Hole boring of crustacean prey by the octopus Eledone cirrhosa (Mollusca, Cephalopoda)

Eledone cirrhosa has been found to make a borehole in the carapace of a high proportion of its crustacean prey. This is the first account of drilling in crustaceans by octopus. The frequency of incidence of the boring behaviour varied between prey species from 17 to 93% of those killed. The incidence of boreholes was higher in crabs killed by small octopuses. Using crabs mainly of the genera Cancer, Carcinus, Corystes and Macropipus , the distribution and orientation of the boreholes was recorded. The boreholes occurred in any part of the carapace but the great majority were found close to the mid-line and in the posterior half. The long axis of the oval penetration was usually aligned with the anteroposterior axis of the crab. The Mediterranean species Eledone moschata was also found to bore crabs, and newly hatched juveniles of this species are capable of boring as early as their second killing of a live crab. No evidence was found that Octopus vulgaris normally bores the carapace of crabs.     

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.     

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.     

Rapid differentiation between Octopus vulgaris Cuvier (1797) and Octopus mimus Gould (1852), using randomly amplified polymorphic DNA

Seventeen specimens of Octopus vulgaris and Octopus mimus were investigated using randomly amplified polymorphic DNA (RAPD). Clearly differentiable RAPD fingerprints allowed a fast and reliable genotypic discrimination of these species. Thus, molecular genetic evidence from total DNA complements recent results of a comparative analysis of mitochondrial sequence data supporting the taxonomic separation of Octopus mimus and Octopus vulgaris .     

Has Octopus vulgaris a second radula?

Octopus vulgaris drills shelled molluscs and measurements showed the radula to be too large to reach into the depths of the holes made. Small teeth were found on the salivary papilla and its seems likely that these are used for excavating the deeper parts of the holes and penetration of the shell.     

Carcinophyly of fish of the genus Careproctus (Scorpaeniformes: Liparidae) in waters of southeastern Sakhalin (Sea of Okhotsk)

In waters of southeastern Sakhalin (Sea of Okhotsk), clutches of snailfishes of the genus Careproctus containing eggs at different stages of development or prolarvae were found on gills of the largest individuals (mainly in males) of three species of crabs (Lithodidae)-Paralomis verrilli (clutches were found in 1.4% of individuals), P. multispina (0.8%), and Lithodes covesi (11.6%). With an increase in the carapace width of lithodid crabs, the amount of eggs of snailfishes deposited in them and their diameter increase. More frequently, clutches are located from the left side of the carapace of crabs. Two-side clutches occur in larger individuals of crabs. No direct relationship between the presence of clutches of snailfishes on gills of lithodid crabs with necrosis or reduction of gills was revealed. The form of relations between lithodid crabs and Careproctus snailfishes was defined as “lodging” with different degree of impact on the host.     

Presence of two neuropeptides in the fusiform ganglion and reproductive ducts of Octopus vulgaris: FMRFamide and gonadotropin-releasing hormone (GnRH)

We have found evidence of FMRFamide-like and cGnRH-I-like immunoreactivity in the central nervous system (CNS) and in the reproductive ducts of both female and male cephalopod Octopus vulgaris. Cell bodies and fibers were immunolocalized in the fusiform ganglion from which the nerves that reach the female and male reproductive ducts arise. FMRFamide-like and cGnRH-I-like immunoreactive nerve endings were present in the oviduct, and in the oviducal gland of the female and in the seminal vesicle of the male. The GnRH-like peptide from the reproductive ducts has been partially characterized by HPLC. The retention time of the Octopus vulgaris GnRH-like peptide was similar to the retention time of cGnRH-I. Based on these observations we suggest that FMRFamide-like and a novel GnRH-like peptide are involved in the control of reproductive ducts of Octopus vulgaris. One possibility is that the peptides affect gamete transport. Another possibility is that they regulate secretory products such as mucus and mucilaginous substances from the oviducal gland and the seminal vesicle. Our data provide further evidence to support the hypothesis of the existence of a central and peripheral peptidergic control of reproduction of Octopus vulgaris.     

Use of the beaks and raduala by Octopus vulgaris in feeding

The role of the chitinous beaks and the radula of the cephalopod Octopus vulgaris Lamarck, when feeding on either live shore crabs or whole dead fish, has been examined. One or more of these mouthparts was removed surgically and the effect on the quantity of food eaten and the method of cleaning the prey followed. The condition of the digestivetract was observed at post-mortem.     

The influence of starvation and copper exposure on the composition of the dorsal carapace and distribution of trace metals in the shore crab Carcinus maenas (L.)

