Beak development of early squid paralarvae (Cephalopoda: Teuthoidea) may reflect an adaptation to a specialized feeding mode

Morphological and morphometric development of the upper jaw (UJ) and lower jaw (LJ) and arm crown of Chiroteuthis cf. veranyi, Liocranchia reinhardti (oceanic species), and Doryteuthis opalescens (neritic species) paralarvae were analyzed in order to verify whether or not they are determined by developmental modes. Jaw measurements were taken, correlated with mantle length (ML) by multiple linear regression to determine relative influences on growth, and compared between species by ANOVA to identify differences. Development was expected to be similar between oceanic species, but was morphologically similar between L. reinhardti and D. opalescens, and morphometrically similar between the latter and C. cf. veranyi. UJ and LJ measurements with highest correlation with ML are larger in L. reinhardti, indicating greater beak development in this species. Rostrum robustness is higher in L. reinhardti, intermediate in D. opalescens, and lower in C. cf. veranyi, hinting at the respective prey type. Teeth (LJ) and slit, characteristics of ancestral cephalopods, are present, disappearing completely and partially on the largest specimens of L. reinhardti and D. opalescens, respectively, and remaining in all sizes of C. cf. veranyi. The results suggest that their presence in early paralarvae reflects an adaptation to sucking the pre-digested internal fluids of prey.     

Foraging, feeding and prey remains in middens of juvenile Octopus vulgaris (Mollusca: Cephalopoda)

Juvenile Octopus vulgaris foraged by chemotactile exploration, mainly in crevices and under rocks. They caught small crustaceans and molluscs, including Lima bivalves, and preferred crabs and Lima in a simple laboratory choice test. Octopuses consumed 30% of their prey away from home, and small remains of prey deposited in the midden were selectively removed by waves and currents resulting in an underestimate of the octopus' intake and diet.     

Digestive absorption in Octopus vulgaris (Cephalopoda: Octopoda)

In Octopus , the caecum, the pancreas and the liver are involved in the absorption of ³H-glycine-labelled food. The caecum exhibits the highest specific activity while the liver absorbs the largest proportion of labelled material. The administration of stained food shows in vivo alternating phases of absorption and secretion in the liver and continuous absorption in the caecum.     

The reproductive strategy of Argonauta nouryi (Cephalopoda: Argonautidae) in the Mexican South Pacific

ABSTRACT

Aspects of the reproductive biology of Argonauta nouryi Lorois, 1852 from the coast of Oaxaca, Mexico, were analysed. A total of 54 specimens with dorsal mantle length (ML) ranging from 6.2 to 41.1?mm were obtained from the stomach contents of five species of large predatory fishes from January 2016 to June 2018. The goals of this study were to collect data on reproductive indicators in order to evaluate the reproductive strategy of A. nouryi in the southeast Mexican Pacific and to use histological analysis to characterise the different ovarian phases based on oogenesis. Immature females (19.6?mm?ML) had sperm in their oviducal glands, indicating that female A. nouryi store sperm long after hectocotyli transmission by males. Potential fecundity was estimated as 31,000–75,026 eggs, with a batch fecundity of 2,000–8,000 eggs. Six distinct developmental stages were observed in the eggs suspended in the A. nouryi shell. Our data indicate that the A. nouryi reproductive strategy includes continuous low batch spawnings, mating early in life, and sperm storage in the spermatheca.     

Drilling by Octopus vulgaris(Mollusca: Cephalopoda) in the Mediterranean

Octopus vulgaris drills holes in the shells of a variety of molluscs. The walls of the cavities drilled exhibit dissolution of mineral and organic material. The features which characterize the cavities have been described. The composition and structure of the shell itself is important in determining the size, shape and form of the cavity drilled, and not the size of the octopus. Capture, drilling the shell, and eating the occupant may take less than one hour.     

