Growth Increments In Statoliths Research Articles

Ommastrephes caroli (Cephalopoda: Ommastrephidae) from the Adriatic Sea: Morphometry, Age, and Genetic Characterization

This study gives the first data on the body and beak morphometric characteristics, age, and genetic structure of neon flying squid, a rarely caught cephalopod in the Adriatic Sea. We identified specimens as recently resurrected Ommastrephes caroli species using two mitochondrial markers, 16S ribosomal RNA gene and cytochrome c oxidase subunit I gene. Overall, 23 juveniles (3 females, 3 males, and 17 unsexed), with a dorsal mantle range of 65–152 mm, were caught in September 2020 in the waters of the Korčula Channel, island of Palagruža, and island of Jabuka, thus providing the most abundant sample of this species in the Mediterranean waters. The length–weight relationship showed an isometric growth. The results of the beak/length regressions suggest hood length is a useful characteristic for biomass estimation studies, as it showed a good linear fit to the dorsal mantle length. Statolith growth increments were easily visible and statolith microstructure analysis was successfully used to determine the age of 22 individuals. The estimated age ranged from 36 to 64 days (mean = 48 days). The back-calculation analysis showed that the squid hatched during July and August 2020, indicating that O. caroli spawns during the warmer, summertime period. Considering the size and age of the caught individuals, the Adriatic Sea could represent a potential feeding ground for this species. The genetic structure analyses indicate the existence of separate Atlantic and Mediterranean/Adriatic subclusters; however, this warrants further investigation.

Squid male alternative reproductive tactics are determined by birth date.

Alternative reproductive tactics (ARTs) are discontinuous phenotypes associated with reproduction, observed in males of many species. Typically, large males adopt a tactic of competing with rivals for mating, while small males adopt a tactic of stealing fertilization opportunities from the large males. The 'birth date hypothesis', proposing that the date of birth influences the determination of each male's reproductive tactic, has been tested only in teleost fish to date. Here, the birth date hypothesis was tested in ARTs of Japanese spear squid Heterololigo bleekeri (consort/sneaker) by analysing statolith growth increments. The birth date significantly differed between consorts (early-hatched) and sneakers (late-hatched). However, no differences were detected in growth history up to 100 days from hatching. Most immature males caught during the reproductive season were larger than sneakers, and their hatch date was similar to that of consorts, suggesting that these immature males had already been following a life-history pathway as a consort. These results indicate that ARTs of H. bleekeri are determined based on their hatch date in early life. This study firstly suggests that the birth date hypothesis applies to aquatic invertebrates, suggesting that the mechanism by which birth date determines the individual phenotype is a phenomenon more common than previously believed.

Age, growth and maturation of Illex coindetii (Cephalopoda: Ommastrephidae) in the eastern Adriatic Sea

Analysis of statolith growth increments was used to determine age and describe growth pattern of broadtail shortfin squid Illex coindetii in the central eastern Adriatic Sea, an important demersal resource in the Adriatic basin. Size-at-age data were obtained from a large sample (N = 476, including 249 males and 227 females) of individuals with dorsal mantle length (ML) from 55 to 216 mm and body weight (BW) from 5.7 to 356.9 g. Estimated age ranged from 52 to 186 days, with an average of 108 days, suggesting the species has a life span of six months. No statistically significant difference in statolith length was found between the sexes. The back-calculation analysis showed that Adriatic I. coindetii hatches continuously throughout the year, with two alternative spawning periods, in summer and winter. Therefore, a generation born in summer reproduces in winter, and generation born in winter reproduces in summer. Hatchlings of the autumn–winter period were significantly larger and heavier with slower growth than their offspring hatched in summer and spring that exhibited faster growth and matured at younger age. Estimated age at first maturity were 137.4 and 109.2 days, for females and males, respectively. Growth was best described by Schnute and logistic model that display asymptotic tendencies by the end of the life span. There were no major differences in growth pattern between different cohorts of each sex, with faster growth recorded at younger age.