1. The influence of starvation and copper exposure on the composition of the carapace of the shore crab, Carcinus maenas has been investigated. The effects of the concentrations of selected trace metals in the carapace and midgut gland have also been examined.2. Differences in nutritional state did not affect the concentrations or relative proportions of the principle carapace components (calcium, chitin and protein), but starvation was associated with a reduction in carapace copper concentration. Copper concentration in the midgut gland increased in “starved” crabs, while midgut gland zinc and calcium concentrations remained unchanged.3. Starvation in combination with copper exposure (0.5 mg Cu/1) resulted in alterations in both carapace composition and trace metal loads. Carapace calcium concentrations were reduced significantly following copper exposure irrespective of the nutritional state of the crabs. However, the reduction was more marked in “fed” crabs than in “starved” animals.4. Copper-exposed crabs exhibited raised carapace copper concentrations while carapace zinc concentrations were depressed. Such changes were most pronounced in copper-exposed “starved” crabs.5. Calcium concentrations in the midgut glands of “starved” copper-exposed animals were significantly elevated compared with those in either control or “fed”, copper-exposed crabs.6. The findings are discussed with regard to their ecotoxicological significance.     

Agonistic interactions between the invasive green crab, Carcinus maenas (Linnaeus) and juvenile American lobster, Homarus americanus (Milne Edwards)

Invasive organisms have the potential for competition with native organisms. In the Southern Gulf of St. Lawrence, juvenile American lobsters have a potential spatial overlap with adult green crabs. Crustaceans use agonistic behaviour to settle disputes, with the larger organism often winning contests for limited resources such as food and shelter. Two experiments were carried out using adult green crabs (53-76 mm carapace width) and juvenile American lobsters (28-57 mm carapace length). The first experiment used a limited food resource. We found that green crabs were the first to the food in all trials, fed in significantly more trials than lobsters and spent a significantly greater proportion of time with the food. The lobsters were only able to displace the green crabs from the food in 2 of 65 attempts. The second experiment was designed to examine shelter competition; unexpectedly some predation by green crabs on lobsters occurred, which allowed us to test hypotheses about how relative size and shelter use affect predation. Green crabs captured and consumed juvenile lobsters in 6 of 11 trials. The lobsters that survived spent significantly more time in shelter. There was no clear relationship between shelter use and size of lobster. The lobsters that were larger in relation to the green crabs suffered a higher rate of predation, which we believe was due to more conspicuous activity and less use of shelter. It appears that green crabs have the potential to negatively impact native juvenile lobster.     

A new shell disease in the mud crab Scylla serrata from Port Curtis, Queensland (Australia)

In 1994 a previously unreported rust spot shell disease was seen in mud crabs Scylla serrata - Forskal from Port Curtis, central Queensland, Australia. Of 673 crabs surveyed, 21.7% had shell lesions. Of these, 82.9% had rust spot lesions on the carapace. The majority of rust spot-affected crabs (78.8%) were female. Rust spot lesions were predominantly non-perforated (89.4%) and 54.8% were bilaterally symmetrical. There was also a gender difference in the areas of the carapace most commonly affected. The main histological features of the rust spot lesion included: a cavity in the upper endocuticle; indentation of the endocuticle below the cavity; remains of muscle attachment adhesive epithelium within the cavity; fibrous connective tissue between the damaged carapace and the attached muscle; and islands of endocuticle in this fibrous connective tissue. Histopathology of the internal organs failed to find evidence of an infectious or parasitic cause of the rust spot lesions. The cause(s) of the syndrome appear(s) to be non-infectious.     

阳澄湖原产及“洗澡”中华绒螯蟹背甲的几何形态分析

为有效确认非阳澄湖产"洗澡蟹"与阳澄湖原产中华绒螯蟹(Eriocheir sinensis)背甲形态的差异,研究运用几何形态分析法,比较研究了前者在阳澄湖中人为"洗澡"式养殖1个月始末时,其与阳澄湖原产蟹的背甲形态特征。背甲的形态分析基于所建立的35个地标点系统来进行,即背甲经图像处理后提取地标点坐标,开展相对扭曲主成分以及判别分析,再利用薄板样条分析和网格变形将形态变异矢量可视化。相对扭曲得分的逐步判别分析结果显示:"洗澡"式养殖前后阳澄湖原产蟹与非阳澄湖产蟹背甲形态差异均极其显著,判别准确率均为100%。网格变形结果进一步发现,与非阳澄湖蟹情况不同,"洗澡"式养殖前后的阳澄湖产蟹背甲形态变化不显著。研究首次定量证实,非阳澄湖产中华绒螯蟹即使在阳澄湖"洗澡"式养殖1个月,背甲形态仍无法与原产蟹趋同。这种差异性具有区别阳澄湖原产和"洗澡"蟹的应用潜力。     

Heterochely and handedness in the shore crab Carcinus maenas (L.) (Crustacea: Brachyura)

A large sample ofadult male Carcinus maenas was 79% right-handed and 21% left-handed. A separate sample of 207 intact adult males was divided into left-handed and right-handed crabs and four measurements were taken from all major and minor chelae. Correlation and regression analyses against carapace width on log-transformed data showed that major chelae of right-handed crabs grow proportionately higher with increasing size and the ideal mechanical advantage increases; concurrently, the fingers of the minor chelae grow proportionately longer. The data for left-handed crabs showed greater variability, especially for minor chelae, providing evidence for the concept that left-handedness arises by reversal of handedness following loss of the major chela from the right-hand side. Records of handedness in large samples of non-ocypodid heterochelous brachyuran crabs show a preponderance of right-handedness.     

