A New C-Type Lectin Homolog SpCTL6 Exerting Immunoprotective Effect and Regulatory Role in Mud Crab Scylla paramamosain

C-type lectin (CTL), a well-known immune-related molecule, has received more and more attention due to its diverse functions, especially its important role in development and host defense of vertebrate and invertebrate. Since the research on crab CTLs is still lack, we screened a new CTL homolog, named SpCTL6 from mud crab Scylla paramamosain. The full-length cDNA sequence of SpCTL6 was 738 bp with a 486 bp of ORF, and the deduced amino acids were 161 aa. SpCTL6 was predicted to have a 17 aa signal peptide and its mature peptide was 144 aa (MW 16.7 kDa) with pI value of 5.22. It had typical CTL structural characteristics, such as a single C-type lectin-like domain, 4 conserved cysteines, similar tertiary structure to that of vertebrate CTLs and a mutated Ca2+ binding motif Gln-Pro-Thr (QPT), clustering into the same branch as the crustacean CTLs. SpCTL6 was highly expressed in the entire zoeal larval stages and widely distributed in adult crab tissues with the highest transcription level in testis. During the molting process of juvenile crabs, the expression level of SpCTL6 was remarkably increased after molting. SpCTL6 could be significantly upregulated in two larval stages (Z1 and megalopa) and adult crab testis under immune challenges. Recombinant SpCTL6 (rSpCTL6) was successfully obtained from eukaryotic expression system. rSpCTL6 exhibited binding activity with PAMPs (LPS, lipoteichoic acid, peptidoglycan, and glucan) and had a broad spectrum bacterial agglutination activity in a Ca2+-dependent manner. In addition, rSpCTL6 could enhance the encapsulation activity of hemocytes and has no cytotoxic effect on hemocytes. Although rSpCTL6 had no bactericidal activity on Vibrio alginolyticus, rSpCTL6 treatment could significantly reduce the bacterial endotoxin level in vitro and greatly improved the survival of S. paramamosain under V. alginolyticus infection in vivo. The immunoprotective effect of rSpCTL6 might be due to the regulatory role of rSpCTL6 in immune-related genes and immunological parameters. Our study provides new information for understanding the immune defense of mud crabs and would facilitate the development of effective strategies for mud crab aquaculture disease control.

Characterization of a population of the Harlequin crab, Lissocarcinus orbicularis Dana, 1852, an obligate symbiont of holothuroids, in Toliara bay (Madagascar)*

Harlequin crabs, Lissocarcinus orbicularis, are commensals found on the integument and in the buccal/cloacal cavity of several species of holothuroids. The population of these crabs was investigated on holothuroids of the barrier reef of Toliara (South-West of Madagascar) from 2002 to 2008. Seventeen holothuroid species were observed and eight were crab hosts. There is generally one adult crab or a heterosexual pair per infested holothuroid but up to ten juveniles were recorded on a Thelenota ananas. Carapace length of the observed L. orbicularis was from 0.3 to 1.4 cm from the tip of the rostrum to the end of the cephalothorax, with a mean length of 0.85 cm. L. orbicularis is characterized by a weak sexual dimorphism (females are bigger than males) and the presence of pereiopods morphologically adapted to fixation on the host integument. Gravid females were observed at each month of the survey indicating that the crab reproduces all the year. Considering our results and personal observations, we also discuss the monogamy mating system of the Harlequin crab.

Morphometry of testis and seminiferous tubules of the adult crab-eating fox (Cerdocyon thous, Linnaeus, 1766)

Body and testicular biometric parameters are very important for establishing reproductive patterns and, consequently, the development of protocols for assisted reproduction in different species. A direct correlation between the testis weight and the sperm population was observed in other studied species, because the testis size primarily reflects the total volume of the seminiferous tubule, its main component. The objective of this study was to determine the testicular volume parameters and correlate data from morphometry of testis and seminiferous tubules with body mass in six adult crab-eating foxes. The mean body weight of the crab-eating foxes in this study was 6.53 kg, with approximately 0.068% allocated to the testicular mass and 0.042% specifically to seminiferous tubules, which represented 87.5% of the testicular parenchyma. The albuginea comprised 12.5% of the testicular mass. The mean diameter of seminiferous tubules was 236 µm, and the mean thickness of the seminiferous epithelium was 62.9 µm. Values of tubular parameters indicate a sperm productivity close to those observed in previously studied carnivores.

Stage-dependent interactions between intertidal crabs: from facilitation to predation

Large parts of the south-western Atlantic soft bottom intertidals are inhabited by the burrowing crab Neohelice granulata (previously known as Chasmagnathus granulatus) and the mud crab Cyrtograpsus angulatus, but adults rarely coexist in the same microhabitat. We describe the influence of burrows of N. granulata on the recruitment dynamic of C. angulatus and the effects of different ontogenetic stages of N. granulata on survival of recruits of C. angulatus. A two summer sampling shows that N. granulata burrows facilitate settlement of both species. To evaluate the mortality of recruits inside burrows, we performed a field experiment with juvenile and adult crab exclusion cages and inclusion of juveniles or adults of N. granulata. The results showed differences in crab sizes between treatments, due to predatory interactions that depended on prey size. When only juveniles of N. granulata were present, the higher mortality of C. angulatus was observed in smaller crabs. However when adults of N. granulata were present, larger juvenile crabs are the ones that suffered the highest mortality. These results show that adults are preying upon larger juveniles (of both species) reducing the mortality of the smaller ones that are preyed by the larger ones. We also measured emigration from these burrowing assemblages using bidirectional pitfall traps which showed that C. angulatus juveniles are leaving the burrows towards the subtidal. Here we demonstrate that N. granulata have positive and negative effects on the settlement of C. angulatus. These results highlight the importance of including stage-dependence relationships to analyse species interaction in marine ecology field works.

