Rearing of Bitterling (Rhodeus amarus) Larvae and Fry under Controlled Conditions for the Restitution of Endangered Populations

Among the several dozen European freshwater fish species, only European bitterling (Rhodeus amarus Bloch) and Rhodeus meridionalis belong to the group of ostrakophilous fish. The embryonic and larval development of the fish in this reproductive group until the time of the yolk sac resorption takes place in the gill cavity of river mussels (Anodonta sp. or Unio sp.). This paper presents the results of the European bitterling Rhodeus amarus being reared under controlled conditions. Bitterling larvae were caught together with river mussels in the natural environment and subsequently placed in a tank for behavioural observations. Bitterling larvae were seen swimming in the water within a week of placing the bivalves under controlled conditions. The bitterling larvae were 8.6 ± 0.11 mm long when they started to swim actively. The rearing was conducted in water at 20 and 26 ± 0.5 °C and lasted for 6.5 months (200 days) in both variants. Initially, the larvae were fed with live nauplii of Artemia salina and subsequently with fodder. The bitterlings in tanks with water at 26 ± 0.5 °C were 66.2 ± 3.0 mm long and weighed 3389 ± 548 mg. For comparison, bitterlings kept in water at 20 ± 0.5 °C were 64.48 ± 3.4 mm long and weighed 3242 ± 427 mg. No larval malformities or mortality were observed during the larvae and fry rearing. The bitterlings had well-developed secondary sexual characteristics and exhibited pre-spawning behaviour at the end of the rearing. This produced suitable bitterling stocking material to be used in the conservation of small or endangered populations.

Micropredator Behaviour of Rocinela dumerilii (Isopoda, Aegidae) on Trachurus trachurus in the Sea of Marmara (Turkey)

Rocinela dumerilii (Lucas, 1849) is obtained on the horse mackerel, Trachurus trachurus (Linnaeus, 1758) from the Sea of Marmara, in Turkey. This species is a free-living organism from the Aegean Sea of Turkey, the Mediterranean Sea and Atlantic. Its micropredator behaviour is discovered for the first time in this study. Elthusa sinuata (Koelbel, 1879) is also collected on the gill cavity of Fries’s goby, Lesueurigobius friesii (Malm, 1874) in this study. This host is a new record for Elthusa sinuata. The morphological characters of Rocinela dumerilii species are given by drawings.

The Emperor’s Cadlina, hidden diversity and gill cavity evolution: new insights for the taxonomy and phylogeny of dorid nudibranchs (Mollusca: Gastropoda)

Dorids are one of the largest nudibranch groups, encompassing more than 2000 species. One of the crucial problems with tracing the evolution of dorids is the relationship between cryptobranch dorids (gill cavity present) and phanerobranch dorids (gill cavity absent). Integrative morphological and molecular studies of the enigmatic Japanese dorid species of the cryptobranch genus Cadlina, C. japonica and ‘C.’ sagamiensis, which were collected by the Emperor of Japan (Shōwa era), are presented here for the first time. It is shown that while C. japonica does belong to the Cadlina clade, another Japanese species ‘C.’ sagamiensis is not part of the cryptobranch dorids of the family Cadlinidae, but is related to both the phanerobranch dorid family, Hexabranchidae, and to the cryptobranch family Cadlinellidae stat. nov. A new genus, Showajidaia gen. nov., and new family, Showajidaiidae fam. nov., are proposed for ‘C.’ sagamiensis, and four new species of the genus Cadlina are described based on a dorid-wide molecular phylogenetic analysis, which is the first substantial update of the dorid family system since 2010. Integration of phylogenetic data with an ontogenetic model of dorid evolution suggests that cryptobranch organization can be most reliably assessed as the ancestral state for the majority of dorids.