Age structure and life cycles of the Argentine shortfin squid Illex argentinus (Cephalopoda: Ommastrephidae) in southern Brazil

Age structure and hatchling dates of the squid Illex argentinus collected by bottom-trawl fishery in southern Brazilian waters were assessed by the analysis of statolith growth increments. Catches occurred between 2001 and 2002, from 23° to 32°S at depths of 100–700 m. Squid from juvenile to post-spawning stages were collected year round, with age estimated from 98 to 320 days and mantle lengths ranging from 112 to 376 mm. Duration of life cycle events based on statolith growth zones revealed that squids can spend about 14% of their lifespan as paralarva (~30 days), 70% as juvenile (~130 days), leaving maturity and spawning condition to the terminal 10–20% (~30–60 days). The results suggest that, unlike estimates available for Patagonian populations, a general 0.5 year lifespan is predicted for I. argentinus off Brazil. The wide range of size-at-ages implied that catches of shortfin squid off southern Brazil probably include squid hatched throughout the year. Mature and spawning squid caught in summer months hatched in winter and spring, while winter catches revealed mature-spawning individuals hatched both in summer/autumn (~6 months of age) and winter/spring periods (~10–11 months of age). It has been argued that such groups may combine both squid resident of Brazilian outer shelf and slope (22°–34°S) with a six months' lifespan and migrating squid originated from the northern Patagonian shelf (~42°S) with 10–11 months' lifespan.

The effect of temperature on growth of early life stages of the common squid Loligo vulgaris

The squid Loligo vulgaris has an extended spawning season within the upwelling system off north-west Portugal, and its paralarvae may thus develop under a wide range of environmental conditions. Both temperature and salinity are expected to affect the metabolism of young squid and we tested their effects on growth during the embryonic and post-hatching phase, based on measurements of growth increments in statoliths of juveniles and adults, using generalized additive models. There was no evidence that statolith increments representing early growth become unreadable in adult statoliths. Variability in the statolith size at hatching was weakly but significantly related to the variables in the model. On the other hand, the effects on statolith growth of both sea surface temperature and of sea bottom temperature were significant during early post-hatching life. Thicker increments are deposited in the statoliths of squid living under higher temperatures, which results in summer hatchers having larger statoliths at the age of 90 days. Inspection of the statolith accretion pattern, using a piecewise linear regression method, revealed an ontogenetic shift in increment width, which may be an indication of the age of transition from paralarva to juvenile. On this basis, it is suggested that the planktonic stage lasts 60 or 90 days, depending on whether the paralarvae lived at higher (>15°C) or lower (<15°C) sea surface temperatures. The life strategy under warmer conditions potentially favours survival by reducing the duration of the vulnerable planktonic phase.

Estimated life span of the Japanese pygmy squid, Idiosepius paradoxus from statolith growth increments

Growth increments in statoliths of Idiosepius paradoxus were observed for aging analysis. The rate of increment formation was examined by staining the statoliths with tetracycline at 5–14 d intervals. In 6 of 16 specimens, increments formed daily, but in the other specimens, increments formed less than one per day. The maximum number of increments observed in males and females were more than 150 and 140, respectively, suggesting a life span of ≥150 and ≥140 d. During the cool season (from November to April), the dorsal mantle length (DML) and the number of increments gradually increased. Specimens collected in June showed bi-modal patterns in DML and the number of increments. Only small specimens were collected from August to October. These results suggest that two generations alternately occurred in the cool season and in the warm season.

Growth and mating of southern African Lycoteuthis lorigera (Steenstrup, 1875) (Cephalopoda; Lycoteuthidae)

Lycoteuthis lorigera is an oceanic squid that is abundant in the Benguela system. Little is known about the biology of this squid except that it is eaten in large numbers by numerous oceanic predators and that males grow to larger size than females, which is unique for oegopsid squid. The aim of this study was to better understand the biology of this species by investigating its age and growth, as well as its mating system. Toward this end, the age of 110 individuals, ranging from 35 to 110 mm, was estimated by counting statolith growth increments. Estimates of age ranged from 131 to 315 days and varied with mantle length. No significant differences were found in the size of males and females of equivalent ages. The relationship between ML and age for both sexes was best described by an exponential growth curve, probably because no early life stages were aged in this study. Only one mature male (ML 160 mm) was aged, and preliminary estimates suggest it was 386 days old. Instantaneous growth rates were low (0.54% ML/day and 1.4% BM/day) but consistent with enoploteuthid growth rates. When the growth rate of L. lorigera was corrected for temperature encountered during the animal’s life, the growth rate was fast (0.47% BM/degree-days) and consistent with the hypothesis that small cephalopods grow fast and that large cephalopods grow older, rather than fast. Mature females were often mated and had spermatangia in a seminal receptacle on the dorsal pouch behind the nuchal cartilage. Males probably transfer spermatangia to the females using their long second and/or third arm pair since the paired terminal organs open far from the mantle opening.