Progenesis in Proctoeces lintoni (Fellodistomidae), a parasite of Fissurella crassa (Archaeogastropoda) in a latitudinal gradient in the Pacific Coast of South America

The fellodistomid Proctoeces lintoni is a common parasite of the gonads of key-hole limpets Fissurella spp. (Archaeogastropoda). It has also been found in the mantle of Octopus vulgaris and as an intestinal parasite of haemulid and gobiesocid fishes. Fissurella crassa, a host for progenetic P. lintoni, can be found from Huarmey, Peni (10 degrees S) to Chiloé, Chile (42 degrees S). Proctoeces lintoni has been found parasitizing fishes and molluscs from Callao, Peni (12 degrees S) to Valdivia, Chile (39 degrees S). Progenesis is thought to be a latitude-dependent phenomenon, and high progenesis is expected at higher latitude. In the present article, the association between latitude and progenesis was examined over a latitudinal gradient of about 3,000 km. Data suggest that progenesis of P. lintoni infecting F. crassa was not associated with latitude. Low levels of progenesis found in the Peruvian population could be a consequence of parasite-induced mortality rather than of low latitude, as would be predicted by the latitude dependence hypothesis.     

SOME ASPECTS OF THE ECOLOGY OF THE FRESHWATER CRAB (POTAMONAUTES PERLATUS MILNE EDWARDS) IN THE UPPER REACHES OF THE BUFFALO RIVER,EASTERN CAPE PROVINCE,SOUTH AFRICA.

Summary

Freshwater crabs (Potamonautes perlatus) are the largest naturally occurring invertebrates in southern African rivers. The ecology of these animals in South African riverine ecosystems is little understood. This study investigates some aspects of the population and feeding ecology of P. perlatus in the upper reaches of the Buffalo River. The densities of crabs (carapace width larger than 25 mm) at two sites in the river ranged between 1.72 and 5.25 crabs m², higher than previously recorded for freshwater crabs in rivers in southern Africa and southern Italy. Twenty-four hour observations revealed that P. perlatus has a nocturnal habit. The diet of P. perlatus was established by examination of the contents of the fore-gut. Crabs with a carapace width smaller than 40 mm fed predominantly on aquatic invertebrates while larger crabs fed on allochthanous material (leaf litter), detritus and algae. Through feeding, crabs reduced the surface area of leaves in the stream by 99.95%.     

Concerning the problem of carcinophilia of <Emphasis Type="Italic">Careproctus</Emphasis> species (Scorpaeniformes: Liparidae) in the North Kurils

Along the east coast of North Kurils, the egg deposits of Careproctus snailfishes (Scorpaeniformes: Liparidae) were revealed in the gill cavity of 9.9% of all golden king crabs, mostly in individuals with carapace of 61–80 mm width (61.6%). The number of Careproctus eggs in the gill cavity of crabs increased with the increase of the carapace width. In fact, 97.0% of the crabs had such egg deposits only at one side of their carapaces. Most of the egg deposits, apparently, belonged to C. cypsellurus and C. furcellus. The number of crabs with egg deposits was related to the number of post-molt individuals. Evidently, egg depositing by Careproctus snailfishes out of the gill cavity of crabs is a rather widespread phenomenon.     

Food and feeding habits of the lesser spotted dogfish, Scyliorhinus canicula (L.), in Isle of Man waters

Stomach contents of the lesser spotted dogfish, Scyliorhinus canicula , from Isle of Man waters were investigated. Dogfish fed opportunistically on a wide range of macrobenthic fauna with hermit crabs, cockles and whelks the dominant prey. Items of secondary importance included various crabs, callianassid shrimps, bivalve molluscs, holothurians, polychaetes and, when locally abundant, herring, Clupea harengus . Dogfish predated more heavily on molluscs than reported in previous studies, reflecting the abundance of molluscs in the associated benthic community.
Composition of the diet altered gradually with dogfish size, reliance on small crustaceans declined and consumption of hermit crabs and molluscs increased with growth. Seasonal changes in the composition of the diet were observed. Feeding intensity was greatest during summer, related in part to increased prey availability, and was least during autumn.     

