Larval development of estuary perch (Macquaria colonorum) and Australian bass (M. novemaculeata) (Perciformes: Percichthyidae), and comments on their life history

Morphological development of the larvae and small juveniles of estuary perch (Macquaria colonorum) (17 specimens, 4.8−13.5 mm body length) and Australian bass (M. novemaculeata) (38 specimens, 3.3−14.1 mm) (Family Percichthyidae) is described from channel-net and beach-seine collections of both species, and from reared larvae of M. novemaculeata. The larvae of both are characterized by having 24−25 myomeres, a large triangular gut (54−67% of BL) in postflexion larvae, small spines on the preopercle and interopercle, a smooth supraocular ridge, a small to moderate gap between the anus and the origin of the anal fin, and distinctive pigment patterns. The two species can be distinguished most easily by the different distribution of their melanophores. The adults spawn in estuaries and larvae are presumed to remain in estuaries before migrating to adult freshwater habitat. However, larvae of both species were collected as they entered a central New South Wales estuary from the ocean on flood tides; such transport may have consequences for the dispersal of larvae among estuaries. Larval morphology and published genetic evidence supports a reconsideration of the generic arrangement of the four species currently placed in the genus Macquaria.

Crab fisheries in Cambodia and the development of crab banks

The crab (swimming crab; Portunus pelagicus) fishery in coastal Cambodia appears to have declined in recent years due to over-fishing and a growth in the number of fishermen, but remains an important source of income for households along the coast. Several initiatives have started since 2007, with support from NGOs, international organizations and the Fisheries Administration (FiA), to test stock enhancement techniques through the release of crab larvae. The so-called “crab bank” initiative involves keeping harvested gravid crabs alive in cages for a few days until they spawn, instead of immediately selling them for consumption or processing. In Cambodia, this initiative has developed within the framework of Community Fisheries (CFis) and thus implies a communitybased approach. The FiA has promoted the continuation of such initiatives; however, the nature of crab fisheries and the results from crab bank initiatives have not been documented in detail. The scope of this study was to understand the diversity of approaches to crab bank development in Cambodia, as well as their operational status and the challenges faced at differen

Larval development and identification of the genus Triglops (Scorpaeniformes: Cottidae)

Prior to Pietsch’s (1993) revision of the genus Triglops, identification of their larvae was difficult; six species co-occur in the eastern North Pacific Ocean and Bering Sea and three co-occur in the western North Atlantic Ocean. We examined larvae from collections of the Alaska Fisheries Science Center and Atlantic Reference Centre and used updated meristic data, pigment patterns, and morphological characters to identify larvae of Triglops forficatus, T. macellus, T. murrayi, T. nybelini, T. pingeli, and T. scepticus; larvae of T. metopias, T. dorothy, T. jordani, and T. xenostethus have yet to be identified and are thus not included in this paper. Larval Triglops are characterized by a high myomere count (42–54), heavy dorsolateral pigmentation on the gut, and a pointed snout. Among species co-occurring in the eastern North Pacific Ocean, T. forficatus, T. macellus, and T. pingeli larvae are distinguished from each other by meristic counts and presence or absence of a series of postanal ventral melanophores. Triglops scepticus is differentiated from other eastern North Pacific Ocean larvae by having 0–3 postanal ventral melanophores, a large eye, and a large body depth. Among species co-occurring in the western North Atlantic Ocean, T. murrayi and T. pingeli larvae are distinguished from each other by meristic counts (vertebrae, dorsal-fin rays, and anal-fin rays once formed), number of postanal ventral melanophores, and first appearance and size of head spines. Triglops nybelini is distinguished from T. murrayi and T. pingeli by a large eye, pigment on the lateral line and dorsal midline in flexion larvae, and a greater number of dorsal-fin rays and pectoral-fin rays once formed.

Larval development of the sidestriped shrimp (Pandalopsis dispar Rathbun) (Crustacea, Decapoda, Pandalidae) reared in the laboratory

Larval development of the sidestriped shrimp (Pandalopsis dispar) is described from larvae reared in the laboratory. The species has five zoeal stages and one postlarval stage. Complete larval morphological characteristics of the species are described and compared with those of related species of the genus. The number of setae on the margin of the telson in the first and second stages is variable: 11+12, 12+12, or 11+11. Of these, 11+12 pairs are most common. The present study confirms that what was termed the fifth stage in the original study done by Berkeley in 1930 was the sixth stage and that the fifth stage in the Berkeley’s study is comparable to the sixth stage that is described in the present study. The sixth stage has a segmented inner flagellum of the antennule and fully developed pleopods with setae. The ability to distinguish larval stages of P. dispar from larval stages of other plankton can be important for studies of the effect of climate change on marine communities in the Northeast Pacific and for marine resource management strategies.

