(1) As previously stated, they practice "external fertilization" by means of "spawning" (i.e., simultaneous extrusion of sperm and oviposition) in the water, but male Ranodon sibiricus with external fertilization produces spermatophores (Pough et al., 2001).

(2) They breed in aquatic habitats, after awaking from hibernation and then immigrating from land to water (the family Plethodontidae, which corresponds to approximately 70% of all urodeles, includes completely terrestrial species throughout the life, and ambystomatids and salamandrids with internal fertilization are counterparts of hynobiids among migratory salamanders), but Hynobius kimurae appears to hibernate in the water.

(3) A female deposits a pair of egg sacs, including a full clutch of unfertilized eggs (in urodeles with internal fertilization, a female deposits fertilized eggs one by one in many places as clumps or non-clumps, e.g., Taricha deposits eggs in clumps, whereas Triturus lays eggs individually; Arntzen, 2002).

(4) Males during scramble competition focus on a pair of egg sacs, instead of a female during and after oviposition (Hasumi, 1994; Hasumi, 2001). In contrast, in urodeles with internal fertilization, males recognize females as limited resources (Pough et al., 2001).

(5) Because "parental care" (i.e., egg-guarding primarily against predators in aquatic development) does not occur, regardless of lentic or lotic habitats, both Dr. Tamotsu Kusano (Tokyo Metropolitan University, Japan) and I do not agree with Nussbaum's (1985) citation of two lotic-breeding species of hynobiids as evidence for parental care in this family (for comparison, e.g., male Andrias japonicus guards eggs in his den, and female plethodontid salamanders brood their eggs deposited on land as terrestrial nesting).

Recent two decade-studies on hynobiids have revealed that the following three life-history traits are common to many species of this family:

(1) Especially in lentic-breeding hynobiids, increased head width of the male during the aquatic phase, i.e., a trait resulted from the swelling of the whole body, is unknown in other families (Hasumi and Iwasawa, 1990).

(2) Unlike nonhynobiids, male hynobiids are characterized by the absence of ÒspermiationÓ (i.e., sperm release from the testes into the vasa deferentia) during fall and, in northern populations, winter months even after the completion of spermiogenesis (Hasumi et al., 1990). This leads to a trait of mating unreadiness during fall or winter months in hynobiids.

(3) Among migratory salamanders (i.e., ambystomatids, hynobiids, and salamandrids) with complex life cycles, hynobiids have unique fall immigration, unrelated to mating, toward terrestrial hibernacula near an aquatic-breeding area (Hasumi and Kanda, 2007). In their counterparts, mating occurs during fall or winter months immediately after completing immigration to the water (e.g., Notophthalmus viridescens: Healy, 1975), except for several northern species or populations where both immigration and mating appear to occur only during spring.

In addition, in hynobiid species there had been only anecdotal evidence that salamander individuals utilize subterranean burrows excavated by small mammals as terrestrial refugia, as has been shown in ambystomatid species, until the following study. Recently, it was confirmed that in Salamandrella keyserlingii at Shaamar, Mongolia, individuals used Muskrat (Ondatra zibethicus) burrows for temporary refuge during daytime in summer (Hasumi et al., 2009).

In this context, hynobiid salamanders are unique among caudate amphibians. Since about half of hynobiids are endemic to Japan, we Japanese biologists have most advantages around the world for the study of hynobiids. However, almost all of these biologists have not yet been aware of the evolutionary significance of the existence of hynobiids. This unawareness overtly prevents the study of hynobiids from developing in the Japanese scientific societies.

Also, many populations of amphibian species have been adversely affected by human-induced pressures such as development and environmental pollution (e.g., Deformity), and consequently have declined within the last three decades. Among hynobiid species, however, conservation measures have met with limited success due to the absolute lack of our understanding of their life-history strategies (i.e., fundamental knowledge of how they exist). I am afraid of the current of the times that all field scientists should engage in any applied studies regarding environment and conservation, rather than basic studies such as breeding ecology, bebavioral ecology, and evolutionary ecology.

Hence, I recommend you will conduct the study of hynobiids in considering both the evolutionarily known traits (see above) and the newly demonstrated traits mentioned in the section on Study Summary, immediately after visiting the present web page. I am very happy to hear this page will help elucidate your study goals when dealing with hynobiids.

*On 18 July 2007, I found a mysterious, grey literature reference saying that Salamandrella keyserlingii (Caudata: Hynobiidae) accomplished internal fertilization (Kuranova and Saveliev, 2006). They stated that in the beginning of July, copulation took place and spermatozoa were found in female oviducts (aquatic-breeding season is from April-May). They also stated that females reserved spermatozoa or fertilized eggs in the oviduct until spring. Within that day, for this reference I asked Dr. David M. Sever (Southeastern Louisiana University, USA), a world ultimate expert on the reproduction of amphibians and reptiles (Sever, 2002). His comments were as follows (he permitted me to cite his comments in my web page):

I am skeptical of their findings. The illustrations of marked sperm in the oviduct are not convincing to me, and the sperm shown in Fig. 5 could be from the testes or sperm ducts. Their findings certainly need confirmation, but if oviductal sperm storage does occur in a hynobiid, that would be most interesting!

I agree with his view. However, even if oviductal sperm storage occurs in this species, I cannot imagine any courtship behavior of how occurs sperm transfer to females (on land?) in such an external fertilizer that does not produce spermatophores. Also, I do not understand why they used the term "newt" for this hynobiid species. Although I have reserved referring to the aforementioned questions for a year, I am now confident in myself to submit these questions here.

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