I have probably described some of this incidentally in some papers/thesis. I may have some photographs, but probably not great ones. BUT, yes, I do have information. The following is off-the-top-of-my-head, so if it differs in my published work then I have misremembered!

This is two questions: ontogeny, and variation within each stage of growth. On the latter, frankly I do not think there is very much except for variation by state of maturity (signalling by pattern). You may have several species. I would suggest taking samples, photographing live, preserving, and partnering with someone to do some DNA work to verify; my guess would be that fish of a given size should show pattern variation only according to male/female (but still the underlying pattern should show them as the same species) and whether they are showing reproductive colours and patterns (male Sicydium punctatum show considerable variation, but they should still be recognisable as the same species; females seem not to show much in the way of special reproductive colouration).

Ontogenetic (including reproductive):

1. As larvae, they hatch with certain pigment patterns* that clearly do not persist to the juvenile stage.

* Bell 94, thesis, &

Bell 2007. Opportunities in Stream Drift: Methods, Goby Larval Types, Temporal Cycles, In situ Mortality Estimation, and Conservation Implications. ...

( most publications are downloadable from http://www.ucs.mun.ca/~kbell/pubs/ )

2. As recruiting postlarvae, they are nearly completely transparent (Sicydium punctatum and S. antillarum).

3. Very quickly upon recruitment to fresh waters and settlement to hard substrate, trunk pigment patterns begin to appear, and first-dorsal fin pigments appear, typically featuring red, blue, and a black spot, and the second-dorsal shows a sub-marginal zone or stripe parallel to the top margin. This is for Sicydium punctatum (Perugia, sensu Brockmann 1965). Sicydium antillarum only at this point becomes reliably differentiable from Sicydium punctatum by the trunk pigments, which are diagrammed in Bell et al 1995 ('Seasonal, inverse...'). Before that, the two species are (so far, to me) indistinguishable except that S. antillarum tends to be larger, but there is overlap so it is not a useable diagnostic except in a statistical sense.

4. As the juvenile Sicydium punctatum becomes a sub-adult, the dorsal fin patterns lose the red and the black spot, and the trunk pigments retain their pattern (Bell et al 95).

5. As Sicydium punctatum become mature, more blue shows in trunk and fins, and to a much greater degree in males. Also in males, the black pigment patterns (angled and intersecting bars) on the body becomes more intense, a sooty black that reflects almost nothing, and the blue between them and on the fins (dorsal I and 11, pectorals, caudal, anal) becomes very intense also. A hint of this can be seen in females (individuals that have been seen to lay eggs, i.e. sex reliably determined), so it would be a mistake to diagnose fish having traces of blue as males.

6. Around spawning and broodcare, it seems to me, a substantial portion of the caudal peduncle of male Sicydium punctatum turns a creamy white. It is possible that this signals "stay away" to differentiate the displays while incubating a nest from an invitation to spawn. (A male does not seem to recognise the female, and may spawn with another; certainly in the group that I watched in captivo for some years there was no detectable monogamy contract!)

7. I have not seen, in adult S. antillarum any variation that would suggest sexual dimorphism or specialised reproductive patterns. That has always surprised me. I have not had S. antillarum spawn in captivo, so if someone achieved that and photographed them well, it would be worthwhile and might confirm or refute my perception.

As said, I've jotted this down quickly, so if anything is unclear or seems wrong, ambiguous, just ask.

All best,

KIM

K.N.I. Bell, PhD

Hi Kim

Thank you for that prompt response. I think we have seen what you described in 3–6. We were puzzled by the dorsal fin colouration (red, white and black, like the T&T national flag) that was obvious in some of the smallest of the fish that we were able to capture by dip netting. We've also seen the blue and less colourful adults at other times.

We're trying to decide whether or not there are two species among the juveniles we recently captured (no adults were observed at sites visited in January 2014). According to old literature (Boeseman 1960) there should be two species of Sicydium in T&T, S. punctatum and S. plumeri.

Dawn