Vladimir Laptikhovsky

Getting under the skin: Autonomous implantation of squid spermatophores

Squid spermatophores are complex structures that store sperm and, when transferred to the female, evert into sper matangia. Some deep-sea squid implant spermatangia into unmodified tissue of the female. Several hypotheses have been proposed to explain this peculiar implantation pro cess. Here, through on board observation of freshly caught deep-sea squid (Moroteuthis ingens), we show for the first time that spermatophores have an autonomous mechanism that enables them to migrate into body tissue. Cephalopod spermatophores are complex secreted struc tures that hold sperm masses and that consist, in part, of an ejaculatory apparatus for releasing the sperm mass and a cement body presumably for attaching the sperm mass to the female (1). Spermatophores are either transferred to the female by the males hectocotylus, a specialized arm, or by a long penis, which is present in species that lack hecto cotyli (2). After being discharged from the spermatophore in the spermatophoric reaction, the sperm mass is encased in a thin covering, with the cement body at one end. This dis charged structure, the spermatangium, may attach to the skin of the female or be deeply embedded in her skin or muscle.

Reproductive biology of Patagonotothen ramsayi (Regan, 1913) (Pisces: Nototheniidae) around the Falkland Islands

The reproductive biology of one of the most abundant notothenioids, Patagonotothen ramsayi, was investigated between February 2003 and November 2004 on the Falkland and Patagonian Shelves (Southwest Atlantic). Male and female P. ramsayi were mature at 27.6 and 24.8xa0cm LT, respectively. P. ramsayi is a total spawner, with a total fecundity ranging between 24,300 and 76,700 eggs. Spawning occurs on the shelf breaks between June and August with the peak in gonado-somatic indices in June. Analysis of length frequency distributions over the year and sex ratios of mature fish during the spawning season may indicate the presence of a nesting and nest guarding behaviour in male fish, similar to other rockcods. Features of its reproductive strategy, which enabled P. ramsayi to dominate the medium-sized demersal fishes on the Patagonian shelf are discussed and compared with those of other nototheniids and cottid sculpins from the Northern Hemisphere.

Reproductive strategies in female polar and deep-sea bobtail squid genera Rossia and Neorossia (Cephalopoda: Sepiolidae)

Female reproductive features have been investigated in five polar and deep-sea bobtail squid genera Rossia and Neorossia (R. macrosoma, R. moelleri, R. pacifica, N.c. caroli and N.c. jeannae). These species are characterized by asynchronous ovary maturation, very large eggs (>10%xa0ML), fecundity of several hundred oocytes, very high reproductive output, and continuous spawning with low batch fecundity. This adaptive complex of reproductive traits evolved in these small animals as an optimum strategy for polar and deep-water habitats.

A comparative study of diet in three sympatric populations of Patagonotothen species (Pisces: Nototheniidae)

The diet of three Patagonotothen species was investigated from the bycatch of near-bottom trawls for squid on the southern Falkland Island shelf. Patagonotothen ramsayi had a moderately diverse diet that was mostly zooplankton, especially amphipods, but included benthos and discards from the fishery, especially squid. P. guntheri also had a moderately diverse zooplankton diet, especially copepods, and benthos and squid damaged by the fishery. The diet of P. tessellata was the most diverse and was mainly benthos, including damaged scallops, with some euphausiids and amphipods. Feeding niche overlap of fish between 10 and 20xa0cm TL for the three species was between 5.8 and 9.2% for each pair of species, indicating relatively little overlap even though all species scavenged on organisms made available by the fishery. Thus the diet of these three Patagonotothen species indicates substantial feeding niche separation, and that the three species are moderately specialised feeders.

Genetic evidence extends the known distribution of Octopus insularis to the mid-Atlantic islands Ascension and St Helena

Recent molecular studies have proved beneficial in providing taxonomic resolution within the Octopus vulgaris species complex, therefore aiding in the appropriate management of this high value global fisheries resource. This study used the mitochondrial barcode of life gene Cytochrome Oxidase subunit I (COI) to investigate the identity of shallow-water benthic octopuses in the mid-Atlantic Ocean and their relationship to members of the Octopus vulgaris species complex. Maximum likelihood and Bayesian phylogenetic inference placed individuals collected from two tropical islands, Ascension and St Helena, into a highly supported monophyletic clade with the North Brazilian species O. insularis (BS = 81, PP = 1), extending the known distribution of O. insularis to Ascension and St Helena Islands. Octopus vulgaris and two other member species of the O. vulgaris species complex, O. tetricus and O. cf. tetricus formed a highly supported monophyletic clade (BS = 99, PP = 1). Interspecific distances between the O. mimus group (O. mimus, O. bimaculoides, O. maya and O. insularis) and the O. vulgaris species group (O. vulgaris, O. tetricus and O. cf. tetricus) ranged from 14.7–26.0%, and an estimated date of divergence suggests these groups diverged from a common ancestor between 19.0 and 40.9 million years ago.