Quantifying factors influencing American lobster (Homarus americanus) predation on the invasive green crab (Carcinus maenas) in Newfoundland,Canada

The European green crab (Carcinus maenas) is a newly invasive species in Newfoundland, where it has likely been present for ≤15 years. The green crab has been found in stomach contents of American lobster (Homarus americanus) in New England and Nova Scotia, Canada, but predation on this species has not yet been quantified in Newfoundland. We conducted feeding experiments to determine whether lobsters from Newfoundland were as likely as those from Nova Scotia (which have coexisted with green crabs for >60 years) to recognize and prey upon this new species. We also performed experiments to determine whether green crabs reach a size refuge from predation and whether factors including starvation, availability of alternate food sources, or habitat complexity would influence the probability of lobster attacking or feeding on green crabs. In our trials, lobster origin had no significant effect on crab predation; lobsters, irrespective of origin, were more likely to consume small (<40 mm carapace width [CW]) and medium (40–65 mm CW) crabs than larger (>65 mm CW) ones. Nevertheless, even small lobsters (73–76 mm carapace length, 300 g) were able to kill and consume the largest green crabs (78 mm CW, 100 g). Green crabs were less likely to be attacked or eaten when an alternative food source was present, suggesting that the lobsters were preying on the crabs, rather than simply killing them in a dispute over territory. The addition of a shelter provided a refuge for the green crabs; however, the crabs were only able to avoid being injured or eaten if this shelter was structurally complex. The green crab is slowly spreading westward around the island of Newfoundland, and so its long‐term effects, interactions with other organisms, and contribution to the diet of Newfoundland lobsters remain to be seen.     

Agonistic interactions between invasive green crabs, Carcinus maenas (Linnaeus), and sub-adult American lobsters, Homarus americanus (Milne Edwards)

The invasive green crab, Carcinus maenas, has recently expanded its range into the Southern Gulf of St. Lawrence, where there is potential for substantial niche overlap with juvenile American lobsters, Homarus americanus. We used two experiments to elicit, record and analyze the agonistic interactions of adult green crabs (carapace width of 63-75 mm) and sub-adult (carapace length of 55-70 mm) lobsters. The first experiment gave each animal equal access to a limited food resource. The green crabs were first to the food in significantly more trials, spent a significantly greater proportion of time with the food, and were able to successfully defend the food from attacks by the heavier lobsters. In the second experiment, we allowed the lobsters to gain possession and initiate feeding on the food before releasing the green crabs. In these trials, the lobsters spent significantly more time with the food, and were able to defend the food from the green crabs. The results of both experiments are discussed in the context of game theory. The different behaviour of the crustaceans in the two experiments is consistent with the “bourgeois” strategy in a hawk and dove game simulation. With this strategy, an animal acts like a hawk if in possession of a resource, but acts like a dove if the other animal is in possession of the resource. The fact that the green crabs were able to physically compete with, and in many cases dominate the larger, heavier lobsters supports the potential for competitive impacts of green crabs on sub-adult lobsters.     

Carapace movements aid air breathing in the semaphore crab,Heloecius cordiformis (Decapoda: Brachyura: Ocypodidae)

Summary While on land and recirculating branchial water the Australian semaphore crab Heloecius cordiformis (Decapoda: Ocypodidae), a semi-terrestrial airbreathing mangrove crab, sequentially depresses and elevates its carapace in a regular pump-like manner. The functional role of these carapace movements in aerial oxygen consumption is investigated. Carapace immobilisation (reversible and non-injurious) did not appear to affect branchial water circulation. In dry crabs (branchial water removed) carapace immobilisation had no effect on the rate of oxygen consumption (VO₂), heart rate or whole-body lactate (WBL) levels. In wet crabs (with branchial water) carapace immobilisation caused VO₂ to drop by 38% from 81 to 46 l O₂ · g^-1 · h^-1, heart rate to decline by 32%, from 2.5 to 1.7 Hz, and WBL levels to increase over 2.5-fold, from 0.27 to 0.67 mg · g^-1, after 3 h of carapace immobilisation. The (VO₂) of carapace-immobilised crabs with branchial water was similar to lung-occluded crabs with branchial water. Severe hypoxia induced physiological responses similar to those of carapace-immobilised crabs with branchial water. After 3 h of severe hypoxia, heart rate had declined by 80%, from 2.2 to 0.43 Hz, and the incidence of carapace pumping slowed by 85%, from 2.4 to 0.37 cycles · min^-1. It is concluded that in the absence of carapace movements branchial water in some way inteferes with lung ventilation. Under normal circumstances water circulation and lung ventilation are mutually exclusive processes (due to their singular dependence on the scaphognathites), yet in Heloecius these processes must be carried out simultaneously. Carapace movements may alleviate this conflict.Abbreviations FF, FR, SF, SR fast-forward, fast-reverse, slow-forward, slow-reverse scaphognathite pumping - MEA Milne Edwards aperture - VO₂ rate of oxygen consumption - WBL whole-body lactate