Larval development of the southern sea garfish (Hyporhamphus melanochir) and the river garfish (H. regularis) (Beloniformes: Hemiramphidae) from South Australian waters

Larval development of the southern sea garfish (Hyporhamphus melanochir) and the river garfish (H. regularis) is described from specimens from South Australian waters. Larvae of H. melanochir and H. regularis have completed notochord flexion at hatching and are characterized by an elongate body with distinct rows of melanophores along the dorsal, lateral, and ventral surfaces; a small to moderate head; a heavily pigmented and long straight gut; a persistent pre-anal finfold; and an extended lower jaw. Fin formation occurs in the following sequence: caudal, dorsal and anal (almost simultaneously), pectoral, and pelvic. Despite the similarities between both species and among hemiramphid larvae in general, H. melanochir larvae are distinguishable from H. regularis by 1) having 58–61 vertebrae (vs. 51–54 for H. regularis); 2) having 12–15 melanophore pairs in longitudinal rows along the dorsal margin between the head and origin of the dorsal fin (vs. 19–22 for H. regularis); and 3) the absence of a large ventral pigment blotch anteriorly on the gut and isthmus (present in H. regularis). Both species can be distinguished from similar larvae of southern Australia (other hemiramphids and a scomberosocid) by differences in meristic counts and pigmentation.

Effects of salinity and temperature on the larval development of a sesarmid crab Neosarmatium trispinosum Davie (Crustacea: Brachyura: Sesarmidae) from mangrove swamp in Okinawa Island, Japan

The larval development of the semiterrestrial sesarmid mangrove crab Neosarmarium trispinosum was studied under laboratory conditions at salinities 0-35%o and constant temperatures of 20-30°C. The larval development consists of five zoeal stages and a megalopa. Larvae survived to the first crab stage at salinities between 15 and 35%o with different percentages. At 0, 5 and 10%o, the larvae died within 12-18 hours without moulting to subsequent stages. The highest survival rate was recorded at 20-25%o and 25-30°C with shortest development duration to the first crab stage ranging from 24-28 days. At the highest salinity (35%o), survival rate was gradually decreased with increasing development duration. There were significant differences (Pdevelopment period among the tested salinities. Results of this study suggest that the larvae of N. trispinosum develop in estuarine water and recruit to the mangrove swamp at the megalopa stage, where they spend the rest of their lives.

Larval development of Micippa platipes Ruppell, 1930, reared under laboratory conditions (Crustacea, Decapoda, Majidae)

The ovigerous female of Micippa platipes Ruppell, 1830, captured from Buleji (Karachi, Pakistan) on February 7, 1993 and was kept under the laboratory conditions. On February 27, 1993 larvae were hatched in prezoeal stage. The presoeal stage of M. platipes passed through two zoeal stages within three to five days at room temperature (17-20C). The larvae are described, illustrated and compared with the larval account of Micippa thalia (Herbst, 1803) given by Kurata, 1969.

Effect of furanace on the development of larval stages of Penaeus monodon Fabricius

Zoea 2(Z SUB-2 ) Mysis 1 (M SUB-1 ) and Postlarva 1 (P SUB-1 ) of P. monodon artificially spawned in closed-system concrete hatchery tanks were bioassayed for their tolerance to the antibiotic furanace. The setup consisted of four 20-liter capacity plastic basins previously conditioned for 15 days with freshwater in full sunlight. During the experiment, each basin was filled with 5 liters of seawater to which was added filtered Chaetoceros and Brachionus to give densities of 5 . 0-7 . 5 x 10 SUP-4 cells/ml and 10-20 individuals/ml, respectively. The following are the properties of the water used throughout the experiments: salinity, 26-32%; pH, 7 . 3-8 . 4; temperature, 25-30 degree C; dissolved oxygen, 4 . 5-8 . 4 ppm; nitrite, 0 . 36-0 . 99 ppm; and ammonia, 0 . 10-0 . 30 ppm. To each basin were added 50 healthy larvae of specific stages of P. monodon. After an initial acclimation of one hour in the medium, preweighed amounts of the antibiotic were added and thoroughly dissolved. The concentrations tested were 1 . 0, 2 . 0 and 3 . 0 ppm. One basin always served as control. After 24 hours of exposure, the surviving population in each basin was counted. The survivors were then examined thoroughly under the microscope for unusual behavior and morphological defects brought about by the exposure. To minimize wide variations in the medium as a result of feeding and other manipulations, the systems were all prepared at 9:00 a.m. each time, and the feeds on two instances, one at 5:00 p.m. and another at 5:00 a.m. Fifteen trials conducted with Z SUB-2 showed survival ranges of 68% to 98% with a mean of 77 . 6% in the controls; 32% to 94% with a mean of 65 . 7% at 1 ppm, and 0% to 56% with a mean of 36 . 5% at 2 ppm. There were no survivors at 3 ppm. Interpolation from the survival-dose curve gave a 24-hr LC SUB-50 of approximately 1 . 6 ppm.

Toxicity of malachite green to the larvae of Penaeus monodon Fabricius

A study was undertaken examining the effect of malachite green on the development and survival of the zoeae, mysis and post-larvae of Penaeus monodon. Sensitivity varied with the different larval stages; the zoeae appeared to be the least tolerant. The prophylactic potentials of malachite green in the control of Lagenidiumand Zoothamnium infesting P. monodon larvae are considered briefly. Toxicity risks may be reduced by application between ecdyses or by the removal of the dye by filtration through activated carbon.