Tied hands: synchronism between beak development and feeding-related morphological changes in ommastrephid squid paralarvae

Ommastrephid squid produce some of the smallest cephalopod hatchlings, whose feeding behavior has not been observed. The present study aimed at indirectly filling this knowledge gap by describing ontogenetic changes in beak morphology and morphometry and integrating these results with published datasets on Illex argentinus arm crown morphology and gut contents. Individuals [0.7–15 mm mantle length (ML)] were measured, weighed, and had their buccal mass extracted. Jaw measurements were correlated with ML to determine whether jaw development occurred linearly with ML. For a 10 mm increment in ML, weight increased 430-fold. The jaws of hatchlings were rudimentary, but in larger paralarvae the rostrum protrudes and the jaw features (teeth, slit, groove) disappear. Increases in ML were predicted by beak robustness indices and rostrum protrusion, with growth discontinuities pointing to faster growth in individuals ≤ 2 mm ML. Morphological changes in the beak and arm crown are in synchrony with a transitional event in the feeding ecology of paralarvae: the onset of active predation on crustaceans and masticating their exoskeletons for ingestion. Integration of the results with published data has led to the proposal of a hypothesis of four size-differentiated developmental stages in the feeding ecology of I. argentinus rhynchoteuthions.

     

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

The 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.     

First description of hatchlings and eggs of Octopus oliveri (Berry, 1914) (Cephalopoda: Octopodidae)

Chromatophore patterns can be used to identify paralarvae at the species level and are used here to distinguish Octopus oliveri (Berry, 1914 Berry, S. (1914) Notes on the collection of cephalopods from the Kermadec Islands. Transactions of the New Zealand Institute 46, 134–149. [Google Scholar]) from other Hawaiian cephalopod paralarvae. Eggs, clutches, and hatchlings are described for the first time in O. oliveri. Preservation times are compared to illustrate variation in founder chromatophore patterns even among individuals of the same brood.     

Extraintestinal gamogony of Aggregata octopiana in the reared common octopus (Octopus vulgaris) (Cephalopoda: Octopodidae)

Aggregata octopiana (Apicomplexa, Aggregatidae) is the most prevalent coccidian in the wild common octopus (Octopus vulgaris), whose heteroxenous life cycle includes gamogony and sporogony undergoing in the octopus digestive tract. In the infected reared octopi, we observed an unusual extraintestinal distribution of the coccidian, with both gamogony and sporogony ongoing in dermal and gill tissue. Oocysts and macrogamonts were embedded in the dermal connective tissue of octopian arms, demarcated by a thin cyst wall or multilayered dark membrane. In gill connective and epithelial tissue all developmental stages were observed, eliciting hemocytic infiltration. Sometimes a complete substitution of the tissue by cysts and developmental stages occurred, resulting in necrosis of gill tissue.     

Crab and mollusc shell drilling by Octopus vulgaris (Mollusca: Cephalopoda) in the Ria de Vigo (north-west Spain)

Octopus vulgaris living in the Ria de Vigo, north-west Spain, sometimes drills a cavity in the carapace of crabs and shells of molluscs. These holes have features with the same characteristics as those made in molluscs by O. vulgaris and in crabs by Eledone cirrhosa when isolated in aquaria. This is the first report of drilling the carapace of crabs by Octopus vulgaris .     

Larval nematodes (Spiruroidea: Cystidicolidae) in Octopus vulgaris (Mollusca: Cephalopoda: Octopodidae) from the northeastern Atlantic Ocean.

Larval nematode parasites (Spiruroidea: Cystidicolidae) are recorded for the first time in Octopus vulgaris Cuvier, 1797 in the northeastern Atlantic Ocean. Prevalence was 16% and mean intensity was 1.46 worms/host. Body length of larval nematodes ranges from 8.3 to 9.3 mm, with a distance from the anterior end to nerve ring from 187.5 to 200 microm, and to excretory pore 194.6-350 microm. Anatomical characteristics, such as deirid, nerve ring, cephalic alae, excretory pore, pseudolabia amphids, sclerotized protuberance, and anus, examined using light microscopy (LM) or scanning electron microscopy (SEM), are illustrated. The nematode was designed as a cystidicolid "Type A" larva. The hemocytic infiltration present in the host tissue around the nematode capsule and the mechanical compression in the infected organs denote the pathogenicity of this nematode. In the study area, O. vulgaris may play the role of an intermediate or paratenic host in the nematode life cycle.     

