS: Maturity assessment · Length at maturity · Fecundity · Parapercis colias · Sex change · Histology Full text in pdf format PreviousNextCite this article as: Brandt KK, Dunn MR, Brouwer SL (2017) Assessing maturity, fecundity and hermaphroditism in blue cod Parapercis colias. Aquat Biol 26:137-148. https://doi.org/10.3354/ab00679 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 26. Online publication date: September 05, 2017 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2017 Inter-Research.

Oviducal glands throughout the gonad development stages: a case study of Octopus mimus (Cephalopoda)

ABSTRACTThe oviducal glands (ODG) play a crucial role in octopus reproduction. Herein, structural changes of each section of the ODG of Octopus mimus are described histologically throughout the gonad development stages (GDS). To do this, the epithelial height, stereociliated or non-stereociliated epithelium, nucleus type (pycnotic or non-pycnotic), epithelial secretions and the value range of the macroscopic maturity index (MaMI), which directly involves ODG status, were measured. The ODG are internally constituted of two glandular units (central and peripheral glands) and one set of receptacles (the spermathecae). High epithelia (40 to 80 μm) were observed in both gland units during periods with low MaMI values (< 0.1) corresponding to III-mature and IV-pre-spawning. The stereociliated epithelium was only apparent in II-maturing and III-mature in both gland units. The nuclei were noticeably pycnotic in the central gland during III-mature, IV-pre-spawning and V-spawning, but pycnotic in the peripheral gland only during VI-depletion. The epithelium was disorganised during VI-depletion, while sulphated acid mucin was only present during III-mature in the central gland. The epithelium transformations during the GDS are related to the functions of the gland units and to their multiple secretions. The ODG histology complements the GDS and provides better reproductive status assessment.

Reproductive biology of bream Abramis brama (L.) in the lower reaches of the Irtysh River, China

The reproductive biology of bream Abramis brama (L.) was studied from 546 fish collected from the lower reaches of the Irtysh River in Xinjiang, north-west China, from March to November 2013. The overall sex ratio (M/F) was 1.06:1, and was not significantly different from the theoretical 1:1 ratio (P>0.5). However, there was a dominance of males during the pre-spawning season (1.33 in March and 1.56 in April, P<0.5), while females were dominant during the peak spawning season (0.88 in June, P<0.5). The monthly variation in gonadosomatic index (GSI) and proportion of gonads at each macroscopic maturity stage, indicated that A. brama spawned once a year with peak spawning occurring from late May to June. The unimodal distribution of oocyte diameter each month indicated that A. brama is a single spawner, with a high degree of spawning synchronicity. The standard lengths (SL50) and ages (A50) at first maturity for males and females, were 178 and 204 mm, and 5.6 and 6.8 years, respectively. The mean absolute fecundity (AF) was 77 311 eggs per fish, and mean relative fecundity (RF) was 162 eggs per gram of body weight (BW). The AF of A. brama increased linearly with increasing of gonad weight (GW), eviscerated weight (EW) and standard length (SL), but was not significantly correlated with age. As, A. brama in the lower reaches of the Irtysh River reaches reproductive maturity relatively late in their life span, is mature for a short period and spawns in aggregations, this fish is vulnerable to overexploitation.

Folding, But Not Surface Area Expansion, Is Associated with Cellular Morphological Maturation in the Fetal Cerebral Cortex

Altered macroscopic anatomical characteristics of the cerebral cortex have been identified in individuals affected by various neurodevelopmental disorders. However, the cellular developmental mechanisms that give rise to these abnormalities are not understood. Previously, advances in image reconstruction of diffusion magnetic resonance imaging (MRI) have made possible high-resolution in utero measurements of water diffusion anisotropy in the fetal brain. Here, diffusion anisotropy within the developing fetal cerebral cortex is longitudinally characterized in the rhesus macaque, focusing on gestation day (G85) through G135 of the 165 d term. Additionally, for subsets of animals characterized at G90 and G135, immunohistochemical staining was performed, and 3D structure tensor analyses were used to identify the cellular processes that most closely parallel changes in water diffusion anisotropy with cerebral cortical maturation. Strong correlations were found between maturation of dendritic arbors on the cellular level and the loss of diffusion anisotropy with cortical development. In turn, diffusion anisotropy changes were strongly associated both regionally and temporally with cortical folding. Notably, the regional and temporal dependence of diffusion anisotropy and folding were distinct from the patterns observed for cerebral cortical surface area expansion. These findings strengthen the link proposed in previous studies between cellular-level changes in dendrite morphology and noninvasive diffusion MRI measurements of the developing cerebral cortex and support the possibility that, in gyroencephalic species, structural differentiation within the cortex is coupled to the formation of gyri and sulci.SIGNIFICANCE STATEMENT Abnormal brain morphology has been found in populations with neurodevelopmental disorders. However, the mechanisms linking cellular level and macroscopic maturation are poorly understood, even in normal brains. This study contributes new understanding to this subject using serial in utero MRI measurements of rhesus macaque fetuses, from which macroscopic and cellular information can be derived. We found that morphological differentiation of dendrites was strongly associated both regionally and temporally with folding of the cerebral cortex. Interestingly, parallel associations were not observed with cortical surface area expansion. These findings support the possibility that perturbed morphological differentiation of cells within the cortex may underlie abnormal macroscopic characteristics of individuals affected by neurodevelopmental disorders.