Age, growth and hatching season of the diamond squid Thysanoteuthis rhombus estimated from statolith analysis and catch data in the western Sea of Japan

Age, growth and hatching season were estimated for the diamond squid ( Thysanoteuthis rhombus) migrating into the Sea of Japan based on analyses of statolith growth increments and length–frequency data of the catch in 1999–2004. Growth rates did not differ significantly between the sexes. The oldest squid was 306 days old, which provides further evidence that T. rhombus has a 1-year life span. The hatching season extended from January to September, with a peak in February–March, and the spawning grounds were suggested to extend from the far southwestern Pacific to the East China Sea. Using aging results from statolith analysis, growth was well described by a logistic formula, which also closely corresponded with the sequential progress of the mean mantle length in size–frequency distribution of the catch. Growth rates varied depending on the time of hatching; earlier-hatched squid grew faster than later-hatched ones, suggesting that the former hatched in warmer upper-stream areas of the Tsushima Current or the Kuroshio region and the latter hatched in colder mid- or downstream areas of the Tsushima Current.

LABORATORY OBSERVATIONS ON THE EARLY LIFE STAGES OF THE DIAMOND SQUID THYSANOTEUTHIS RHOMBUS

The early life stages of the diamond squid Thysanoteuthis rhombus from early embryogenesis to post-hatching (0 – 7 days old) were observed through laboratory incubation using egg masses collected in the southern Sea of Japan. The egg diameter and mantle length increased during embryonic development through hatching. Mantle-length growth was linear over time, and the growth rate was significantly higher at 258C than at 208C. The inner yolk was located on the dorsal side of the mantle cavity and increased in volume through hatching. Immediately after they hatched, the hatchlings remained on the bottom of culture plates with their ventral sides facing up, but 2– 3 days after hatching they began to swim with their dorsal sides facing up. Feeding experiments were conducted, but none of the hatchlings fed. Statolith growth increments were shown to form daily. Ontogenetic changes that occur from fertilization through post-hatching are discussed.

Spatial and temporal variation in age and growth in juvenile Loligo forbesi and relationships with recruitment in the English Channel and Scottish waters

In many cephalopod stocks, resource abundance and fishing yields depend on the recruitment of the annual cohort. Loliginid squids such as Loligo forbesi are present in the English Channel and in Scottish waters. Variation in age and growth in juvenile Loligo forbesi of these two areas was investigated at the spatial and temporal scale, and inter-annual differences in growth were related to recruitment variation to test density dependence in squid growth in both populations. Spatial and temporal differences in growth were analysed in five cohorts that showed marked differences in recruitment abundance. Biological sampling showed that recruitment occurred in late autumn and spring in Scottish waters and in summer in the English Channel. In both fishing seasons, monthly samples collected at fish markets were analysed and ages of juveniles (mantle length < 200 mm) were determined using daily statolith growth increments. Age determination indicated that recruits were older than previously thought (about 8 to 11 months). Back-calculated hatching dates were used to estimate growth variation during the pre-recruitment stage. Exponential growth models adequately described size-at-age data. Linear modelling demonstrated inter-annual and spatial significant differences in growth rates. Influence of the hatching month (within or between cohorts) on growth was detected. To improve our understanding of recruitment variability, this study addresses the question: Does early growth vary in relation with recruitment? Available recruitment estimates appeared to be related to annual growth rates; density dependence in squid growth is suggested for the English Channel population.