Oxygen consumption and ammonia excretion rates in Octopus maya,loligo forbesi and Lolliguncula brevis (Mollusca: Cephalopoda)

Oxygen consumption and ammonia excretion rates were investigated in young Octopus maya (hatching to 139 days old; 0.11–81.23 g wet body weight, BW; 22.5–23.9°C), young squids of Loligo forbesi (hatching to 45 days old; 9.4–115.3 mg BW; 12.3–13.1°C) and young squids of Lolliguncula brevis (2.00–39.98 g BW; 23.8–24.7°C). Except at hatching, oxygen consumption and ammonia excretion rates on an individual basis (M) of these three cephalopods increased linearly with increasing body weight (BW) expressed as M = aBW^b . Values of b for oxygen consumption were 0.900, 0.910 and 0.848 and for ammonia excretion were 0.744, 0.809 and 0.751 for O. maya, L. forbesi and L. brevis, respectively. Among the three species the value a varied widely, while b was similar for both oxygen consumption and ammonia excretion rates. Based upon these data, metabolism for hatchlings of O. maya and L. forbesi was estimated to be relatively lower than that of older juveniles. The O/N ratios for hatchlings of O. maya and L. forbesi were relatively high and indicate an apparent dependence upon lipids in the immediate post‐hatching period, followed by standard protein energy utilization thereafter.     

'Home' choice and modification by juvenile Octopus vulgaris (Mollusca: Cephalopoda): specialized intelligence and tool use?

Analysis of 'homes' occupied by juvenile Octopus vulgaris shows flexible behaviour which may indicate specialized intelligence and tool use. Octopuses occupied sheltered areas for a short time, average 10 days, but stayed longer in larger homes and in areas where preferred prey was available. They did not simply respond to perceptual characteristics of a site, but instead chose locations potentially suitable and modified them by removing rocks and sand and bringing in items partially to block the aperture.     

Morphological and genetic description of Octopus insularis, a new cryptic species in the Octopus vulgaris complex (Cephalopoda: Octopodidae) from the tropical southwestern Atlantic

A medium-sized Octopus species is described based on materialcollected in shallow equatorial waters around the oceanic islandsof Fernando de Noronha Archipelago, Rocas Atoll, St Peter andSt Paul Archipelago and the mainland of northeastern Brazil.The new species, Octopus insularis, is described morphologically,and also characterized by the large mitochondrial subunit ribosomalRNA gene (mt 16S rDNA). The new species has relatively shortand stout arms, rugose reddish brown skin in preserved specimens,8 to 11 gill lamellae on the outer demibranchs, small ligula,characteristic symmetrical radula, spermatophore and beak, smalleggs and high fecundity (213,000 oocytes under 1.5 mm diameter).The habitats and skin patterns of living animals are brieflydescribed. The new species differs both morphologically andgenetically from Octopus vulgaris in the Mediterranean, Venezuelaand southern Brazil. (Received 10 November 2006; accepted 19 October 2007)     

The early life of Octopus vulgaris (Cephalopoda: Octopodidae) in the plankton and at settlement: a change in lifestyle

Newly hatched young of the benthic, coastal-living octopod, Octopus vulgaris , enter the plankton and remain there for perhaps eight weeks. At hatching the arms are short and bear a few, large, primary suckers. The buccal mass is relatively large in proportion to the size of the animal. The eyes are large. The central nervous system has fairly well-defined lobes, some of which develop earlier than others. We shall follow the development of several features of O. vulgaris from hatching, through its life in the plankton until settlement and correlate them with changes in the brain and behaviour.     

The ultrastructure of chondrocytes in the cartilage of Sepia officinalis and Octopus vulgaris (Mollusca, Cephalopoda)

Thin sections of cartilage from the chondrocranium of cuttle fish and octopus were examined using the transmission electron microscope. It was found that cephalopod chondrocytes differed considerably from the chondrocytes of vertebrate cartilage; in particular they possessed many long and ramifying cytoplasmic processes and had an ultrastructure typical of protein-secreting cells. They did not, however, contain secretory granules; while vesicles and rough endoplasmic reticulum cisternae seemed to open directly to the cell surface. The cell body and processes contained cytoskeletal structures: microtubules were easily recognized, but intermediate and thin filaments were difficult to make out as they were frequently clumped into bundles. Some chondrocytes contained conspicuous accumulations of hemocyanin. The cytoplasmic processes possessed intercellular contacts similar to gap junctions. Also present on processes and the cell body were cell-extracellular matrix focal adhesions. The chondrocytes were not polarized or arranged in any preferential spatial order, however, with their processes they formed a three-dimensional network throughout the cartilage tissue. Ultrastructural findings are discussed in relation to the singular morphofunctional characteristics of cephalopod cartilage which shares features with both the cartilage and bone of vertebrates.     

