Re: NANFA-L-- Not the worlds smallest fish.

Michael Sandel (kwksand-in-yahoo.com)
Fri, 27 Jan 2006 09:07:50 -0800 (PST)

Good points Chris. I overlooked the discussion in the Kottelat et al. article.

I think Kottelat et al. is wrong, here's why.

1. Maximum recorded size for an individual is 10.3 mm (P. progenetica) vs 8.4 mm (S. brevipinguis).

2. Larger size of smallest sexually mature individual is 7.9 mm (female P. progenetica) vs 6.6-7.7 mm (male S. brevipinguis).

Kottelat et al. argue that Watson and Walker can't objectively diagnose sexually mature male S. brevipinguis without histology, which is correct. However, 5 of 6 Schindleria were male. All of the males were smaller than the smallest sexually mature Paedocypris. Of these 5 males (5.1-7.7 mm SL), urogential papillae measures 0.2-0.5 mm. With a fish this small, they have a developmental series. W & W also examined 13 S. pietschmanni (4.413.6 mm); and 12 S. praematura (4.015.4 mm). This would help them compare and diagnose characters that indicate sexual development. My guess is that histology will reveal sexual maturity in S. brevipinguis is ~6.6 mm, which is the SL-in-which urogenital papillae reach max length (0.5 mm), and what was estimated by W & W in 2004.

Kottelat et al. imply that Watson and Walker (2004) are uncertain in their size-at-maturity measurements (6.5-7.0 etc.), yet in the very same article they report max size of P. progenetica as 10.3 and 10.5 mm (page 2 and 4). Which one is the true max size?


They also say the largest recorded T. nanus was 10.2 mm, which is smaller than the max size for P. progenetica! (page 4)

"That means, however, that Trimmatom nanus, another marine
gobioid (Gobiidae), which has 'fully developed eggs ... present from a
standard length of 8 mm and greater' (largest known individual 10.2 mm)
(Winterbottom & Emery 1981), is the smallest previously recorded
vertebrate."


Actually they ignored Winterbottom 1989, which reports max size for T. nanus to be 11.7 mm.

The largest recorded individual P. progenetica is 22.6% larger than the largest S. brevipinguis. The urogenital papillae of S. brevipinguis is developed-in-6.6 mm SL. The smallest recorded sexually mature P. progenetica is 19.7% larger than the 6.6 mm S. brevipinguis.

Hope this didn't sound too argumentative. I am interested, so I wanted to pass along what I found.

Mike


Christopher Scharpf <ichthos-in-comcast.net> wrote:
> Schindleria brevipinguis {Saltwater Goby} 6.5 mm! (Watson and Walker 2004)

Kottelat et al. question the veracity of this record:

"An Australian marine gobioid fish, Schindleria brevipinguis (family
Schindleriidae), was recently presented as 'almost certainly' the world's
smallest vertebrate maturing 'by 7 mm',-in-'7-8 mm' or '6.5-7 mm' on
different pages in the paper (Watson & Walker 2004). Of the six known
specimens, however, sexual maturity was objectively established only for the
single female measuring 8.4 mm. Maturity of the smaller males seems to have
been inferred from the presence of the genital papilla as specimens were not
dissected. Without histological examination, sexual maturity can be
objectively established only by the presence of ripe eggs in the female's
ovaries.
Furthermore ...

"The discovery of P. progenetica, with a mature female of just 7.9 mm and a
maximum size of 10.3 mm, makes it the smallest recorded vertebrate species,
slightly smaller than the marine goby T. nanus. Paedocypris micromegethes,
the females of which mature-in-8.8 mm (maximum 11.6 mm), comes a close
second as the smallest freshwater vertebrate.

"The 7.9 mm mature female of P. progenetica is not an unusually small
individual. The 1 mm mesh size that we use in peat swamps only rarely
catches specimens smaller than 7 mm and, therefore, introduces a size bias
in our samples. Our largest sample contains 56 females (MZB5998, 5999, ZRC
43199), including the 7.9 mm one and the individuals unambiguously
identifiable as females are 5.9-8.3 mm. The largest female is only slightly
larger than the smallest mature one."

Not taking sides here. It's just what the paper says.

Chris Scharpf
Baltimore
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