Reproductive traits of Octopus maya (Cephalopoda: Octopoda) with implications for fisheries management

ABSTRACTOctopus maya is the main species caught in Mexico. From September 2007 to June 2008, its sex ratio, reproductive season, frequency of non-vitellogenic and vitellogenic oocytes, reproductive indices, and size and weight at maturity, were evaluated. The monthly sex ratio was significantly different from 1:1. The major reproductive season occurs during February to June (dry season) in Yucatan. May−June is the common reproductive season to both Yucatán and Campeche populations. Higher frequencies of vitellogenic oocytes (> 50%) were found from January-March and in May. From five reproductive indices, only the macroscopic and microscopic maturity indices were the best descriptors of the reproductive season in females, whilst only the reproductive complex index was the best descriptor in males. The weight at sexual maturity (BW50%) was 335 g for females and 242 g for males. The size at sexual maturity (DML50%) was 12.58 cm for females and 7.42 cm for males. It is recommend revising the minimum catch size by following these results. The reproductive traits here evaluated could contribute to the recently created Plan for Management of Octopus Fisheries, in particular action line no. 1.4, which refers to protection of females during breeding, and to their protection throughout the entire reproductive season.

Reproductive tactics of male bearded goby (Sufflogobius bibarbatus) in anoxic and hypoxic waters

The bearded goby (Sufflogobius bibarbatus), a key species in the northern Benguela Upwelling Ecosystem, tolerates extremely low levels of oxygen. Yet little is known about how its reproduction is affected by these harsh living conditions. The distribution patterns of alternative reproductive tactics of male bearded goby across the continental shelf off Namibia were investigated. Histology and stereology were for the first time used to validate macroscopic maturity development by estimating volume fraction of the different stages of spermatogenesis using “Delesse principle”, an approach so far for teleosts barely used in studies on testes but applied in advanced oocyte estimation. The macroscopic scale appeared suitable for the purpose, and the prevalence of territorial and sneaker tactics could therefore be documented. The sneakers had relative large testes and small seminal vesicles (SV), with the opposite being the case for the territorials. A third, numerous category with intermediate sized testes and SV was also recognized with unclear underlying tactical rationale, although regression analyses indicated similar investment in testes weight in relation to somatic weight as for the territorials. Low oxygen levels were the most important factor limiting spawning activity in territorial males. Our data suggested the existence of a spawning site on the outer shelf of the central Namibian shelf where the bottom water is hypoxic (oxygen saturation of 6.2–6.7%) while the anoxic middle shelf area (oxygen saturation of 1.7–2.9%) appeared to show too low oxygen levels for spawning to take place. Hence, significant parts of this large shelf area appear unsuited for successful reproduction of the bearded goby, in particular for nest building by the territorials.

Decision tree analysis for the determination of relevant variables and quantifiable reference points to establish maturity stages in Enteroctopus megalocyathus and Illex argentinus

Abstract Determining the maturity condition of a large number of individuals is crucial for stock assessment and management of cephalopod populations, but this task is difficult to conduct in practice. We propose a novel approach for maturity stage classification using observer-independent criteria. Relevant morphological variables for classification are determined via decision tree (DT) analysis. Using Illex argentinus and Enteroctopus megalocyathus as case studies, individuals were sexed and assigned to a maturity stage defined by specific macroscopic maturity scales. Also, for each individual, the weight of the gonad, accessory glands/ducts, mantle length, and total weight were recorded and maturity indices were calculated (Hayashi index and gonadosomatic index). Two different DT models were fitted: one considering all maturity stages and the other considering only intermediate maturity stages since these are the most difficult to determine in practice. For the classification of I. argentinus among all stages, the weights of the nidamental gland and oviducts were the most relevant variables for females (misclassification 23%), while spermatophoric complex and testis weights were the key variables for males (misclassification 23%). For classification of intermediate stages only, the nidamental gland and spermatophoric complex weights were the most relevant variables to classify females (misclassification 19%) and males (misclassification 21%), respectively. For E. megalocyathus, the oviducts and ovary weights of females and the terminal organ weight of males were the most relevant variables for classification among all maturity stages (misclassification 16% and 18%, respectively). For intermediate maturity stages, the same variables were most important and misclassification improved to 13% for both sexes. Gonadosomatic and Hayashi's indices were not relevant in either model. DTs based on measurements of cephalopod reproductive systems revealed a simple classification system for maturity stages using only a few variables that are easy to measure in the field and are independent of observer training.

Contrasting macroscopic maturity staging with histological characteristics of the gonads in female Octopus vulgaris

We contrasted histological characteristics with a macroscopic maturity scale in Octopus vulgaris. Seven histological stages of maturation were identified, and a stereological method was used to develop a new histological maturity index (HMI). This index was related to the gonadosomatic index giving the possibility to estimate the histological stage of individual octopus without sampling the gonads. However, the existing macroscopic maturity scale produced some degree of overlap along the range of HMI, suggesting that this macroscale at this moment might be just good enough to separate immature from fully mature individuals. A histological maturity criterion based on the presence of a larger proportion of folding oocytes compared to earlier microstages resulted in a size at maturity of 1.5 kg. However, using two different macroscopic criteria, size at maturity was 1.3 and 2.3 kg. The estimate of size at maturity is therefore sensitive to the maturity criteria used. The maturation cycle of female O. vulgaris was seasonal, peaking in spring months and reaching a maximum of reproductive activity in April independently of the maturation criteria used. Oogenesis was reviewed and found to be an asynchronic process. Our results suggest that there is a need to examine all these issues in other cephalopod species.