Preserved algae as food for Penaeus monodon larvae

Uni-algal cultures of C. calcitrans, S. costatum, T. chui and Isochrysis sp. obtained from the laboratory were harvested. The harvest, preserved by either freezing or sun-drying, was fed to the larvae of P. monodon . Among the test algal species, Chaetoceros and Tetraselmis were used in larval feeding trials with frozen food while Chaetoceros, Tetraselmis and Isochrysis species were utilized in feeding experiments with sun-dried algae. Their relative effects on larval survival and development were assessed. Results showed that, except the alum-flocculated cells, both frozen Chaetoceros and Tetraselmis can support survival at the zoea stage. Best survival of 68% was atained with dried Chaetoceros followed by Tetraselmis at 44%. Dried Isochrysis did not perform as well, a significantly low survival of only 25% was obtained.

In-vitro effect of fungicides on hyphal growth and sporogenesis of Lagenidium sp. isolated from Penaeus monodon larvae and Scylla serrata eggs

The sensitivity of Lagenidium, isolated from Penaeus monodon, Scylla serrata , to 34 antimycotics was determined. Effects on the development of vesicles, zoospores and mycelial growth were evaluated. Although mycoidal levels of the chemicals tested will be ideal for lethal treatment on control of the fungus, the high dose required may be lethal to the host, thus the use of mycostatic concentrations is more practical. Treatments of rearing water containing larvae, adult shrimps or crabs should be done only after preliminary tolerance experiments using at least the mycostatic dose prove to be safe for the hosts. Mycocidal doses can be used for determining disinfection doses of equipment and facilities used in rearing procedures as well as for destroying batches of infected larvae.

Larval and postlarval development of the window-pane shell, Placuna placenta L. (Bivalvia: Placunidae)

Stages of development of P. placenta from the straight-hinge veliger to the adult are described. Mature larvae metamorphose at lengths from 220-230 m. Larvae probably attach byssally to the water surface at metamorphosis and remain in the plankton for some time before finally settling on the mud bottom.

Optomotor reaction of milkfish larvae and juveniles

The development of the optomotor reaction (OMR) in milkfish (Chanos chanos), from the larval, through the metamorphic, to the juvenile stage was observed. The period from the appearance of the pelvic fins until the complete disappearance of the finfold was named ”metamorphic stage”. While the larvae showed strong rheotactic responses, their OMR was somewhat weak. It was clear that the OMR underwent a big change through the metamorphic stage, and became strong and almost perfect in the juveniles.

Embryonic and larval development of Mystus gulio (Ham.)

Mystus gulio eggs are strongly adhesive and contain relatively small yolk (0.75-1.0 mm). The egg envelop is thick and transparent. First cleavage (two cells), four cells, eight cells, sixteen cells and multi cells stages were found 20, 25, 35-40, 60 and 70 minutes after fertilization, respectively. The morula stage was visualized within 1.5 h after fertilization. The heart beat visible and the circulatory system commenced after 16 h of fertilization. Embryos hatched 18-20h after activation of egg. The newly hatched larva measured 2.82±0.03 mm in length and 0.32±0.06 mg in weight. The yolk sac was fully absorbed by the third day though larvae commenced exogenous feeding even before completion of yolk absorption. A 5-day old post larva began wandering in search of food. Ten-day old post larvae endowed with eight branched rays in dorsal fin and seven in caudal fin. Fifteen-day old post larvae had the pectm:al spine become stout though the embryonic fin folds had to be disappeared. The length of fingerlings ranged from 25-30 mm after 30 days, and their external features were just like those of an adult except that they were not sexually matured.

Supply of Astaxanthin and its combinations through live feed (Moina micrura) enrichment affects the growth, survival and fatty acid profile of Macrobrachium rosenbergii larvae

A study was carried out with three replicates to determine the effects of feeding Moina micrura enriched with astaxanthin alone (M1) or astaxanthin in combination with either vitamin E (M2), vitamin D (M3) or Cod Liver oil (M4) on the growth, survival and fatty acid composition of giant fresh water prawn Macrobrachium rosenbergii (de Man) larvae. Growth rate was expressed as the time taken to the settlement of 95% post larvae. Maximum growth, the lowest time taken to the 95% PL settlement (38.5±0.50 days), was observed in larvae fed with M3 Moina. The highest survival rate (66.0±1.00%) was observed in those fed with M4 Moina and the second highest survival (61.0±1.00%) and growth rates (40.0±0.00 days) were shown with M2 Moina. The minimum values for both growth (42.5±0.50 days) and survival (33.0±1.50%) were observed in the group fed un-enriched Moina. Results also showed that the survival of prawn larvae increased as the quantities of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased in the dietary Moina. The highest levels of EPA (5.57±0.21%), DHA (3.50±0.21%) and highest total Highly Unsaturated Fatty Acids (HUFA) (13.87±0.68%) were seen in the Moina fed on astaxanthin and Cod Liver Oil (CLO). The results of the study showed that the nutritive quality of Moina, with respect to important fatty acids, can be increased by enrichment and will influence the growth, survival and the fatty acid composition of fresh water prawn larvae fed on them.