Pipefish Species Research Articles

Exploitation and trade of Australian seahorses, pipehorses, sea dragons and pipefishes (Family Syngnathidae)

Seahorses and their syngnathid relatives have provided a focus for efforts to ensure sustainable use of marine resources, with new international trade controls (CITES Appendix II) implemented in May 2004. We demonstrate how a study of international trade can be used to assess relative levels of threat and set domestic research and conservation priorities. Australia has remarkably high syngnathid biodiversity with at least 14 seahorse species, two endemic sea dragon species, and 90 species of pipefishes and pipehorses found in its territorial waters. Our objectives were to quantify species, trade routes, volumes, values and temporal trends in syngnathid trade to and from Australia. We found that Australia is probably the major global supplier of dried pipehorses Solegnathus spp.. These fishes, including at least one endemic species, are sourced from trawl bycatch and comprise Australia's largest syngnathid export, by both volume and value. Research is urgently needed to evaluate the impacts and sustainability of trawling on pipehorse populations. Australia is also the sole supplier of two sea dragon species, Phycodurus eques and Phyllopteryx taeniolatus, for the live aquarium trade. Although lucrative, the number of wild-caught individuals involved in this trade was relatively low and probably of low conservation risk relative to habitat loss. Exports of seahorses and other pipefish species, and imports of all syngnathid species, are minor on a global scale, although the burgeoning aquaculture industry for seahorses requires careful evaluation for its potential impacts on wild populations.

Diet composition and feeding strategy of the southern pipefish Syngnathus folletti in a Widgeon grass bed of the Patos Lagoon Estuary, RS, Brazil

Pipefish species are poorly known representatives of the family Syngnathidae, which have been increasingly threatened by anthropogenic activities. We describe the diet composition and feeding strategy of southern pipefish Syngnathus folletti inhabiting a Widgeon grass (Ruppia maritima L.) bed in the estuarine zone of Patos Lagoon, southern Brazil. We also investigated whether mouth gape affected the size of prey items consumed and based on indirect evidence, we suggest possible pipefish foraging movements within the bed. Individuals were collected from December 1994 to March 1995 in a Ruppia maritima bed located in the Patos Lagoon Estuary during day and night periods. We analyzed the stomach contents of 108 individuals (54 females and 54 males). Both genders seemed to be diurnal carnivores with diets composed primarily of copepods and isopods. Mixed feeding strategies were evident with varying degrees of specialization on different prey types. Females had a more diverse diet both in prey richness as in prey size range, whereas males fed primarily on smaller prey, the isopod U. peterseni and copepods. Gender-based diet differences suggest that females may be more mobile and active inside the Widgeon grass bed than males. The average size range of the two dominant prey items fitted well to the pipefish mouth gape (0.4 to 1.4mm). However, a few female individuals were able to consume prey three times larger than their maximum gape. A diagram of prey microhabitat suggested that both genders browse and capture invertebrates over the entire vegetated substrate provided by the Widgeon grass bed.

Embryogenesis in the Dwarf Seahorse, Hippocampus zosterae (Syngnathidae)

Embryogenesis of the dwarf seahorse, Hippocampus zosterae, was studied by scanning electron microscopy of a series of developmental stages. Stages ranged from initial cleavage of the egg through term embryos. Embryos hatch from their egg envelopes about midway through development, yet remain nestled in stromal chambers of vascularized epithelium within the male brood pouch until their yolk reserves are consumed. The difference in body shape between the pipefish and seahorse first becomes discernible during mid-development, just before hatching. At this stage, embryos begin to develop their characteristic prehensile tail in contrast to the straight body and typical caudal fin of most species of pipefish. Post-hatching, ‘yolk-sac’ larvae have a well developed head, that is set at a right angle to the body axis, and fully formed fins. As seahorse embryos approach term, lepidotrichia calcify, and the prehensile tail is capable of muscular contraction. Dermal scutes first appear at this stage and ossify in the term embryo. The dermal armor is then fully formed and functional. At term, the yolk reserves have been depleted, and the young are released from the brood pouch as free-swimming, free-feeding miniature versions of the adults.

