Population characteristics of two seahorses, Hippocampus coronatus and Hippocampus mohnikei, around seagrass beds in the southern coastal waters of Korea

Population characteristics of two seahorse species, Hippocampus coronatus and Hippocampus mohnikei, in seagrass beds in the southern coastal waters of Korea were determined based on field observations. In Zostera beds in the Yeosu area, there was a mean density of 2.9 seahorses per 1,000?m² for H. coronatus and 1.4 seahorses per 1,000?m² for H. mohnikei. The greatest numbers of young individuals of both species were observed in July, with numbers decreasing through November. The male:female sex ratio was 1:1.6 for H. mohnikei and 1:1.7 for H. coronatus. Breeding males of H. coronatus and H. mohnikei were observed from July to November and from July to September, respectively. Within the study site, the populations of the two seahorse species exhibited low density and patchy distributions, with variation in temporal abundance being significantly correlated with water temperature. The findings of this study provide the basis for future research on the population status of H. coronatus and H. mohnikei in seagrass beds.     

Genetic Variations in Two Seahorse Species (Hippocampus mohnikei and Hippocampus trimaculatus): Evidence for Middle Pleistocene Population Expansion

Population genetic of seahorses is confidently influenced by their species-specific ecological requirements and life-history traits. In the present study, partial sequences of mitochondrial cytochrome b (cytb) and control region (CR) were obtained from 50 Hippocampus mohnikei and 92 H. trimaculatus from four zoogeographical zones. A total of 780 base pairs of cytb gene were sequenced to characterize mitochondrial DNA (mtDNA) diversity. The mtDNA marker revealed high haplotype diversity, low nucleotide diversity, and a lack of population structure across both populations of H. mohnikei and H. trimaculatus. A neighbour-joining (NJ) tree of cytb gene sequences showed that H. mohnikei haplotypes formed one cluster. A maximum likelihood (ML) tree of cytb gene sequences showed that H. trimaculatus belonged to one lineage. The star-like pattern median-joining network of cytb and CR markers indicated a previous demographic expansion of H. mohnikei and H. trimaculatus. The cytb and CR data sets exhibited a unimodal mismatch distribution, which may have resulted from population expansion. Mismatch analysis suggested that the expansion was initiated about 276,000 years ago for H. mohnikei and about 230,000 years ago for H. trimaculatus during the middle Pleistocene period. This study indicates a possible signature of genetic variation and population expansion in two seahorses under complex marine environments.     

Specific authentication of Hippocampus based on SNP markers

Seahorses, which are used as traditional Chinese medicine, have large market demands and premium price. Because of overfishing, many seahorse species are endangered and listed in IUCN Red List. The purpose of this study was to develop a simple, rapid and reliable molecular method for specific authentication of seahorse species. Cytochrome c oxidase subunit I (COI) sequences were analyzed for molecular authentication of seahorses in this study. Many single nucleotide polymorphism (SNP) sites were detected among COI sequences of nine seahorse species. Based on the SNP sites, four pairs of modified specific primers were designed respectively for authentication of Hippocampus kuda, Hippocampus japonicus, Hippocampus trimaculatus and Hippocampus kelloggi using allele-specific PCR. Moreover, a multiplex allele-specific PCR for simultaneous authentication of H. kuda, H. japonicus and H. trimaculatus was also developed. The study showed that allele-specific PCR required no sequencing and electrophoresis, and the only necessity is to add fluorochrome into PCR products. Hence the whole authentication procedure only takes about 1.5 h. This work provides an effective method for rapid and reliable identification of seahorse species.     

Two new species of seahorses (Syngnathidae, Hippocampus) from the Middle Miocene (Sarmatian) Coprolitic Horizon in Tunjice Hills, Slovenia: The oldest fossil record of seahorses

Two new and the only known extinct seahorse species Hippocampus sarmaticus and Hippocampus slovenicus are described from the Middle Miocene beds (Lower Sarmatian) in Slovenia, representing the oldest known fossil record of seahorses. Hippocampus sarmaticus was most similar to the extant seahorse species Hippocampus trimaculatus, while H. slovenicus can be most easily compared to the extant pygmy seahorses H. bargibanti, H. denise, and H. colemani. These Sarmatian seahorses lived among seagrasses and macroalgae in the temperate shallow costal waters of the western part of the Central Paratethys Sea.     

New records of the Japanese seahorse Hippocampus mohnikei in Southeast Asia lead to updates in range,habitat and threats

New records of the Japanese seahorse Hippocampus mohnikei from Cambodia, Malaysia, Thailand and Vietnam, along with recently published studies from India and Singapore, have greatly expanded the known range of H. mohnikei within Southeast Asia. These new records reveal novel habitat preferences and threats to H. mohnikei in the region. Although the global conservation status of H. mohnikei is classified as Data Deficient according to the IUCN Red List of Threatened Species, new sightings indicate that this species is found in similar habitats and faces similar threats as other Hippocampus species that are considered Vulnerable.     