DNA markers indicate that distinct spawning cohorts and aggregations of Patagonian squid, Loligo gahi , do not represent genetically discrete subpopulations

The Patagonian squid, Loligo gahi D’Orbigny, has been described as having temporally and spatially identifiable spawning aggregations. Variation at six microsatellite loci was used to assess whether seasonal and geographical spawning groups around the Falkland Islands represent distinct sub-populations. Genetic variation at these loci is high in this species (mean expected heterozygosity=0.87; mean number of alleles=14.7). No evidence of significantly different allele frequencies was found, either between samples from putative spawning cohorts or geographical areas, indicating that L.gahi around the Falkland Islands comprise a single genetically homogeneous population. Age structure analysis of samples (from statolith growth increments) indicated substantial spread in hatching dates among individuals of similar size and maturity status, suggesting the potential for extensive interbreeding between seasonal cohorts. A sample of L.gahi from the SE Pacific (Peru) displayed distinctly different gene frequencies (and allele size distribution at one locus) from SW Atlantic samples, supporting the suggestion that SE Pacific and SW Atlantic populations may represent distinct subspecies.

Age studies based on daily growth increments in statoliths and growth lamellae in cuttlebone of cultured Sepia officinalis

One hundred and six individuals of Sepia officinalis were cultured throughout its life cycle in two different temperature regimes: 13–15°C and 18–20°C. The number of increments in the statoliths and the number of lamellae in the cuttlebone were read at known ages in different individuals. The formation of growth increments in the statoliths was linearly related with individual age, but it was independent of temperature. By comparison between the slope of these linear relationships and the bisecting line, the hypothesis "1 increment=1 day" was validated in individuals as old as 240 days. In specimens older than 240 days, the number of increments was underestimated due to the poor resolution of the later growth increments. The maximum number of days in captivity (420) was about 80% of the life span estimated for this species in the area studied. Preliminary validation was also obtained from statoliths marked with tetracycline. Increments between tetracycline marks were not visible. The mean distance between marks in ten statoliths was 44 µm (±6). Considering the same distance in statoliths of wild individuals, the mean number of increments counted was 37 (±6). This result is very close to the 40 days passed between both tetracycline marks. A straight line significantly different for each culture temperature defined the relationship between number of the cuttlebone lamellae and age. The number of lamellae in the cuttlebone does not correspond to the real age. The time necessary for the formation of one lamella was 8±2.3 days at 13–15°C, whereas the deposition of one lamella lasted 3.1±1.06 days at 18–20°C. In conclusion, the periodicity for lamellar deposition can be defined only if the temperature where the animal lived is considered.

Age and Growth of the Myosid Squid Loliolus Noctiluca in Western Port, Victoria, Determined from Statolith Microstructure Analysis

Growth in Loliolus noctiluca (Myopsida: Loliginidae) in Western Port, Victoria, Australia was studied from statolith growth increments. Tetracycline staining experiments verified previous work on tropical forms of this species that showed growth increments to be deposited daily. A logistic growth function described the relationship between length and increment number. There appear to be major differences in the form of growth, longevity and life history pattern between tropical and temperate forms of this species. These are probably attributable to differences in environmental conditions.

Age and growth of the mesopelagic squid Ancistrocheirus lesueurii (Oegopsida: Ancistrocheiridae) from the central-east Atlantic based on statolith microstructure

Statolith microstructure was studied in 56 Ancistrocheirus lesueurii (25 to 423 mm of mantle length, ML) caught in the central-east Atlantic. Statolith growth increments were grouped into three main growth zones, distinguished mainly by increment width. The second transition in the statolith microstructure (from Zone 2 to Zone 3) coincides with the life history shift from epipelagic and upper mesopelagic to a bathyal habitat. Second-order bands (mean 27.65 growth increments) and sub-bands (mean 13.6 growth increments) within statolith microstructure appeared to be related to the lunar cycle. Striking sexual dimorphism is reflected in the age and growth rates: males live ca. 1 yr, while females only start maturing at this age and obviously live >1.5 yr. A. lesueurii is a slow growing squid, attaining 25 to 30 mm ML at the age of 100 d. After ontogenetic migrations into bathypelagic waters at ML > 30 to 35 mm, growth rates gradually decrease to the minimum known values for squids. Based on back-calculated hatching dates, A. lesueurii hatches throughout the year with a peak between November and March.