The myth of the sperm cloud – or why is testes size not affected by spawning mode in seahorses and pipefishes

One can predict fish species that spawn externally to have larger testes for their body size than internal fertilizers, to produce greater numbers of sperm as a response either to increased risk of sperm competition from sneaker males, or to counter the dilution of sperm in open water. Using museum specimen, we measured testis and body mass of 95 mature males, belonging to 21 genera of the family Syngnathidae (pipefishes and seahorses). In this family all species show paternal care, ranging from eggs being simply attached to the skin of the male, to completely enclosed in a brood pouch. The former unprotected group is thought to fertilize the eggs externally, whereas the latter protected group has internal fertilization, as the male fertilizes the eggs inside his own pouch. Hence, expecting smaller relative testis investment in the genera that have protected compared to unprotected brood care, to our surprise we found this not to be the case. Instead, all genera showed the same relationship between testis and body mass, regardless of brooding type. New results of ours, however, from Nerophis ophidion, a pipefish species that lacks brood pouch, show that the mode of fertilization in older literature (external fertilization after egg transfer when the male sinks through a sperm cloud) has been misjudged, and that this pipefish in fact, has internal fertilization inside the female before egg transfer. If this exciting finding proves to be true for other pouchless Syngnathids as well, the mystery of the museum data will be resolved.

The genetic mating system and tests for cuckoldry in a pipefish species in which males fertilize eggs and brood offspring externally.

Highly variable microsatellite loci were used to study the mating system of Nerophis ophidion, a species of pipefish in which pregnant males carry embryos on the outside of their body rather than in an enclosed brood pouch. Despite this mode of external fertilization and brooding, otherwise rare in the family Syngnathidae, the genotypes of all embryos proved to be consistent with paternity by the tending male, thus indicating that cuckoldry by sneaker males is rare or nonexistent in this species. N. ophidion is a phylogenetic outlier within the Syngnathidae and its reproductive morphology is thought to be close to the presumed ancestral condition for pipefishes and seahorses. Thus, our genetic results suggest that the evolutionary elaboration of the enclosed brood pouch elsewhere in the family was probably not in response to selection pressures on pregnant males to avoid fertilization thievery. With regard to maternity assignments, our genotypic data are consistent with behavioural observations indicating that females sometimes mate with more than one male during a breeding episode, and that each male carries eggs from a single female. Thus, the polyandrous genetic mating system in this species parallels the social mating system, and both are consistent with a more intense sexual selection operating on females, and the elaboration of secondary sexual characters in that gender.

Reproductive ecology of five pipefish species in one eelgrass meadow

Synopsis Pipefishes have rarely been watched in the wild and have never before been followed in their common seagrass habitats. This study explores the reproductive ecology of five species of pipefishes living in a Swedish eelgrass meadow during parts of four breeding seasons, tagging four of the species. Pipefish are remarkable for their specialised paternal care: only males aerate, osmoregulate and nourish the developing embryos. Two of the species (Entelurus aequoreus andNerophis ophidion) have simple ventral gluing of eggs on the trunk while three species (Syngnathus acus, S. rostellatus andS. typhle) have fully enclosed brood pouches on their tails. Males of the former species receive eggs from one female while males of the genusSyngnathus receive partial clutches from several females. Sex ratios of adults on the site differed from equal to male-biased to female-biased, according to species.S. typhle were most numerous and were resighted most often. They were present throughout the breeding season whereas there were temporal shifts in the presence of the other species on the meadow and in some sex ratios. Most species occurred in the deeper, denser part of the meadow but there was some habitat separation by species and sex. All species tended to stay low in the eelgrass, primarily coming up above the eelgrass to display and mate. No species showed site fidelity either to a home range or to the meadow, withE. aequoreus adults spending least time on the meadow. Sexual size dimorphism differed: males were larger inS. rostellatus, the same size inS acus and smaller in the other species. Although the species overlap in habitat requirements and breeding season, the only observed interspecific interactions were abortive courtships betweenSyngnathus species.

Trophic ecology of two congeneric pipefishes (Syngnathidae) of the lower York River, Virginia

The northern pipefish, Syngnathus fuscus, and the dusky pipefish, S. floridae, co-exist in eelgrass beds in the lower York River. To compare the trophic ecology of both pipefishes, gut contents of 3488 northern pipefish, and 1422 dusky pipefish were examined and quantified by dry weight. Samples were taken with a dip net from May through November 1992. Syngnathus fuscus fed mainly on amphipods (Gammarus mucronatus, Amphithoe longimana, and Caprella penantis), and to a lesser degree on copepods, and isopods (Edotea spp. and Erichsonella attenuata). Syngnathus floridae fed mainly on grass shrimps (Palaemonetes pugio, P. vulgaris, and Palaemonetes eggs), and to a lesser degree on copepods, isopods, and mysids (Mysidopsis bigelowi). No seasonal trends were observed in the feeding habits of these pipefishes. Specimens of both species smaller than 100 mm TL fed mainly on copepods. Larger S. fuscus fed on amphipods, while larger S. floridae fed on grass shrimps. Schoener's diet overlap index revealed high consumption of the same prey type by both pipefish species only in July, but only for those specimens smaller than 110 mm TL. Food partitioning between both pipefish was associated with different snout sizes and shapes.