Dicyema shorti n. sp. (phylum Dicyemida) from Octopus burryi (Mollusca: Cephalopoda: Octopodidae) in the Gulf of Mexico

Nematogens and vermiform embryos of a new species of Dicyema are described from an octopus collected off Veracruz, Mexico. Dicyema shorti n. sp. is a small dicyemid species that rarely exceeds 500 microm in length. It is further characterized by the presence of 18 peripheral cells in the vermiform stages, a conical-shape calotte, and an axial cell that extends to the base of the propolar cells. Other stages in the life cycle of the parasite are not known. This is the first dicyemid to be described from Octopus burryi Voss. 1950, and also from both the southern Gulf of Mexico and the country of Mexico.     

A comparative microscopic and ultrastructural study of perichondrial tissue in cartilage of Octopus vulgaris (Cephalopoda, Mollusca)

The microscopic and submicroscopic structures of perichondrial tissues in the head cartilages of Octopus vulgaris were studied by polarized light and transmission electron microscopy. The orbital cartilages possess a birefringent layer parallel to the surface of the cartilage; ultrastructurally, this layer, which may be considered perichondrial tissue, has the typical organisation of connective tissue but does not possess the stratification of collagen laminae found in vertebrate perichondria. Perichondrial extracellular matrix is clearly distinct from that of cartilage because its collagen fibrils are of a larger diameter than collagen fibrils from cartilage. In addition, perichondrial fibroblasts are characteristically located at the center of collagen fibers. In the cerebral cartilage, the perichondrium is absent or discontinuous in relation to complex interconnections between cartilage and connective fibres, muscle fibres, blood vessels and nerve. Distinctive cartilage-lining cells, rich in electron dense cytoplasmatic granules, are stratified either along the cartilage surface or along vessels and muscle fibres that penetrate within the cartilage. The perichondrium of cephalopod cartilage, whose structure varies according to the location and function of its skeletal segments, mimics that of vertebrate perichondrium, exemplifying the high level of tissue differentiation attained by cephalopods.     

Population dynamics and stock assessment for Octopus maya (Cephalopoda: Octopodidae) fishery in the Campeche Bank, Gulf of Mexico

The octopus (Octopus maya) is one of the most important fish resources in the Mexican Gulf of Mexico with a mean annual yield of 9000 ton, and a reasonable number of jobs created; O. maya represents 80% of the total octopus catch, followed by Octopus vulgaris. There are two artisanal fleets based on Octopus maya and a middle-size fleet that covers both species. Catch-at-length structured data from the artisanal fleets, for the 1994 season (August 1st to December 15th) were used to analyze the O. maya population dynamics and stock and to estimate the current level of exploitation. Von Bertalanffy growth parameters were: L infinity = 252 mm, mantle length; K = 1.4 year-1; oscillation parameters C = 1.0, WP = 0.6; and tz = 0.842 years. A rough estimate of natural mortality was M = 2.2, total mortality from catch curve Z = 8.77, and exploitation rate F/Z = 0.75. This last value suggests an intensive exploitation, even when yield per recruit analysis indicates both fleets may increase the minimum legal size on about 10% to increase yields. The length-based VPA also shows that the stock is being exploited under its maximum acceptable biological limit. These apparently contradictory results are explained by biological and behavioral characteristics of this species. Because most females die after reproduction, a new gross estimation of natural mortality was computed as M = 3.3. The new estimate of exploitation rate was F/Z = 0.57. This new value coincides with results from the length-VPA and the Thompson and Bell methods, the former suggesting that a reduction of 20% in fishing mortality may provide larger yields. This fishery resource is fully exploited and current management measures must be revised to sustain and probably optimize yields.