Preliminary study on domestication of coconut crab (Birgus latro)

<p>Preliminary study on domestication of coconut crab (<em>Birgus latro</em>) had been done since June - November 2004 and December - 2005 February 2006. Study was carried out in two locations namely Laboratory of Sekolah Tinggi Kelautan dan Perikanan, Palu to study adult crab, and Laboratory of Ecobiology of Faculty of Fisheries and Marine Science, Bogor Agricultural University to study crab in clomang stage. Adult crabs were collected by using some fishing gears namely trap, net and directly using bamboo stick. Domestication was done in rearing batch sized 1x1x1 m³ with artificial nests (30x15x15 cm³), and small batch for water (7x10x10 cm³). While for clomang stage, crabs were reared in aquarium (80x40x40 cm³) with debris and small water batch. Result showed that adult crab had a survival rate around 12.5-0%, and mortality around 50-87.5%. A similar result was also in clomang stage, which was 12.5% for survival rate and 87.5% for mortality. Adult coconut crab was preferred to feed coconut than other food likely vegetable and chick.</p> <p>Keywords: domestication, coconut crab, <em>Birgus latro</em>, food habit</p> <p> </p> <p>ABSTRAK</p> <p>Penelitian awal mengenai kajian awal penangkaran kepiting kelapa (<em>Birgus latro</em>) dilakukan pada bulan Juni - November 2004 dan Desember 2005 Februari 2006. Pelaksanaan penelitian di lakukan di dua tempat, yaitu Laboratorium Sekolah Tinggi Kelautan dan Perikanan, Palu untuk percobaan kepiting dewasa, dan Laboratorium Ekobiologi Fakultas Perikanan dan Ilmu Kelautan IPB Bogor, untuk percobaan kepiting tahap klomang. Kepiting dewasa ditangkap dengan menggunakan beberapa peralatan a.l. perangkap, jaring dan secara langsung dengan tongkat. Penangkaran dilakukan di bak-bak peliharaan berukuran 1x1x1 m³ yang dilengkapi dengan tempat persembunyian (30x15x15 cm³), dan bak kecil tempat air (7x10x10 cm³). Sedangkan kepiting tahap klomang dipelihara di akuarium (80x40x40 cm³) yang diberi daun/serasah dan tempat air. Hasil uji coba penangkaran kepiting kelapa dewasa menunjukkan bahwa tingkat survival rate berkisar 12,5-50%, dan tingkat mortalitasnya sebesar 50-87,5%. Keadaan yang serupa juga dijumpai pada stadia klomang dimana survival ratenya sebesar 12,5% dan mortalitasnya sebesar 87,5%. Dari uji coba makanan yang diberikan, diketahui bahwa kepiting dewasa kebanyakan lebih menyukai kelapa, dibandingkan jenis makanan yang berupa sayur ataupun ayam.</p> Kata kunci: penangkaran, kepiting kelapa (<em>Birgus latro</em>), makanan.

Lychnorhiza lucerna Haeckel (Scyphozoa, Rhizostomeae) and Libinia ferreirae Brito Capello (Decapoda, Majidae) association in southern Brazil

Associations between jellyfish and other organisms are frequently reported. Neverhteless, few of those records include crabs inhabiting medusae. Lychnorhiza lucerna Haeckel, 1888 were sampled (n = 1988) on the coast of the State of Paraná (25º20'-25º55'S, 48º10'-48º35'W), southern Brazil, from December 1997 to December 2004. Eight percent (166 individuals) of the medusae had one spider crab Libinia ferreirae Brito Capello, 1871 living within its subgenital porticus or on the oral arms. Megalopal stages of the same crab were also found on three jellyfish. All crabs associated with L. lucerna were young and smaller (< 3 cm) than solitary crabs caught on the bottom. Thus, L. ferreirae probably colonizes the jellyfish as a late larva and uses it as a floating nursery before becoming free-living on the ocean bottom as a typical adult crab.

Life history of Allopetrolisthes spinifrons, a crab associate of the sea anemone Phymactis clematis

Allopetrolisthes spinifrons is an ectocommensal crab of the sea anemone Phymactis clematis. The population biology of A. spinifrons in north central Chile was examined between January and December 1996. During 1996, 74% of P. clematis in the rocky intertidal zone hosted at least one commensal crab. In most cases, one sea anemone was inhabited by a single adult crab, either male or female. A few sea anemones hosted two or more crabs, one usually being an adult and the others juveniles or small crabs that just had recruited to the host. The sex ratio of adult crabs was ∼1:1 during most months. Reproduction occurred with similar intensity throughout the year as indicated by the continuous presence of reproductive females. Similarly, recruitment of A. spinifrons occurred throughout the year with the exception of late winter when no megalopae and small juveniles were found on sea anemones. Fecundity of female crabs varied between 121 and 5661 eggs per female (6·9–19·2 mm carapace length) and was significantly higher during the austral winter (July) than during the summer (December). The fact that most sea anemones were inhabited by a single adult crab indicates that hosts may be monopolized by individual crabs. Resource requirements may prohibit adult crabs from sharing a host individual with another large crab, while adult tolerance towards juveniles may facilitate the maintenance of local populations.