The embryonic phase and its implication in the hatchling size and condition of Atlantic bobtail squid Sepiola atlantica (original) (raw)
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Marine Biology Research, 2012
An investigation of the distribution and general biology (size, maturation and fecundity) of the sepiolid Sepietta oweniana off the Portuguese Coast is presented based on 594 specimens collected during research cruises between 1997 and 2008. Statolith microstructure was examined in 35 animals. S. oweniana was mainly encountered on the southwestern and southern continental slopes, while it was rare north of 388N. Female mantle length (ML) ranged from 13.9 to 35.7 mm, male ML from 12.5 to 28.0 mm; specimens of both sexes being significantly larger in the southeastern area. Potential fecundity was 18Á616 (mean 2349104) oocytes and mean mature oocyte diameter varied 2.3Á3.4 mm. The year-round presence of mature animals, asynchronous ovulation, the presence of mature specimens over a range of different sizes and the occurrence of feeding activity throughout spawning are indicative of a continuous spawning strategy in this species. Growth increments were present in all statoliths, being narrow and nearly uniform in width. The total number of growth increments registered from the specimens sampled varied between 103 and 179; with a similar range in males (n 017) and females (n018). Putative age estimates suggest an age approximation of 4.5Á6 months for mature and spent females and 5Á 5.5 months for mature males.
2003
Egg masses of the loliginid squid Loligo vulgaris Lamarck, 1798 are attached to hard substratum or branched sessile organisms on the sea bottom. Embryonic development lasts from a few weeks to a few months, depending on the environmental water temperature. Because embryonic statolith growth of L. vulgaris is very sensitive to temperature under laboratory conditions, we analyzed the possibilities of determining past events in the squid's early life from analysis of the embryonic area of statoliths of wild squid populations. The relationship between egg-incubation temperature and daily growth of embryonic statoliths under laboratory conditions was determined by tetracycline markings at 10 incubation temperatures ranging from 12 to 24.7°C. In addition, the mean width of embryonic increments in statolith collections of wild L. vulgaris from the Eastern Atlantic (Saharan Bank and NW Iberian Peninsula) and the Mediterranean Sea (Central and Eastern) was calculated. The temperature inferred from the embryonic increment widths of the statoliths of wild squid indicates that embryonic development of L. vulgaris in the regions sampled is likely to occur at temperatures ranging from 12 to 17°C. Mediterranean squid have wider embryonic increments than Atlantic squid, reflecting the slightly higher water temperatures in the Mediterranean Sea during the development of the egg masses. Eggs of L. vulgaris spawned off the NW Iberian Peninsula were estimated, on average, to remain at sea for 47 d, 1 wk longer than Mediterranean eggs (nearly 1 mo longer when comparing minimum and maximum ranges). A longer incubation time for egg masses attached to the sea bottom increases mortality risks. Conversely, slow development at a lower temperature can improve yolk conversion, producing larger hatchlings, and increased hatching competence is expected from such squid. Therefore, a compromise between longer-versus-shorter incubation time and related characteristics does exist.
Invertebrate Biology, 2012
Atlantic bobtail squid (Sepiola atlantica) in northwest Spain show seasonal variation in population structure, with juvenile abundance peaking during summer and autumn. However, whether similar patterns exist for reproduction is unknown. Therefore, we describe the reproductive biology of 505 specimens of S. atlantica collected monthly during two consecutive years at two different sites off of Areamilla beach in the Rı´a de Vigo. Mature males displayed a type of sexual dimorphism previously unknown in members of this species, developing a muscular nodule in the base of each of the ventral arms over ontogeny. Reproductive output of both sexes was similar to that of other bobtail squids. Relative oocyte size (~10% mantle length) appeared to be similar to those of other bobtail squids. Females did not show evidence of having mated before complete maturity. Females of S. atlantica have group-synchronous ovary maturation, with a positive correlation between female mantle length and ripe oocyte mass, suggesting a terminal investment strategy. Atlantic bobtail squids displayed the same seasonal patterns of reproductive traits at both sampling sites, with significant differences in reproductive activity between males and females. We consider reproductive traits in these small animals as adaptations to the coastal shelf lifestyle.
Spawning strategy in Atlantic bobtail squid Sepiola atlantica (Cephalopoda: Sepiolidae)
Helgoland Marine Research, 2011
This study aimed to determine the spawning strategy in the Atlantic bobtail squid Sepiola atlantica, in order to add new information to the knowledge of its reproductive strategy. A total of 12 females that spawned in aquaria were examined. Characteristics of the reproductive traits and egg clutches were similar to those of other known Sepiolidae. Clutch size varied from 31 up to 115 eggs. Females of this species had incorporated up to 1.58 times of their body weight into laid eggs. The size of laid eggs showed a positive correlation with maternal body size, supporting the idea that female size is a determinant of egg size. Our data suggest that S. atlantica is an intermittent terminal spawner, and that its spawning strategy comprises group-synchronous ovary maturation, multiple egg laying, and deposition of egg clutches in diVerent locations. The obtained data provide insights for future comparative studies on reproductive allocation.