Cephalopod embryonic shells as a tool to reconstruct reproductive strategies in extinct taxa

An exhaustive study of existing data on the relationship between egg size and maximum size of embryonic shells in 42 species of extant cephalopods demonstrated that these values are approximately equal regardless of taxonomy and shell morphology. Egg size is also approximately equal to mantle length of hatchlings in 45 cephalopod species with rudimentary shells. Paired data on the size of the initial chamber versus embryonic shell in 235 species of Ammonoidea, 46 Bactritida, 13 Nautilida, 22 Orthocerida, 8 Tarphycerida, 4 Oncocerida, 1 Belemnoidea, 4 Sepiida and 1 Spirulida demonstrated that, although there is a positive relationship between these parameters in some taxa, initial chamber size cannot be used to predict egg size in extinct cephalopods; the size of the embryonic shell may be more appropriate for this task. The evolution of reproductive strategies in cephalopods in the geological past was marked by an increasing significance of small‐egged taxa, as is also seen in simultaneously evolving fish taxa.

Expanded description of Opisthoteuthis hardyi based on new specimens from the Patagonian slope

Opisthoteuthis hardyi was originally described from a single male specimen caught near Shag Rocks (north-west of South Georgia) and no further specimens have been attributed to this species. During research fishing on the Patagonian slope to the south-east of the Falkland Islands 33 specimens of Opisthoteuthis were caught at depths ranging from 630 to 1391 m. Morphological measurements indicated that these specimens were conspecific to the holotype of O. hardyi. The mitochondria gene 16S rDNA was sequenced from two of these specimens and compared with a published sequence of the holotype and other Opisthoteuthidae to confirm the morphological data. This extends the geographical and bathymetric range of the species, which spans the Antarctic Polar Front. We also expand the original description, providing details of the digestive system and of the female reproductive system, with preliminary estimates of fecundity.

Mating tactics in the sub-Antarctic deep-sea squid Onykia ingens (Cephalopoda: Onychoteuthidae)

The behavior of polar deep-sea nekton is very poorly known. To obtain insight into mating behavior of the abundant and ecologically important sub-Antarctic deep-sea squid Onykia ingens, our goals were to (1) quantify spermatophore production; (2) determine the preferred location for spermatangia deposition; (3) investigate whether male and female O. ingens mate with multiple mates; and (4) discuss the location of implanted spermatangia in light of mating behavior and egg fertilization. Toward this end, we examined male and female O. ingens specimens from Falkland Island and New Zealand waters. Male O. ingens store up to 198 spermatophores (mean 103xa0±xa061; nxa0=xa012) in their reproductive system, which are produced over a period of considerable somatic growth (200–400xa0mm ML), and which may have a considerable size range. Males insert their long extendible terminal organ in the mantle cavity of the female, potentially through the funnel, to deposit spermatophores in one or more of four regions on the female’s body. Most implanted spermatangia (52.5xa0%) were found in the funnel region, but many were also found inside the mantle cavity closer to the oviducts. Males with longer terminal organs therefore may be able to position closer to the oviducts where fertilization chances are higher than for spermatangia located in the funnel region. The number of implanted spermatangia per individual female (4–60, mean 29xa0±xa020; nxa0=xa024), the multiregional spermatangia deposition, and the different outer appearance of spermatangia, suggested that females have multiple mating events. Since males produce more spermatophores (up to 200) than the number of spermatangia in one region (<60), it is likely that males too mate with more than one female. We show how quantitative assessment of reproductive characteristics can provide insight into the reproductive behavior of deep-sea species for which in situ observations are currently lacking.

Techniques for Estimating the Age and Growth of Molluscs: Cephalopoda

ABSTRACT Gastropoda is a large and diverse group of the Mollusca found almost ubiquitously throughout freshwater, terrestrial, and marine habitats. Marine gastropods often support large commercially important fisheries, many of which are facing concerns over sustainability as landings have increased and populations have dwindled over recent decades. For effective fishery management, the inclusion of an age estimation technique is vital to understand growth rates and population structures to feed into analytical stock assessments. Unlike many bivalve species, gastropods are often difficult to age, especially those which exhibit planispiral coiling of their shells, as no single growth axis can be easily uncovered via sectioning. This review covers a range of techniques that can be used to estimate age and growth rates for many marine gastropod species. Although there is no universal aging technique to cover all species, individual techniques have varying success levels for different species groups.

Age and growth rate estimations of the commercially fished gastropod Buccinum undatum

Calculating age and growth rate for the commercially important whelk, Buccinum undatum in the aid of fishery management has historically been undertaken using growth rings on the organic operculum. This is difficult due to their poor readability and confusion between two different sets of growth lines present. Recent work presented the calcium carbonate statolith as an alternative for age determination of B. undatum. Here we compare the use of statoliths and opercula, comparing their readability and creating growth curves for three distinct populations across the United Kingdom. Using these data, we also test the most appropriate growth equation to model this species. Lastly, we use oxygen isotope analysis of the shells to assign accurate ages to several individuals from each site. These data were used to test the accuracy of statolith and operculum ages. Statoliths, whilst more time consuming to process have improved clarity and accuracy compared with the opercula. This improved readability has highlighted that a Gompertz growth function should be used for populations of this species, when in past studies, von Bertalanffy is often used. Statoliths are a viable improvement to opercula when assessing B. undatum in the context of fishery monitoring and management.