Novel life‐history data for threatened seahorses provide insight into fishery effects

Life‐history variables for three incidentally captured species of seahorse (Kellogg's seahorse Hippocampus kelloggi, the hedgehog seahorse Hippocampus spinosissimus and the three‐spot seahorse Hippocampus trimaculatus) were established using specimens obtained from 33 fisheries landing sites in Peninsular Malaysia. When samples were pooled by species across the peninsula, sex ratios were not significantly different from unity, and height and mass relationships were significant for all species. For two of these species, height at physical maturity (H_M) was smaller than the height at which reproductive activity (H_R) commenced: H. spinosissimus (H_M = 99·6 mm, H_R = 123·2 mm) and H. trimaculatus (H_M = 90·5 mm, H_R = 121·8 mm). For H. kelloggi, H_M could not be estimated as all individuals were physically mature, while H_R = 167·4 mm. It appears that all three Hippocampus spp. were, on average, caught before reproducing; height at 50% capture (H_C) was ≥H_M but ≤H_R. The results from this study probe the effectiveness of assessment techniques for data‐poor fisheries that rely heavily on estimates of length at maturity, especially if maturity is poorly defined. Findings also question the sustainability of H. trimaculatus catches in the south‐west region of Peninsular Malaysia, where landed specimens had a notably smaller mean height (86·2 mm) and markedly skewed sex ratio (6% males) compared with samples from the south‐east and north‐west of the peninsula.     

Optimization of hydrolysis conditions, isolation, and identification of neuroprotective peptides derived from seahorse Hippocampus trimaculatus

Hippocampus trimaculatus is one of the most heavily traded seahorse species for traditional medicine purposes in many countries. In the present study, we showed neuroprotective effects of peptide derived from H. trimaculatus against amyloid-β₄₂ (Aβ₄₂) toxicity which are central to the pathogenesis of Alzheimer’s diseases (AD). Firstly, H. trimaculatus was separately hydrolyzed by four different enzymes and tested for their protective effect on Aβ₄₂-induced neurotoxicity in differentiated PC12 cells. Pronase E hydrolysate exerted highest protection with cell viability value of 88.33 ± 3.33 %. Furthermore, we used response surface methodology to optimize pronase E hydrolysis conditions and found that temperature at 36.69 °C with the hydrolysis time 20.01 h, enzyme to substrate (E/S) ratio of 2.02 % and pH 7.34 were the most optimum conditions. Following several purification steps, H. trimaculatus-derived neuroprotective peptides (HTP-1) sequence was identified as Gly-Thr-Glu-Asp-Glu-Leu-Asp-Lys (906.4 Da). HTP-1 protected PC12 cells from Aβ₄₂-induced neuronal death with the cell viability value of 85.52 ± 2.22 % and up-regulated pro-survival gene (Bcl-2) expressions. These results suggest that HTP-1 has the potential to be used in treatment of neurodegenerative diseases, particularly AD. Identification, characterization, and synthesis of bioactive components derived from H. trimaculatus have the potential to replace or at least complement the use of seahorse as traditional medicine, which further may become an approach to minimize seahorse exploitation in traditional medicine.     

Fishers' knowledge and seahorse conservation in Brazil

From a conservationist perspective, seahorses are threatened fishes. Concomitantly, from a socioeconomic perspective, they represent a source of income to many fishing communities in developing countries. An integration between these two views requires, among other things, the recognition that seahorse fishers have knowledge and abilities that can assist the implementation of conservation strategies and of management plans for seahorses and their habitats. This paper documents the knowledge held by Brazilian fishers on the biology and ecology of the longsnout seahorse Hippocampus reidi. Its aims were to explore collaborative approaches to seahorse conservation and management in Brazil; to assess fishers' perception of seahorse biology and ecology, in the context evaluating potential management options; to increase fishers' involvement with seahorse conservation in Brazil. Data were obtained through questionnaires and interviews made during field surveys conducted in fishing villages located in the States of Piauí, Ceará, Paraíba, Maranhão, Pernambuco and Pará. We consider the following aspects as positive for the conservation of seahorses and their habitats in Brazil: fishers were willing to dialogue with researchers; although captures and/or trade of brooding seahorses occurred, most interviewees recognized the importance of reproduction to the maintenance of seahorses in the wild (and therefore of their source of income), and expressed concern over population declines; fishers associated the presence of a ventral pouch with reproduction in seahorses (regardless of them knowing which sex bears the pouch), and this may facilitate the construction of collaborative management options designed to eliminate captures of brooding specimens; fishers recognized microhabitats of importance to the maintenance of seahorse wild populations; fishers who kept seahorses in captivity tended to recognize the condtions as poor, and as being a cause of seahorse mortality.     

Thanatosis in the Brazilian seahorse <Emphasis Type="Italic">Hippocampus reidi</Emphasis> Ginsburg, 1933 (Teleostei: Syngnathidae)

The present study reports thanatosis behavior in Hippocampus reidi seahorses. We observed two different types of tonic immobility during seahorse handling, both in the laboratory and in field studies. In the former, the seahorses assumed a stretched posture, and in the latter, pointed their heads towards their bellies and curled their tails in a spiral towards their abdomen. The displays lasted 124 ± 100 s (n = 3) in the laboratory and 155 ± 7.07 s (n = 5) in the field. Camouflage is the seahorses primary defense from predators and our observations suggest that thanatosis is a secondary strategy that could be more effective than retaliation or escaping predators, due to the fact that seahorses lack teeth and have limited swimming ability. The responses caused by fear occurred after manipulation, allowing for the conclusion that the seahorse H. reidi may use thanatosis as a secondary defense strategy under major stress events.