2010
Rossia macrosoma was investigated based on material collected from the eastern Mediterranean Sea, to determine potential fecundity (PF), reproductive strategies and size at maturity. The female potential fecundity ranged between 126 and 931, while the value was 15 to 103 for male spermatophores. Egg sizes varied from 0.2 to 10.0 mm, and spermatophore lengths ranged from 12.3 to 18.8 mm. Animals became mature at smaller sizes than those from the western Mediterranean, thus, their maximum sizes were smaller either. According to egg diameter distributions in gonads, R. macrosoma has asynchronous ovary maturation, spawning more than once. Therefore, R. macrosoma is an intermittent spawner similar to other sepiolid species.
Embryonic stages of the Patagonian squid Loligo gahi (Mollusca: Cephalopoda)
Veliger -Berkeley-
The embryonic development of Loligo gahi was observed from 4-day-old eggs to natural hatching. Egg strands spawned in the Valparaíso Bay, Chile, were transported to an open system tank for incubation. Temperatures ranged from 12.9°C to 13.5°C, salinities from 34%c to 35%c, and the photoperiod was 12L:12D. The period from spawning to hatching ranged from 30-35 days. The diameter of individual eggs ranged from 2.5-3.2 mm, and the dorsal mantle length of hatchlings varied from 2.6-3.1 mm. The pattern of chronological appearance of organs was quite similar to loliginid species prevíously examined (Loligo aff. gahi, Loligo bleekeri, Loligo pealei, Loligo vulgaris reynaudii, and Loligo forbesii). However, L. gahi had a different (faster) development time and a smaller embryo and hatchling size than L. bleekeri (Japan) and L. forbesii (eastern Atlantic Ocean). Differences (heterochronies) among species are discussed. Allometric growth of embryonic development in L. gahi using seven morphometric parameters was undertaken.
Flexible reproductive strategies in tropical and temperate Sepioteuthis squids
A major diculty confronting the determination of cephalopod reproductive life history is assessing over what portion of the life span an individual is reproductively mature and actively depositing eggs. This paper assesses the potential of the tropical Sepioteuthis lessoniana and two genetic types of the temperate Sepioteuthis australis, to spawn multiple batches of eggs at discrete times throughout the adult life span. This is achieved by histological examination of the ovarian gametogenic cycle and detailed morphological assessments of the reproductive system, in conjunction with other biological information. The genetic type of S. australis found at the northern limits of its Australian distribution showed evidence of a high correlation between body size and quantity of mature eggs, suggesting that eggs may be accumulating to be laid in a single batch. Although maturation was also a sizerelated process in S. lessoniana and Tasmanian S. australis, oviduct size was not correlated with body weight in mature females, which is indicative of multiple spawning. Further supporting evidence includes relatively low gonadosomatic indices, the heavier weight of the ovary relative to the oviduct, and the feeding activity of mature animals. Mature S. lessoniana and S. australis individuals were present at each location over very wide age and size ranges. In Tasmanian waters, there were distinct seasonal dierences in the reproductive biology of S. australis. Summer-caught individuals had much higher gonadosomatic indices and may have been laying larger batches of eggs compared with winter-caught individuals. Summer-caught females also showed a negative correlation between egg size and egg number within the oviduct, suggesting that some individuals were producing fewer, larger eggs and others many smaller eggs. Evidence suggests that considerable¯exibility is inherent in the reproductive strategy of both S. lessoniana and S. australis. Marine Biology (2001) 138: 93±101 Ó Springer-Verlag 2001 Communicated by O. Kinne, Oldendorf/Luhe
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 (.158C) or lower (,158C) sea surface temperatures. The life strategy under warmer conditions potentially favours survival by reducing the duration of the vulnerable planktonic phase. (2006) Oceanography and fisheries of the Canary Current/Iberian region of the eastern North Atlantic. In Brink K.H. and Robinson A.R. (eds) The sea. Volume 14B: the global coastol ocean. Cambridge, MA: Harvard University Press, pp. 877-931. Arkhipkin A.I. (2004) Diversity in growth and longevity in short-lived animals: squid of the suborder Oegopsina. Marine and Freshwater Research 55, 341-355. Arkhipkin A.I. (2005) Statoliths as 'black boxes' (life recorders) in squid. Marine and Freshwater Research 56, 573 -583.