Description of the first cryptobranch onchidoridid Onchimira cavifera gen. et sp. nov., and of three new species of the genera Adalaria Bergh, 1879 and Onchidoris Blainville, 1816 (Nudibranchia: Onchidorididae) from Kamchatka waters

The opisthobranch fauna of the SE Kamchatka peninsula (NW Pacific, Russia) has been intensively investigated for the first time resulting in 21 species found, and six new records for Kamchatka. A unique onchidoridid species with a well defined, closeable gill pocket into which gills can be fully retracted, and which does not fit with any existing genus is described as Onchimira cavifera gen. et sp. nov. in anatomical detail. Onchimira cavifera is remarkable in that it combines characteristic features of cryptobranch dorids with those of phanerobranch onchidoridids. Its role as a missing link and new evidence for evolutionary reduction of the gill cavity within phanerobranch dorid lineages is discussed. In addition, two new species of the genus Adalaria, A. slavi sp. nov. and A. olgae sp. nov., are described based on numerous newly collected specimens showing little intraspecific variations, but clear differences to all previously described Adalaria species. A review of the presently known Adalaria species including SEM data of the radula and labial cuticle is presented in order to highlight differences among the newly discovered taxa. A new species of the nudibranch genus Onchidoris, O. macropompa sp. nov., is described. A comparative table of all presently known Onchidoris species is presented.

Anphira branchialis GEN. ET SP. NOV. (CRUSTACEA, ISOPODA, CYMOTHOIDAE) A GILL CAVITY PARASITE OF PIRANHAS (Serrasalmus SPP.) IN THE BRAZILIAN AMAZON

Anphira branchialisgen. et sp. nov. (Crustacea, Isopoda, Cymothoidae) is described from the dorsal areas of the gill chambers of three species of piranhas (Serrasalmusspp.). The fishes were caught in rivers near Manaus, Amazonas State and on Maracá island, Federal Territory of Roraima, Brasil. The new genus and species is characterized by having large, flat coxal plates on ail 7 pereonites. These plates usually extend beyond the margins of the following segments and the 7th ones extend nearly to the pleotelson and cover the lateral margins of the pleonites. The mandible of this species is rounded, "foot shaped" and without incisor. The mandibular palp is short and stout. The maxillules have 3 terminal and 2 subterminal spines. The pleopods are simple lamellar structures with rounded tips. Evidence is presented that these parasites feed on gill filaments.

Experimental Studies of the Reproductive Behaviour of the Parasitic Copepod Lernaeocera Branchialis (Pennellidae)

Egg-producing Lernaeocera branchialis (L.) are usually found in the gill cavity of cod (Gadus morhua (L.)) and whiting (Merlangius merlangus (L.)) (Kabata, 1979). The early larval development of the copepod includes two free-swimming nauplius stages followed by the first infective stage, the copepodite (Sproston, 1942). On an intermediate host, usually flounder (Platichthys flesus (L.)), the copepodite moults into a chalimus larva which is attached by its frontal filament to the gill tips of its host. After four successive chalimus stages, the parasite reaches maturity and copulation occurs on the flatfish host.

Survival of Steelhead Trout (Salmo gairdneri) Eggs, Embryos, and Fry in Air-Supersaturated Water

Egg, embryo, fry, and swim-up stages of steelhead trout (Salmo gairdneri) were exposed to water at total gas saturation levels ranging from 130 to 115%. Eggs, embryos, and newly hatched fry were not affected at 126.7%, but at about day 16 posthatch when the fish began swimming up deaths occurred rapidly, and at the end of the test post button-up mortality ranged from 99% at 126.7% saturation to 45% at 115.3% saturation. Bubbles in the mouth, gill cavity, and yolk sac caused flotation and severe respiratory difficulties. Rupture of yolk-sac membranes also caused death. No differences were noted in survival between fish exposed from egg to fry, and those exposed only from swim-up to fry stage. In summary, there were differences in susceptibility among steelhead life stages to air-supersaturated water; eggs, embryos, and pre-swim-up larvae were more resistant than swim-up and later fry stages. Key words: trout, steelhead, supersaturation, gas-bubble disease, Salmo gairdneri, temperature, fish culture

Commensalism between a liparid fish, Careproctus sp., and the lithodid box crab, Lopholithodes foraminatus

Fish eggs containing Careproctus embryos were found in the gill cavity of Lopholithodes foraminatus caught off British Columbia. Because the gills were collapsed and displaced, thus implying impaired respiration for the crab, we consider this fish–crab association to be commensal rather than symbiotic. The embryos are probably those of C. melanurus. Because of previous reports of other Careproctus sp. depositing eggs in king crabs (Paralithodes camtschatica), further investigations to indicate the host specificity of this liparid–lithodid relationship are needed.