Male avoidance of parasitized females explained by direct benefits in a pipefish

The influence of the parasitic trematode,Cryptocotylesp., on male mate choice in a species of pipefish,Syngnathus typhle, was studied. This parasite induces visible black spots in the skin of pipefish, but cannot be transmitted directly from one pipefish to another. In a mate-choice experiment the males spent more time with females with few or no black spots than with females with many black spots. This result was obtained in experiments with natural variation in parasite load, and also in experiments in which black spots were manipulated using tattoo ink. This suggests that males discriminate against parasitized females by using visual cues. In another choice experiment, males did not show any preference between males with or without black spots, suggesting that the discrimination occurs only in a sexual context. There was a negative correlation between parasite load and female fecundity. As a result, males mating with unparasitized females may benefit directly by fertilizing more eggs.

Plasma levels of sex steroids in three species of pipefish (Syngnathidae)

The pipefishes (Syngnathidae) are marine teleosts in which the males brood the young. In some species sex-role reversal occurs when, contrary to the usual pattern, females compete more intensely than males for access to mates. This paper reports an investigation of the sex hormones of males and females to see whether they deviate from the "normal" teleost pattern. To that end, plasma levels of the androgens testosterone (T), 11-ketotestosterone (OT), 11β-hydroxytestosterone, 11-ketoandrostenedione, and 11β-hydroxyandrostenedione (OHA), together with 17α-hydroxy-20β-dihydroprogesterone (17,20-P) and 17β-estradiol (E2), were measured by means of radioimmunoassay in three species of pipefish: Nerophis ophidion, Syngnathus typhle, and Syngnathus acus. Plasma levels of OT, the dominant circulating androgen in breeding males of most teleost species, was found to be highest in breeding males and low or non-detectable later in the brooding males. This observed decline in male OT levels from the prespawning to the postspawning (=brooding) period is in general agreement with what has been found in other teleosts. In both breeding and brooding S. acus males, T was quantitatively the dominant androgen, whereas OHA was the major androgen in S. acus females, as well as in the females and breeding or brooding males of both S. typhle and N. ophidion. In breeding S. acus and S. typhle males the levels of T, OHT, and OT were higher than in corresponding brooding males and females. The 17,20-P level was below detection limit. E2 was also usually non-detectable, but was most consistently found in breeding Syngnathus males.

Reproductive Success of Females Limited by Males in Two Pipefish Species

We investigate whether males limit the reproductive success of females in the two pipefish species Syngnathus typhle and Nerophis ophidion. Syngnathus typhle is sexually monomorphic, and courtship behavior does not differ between the sexes. In N. ophidion, on the contrary, females are larger, more colorful, and more active during courtship, possessing appearance-enlarging skin folds. In both species, males brood the offspring on their bodies, one internally and one externally. Males do not invest more energy in reproduction than do females, and in the sexually dimorphic species, males invest even less than females do. Natural sex ratios are equal in both species. Experimentally, we provided each female with an excess of males (i.e., three), in order to measure a female's maximal reproductive rate, and found that females of both species produced more eggs, or produced them at a faster rate, than naturally available males could care for. Within the time span of one male pregnancy, S. typhle females filled an average of 1.9 males and N. ophidion an average of 1.8 males; both numbers are significantly more than one (which is the average mate availability in natural populations). Measured in another way, during one male pregnancy, S. typhle and N. ophidion females both produced 41% more eggs than needed to fill a male, significantly more than no egg surplus in both species. Therefore, brood space and the rate of embryonic development limit female reproduction in these species. There was no significant difference between the species, however. Syngnathus typhle males might be expected to be less limiting than N. ophidion males, but sexual size dimorphism may be absent in S. typhle because, by contrast with N. ophidion, larger males enjoy greater reproductive success. Directional selection for increased male size may decrease sexual size dimorphism in S. typhle. At any rate, the limitation of the reproductive success of one sex by the other seems to be a necessary but not sufficient prerequisite for the evolution of sexual dimorphism and "sex roles."

