32 research outputs found
Reproduction in Heteroteuthis dispar (RĂŒppell, 1844) (Mollusca: Cephalopoda): a sepiolid reproductive adaptation to an oceanic lifestyle
Small cephalopods of the genus Heteroteuthis are the most pelagic members in the family Sepiolidae. This study examines the reproductive biology of Heteroteuthis dispar (RĂŒppell, 1844), the first such study on any member of the genus, based on 46 specimens (27 females and 19 males) collected during the Mar-Eco cruise in the North Atlantic in the region of the Mid-Atlantic Ridge in 2004, and compares it with reproductive features in the less pelagic members of the family. The unusually large spermatophores of the males have a very small ejaculatory apparatus and cement body, relative to the size of the sperm mass. Females first mate when they are still maturing: a large sperm mass (up to 3.4% of the female body mass), consisting of one to several spermatangia, was found in an internal seminal receptacle of the majority of the females examined regardless of their maturity state. The seminal receptacle has a unique form and position in this species. The receptacle is a thin-walled sac at the posterior end of the visceral mass that is an outpocketing of, and opens into, the visceropericardial coelom. Spermatangia and sperm from the spermatangia apparently enter into the visceropericardial coelom (which is mostly occupied by the ovary) from the seminal receptacle indicating that ova are fertilised internally, a strategy unknown for decapodiform cephalopods (squid and cuttlefish), but present in most octopods. Fecundity of Heteroteuthis dispar (1,100â1,300 oocytes) is much higher than in other sepiolids whereas the egg size (mean max. length âŒ1.6 mm) is the smallest within the family. Spawning is continuous (sensu Rocha et al. in Biol Rev 76:291â304, 2001). These and other reproductive traits are discussed as being adaptations to an oceanic lifestyle
La maturation sexuelle chez les mïżœles d'Octopus vulgaris (Cephalopoda: Octopoda), en relation avec le rïżœflexe photo-sexuel
Essential fish habitats and hotspots of nektoâbenthic diversity and density in the western Mediterranean
1. Since the 1990s, most currently assessed Mediterranean nektoâbenthic stocks
have been exploited above maximum sustainable yield and have declined. This
study explores the coâoccurrence of essential fish habitats for the most important
nektoâbenthic resources exploited by bottomâtrawl fisheries in the western
Mediterranean and areas of importance for nektoâbenthic communities.
2. Fisheryâindependent data obtained from Mediterranean scientific bottomâtrawl
surveys were used to identify persistent hotspots of recruitment for the most
important nektoâbenthic species around the Iberian Peninsula and the Balearic
Islands between 2002 and 2016, as an indicator of their essential fish habitats.
Likewise, hotspots of nektoâbenthic community diversity and density were also
determined, as an estimate of key areas for nektoâbenthic communities.
3. Areas of overlap of persistent hotspots of recruitment and of community species
richness and density were mainly found on the deep shelf and the upper slope
(100â200 m and 200â500 m deep respectively).
4. These overlapping areas could be of particular interest in the development of fishery
management plans aiming to implement an ecosystem approach to fisheries. Protection, through temporary or permanent closures, of the overlapping areas identified
would contribute to improving both the sustainable exploitation of the main target
species of bottomâtrawl fisheries and the conservation of nektoâbenthic communities
Reproductive traits of sandbird octopus, Amphioctopus aegina (Gray, 1849) from Mandapam coastal waters (Palk Bay), Southeast Coast of India
Fecundity and reproductive strategies in deep-sea incirrate octopuses (Cephalopoda: Octopoda).
Coleoid cephalopods show flexibility in their reproductive strategies or mode of spawning, which can range from simultaneous terminal spawning over a short period at the end of the animalâs life to continuous spawning over a long period of the animalâs life. Although a simultaneous terminal spawning strategy is typical of shallow water temperate octopuses, it is not known whether deep-sea octopods would have the same reproductive strategy. The reproductive strategies and fecundity were investigated in nine species of deep-sea incirrate octopuses: Bathypolypus arcticus, Bathypolypus bairdii, Bathypolypus ergasticus, Bathypolypus sponsalis, Bathypolypus valdiviae, Benthoctopus levis, Benthoctopus normani, Benthoctopus sp., and Graneledone verrucosa (total n = 85). Egg-length frequency graphs and multivariate analysis (principal components analysis) suggest that B. sponsalis has a synchronous ovulation pattern and therefore a simultaneous terminal spawning strategy. Although a simultaneous terminal spawning strategy is most likely for B. levis and B. normani, the egg-length frequency graphs and multivariate analysis also suggest a greater variation in egg-lengths which could lead to spawning over an extended period