Age of the micronektonic squid Pterygioteuthis gemmata (Cephalopoda: Pyroteuthidae) from the central-east Atlantic based on statolith growth increments

Pterygioteuthis gemmata Chun, 1910 occurs worldwide in tropical oceanic waters except in the western Atlantic, Caribbean and Mediterranean Seas.This species is one of the smallest oceanic squids, with mature males and females attaining 25 and 32 mm mantle length (ML), respectively. Paralarvae, juveniles and adults of P. gemmata are most common in epipelagic and mesopelagic waters of the tropical Atlantic. Their abundance is approximately similar to that of the predominant epiand mesopelagic tropical squids, the micronektonic Abraliopsis atlantica (Enoploteuthidae), Onychoteuthis banksi (Onychoteuthidae) and planktonic cranchiids. The biology of P. gemmata is poorly-known. The hectocotylus of males lacks a chitinous hook which is found in the closely-related species Pterygioteuthis giardi; additionally in females only the right oviduct is functional.'Because of frequent occurrence of both mature females and small paralarvae (1.3-1.5 mm ML), spawning of P. gemmata has been considered to take place in upper epipelagic layers of the Gulf of Guinea. Juveniles (> 100 mm ML) and adults make diel vertical migrations, ascending to the epipelagic water layers at night and descending into mesopelagic layers during the daytime. Age and growth rates in micronektonic oceanic squids have been studied by statolith ageing techniques in the enoploteuthids Abraliopsis atlantica, Abraliopsis pfefferi and Enoploteuthis leptura from the tropical Atlantic-and Abralia tngonura from the North Pacific. The daily nature of growth increments within A. trigonura statoliths has been validated by statolith analysis in newly hatched paralarvae kept in aquaria. It has been found that all these enoploteuthids are rather slow-growing animals with life span of around 6 months.-The aim of this study was to estimate growth rates and maximum age of mature P. gemmata by statolith growth increment studies. Ninety-five Pterygioteuthis gemmata of 10-32 mm ML were caught during the biological surveys of the orange-back squid Sthenoteuthis pteropus (Ommastrephidae) in the central-eastern Atlantic carried out by Russian research vessels 'Prognoz' and 'Ocher' in June-September 1985 and in September 1988. Samples were taken in open waters of the western part of the Gulf of Guinea (latitudes 215'N-3°3O'S and longitudes 4°05'-15°W) off the Exclusive Economic Zones of African countries. Squid were caught at night (20-04 h) at depths of 25-300 m using the Russian zoological pelagic trawl RT/TM 33 type (vertical opening 8-10 m) equipped with a 6 mm mesh liner. Squid were identified using the key elaborated by Nesis. The dorsal mantle length was measured to the nearest 1 mm. Maturity stages were assigned from the scale developed for omnastrephid squids. Statoliths were removed from 12 maturing and mature females and 4 mature males with mantle lengths close to maximum known values for this species. Statoliths were then stored in 96% ethanol for further analysis in the laboratory using statolithageing techniques. Total statolith length (TSL) was measured after Clarke. From each pair, one statolith was ground, first the anterior side, then posterior side on a wet waterproof sandpaper (1500 grit) and embedded in Canada balsam. Growth increments were counted from the nucleus to the edge of the lateral dome by two observers using the eye-piece micrometer of a 'Biolam-R14' light microscope (magnification x400). Statolith growth increments were well-resolved and similar in appearance and microstructure to daily gTowth increments of the enoploteuthid A. trigonura. Assuming them to be daily, the total number of growth increments in the ground statolith of P. gemmata was considered to be the age of the squid in days. Total number of growth increments for each specimen was obtained as an average of count numbers, if deviation between the average and counts was less than 5%.

Age and growth of the short-finned squidIllex coindetiiin Galician waters (NW Spain) based on statolith analysis

Age and growth of Illex coindetii in the fishery northwest of Spain were estimated from statolith growth increments. 341 statoliths were examined (170 males, 171 females) from individuals of 48–379 mm mantle length (ML). The maximum size of squids was 279 mm ML for males and 379 mm ML for females. Weight-at-length of mature males was greater than that of immature males and mature and immature females. Lifespan was estimated at 13 months for males and 15 months for females. Recruitment to the fishery occurred approximately at three months of age. Mantle length instantaneous relative growth rates were 0.72 mm d−1 for males and 0.84 mm d−1 for females. Weight growth rate was 2.22 g d−1 for males and 3.66 g d−1 for females. Maturity stages, however, influenced increase in weight in both sexes, such that weight-at-age was greater for mature than for immature individuals. The age at which individuals mature is variable, ranging from 140 to 271 d in males and between 183 and 285 in females. Growth rates in both sexes were dependent on the season of hatching. Squids hatched in winter attained larger sizes for the same age than squids in other seasons. These seasonal differences in growth were only evident after squids had reached 8 months of age. Reading daily increments in statoliths seems to be a reliable technique for studying the age and growth of Illex coindetii.