Habitat selection and diet in two species of pipefish from seagrass: sex differences

Habitat selection and diet in two species of pipefish from seagrass: sex differences

Reproductive Costs in Two Sex-Role Reversed Pipefish Species (Syngnathidae)

(1) In two species of pipefish (Syngnathidae) the reproductive costs of the two sexes were compared to see how they might influence patterns of sex-role reversal. (2) In Syngnathus typhle, males brood their offspring in a brood pouch, providing them with nutrients and oxygen. Sexes are monomorphic. Males faced reproductive costs in terms of a lower food intake compared with females. Also, males grew more slowly than females, which yields a cost to future reproduction, as larger males could brood more offspring. No sexual difference in predation risk was found. The over-winter survival of males was probably lowered because intestinal fat deposition was delayed as a result of their reproductive efforts. (3) In Nerophis ophidion, males brood their offspring attached to their ventral body side, and provide them with nutrients and oxygen. Sexes are dimorphic, females being larger and brighter in colour. Males suffered an increased predation risk when brooding. No indications of energetic costs were found, e.g. through a lowered food intake or a slower growth rate. (4) Reproductive costs differed in the two species, probably reflecting differences in brood care. However, in both species the limiting sex, males, faced higher reproductive costs than females, as would be expected in sex-role reversed animals.

Mate choice, fecundity and sexual dimorphism in two pipefish species (Syngnathidae)

In order to understand the causes of sexual dimorphism, mate choice and size-related fecundity were studied in two pipefish species, Syngnathus typhle and Nerophis ophidion. Sexual dimorphism is more pronounced in N. ophidion; females are larger, have sexual colourings, and are more active during courtship. In S. typhle the sexes are alike in all these respects. Males brood their offspring in both species. In N. ophidion fecundity was positively correlated with both body size and the amount of sexual colouring in females. In males no correlation between body size and fecundity, or between body size and embryo size existed. Predictably, in mate choice experiments with equal-sized females, males chose females with more extensive sexual colourings. We explain sexual dimorphism in this species as a consequence of both natural selection (fecundity increases with size in females but not in males) and sexual selection (males prefer larger females). We argue that sexual size dimorphism did not evolve by selection minimizing overlap in food niches between the sexes, because food production is high in the Zostera beds where the fishes live, and no size dimorphism was found in the sympatrically occurring S. typhle. Furthermore, in N. ophidion dimorphism is not greater in a particular mouth character than in overall body size. In S. typhle egg size and the average number of eggs transferred per spawning were positively correlated with female body size. Apparently more energy per offspring was provided by larger males than by smaller males, and larger males also carried more offspring. As predicted, large mates were preferred by both sexes in mate choice experiments. This is explicable in terms of both natural selection (fecundity increases with size in both sexes) and sexual selection (both sexes prefer large mates). As a consequence of selection acting in the same direction in both sexes, sexual dimorphism is absent in S. typhle.

Reversed sex roles and parental energy investment in zygotes of two pipefish (Syngnathidae) species

Reversed sex-roles and parental energy investment in zygotes of two pipefish (Syngnathidae) species

Population dynamics and feeding ecology of pipefish (Syngnathidae) associated with eelgrass beds of Western Port, Victoria

Three species of pipefish, Urocarnpus carinirostris Castelnau, Vanacarnpus phillipi (Lucus) and Mitotichthys semistriatus (Kaup), occurred regularly in collections from eelgrass beds of Western Port. A fourth species, Stigmatopora nigra Kaup, was rare. U. carinirostris and V. philippi dominated catches. Brooding males were present for 6-9 months of the year, juveniles were recruited in summer and early autumn, and both species were annual. The pipefish fauna included two main behavioural types. V. phillipi and M. sernistriatus oriented themselves horizontally and were relatively strong swimmers. U. carinirostris and S. nigra were more sedentary, attaching themselves to benthic vegetation by means of a prehensile tail. The latter two species closely mimicked eelgrass leaves in movements, orientation and colour. All inhabited the eelgrass leaf canopy except V. phillipi, which occupied the sediment-water interface. The pipefish were visually orienting, sit-and-wait predators. Pelagic or epibenthic copepods and small epibenthic amphipods comprised the bulk of diets; only V. phillipi ingested polychaetes and plant detritus.

Description of a new species of pipefish (Siphostoma scovelli) from Corpus Christi, Texas

Description of a new species of pipefish (Siphostoma scovelli) from Corpus Christi, Texas