Age and growth of planktonic squids Cranchia scabra and Liocranchia reinhardti (Cephalopoda, Cranchiidae) in epipelagic waters of the central-east Atlantic

Statolith microstructure was studied in two abundant planktonic cranchiids, Cranchia scabra (56 specimens, 38-127 mm mantle length, ML) and Liocranchia reinhardti (34 specimens, 99-205 mm ML) sampled in epipelagic waters of the western part of the Gulf of Guinea (tropical Atlantic). Growth increments were revealed in ground statoliths of both species. It was possible to dis- tinguish two growth zones in statolith microstructure by their colour in reflected light of the micro- scope: the translucent postnuclear zone and pale white opaque zone. Assuming that growth increments in statoliths were produced daily, ages of the largest immature Cscabra and L.ranhardti were 166 and 146 days, respectively. Both cranchiids are fast-growing squids with growth rates in length resembling those of juveniles of tropical ommastrephids and Thysanoteuthis rhombus. Liocranchia reinhardti grows fasten its growth rate in ML is approximately twice that of same-aged Cscabra.Thc life cycle of both cranchiids consists of two phases. During their epipelagic phase, Oscabra and Lreinhardti feed and grow rapidly from paralarvae to immature young in the epipelagic waters, attaining 120-130 and 170-200 mm ML by ages of 4-5 months, respectively. Then they change their life style to a deepwater phase.

Growth and reproduction in the mesopelagic-boundary squid Abralia trigonura

Abralia trigonura is a small squid that is an important member of the mesopelagic boundary community around Hawaii. Squids were aged by examining statolith growth increments, and various reproductive parameters were measured. Female longevity is ∼6 mo, and they become sexually mature at ∼3.5 mo. Male longevity is the same, but they become sexually mature at ∼2.5 mo. This species appears to be a multiple spawner, and peculiarities in the number of eggs found in the oviducts suggests that they spawn every few days. Possible advantages of this reproductive mode are examined.

Statolith microstructure of seven species of Antarctic squid captured in Prydz Bay, Antarctica

The statolith microstructure was examined from seven species of seven families of Antarctic squid captured in Prydz Bay (n=23). Five of the species (Kondakovia longimana, Psychroteuthis glacialis, Brachioteuthis sp., Mastigoteuthis psychrophila, Galiteuthis glacialis) had very clear statolith growth increments which could be enumerated from the nucleus to the statolith margin. These increments were similar in appearance to daily statolith increments in other temperate and tropical squids. Psychroteuthis glacialis also had two distinct zones which may reflect growth during the pelagic and demersal phases of the life cycle. Total statolith increment counts were not possible on two of the species (Bathyteuthis abyssicola and Alluroteuthis antarcticus). The statolith microstructure of Bathyteuthis abyssicola had some very faint increments near the nucleus but increments were not visible in most of the statolith microstructure, while the statolith microstructure of A. antarcticus was indistinct in the nuclear region (possibly due to the formation of a second primordium during ontogenesis). Future research may reveal that statolith increments are useful tools for Antarctic squid age and growth studies.

Interannual growth differences in the oceanic squid Todarodes angolensis Adam in the northern Benguela upwelling system, based on statolith growth increment analysis

Analysis of growth by year of hatching was estimated from the statolith growth increments of the oceanic squid Todarodes angolensis in three consecutive years. Samples were taken between November 1987 and February 1990 in the northern Benguela upwelling system. Growth increments suggested that hatching took place throughout the year and that the life cycle was ≈ 1 yr. From the onset of sexual maturity in the final third of the life cycle, growth rates were subject to considerable individual variation. Growth rate was significant highest in the 1987 year class, presumably because of exceptionally cool environmental conditions in the Benguela region. The response of T. angolensis to interannual environmental variability in the northern Benguela system is discussed. The results from this study suggest that it will be important to consider variability in growth rate in relation to environmental conditions, in future studies of squid age and growth.